leveling of the curve of spee in deep overbite cases
TRANSCRIPT
LEVELING OF THE CURVE OF SPEE
IN DEEP OVERBITE CASES
TREATED WITH THE INCOGNITOTM LINGUAL
ORTHODONTIC APPLIANCE SYSTEM:
A RETROSPECTIVE CEPHALOMETRIC ANALYSIS
by
Jessica Nardone
A thesis submitted in conformity with the requirements
for the degree of MSc
Graduate Department of Orthodontics,
Faculty of Dentistry, University of Toronto
Copyright by Jessica Nardone (2012)
Jessica Nardone Convocation Year 2012, MSc. Department of Orthodontics, Faculty of Dentistry, University of Toronto
ABSTRACT
An excessive curve of Spee (COS) is a common orthodontic finding, particularly in patients with a deep overbite
(OB). The purpose of this analysis was to evaluate COS leveling and OB correction in patients treated with
IncognitoTM, a customized lingual appliance system. Pre- and post-treatment cephalometric radiographs were
compared for 34 patients with a deep OB and excessive COS treated with IncognitoTM. The mean pre- and post-
treatment COS was 1.78 mm (SD: 0.36 mm) and 0.37 mm (SD: 0.41 mm) respectively, indicating a significant
amount of leveling (-1.41 mm, SD: 0.49 mm, p<0.001). The mean pre- and post-treatment OB was 5.80 mm (SD:
1.26 mm) and 2.91 mm (SD: 0.86 mm) respectively, demonstrating a significant reduction in OB (-2.89 mm, SD 1.27
mm, p<0.001). COS and OB correction was accomplished by incisor proclination, and a greater (but not significantly
different) amount of mandibular incisor intrusion versus premolar and molar extrusion.
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ACKNOWLEDGEMENTS
I would like to extend special thanks to several individuals:
To my research supervisor Dr. Bryan Tompson for his patience and support throughout the ‘evolution’ of my
master’s project and particularly for providing me with the opportunity to be a part of the Orthodontic family at
the University of Toronto where I was able to fulfill my dream of becoming an Orthodontist; To my research
committee advisors Dr. Sunjay Suri and Dr. Angelos Metaxas for their constructive advice and encouragement; To
Dr. Rick Walker for the creation of a cephalometric tracing sequence and custom analysis using Dentofacial
PlannerTM; To Dr. Cliff Alexander for his creative inspiration and facilitation of data collection; To Dr. Neil
Warshawsky, Dr. Hilton Goldreich, Dr. David Hime, Dr. Neal Kravitz, Dr. Leslie Pitner for their contribution of cases
towards the sample; To Sheila Suzuki and 3M Unitek© for their resourcefulness and support in understanding the
IncognitoTM system.
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TABLE OF CONTENTS
ABSTRACT .................................................................................................................................................................................... ii
ACKNOWLEDGEMENTS .......................................................................................................................................................... iii
LIST OF TABLES .......................................................................................................................................................................... v
LIST OF FIGURES ....................................................................................................................................................................... vi
LIST OF APPENDICES ............................................................................................................................................................. vii
I. INTRODUCTION AND STATEMENT OF THE PROBLEM ................................................................................. 1 SIGNIFICANCE OF THE PROBLEM ........................................................................................ 4
II. REVIEW OF THE LITERATURE............................................................................................................................... 5 THE CURVE OF SPEE (COS) ..................................................................................................... 5
ORTHODONTIC LEVELING OF THE COS ............................................................................. 7 LEVELING WITH LABIAL APPLIANCES ............................................................................... 9
STUDY METHODS USED TO MEASURE THE COS ........................................................... 12 DEMAND FOR ESTHETIC APPLIANCES ............................................................................. 17 LINGUAL ORTHODONTICS ................................................................................................... 18 INCOGNITOTM ........................................................................................................................... 20 EXCESSIVE COS, DEEP OVERBITE, AND INCOGNITOTM ............................................... 23 LEVELING WITH LINGUAL APPLIANCES .......................................................................... 26
III. PURPOSE ................................................................................................................................................................... 27
IV. HYPOTHESES ............................................................................................................................................................ 28
V. MATERIALS AND METHODS ................................................................................................................................ 29 SAMPLE ....................................................................................................................................... 29 ETHICS ......................................................................................................................................... 30 RECORDS .................................................................................................................................... 31 LATERAL CEPHALOMETRIC ANALYSIS ............................................................................ 34 CEPHALOMETRIC IMAGE CALIBRATION ........................................................................ 45 STATISTICS ................................................................................................................................ 47
VI. RESULTS ..................................................................................................................................................................... 50 SUCCESS OF COS LEVELING .................................................................................................. 50 SUCCESS OF OB REDUCTION ................................................................................................ 51 DENTAL MOVEMENTS ............................................................................................................ 52 MANDIBULAR ROTATION .................................................................................................... 57 OTHER CEPHALOMETRIC MEASUREMENTS ................................................................. 59 POTENTIALLY CONFOUNDING FACTORS ....................................................................... 60 ACCURACY OF S-N MEASUREMENT FOR CALIBRATION ............................................. 63 ERROR STUDY........................................................................................................................... 64
VII. DISCUSSION ............................................................................................................................................................... 66
VIII. CONCLUSIONS ........................................................................................................................................................... 78
IX. REFERENCES ............................................................................................................................................................. 79
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LIST OF TABLES
Table 1: Change in depth of COS from pre- to post-treatment and significance
from paired t-test ................................................................................................................................................................... 50 Table 2: Change in OB from pre- to post-treatment and significance from paired
t-test. ........................................................................................................................................................................................... 51 Table 3: Changes in mandibular incisor, premolar and molar distances to Mandibular Plane from pre- to post-
treatment and significance from paired t-tests ............................................................................................................ 52
Table 4: Differences in mandibular incisor intrusion versus premolar and molar extrusion and significance from paired t-tests ............................................................................................................................................................................. 53
Table 5: Changes in mandibular incisor and molar mean inclination from pre- to
post-treatment and significance from paired t-tests .................................................................................................. 54 Table 6: Changes in maxillary incisor and molar mean distances to Palatal Plane
from pre- to post-treatment and significance from paired t-tests ......................................................................... 55 Table 7: Changes in maxillary incisor and molar mean inclination relative to Palatal Plane from pre- to post-
treatment and significance from paired t-tests ............................................................................................................ 56 Table 8: Changes in Y-axis angle, Mandibular Plane angle, and Face Height Ratio
from pre- to post-treatment and significance from paired t-tests ......................................................................... 57 Table 9: Changes in angles SNA, SNB, and ANB from pre- to post-treatment and significance from paired
t-tests ........................................................................................................................................................................................... 69 Table 10: Potential confounding factors ............................................................................................................................................. 60 Table 11: Mean and absolute differences in measurements for S-N and S-Ba from pre- to post-treatment and
significance from paired t-tests for 21 subjects with scales on both cephalograms ........................................ 63 Table 12: Tests for intra-examiner reliability of cephalometric measurements ................................................................... 64
Table 13: Test for inter-examiner reliability of cephalometric measurements .................................................................... 65
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LIST OF FIGURES
Figure 1: The Curve of Spee ............................................................................................................................................................1 Figure 2: IncognitoTM lingual bracket-archwire system ......................................................................................................3 Figure 3: Extrusion of molars and resultant downward and backward
mandibular rotation ................................................................................................................................................... 11 Figure 4: Common method of measuring COS depth from orthodontic casts .......................................................... 14 Figure 5: Difference in COS measurements depending on reference points .............................................................. 16 Figure 6: CBCT orientation planes ............................................................................................................................................ 32 Figure 7: CBCT X-ray beam projection options ..................................................................................................................... 33 Figure 8: Lateral cephalometric landmarks identified ....................................................................................................... 35 Figure 9: Lateral cephalometric planes utilized ................................................................................................................... 36 Figure 10: Measurements used to determine COS leveling ............................................................................................... 39 Figure 11: Depth of COS at pre-treatment and post-treatment ....................................................................................... 49 Figure 12: OB at pre-treatment and post-treatment ........................................................................................................... 50 Figure 13: Mandibular incisor, premolar and molar distances to Mandibular
Plane at pre- and post-treatment .......................................................................................................................... 53 Figure 14: Inclination of maxillary and mandibular incisors at pre- and post-treatment ....................................... 56 Figure 15: Effects of posterior inter-arch elastics and posterior bite opening
props on mandibular first molar extrusion ......................................................................................................... 61
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LIST OF APPENDICES Appendix 1: Abbreviations/Acronyms........................................................................................................................................... 86 Appendix 2: Cephalometric landmark definitions ..................................................................................................................... 87 Appendix 3: Questionnaire for each case .................................................................................................................................... 88 Appendix 4: Example of DFP tracing and measurements ...................................................................................................... 89 Appendix 5: Lateral cephalometric measurements at pre- and post-treatment, results, and significance
from paired t-tests....................................................................................................................................................... 90 Appendix 6: Mandibular incisor intrusion versus premolar and molar extrusion, and significance from
paired t-tests ................................................................................................................................................................. 97 Appendix 7: Error study results – Intra-examiner reliability ................................................................................................ 98 Appendix 8: Error study results – Inter-examiner reliability ................................................................................................. 99 Appendix 9: Calibration data and results: cephalograms with scales on both pre-
and post-treatment images ................................................................................................................................... 100 Appendix 10: Calibration data and results: cephalograms without a scale on one of
pre- or post-treatment images ........................................................................................................................... 101
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1
I. INTRODUCTION AND STATEMENT OF THE PROBLEM
An excessive curve of Spee (COS) in the mandibular dentition is a frequent finding in
patients presenting for orthodontic treatment. The COS refers to the anatomic
curvature of the mandibular dentition and can be explained as the arc of a curved plane
that lies tangent to the cusp tips and incisal edges when viewed from the sagittal
direction (Marshall et al., 2008).
Figure 1. Curve of Spee
Leveling of this curve is an early treatment goal in the sequence of orthodontic
mechanotherapy, and while it can often be challenging, it is a necessary component of
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treatment if one hopes to achieve what would be considered an ideal occlusion (Proffit,
2007; Andrews, 1972).
A sound understanding of biomechanical principles is essential for the orthodontist to
arrange the most effective treatment plan, select the most appropriate appliances and
techniques, deliver only desirable tooth movement, and maintain control of unwanted
side effects. This goes for both leveling of the COS, as well as all other stages of
orthodontic treatment. However, orthodontic force systems used in even simple routine
orthodontic mechanics are considered to be indeterminate force systems, meaning that
there are far too many unknowns to possibly be able to predict the exact three
dimensional forces experienced at each tooth, and consequently, the expected tooth
movement. In addition, there are factors that are already beyond the control of the
practitioner, such as growth and individual tissue responses to orthodontic appliances
(Badawi, 2009). It is for this reason that many studies have investigated the effects of
various orthodontic appliances by carrying out clinical trials, (ie. introducing an active
appliance to a patient’s dentition and then describing the outcome) thereby providing
evidence-based knowledge.
A number of clinical studies have been performed in order to explore the ways in which
different orthodontic appliances and techniques have gone about effecting tooth
movement during the course of leveling of the COS (Dake et al., 1989; Weiland et al.,
1996; Berstein et al., 2007). However, all of the studies that have examined the
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correction of an excessive COS, with the exception of a single investigation (Hong et al.,
2001), have concentrated on labial appliances.
With a continuing rise in the number of adult patients seeking orthodontic treatment, a
demand for more esthetic appliances has become increasingly apparent. This has been
demonstrated by growth in the fabrication industries of ceramic brackets, transparent
aligners, and lingual appliances. IncognitoTM (Figure 2), a fully customized lingual
bracket-archwire system, has incorporated a number of technological advances that
have allowed it to overcome many of the challenges previously experienced with earlier
lingual appliances (Wiechmann, 2003). Studies involving this lingual system have
surfaced in the orthodontic literature over the last decade, and have explored various
aspects of treatment with the appliance. To date, no study has investigated the way in
which this appliance directs tooth movement during the course of leveling of an
excessive COS.
Figure 2. IncognitoTM lingual bracket-archwire system.
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SIGNIFICANCE OF THE PROBLEM
It is theorized that leveling of the COS while using a lingual continuous archwire such as
IncognitoTM might be accomplished by tooth movements different from those produced
by other orthodontic archwire techniques studied in the past (Dake et al., 1989; Weiland
et al., 1996; Berstein et al., 2007). The direction of tooth movements has implications
not only for the position of any given tooth within the jaw, but also the position of the
mandible in relation to the rest of the craniofacial apparatus. Of particular interest, is
the knowledge of how a lingual continuous IncognitoTM archwire might direct tooth
movement to accomplish leveling in comparison to the way in which a labial continuous
archwire achieves this same task. Studies focused on various aspects of lingual
appliances have continued to increase in the orthodontic literature as the method of
treatment has become more widely used, however investigations examining lingual
orthodontics and occlusal leveling in particular are almost non-existent.
It is essential for orthodontic specialists to be cognizant of the actions and reactions of
any appliance they may select to provide orthodontic therapy, so that they are able to
deliver predictable and controlled tooth movement while minimizing undesirable side
effects. It is therefore valid and important to investigate the way in which leveling and
concomitant deep overbite (OB) correction is achieved in patients treated with the
IncognitoTM lingual bracket-archwire system.
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II. REVIEW OF THE LITERATURE
THE CURVE OF SPEE (COS)
The presence of a COS is common finding of variable depth in the occlusal arrangement
in the general population. The first description of the curve is credited to Ferdinand Graf
von Spee who published his work in 1890 after thorough examination of the dentitions
belonging to a series of skulls with abraded teeth. He defined the line of occlusion as the
line on a cylinder tangent to the anterior border of the condyle, the occlusal surface of
the second molar, and the incisal edges of the mandibular incisors (Spee, 1890).
Clinically in orthodontics today, the COS refers to the occlusal curvature of the
mandibular dentition that runs tangent from the buccal cusp tips of the posterior molars
to the incisal edges of the anterior incisors when viewed in the sagittal plane (Marshall
et al., 2008).
Marshall et al. (2008) described the development of the COS by evaluating the dental
casts of subjects taken at seven serial time points throughout growth and maturation.
The findings, coincident with those of Bishara et al. (1989), Ash et al. (1993), and Carter
and McNamara (1998) suggested that the depth of the COS is minimal in the deciduous
dentition, increases largely with the eruption of the central incisors and first permanent
molars, and finally reaches a maximum with the eruption of the permanent second
molars where it remains stable throughout adolescence and into adulthood. The
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authors attempted to provide an explanation as to why the curve might develop,
suggesting that perhaps the mandibular molars and incisors are permitted to erupt
beyond the original occlusal plane due to the fact that they erupt earlier than their
maxillary antagonist and are therefore unopposed (Marshall et al., 2008). Logically, this
unopposed eruption would be expected to be even more exaggerated in Class II dental
or skeletal relationship, leading to an excessive deepening of the COS. A recent study
which examined 100 untreated adolescents confirmed this assumption when they found
that the COS was in fact the most severe in Class II Division 2 subjects, followed by Class
II Division 1 subjects, then Class I subjects, with the least amount of depth detected in
Class III subjects (Ahmed et al., 2011). Overall, the development of the COS is likely due
to a combination of factors including dental eruption timing, craniofacial variation, and
neuromuscular factors (Marshall et al., 2008).
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ORTHODONTIC LEVELING OF THE COS
In describing his “six keys to normal occlusion”, Andrews (1972) noted that in non-
orthodontic normal subjects, the occlusal plane ranged from flat to a slight COS.
(‘Normal’ referred to the fact that these subjects were judged by professionals to not
benefit from orthodontic treatment). He illustrated that a deep COS in the mandible
would result in a more confined space for the maxillary dentition, making it impossible
to achieve a normal occlusion; the only way feasible to attain the most favourable
intercuspation was to have a COS that was nearly level. Andrews (1972) discussed a
natural tendency for deepening of the COS with aging; with continued growth of the
mandible beyond that of the maxilla, the mandibular incisors restricted by the maxillary
incisors would be forced to move backwards and upwards. Andrews (1972) thus
included the occlusal plane as his 6th key to normal occlusion, advocating that leveling of
the COS should be a treatment goal in orthodontic therapy.
While it may present a challenge to the orthodontist, the correction of an excessive COS
and concomitant reduction of a deep OB is a day-to-to practice in the orthodontic office
setting. Leveling of the occlusal plane is almost always indicated and according to Proffit
(2007) should be performed as a part of the first major stage of comprehensive
orthodontic treatment. A variety of the techniques for leveling are available, and involve
either extrusion of premolars and molars, intrusion of incisors, or by some combination
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of both. The method selected should be based on the specific characteristics of not only
the patient’s malocclusion, but also their overall craniofacial proportions (Proffit, 2007).
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LEVELING WITH LABIAL APPLIANCES
Leveling techniques using conventional labial brackets and archwires have been widely
studied. A continuous archwire approach, such as the one described by Tweed (1966),
utilizes a single archwire that engages all of the mandibular teeth, often with a reverse
COS formed into its shape. This method has been shown to level the COS with a
tendency to do so by extrusion of mandibular premolars and molars, and less so by
intrusion of incisors (Dake and Sinclair, 1989; Weiland et al., 1996; Carcara et al., 2001;
Bernstein et al., 2007). The rationale behind these dental movements is that the
premolar and molar teeth experiencing extrusive forces encounter less resistance in
comparison to the incisor teeth experiencing intrusive forces directed into the bony
alveolar process. Therefore, although both extrusive and intrusive tooth movements
take place, the former tends to occur more readily.
In contrast, a labial non-continuous bracket and archwire approach has been shown to
produce leveling in a different matter. The utility arch method described by Ricketts
(1976) involves the use of a ‘bypass’ archwire; the wire is engaged only into the molar
and incisor brackets, and exhibits gingival step-down bends to extend across the
premolars and canines, by this means bypassing them. Somewhat similar, the
segmented arch method described by Burstone (1962, 1966, 1977) involves segmented
wires and an intrusion arch; a full archwire is segmented at some point between the
premolars and incisors on both sides, and the use of an auxiliary intrusion arch is
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inserted into the molar tubes, lies passively at a position apically to the incisor, but is
then forced to the incisor crown level and ligated to the incisor segment.
These non-continuous archwire approaches have been shown to level the occlusal plane
more so by incisor intrusion than by posterior extrusion (Dake and Sinclair, 1989;
Weiland et al., 1996). The key to this method is the avoidance of pitting the intrusion of
one tooth against the extrusion of its neighbour, as a continuous archwire would do,
since extrusive movements would dominate (Proffit, 2007). Instead, the strong posterior
tooth segments are separated from the smaller anterior tooth segment used as heavy
anchorage units for delivery of intrusive forces at the incisors (Burstone, 1977).
It is important to consider the additional effects of either technique. The extrusion of
posterior teeth found with the continuous archwire technique is often accompanied by a
downward and backward rotation of the mandible necessary to provide space for the
molars to erupt into (Figure 3) (Engel et al., 1980; Carcara et al., 2001). This may or may
not be a favourable effect depending on the patient’s initial vertical and horizontal
proportions. For example in a long faced individual or a patient with a pronounced Class
II malocclusion, downward and backward rotation of the mandible would worsen both
the face height proportions and the Class II severity. As for the non-
continuous/segmented archwire approach, while this method might prevent the down
and backward rotation of the mandible, it does carry with it alternative considerations,
such as a potential increased risk of external apical root resorption if appropriately light
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forces levels are exceeded (Weiland et al., 1996; Bernstein et al., 2007; Otto et al.,
1980; Dake & Sinclair, 1989; Weltmann et al., 2010).
Figure 3. Extrusion of molars and resultant downward and backward mandibular rotation (solid line = pre-treatment; dotted line = post-treatment)
Despite the method chosen, long term studies seem to suggest that leveling of the COS
is a relatively stable orthodontic movement, and when relapse does occur, it is usually
only minimal (Dake & Sinclair, 1989; Kinzel et al., 2002; Shannon & Nanda, 2004; Preston
et al., 2008).
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STUDY METHODS USED TO MEASURE THE COS
Since this investigation planned to evaluate occlusal plane leveling (along with a number
of other parameters) it is relevant to discuss the ways in which prior studies have gone
about describing and more importantly quantifying the COS.
Dating back to the original description of the curve, Spee himself directly examined the
dentitions of human archeological skulls and simply described the presence and
premises of the curve (Spee 1890). Other studies have also used human skulls to study
the curve of Spee in attempts to describe its form in prehistoric populations (Hitchcock,
1983), associate its depth with interproximal and occlusal attrition as well as third molar
impaction (Sengupta et al., 1999), relate its direction to the orientation of the masseter
muscle and therefore its contribution to crush/shear ratio of posterior molar tooth
function (Osborn, 1993).
In the field of orthodontics, it is often of more interest, and is altogether more practical,
to study the dentitions of living patients. Typically the COS has been measured outside
of the patient’s mouth using one of two methods: orthodontic study models, and/or
lateral cephalometric images (Baldridge et al., 1969; Sondhi et al., 1980; Bishara et al.,
(1989); Braun et al., 1996; Carter et al., 1998; Ferrario et al., 1999; Carcara et al., 2001;
De Praeter et al., 2002; Bernstein et al., 2007; Marshall et al., 2008; Ash et al., 2010).
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This allows for a more practical manner of examination as well as the collection of serial
records that can be compared over time.
Ferrario et al., (1999) utilized casts in their evaluation of the mandibular dental arch
curvature, and formulated a complex equation where the curvature of the occlusal
plane was modeled by a sphere, and the COS was expressed in reference to the radius
of that sphere.
A more simplified and common clinical method of quickly evaluating the COS using
study models is to lay the mandibular cast upside-down on a flat surface such that the
model would be tripoded on the most extruded molar cusps on the right and left sides
posteriorly and the most extruded incisor tip anteriorly (Braun et al., 1996). From here,
the depth of the curve can then merely ranked in severity (mild/moderate/severe) or
precisely measured.
A modification of this method has been to upright the mandibular model, and whether
from the model directly or the a sagittal photograph of the model, draw an imaginary
line (the “COS line”) from the molar cusp of choice to the most extruded incisor tip and
then quantify the curve (Marshall et al., 2008). Baldridge et al., (1969) quantified the
COS by expressing the sum of the perpendicular distances from the most intruded
premolar to the COS line of both the right and left sides. Sondhi et al., (1980) calculated
the sum of all of the perpendicular distances of each cusp tip in the mandibular arch to
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the COS line, while Bishara et al., (1989) considered the average of the sum of the
perpendicular distances. Braun et al., (1996) used the sum of the only the greatest
perpendicular distances of both sides. However the most common method amongst the
literature and also the most practical method used in day-to-day clinical diagnostic case
workups appears to have been the quantification method used by Carter and
McNamara (1998), Carcara et al., (2001), Marshall et al. (2008), and Ash and Wheeler
(2010), where greatest perpendicular distance on each the left side and right side were
recorded and averaged.
Figure 4. Common method for measuring COS depth from orthodontic casts
Traditionally (and still currently), COS measurements have been made on orthodontic
casts using a ruler or electronic caliper. Some recent studies have utilized sophisticated
tools such as the push dial indicator (L.S. Starrett, Athol, Mass), an engineering
instrument capable of measuring to ten-thousandths of an inch (Shannon and Nanda,
2004), or virtual 3D models supplemented by software programs dedicated to
performing a wide array of measurements (Cheon et al., 2008).
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Evaluation of the COS has also taken place with the use of lateral cephalometric
radiographs. The same principles apply, where some form of a COS line joining a molar
cusp and incisor tip is used as a reference plane and the distance to the most intruded
premolar is measured either by a ruler on a plain film, or by a computer software
program on a digital film (Bernstein et al., 2007). To ensure the accuracy of the lateral
cephalometric method to evaluate the COS depth, Bernstein et al., 2007 compared the
COS measurements obtained from dental models versus the COS measurements
obtained from lateral cephalograms for 31 subjects at three separate time intervals.
Statistical analysis showed that there were no significant differences (p <0.01) between
the COS measurements recorded from the two different methods.
The use of lateral cephalograms to measure the COS allows simplification of most study
methods, including the design to follow in this paper. Previously, a number of studies
have gone about quantifying the COS and documented how it changes following growth
or orthodontic therapy by measuring dental casts from different time points (Dake et al.,
1989; Weiland et al., 1996; Preston et al., 2001; De Praeter et al., 2002; Marshall et al.,
2008). But it was also necessary to collect lateral cephalometric radiographs in order to
reveal the specific dental movements that took place, such as intrusion, extrusion,
proclination, etc. The ability to measure all of these variables on a single patient record,
the lateral cephalogram, facilitates easy record collection, and simplifies the overall
measurement process (Bernstein et al., 2007).
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When comparing raw COS measurements from study to study, it is important to take
into consideration the exact teeth and more specifically the cusps used as reference
points used to create the so called “COS line” and the point used to indicate the curve’s
depth. For example, if the COS line is considered to be a line connecting the most
extruded central incisor and the distobuccal cusp of the 2nd molar, versus the incisor
with the mesiobuccal cusp of the 1st molar, it might be expected that the COS would
appear more excessive using the former reference points.
Figure 5. Difference in COS measurements depending on reference points used for the COS line.
The same type of effect would be seen if the depth of the COS is measured from the
cusp tip of the first premolar versus the second premolar versus the premolar judged as
most intruded. While these factors would certainly affect the COS measurement at any
cross-sectional time period, they would have less effect on the change in the COS
measurement from one time point to another, which is arguably the more relevant
observation in most instances.
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DEMAND FOR ESTHETIC APPLIANCES
The number of adults seeking orthodontic treatment has considerably increased (and
continues to increase) over the last 30 years. From the years 1970 to 2003, the
percentage of patients identified as adults among orthodontic practices in the United
States has increased by 800%, with a ratio of approximately 1 in 5 patients being adults
(Keim et al., 2003). The growing interest in adult orthodontics can be attributed to a
number of factors: the improvement in the esthetics of appliances, advances in
orthognathic surgical procedures, development of intra-arch anchorage devices such as
miniscrews and bone plates, multidisciplinary collaboration of dental specialties, and an
overall increase in social acceptance of adult orthodontics (Graber et al., 2005). With the
number of adult orthodontic patients on the rise, there has been an evident increase in
the demand for esthetic appliances such as invisible aligners or lingual brackets and
archwires. Although transparent aligners have gained a tremendous amount of
attention, they do not come without inherent limitations. Complex malocclusions,
including those with crowding or spacing greater than 5 mm, skeletal anterior-posterior
discrepancies greater than 2 mm, severe rotations or tipping, open bites, extruded
teeth, short clinical crowns, and arches with multiple missing teeth, are all conditions
that may be considered as “too difficult” or even “contraindicated” for treatment with
Invisalign, a transparent appliance widely used today (Phan, 2007).
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LINGUAL ORTHODONTICS
Considerably different from transparent aligners, certain lingual orthodontic systems
have been reported to be capable of treating even the most complicated of
malocclusions. It is said that some lingual appliances are proficient at treating any
malocclusion that a labial appliance would be capable of correcting, and the result is of
comparable success (Smith et al, 1986; Fulmer and Kuftinec, 1989; Hong et al., 2000;
Kyung, 2006; Wiechmann et al., 2008; Wiechmann et al., 2010).
When the lingual orthodontic treatment technique was introduced in the late 1970’s,
the idea was thrilling to both orthodontists and patients alike that orthodontic therapy
could be carried out with nearly invisible (hidden) brackets and little reliance on patient
compliance (given the fact that it is a bonded appliance) (Fujita, 1979; Alexander et al.,
1982). However, the technique initially presented many challenges, such as increased
time spent due to more difficult bracket and archwire application, biomechanical issues
related to smaller inter-bracket distances, and patient comfort issues due to appliance
impingement on the sensitive tongue space (Diedrich, 1984; Wiechmann, 1999;
Wiechmann et al., 2008). Recent laboratory and clinical developments have overcome
many of these challenges leading to the increase in popularity of the lingual technique
by orthodontists and more importantly to the production of successful case results.
These cases include those involving extraction, non-extraction, Class II functional
correctors, auxillary use of miniscrews, and even those treated with orthognathic
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surgery (Smith et al., 1986; Fulmer and Kuftinec, 1989; Hong et al., 2000; Kyung, 2006;
Wiechmann et al., 2008; Wiechmann et al., 2010).
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INCOGNITOTM
TOP-Service fur Lingualtechnik GmbH is a company from Germany founded in 1997
which has become one the leading providers of lingual orthodontic therapy. Led by Dr.
Dirk Wiechmann, the company developed the iBracesTM lingual orthodontic system,
later renamed IncognitoTM which utilizes completely customized brackets and archwires
(Wiechmann, 2002; Wiechmann 2003).
While the trend for labial orthodontics has been in the direction of pre-fabricated
straightwire appliances with fully pre-prescribed bracket slot and base morphologies,
the philosophy behind the fabrication of the innovative IncognitoTM lingual orthodontic
system is quite the opposite (Andrews, 1976; Wiechmann, 2002).
In regards to the bracket, extensive individualization of the bracket base was seen to be
absolutely essential from the viewpoint of the manufacturers, due to the wide variability
in lingual tooth surface anatomy from patient to patient, but also within a single patient
from tooth to tooth (Wiechmann, 1999a; Wiechmann, 2002; Wiechmann et al., 2003).
The archwire itself was also determined to require extensive customization. Because
each lingual bracket is designed to have the lowest profile possible and thus the greatest
patient comfort, the distance from the bracket slot to the labial surface differs from
tooth to tooth, with the greatest difference occurring between the canine and premolar.
21
To accommodate these discrepancies the archwire is fabricated to incorporate
customized 1st order bends (Wiechmann, 1999b).
The clinical, laboratory, and technological procedures involved in the IncognitoTM lingual
system can be described as follows: The orthodontist is responsible for taking a two-
phase silicone impression of the arch(es) to be treated which is then sent to an
IncognitoTM laboratory (Wiechmann, 2002). Two sets of plaster casts are poured, one
which will remain as the malocclusion model and the other which will be used to
carefully create a wax set-up of the targeted outcome (Wiechmann 1999; Wiechmann
2002). The wax set-up prediction model is digitized with a high-resolution 3-D scanner
(GOM, Braunschweig, Germany) transforming it into a virtual model. A computer
software program called the Professional Transfer Optimised Positioning System (TOP
Service/3M Unitek, Monrovia, CA, USA) is used to generate a customized virtual bracket
base on the lingual surface of each tooth followed by optimal bracket body positioning.
A high-precision prototyping machine (Materialise, Leuven, Belgium) transforms these
virtual brackets into wax analogs that are then cast in a high-gold alloy. The final
brackets are set on the malocclusion model with a water-soluble bonding agent, and a
two-phase bonding tray is created to facilitate an indirect bonding technique by the
orthodontist (Wiechmann et al., 2003). A series of archwires are custom bent to
incorporate highly complex geometries by bending robots developed by the Orthomate
system (Orametrix, Dallas, TX, USA). The wire sequence is designed to progress in a
manner similar to labial orthodontics, first achieving aligning and leveling, then space
22
closure if required, and finally finishing (Wiechmann, 1999a). The bends delivered to the
wires are calculated in such a way to incrementally reposition teeth from the original
malocclusion to the positions predicted during the wax set-up stage.
23
EXCESSIVE COS, DEEP OB and INCOGNITOTM
It is theorized that treatment with the IncognitoTM lingual orthodontic bracket-archwire
system might be particularly effective at leveling of an exaggerated COS and reducing a
deep OB, primarily by true incisor intrusion, for the following reasons:
1. The lingual position of the brackets on the maxillary incisors simulates an
anterior bite plane or turbo effect, should the mandibular incisors prematurely
contact the maxillary incisor brackets during bite closing. This interference would
create intrusive forces directed against both the maxillary and mandibular
incisors, and as a result would be expected to encourage the anterior teeth to
intrude (Fujita et al., 1980; Smith et al., 1986; Hong et al., 2001). These effects
would contribute to both COS leveling and OB reduction.
2. The lingual position of the bracket and archwire allocates the point of application
of force delivered by the appliance at only a short distance away from the center
of resistance of the incisors. Therefore, if an intrusive force was applied to
incisors of a normal or slightly proclined inclination, the teeth would be expected
to experience more true intrusion and less of a tendency to procline. In contrast,
an intrusive force directed through a labial bracket that is located at a greater
distance to the center of resistance, would result in the production of a
biomechanical moment and a tendency to procline, rather than truly intrude
24
(Proffit, 2007). Although relative intrusion from proclination may still contribute
to COS leveling and OB correction, there are often cases where true incisor
intrusion may be more desirable.
Therefore, in contrast to a continuous labial archwire which has been shown to level the
COS via greater posterior dental extrusion and lesser anterior dental intrusion (Dake and
Sinclair, 1989; Weiland et al., 1996; Bernstein et al., 2007), a continuous lingual
IncognitoTM archwire would be hypothesized to achieve leveling via greater anterior
intrusion and lesser posterior extrusion.
The above rationale also includes the expectation that only a limited degree of incisor
proclination would ensue, and there would be little-to-no effect of mandibular jaw
rotation given limited posterior dental extrusion.
However, there exists a number of patient or treatment variables that could potentially
alter these expected outcomes. For example, the use of posterior bite opening prop
would have added an intrusive force to the molars, thereby lessening the amount of
molar extrusion, but at the same time it would reduce the anterior bite block/turbo
effect of the incisor brackets, thereby lessening the amount of true incisor intrusion.
Contrastingly, the use of posterior interarch elastics would add an extrusive force to the
molars, thereby enhancing the amount of molar extrusion. Hypodivergent,
brachycephalic type growers (those with small ratios of upper to lower face heights,
25
typically exhibiting strong masticatory musculature) might have a natural intrusive effect
on the molars due to strong bite forces, thereby lessening the amount of molar
extrusion (Bell et al., 1984; McDowell & Baker, 1991). And finally, crowded dentitions
might be expected to experience a greater amount of extrusive dental movements and
proclination as a means to gain space required for leveling (Baldridge et al., 1969;
Germane et al., 1992).
26
LEVELING WITH LINGUAL APPLIANCES
After thorough review of the existing literature, only a single study could be identified
that has investigated occlusal plane leveling using a lingual bracket system and archwire.
This study by Hong et al. (2001) examined the effect of a reverse curve lingual archwire
on the incisors and molars in the mandibular dentition during the initial stage of leveling
in subjects with a deep OB. Subjects were treated with the pre-fabricated Fujita bracket
mushroom archwire appliance (Fujita, 1982), one of the earliest lingual orthodontic
systems. The results showed that the continuous lingual archwire did in fact produce a
greater amount of incisor intrusion than molar extrusion to accomplish occlusal plane
leveling, in accordance with the hypothesis of this very manuscript. However, a
noteworthy limitation of the study was that it included a sample size of only 8 subjects.
Nonetheless, the investigation is the only existing evidence contributing to the current
body of knowledge related to leveling and OB correction with lingual appliances.
27
III. PURPOSE
The purpose of this retrospective radiographic analysis was:
1. To determine if the plane of occlusion was leveled and the incisor vertical
overlap was reduced in this sample of adult subjects with a deep OB and an
excessive COS treated with IncognitoTM.
2. To examine the dental movements and other maxillo-mandibular changes that
contributed to occlusal plane leveling and incisor overlap reduction in this
sample of adult subjects with a deep OB and an excessive COS treated with
IncognitoTM.
3. To compare the relative amounts of incisor intrusion versus premolar and molar
extrusion in this sample of adult subjects with a deep OB and an excessive COS
treated with IncognitoTM.
28
IV. HYPOTHESES
(H1): Significant differences exist between the pre- and post-treatment lateral
cephalometric measurements for the COS depth, OB, and other variables selected for
evaluation in this sample of adult subjects with a deep OB and an excessive COS treated
with IncognitoTM.
(H01): No significant differences exist between the pre-treatment and post-treatment
lateral cephalometric measurements for the COS depth, OB, and other variables
selected for evaluation in this sample of adult subjects with a deep OB and an excessive
COS treated with IncognitoTM.
(H2): Significant differences exist between the amount of incisor intrusion and
premolar/molar extrusion calculated from pre- to post-treatment cephalometric
measurements in this sample of adult subjects with a deep OB and an excessive COS
treated with IncognitoTM.
(H02): No significant differences exist between the amount of incisor intrusion and
premolar/molar extrusion calculated from pre- to post-treatment cephalometric
measurements in this sample of adult subjects with a deep OB and an excessive COS
treated with IncognitoTM.
29
V. MATERIALS AND METHODS
SAMPLE
The sample of patient was collected from a number of orthodontists across North
America. A list of known IncognitoTM providers were emailed by the investigator, given
a brief explanation of the proposed investigation, and were welcomed to contribute one
or more sets of radiographic records belonging to patients of their offices who satisfied
the inclusion criteria for the study at hand. Cases qualifying as suitable included patients
who fit the following criteria:
Full maxillary and mandibular orthodontic treatment with IncognitoTM
Pre-treatment overbite of at least 50%
Pre-treatment COS of at least 1.5 mm
Non-growing
Treated non-extraction
Good quality pre-treatment and post-treatment cephalometric radiographs
Of the 21 orthodontists contacted, all responded to the email, but only 5 were able to
contribute cases. In total, 69 cases were initially collected; 46 from Dr. Neil Warshawsky
(Chicago, Illinois), 11 from Dr. David Hime (Austin, Texas), 6 from Dr. Hilton Goldreich
(Plano, Texas), 5 from Dr. Leslie Pitner (Columbia, South Carolina) and 1 from Dr. Neal
Kravitz (South Riding, Virginia).
30
ETHICS
All patients included in the study had given consent to the treating orthodontist for the
release of their records to be used for research purposes prior to initiating treatment.
Patient information such as name, gender, date of birth, limited treatment notes, as
well as specific radiographic records were made available only to the primary
investigator, who ensured that all patient identifiable factors were, from that point
onwards, concealed and protected for the privacy of the patients. Ethics approval was
obtained from the University of Toronto Health Sciences Research Ethics Board (REB) for
the undertaking of this study.
31
RECORDS
For each case, a pre- and post-treatment lateral cephalometric radiograph was
submitted. The orthodontists were also asked to provide some specific information
pertaining to the individual patient and treatment procedures by completing a short
questionnaire [See Appendix 3].
After closer examination of the images, 35 cases were excluded from the study by the
investigator. The most common reason for exclusion was lack of a means for calibration
of a pre- or post-treatment radiograph. Other causes for exclusion included poor image
quality, improper head positioning, gross anatomical asymmetries, and presence of
dental implants. This resulted in a remainder of 34 cases in total for the investigation.
Majority of the cephalograms were submitted as digital radiographs in a JPEG file
format. However, in some instances, a case was submitted with a pre-treatment digital
lateral cephalometric radiograph, but a post-treatment cone beam computed
tomography (CBCT) acquisition in a DICOM file format (or vice versa: pre-treatment
CBCT and post-treatment digital cephalogram). These CBCT files required reformatting,
which was accomplished using Dolphin Imaging v11.3 (Patterson Dental Supply Inc,
Chatsworth CA, USA) in order to transform the three-dimensional data into two-
dimensional images that closely resembled conventional lateral cephalometric
32
radiographs. Two important steps in the reformatting process included orientation of
the skull to a standard head position, and selection of the x-ray beam projection path:
1. Image Orientation:
a. Coronal plane: adjusted such that it runs through the external auditory
meatus (as would the ear rods in a conventional cephalogram)
b. Horizonal plane: adjusted to run through the Frankfort Horizontal Plane,
Porion – Orbitale (as a patient would be asked to posture for a conventional
lateral cephalogram)
c. Axial plane: adjusted to run through the midsagittal structures including
Sella, Nasion and Anterior Nasal Spine (to ensure accurate magnification at
the midline structures)
Figure 6. CBCT Orientation Planes
33
2. X-ray beam Projection - Orthogonal vs Perspective:
Dolphin 3D provides the tools to build two-dimensional (2D) x-ray images
with the option of simulating either an orthogonal x-ray beam projection or a
perspective x-ray beam projection. In an orthogonal projection, lines are
projected in a parallel manner through the skull, resulting in a 2D image with
0% magnification. Whereas in a perspective projection, lines are projected in
a slightly divergent manner, similar to the path of a typical x-ray beam, and
thereby resulting in an 2D image with a default magnification of 9.7%. Since
the reformatted CBCTs were to be compared to conventional cephalograms,
the perspective projection was selected in order to make the two images
more similar and thus more comparable.
Figure 7. CBCT X-ray beam projection options
34
LATERAL CEPHALOMETRIC ANALYSIS
All 68 cephalometric images were then uploaded to Dentofacial Planner (DFP) v.9 beta
(Dentofacial Research Inc., Toronto ON, Canada). The DFP program designer created a
customized tracing sequence and cephalometric analysis that included landmarks and
measurements specifically relevant to this study. All cephalometric images were traced
in random order by the investigator in order to avoid bias.
The landmarks identified for each cephalogram included:
N: Nasion
Or: Orbitale
PNS: Posterior nasal spine
ANS: Anterior nasal spine
A: “A” point
U1: Incisal tip of most extruded maxillary incisor
U1c: Centroid of most extruded maxillary incisor
U6: Mesial cusp tip of maxillary first molar
L1: Incisal tip of most extruded mandibular incisor
L1c: Centroid of most extruded mandibular incisor
L4: Cusp tip of mandibular first premolar
L6: Mesial cusp tip of mandibular first molar
B: “B” point
35
Gn: Gnathion
Me: Menton
Go: Gonion
Po: Porion
Ba: Basion
S: Sella
[See Appendix 2: Lateral Cephalometric Landmark Definitions]
Figure 8. Lateral cephalometric landmarks identified
36
The planes utilized for the analysis included:
SN: Cranial Base Plane (S to N)
FH: Frankfort Horizontal Plane (Po to Or)
PP: Palatal Plane (ANS to PNS)
COS plane: Curve of Spee Plane (L6 to L1)
MP: Mandibular Plane (Go to Gn)
Figure 9. Lateral cephalometric planes utilized
37
An entire list of measurements recorded in the DFP analysis included:
SNA (o): angle between points Sella to Nasion to A Point
SNB (o): angle between points Sella to Nasion to B Point
ANB (o): angle between points A Point to Nasion to B Point
Y-axis (o): angle between Frankfort Horizontal Plane and Sella to Gnathion line
SN to PP (o): angle between Cranial Base Plane and Palatal Plane
SN to MP (o): angle between Cranial Base Plane and Mandibular Plane
FHR: ratio of upper face height (Na-ANS) to lower face height (ANS-Me)
U1 to PP (o): angle between maxillary incisor long axis to Palatal Plane
U1 to PP (mm): distance from maxillary incisor tip perpendicular to Palatal Plane
U1c to PP (mm): distance from maxillary incisor centroid perpendicular to
Mandibular Plane
U6 to PP (o): angle between maxillary first molar long axis (determined as the
perpendicular to a tangent line connecting the mesiobuccal and distobuccal cusp
tips) to Palatal Plane
U6 to PP (mm): distance from maxillary first molar mesiobuccal cuspt tip
perpendicular to Palatal Plane
*L1 to MP (o): angle between mandibular incisor long axis to Mandibular Plane
*L1 to MP (mm): distance between mandibular incisor tip perpendicular to
Mandibular Plane
*L1c to MP (mm): distance between mandibular incisor centroid perpendicular
to Mandibular Plane
38
L6 to MP (o): angle between mandibular first molar long axis (determined as the
perpendicular to a tangent line connecting mesiobuccal and distobuccal cusp
tips) to Mandibular Plane
*L6 to MP (mm): distance from mandibular first molar mesiobuccal cusp tip
perpendicular to Mandibular Plane
*L4 to MP (mm): distance between mandibular first premolar cusp tip
perpendicular to Mandibular Plane
*L4 to COS (mm): depth of the COS; distance from mandibular first premolar
cusp tip perpendicular to COS line
OB (mm): difference in the distance between U1 perpendicular to PP (mm) and
L1 perpendicular to PP (mm)
S-N (mm): distance from Sella to Nasion
S-Ba (mm): distance from Sella to Basion
UFH (mm): distance from Nasion to Anterior Nasal Spine
LFH (mm): distance from Anterior Nasal Spine to Menton
*Measurements relevant to COS leveling, demonstrated in figure below.
39
Figure 10. Measurements used to determine COS Leveling
40
Success of COS Leveling
Any change in the excessive COS in this sample treated with IncognitoTM was examined
by comparing the pre- and post-treatment COS depth measurements. COS depth was
obtained by measuring the linear distance from the mandibular first premolar cusp tip
perpendicular to the COS line [L4 to COS line (mm)].
A decrease of COS depth would indicate leveling of the occlusal plane.
Success of OB Correction
Any change in the deep OB relationship in this sample treated with IncogitoTM was
examined by comparing the pre- and post-treatment incisal overlap. Incisal overlap was
obtained by calculating the difference between the distance of maxillary incisor tip
perpendicular to Palatal Plane, and the distance of the mandibular incisor tip
perpendicular to the Palatal Plane [OB (mm)].
A decrease of incisal overlap would indicate a reduction of the deep OB.
41
Dental Movements Contributing to COS Leveling and OB correction
Mandible:
Intrusion/Extrusion
The vertical, or intrusive/extrusive dental movements produced by IncognitoTM that may
have contributed to leveling of the COS were determined by comparing pre- and post-
treatment linear distances from the mandibular first molar mesial cusp tip [L6 to MP
(mm)], first premolar cusp tip [L4 to MP (mm)], and lower incisor centroid [L1c to MP
(mm)], perpendicular to the Mandibular Plane.
A decrease in the measurement L1c to MP (mm) would indicate mandibular
incisor intrusion.
An increase in the measurement L4 to MP (mm) would indicate mandibular
premolar extrusion.
An increase in the measurement L6 to MP (mm) would indicate mandibular
molar extrusion.
42
Relative Intrusion/Extrusion
The tipping, or relative intrusive/extrusive dental movements that may have contributed
to COS leveling by IncognitoTM were determined by comparing pre- and post-treatment
measurement of the the mandibular incisor angulation to the Mandibular Plane [L1 to
MP (o)] as well as the mandibular molar angulation to the Mandibular Plane [L6 to
MP(o)].
An increase in the measurement L1 to MP (o) would indicate mandibular incisor
proclination.
A decrease in the measurement L6 to MP (o) would indicate mandibular molar
distal tipping.
43
Maxilla:
Similar maxillary intrusive/extrusive and relative intrusive/extrusive dental movements
of the incisor and molar were also taken into account in order to complement the
findings observed in the mandibular dental arch. They were important to take into
consideration as they may have contributed to overbite correction, leveling and also
potentially mandibular jaw rotation.
A decrease in the measurement U1c to PP (mm) would indicate maxillary incisor
intrusion.
An increase in the measurement U6 to PP (mm) would indicate maxillary
extrusion.
An increase in the measurement U1 to PP (o) would indicate maxillary incisor
proclination.
A decrease in the measurement U6 to PP (o) would indicate maxillary molar distal
tipping.
44
Mandibular Rotation
Mandibular rotation, a common side effect of molar extrusion, was examined by
comparing the pre- and post-treatment angles of Sella-Nasion to Mandibular Plane [SN
to MP(o)], Frankfort Horizontal to Sella-Pogonion [Y-axis (0)], as well as the face height
ratio [FHR; (N-ANS/ANS-Me)]
An increase in SN to MP (o), Y-axis (0), and/or a decrease in the FHR would be
indicative of downward and backward rotation of the mandible.
45
CEPHALOMETRIC IMAGE CALIBRATION
Because lateral cephalograms were be obtained from a number of different orthodontic
offices using a number of different radiographic machines to acquire the images, proper
calibration of the images was an essential step in the process in order to be able to
accurately compare the linear measurements between patients and in some cases
within the same patient. In most instances, a midsagittal millimetric scale was available
on the image. The DFP program designer created a custom tool that made it possible
calibrate the images. The tool allowed for the user to select two points on the image
midsagittal scale and then indicate the known distance between them. Following this
step, all linear measurements were automatically deduced relative to that distance.
With this method in place, the various magnification factors inherent to different
radiographic machines could be considered negligible.
In some cases, only one of the pre- or the post-treatment images had a millimetric scale
available for calibration. In these instances the Sella (S) and Nasion (N) landmarks were
used as the two points for the calibration tool, and the known distance between them
was obtained from the stable S-N measurement on the image of that patient which did
include a millimetric scale. The anatomical position of sella turcica has been shown to
remain quite stable following the completion of growth, and in addition it has been
shown to be reliably detectable (Bjork, 1955; Ford, 1958; Scott, 1970; van der Linden,
1971; Baumrind and Frantz, 1971). It is for this reason that it is used in the majority of
46
cephalometric analyses for registration of superimposition. Although Nasion has shown
some instability during growth but only to a much smaller extent during adulthood (Arat
et al., 2010), it was assumed that in the relatively short period of time between bonding
and debonding of IncognitoTM, the distance between S and N would be reasonably
stable, mainly supported by the fact that the subjects included in this study were all
non-growing adults.
To confirm the stability of the all of these measurements within the sample, S-N (as well
as S-Ba) measurements were compared from pre- to post-treatment for the 21 patients
that did include midsagittal scales on both cephalograms.
No significant difference in these measurements from pre- to post-treatment
would indicate that S-N and S-Ba are stable over the duration of time of
IncognitoTM therapy in this sample and therefore reliable to use for calibration.
To further validate the use of the S-N measurement for calibration, when the known S-N
distance was input for a cephalogram with a missing scale, the resulting output
measurement for S-Ba was crosschecked with the S-Ba measurement obtained from the
cephalogram that did have a scale.
Agreement in the pre- and post-treatment S-Ba measurements for the 13 cases
with one missing scale would indicate that calibration using the S-N
measurement was accurate and reliable.
47
STATISTICS
All lateral cephalometric measurements were entered into Microsoft Excel. Averages
for pre- and post-treatment measurements, as well as the individual changes and
average changes from pre-to post-treatment measurements were determined. Paired t-
tests were conducted to determine if the changes in these cephalometric
measurements experienced during treatment with IncognitoTM were significant.
To ensure normality of the data and support the use of parametric statistical tests, all
pre-treatment measurements as well as the calculated differences from pre- to post-
treatment were entered into SPSS Statistics Version 20 (IBM Corporation, 2011) and
histograms were created and examined.
Because the sample size was not large enough to run more complex statistical tests
commonly used to reveal associations or the effects of potentially confounding factors,
visual box plots were created to at least allow the possibility of making some inferences.
Intra-examiner and inter-examiner reproducibility cephalometric measurements was
examined by having the primary investigator as well as another orthodontist digitally re-
trace 20 randomly selected cephalograms from the sample at a date approximately
three months after the initial tracing and measurements were originally carried out.
48
Then statistical error tests were performed to compare the agreement between original
and repeated measurements.
The intraclass correlation coefficient (ICC) was determined using computations
output from SPSS. In general, the ICC reflects the ratio of two variances: the
variance due to the measured subjects (2), divided by the variance due to the
subjects (2) plus the variance due to the investigator (
2). The formula for the
ICC can therefore be expressed as:
The Dahlberg statistic was determined using Microsoft Excel. This measure of the
error variance is commonly used in orthodontic investigations, and therefore is
important to include in this study for means of comparison with other similar
studies (Houston, 1983; Battagal, 1993). Replicate measurements for each
cephalogram are compared and the standard deviation of each of the paired
measurements from its pair mean are calculated from the following formula:
where Se is the standard deviation of the differences of each of the replicates
from its mean; n is the number of radiographs recorded; and d is the difference
between the first and second recordings (Battagel, 1993).
49
To ensure the accuracy of the S-N measurement as a means for calibration for the 13
cephalograms lacking a millimetric scale, paired t-tests were performed on the sample
of 21 subjects for the measurements S-N and S-Ba to detect if any changes occurred
over the treatment period.
If no significant difference was found, then S-N and S-Ba were considered stable,
and any small difference actually found can be attributed to minor landmark
identification error.
With this having been the case, absolute differences and standard deviations for these
measurements were calculated to serve as a guide to outline the extent of error that
would be considered acceptable when comparing the measurements between partner
cephalograms.
Ie. If the average measurement for S-Ba in the sample of 21 subjects with scales
on both pre- and post-treatment cephalograms was overshot by mm (+ mm)
or undershot by mm (- mm), then the average error would be equal to|
mm| amount of standard deviation. Therefore when a cephalogram with a
missing scale was calibrated using the known S-N from its partner cephalogram,
the resulting output measurement for S-Ba had to be within mm + of the S-Ba
measurement on its partner cephalogram. Only one standard deviation was
selected in order to restrict the allowable error to the smallest reasonable
amount.
50
VI. RESULTS
SUCCESS OF COS LEVELING
Table 1. Change in depth of COS from pre- to post-treatment and significance from paired t-test.
The average depth of the COS in this sample treated with IncognitoTM at pre- and post-
treatment was 1.78 mm (SD: 0.36 mm, range: 1.50 to 2.90 mm) and 0.37 mm (SD: 0.41
mm, range: -0.30 to 1.00 mm) respectively, demonstrating an average amount reduction
of -1.41 mm (SD: 0.49 mm, range: 0.60 to 3.00 mm), or 79%. This change in COS depth
was found to be highly statistically significant (p<0.001) and reflected a substantial
amount of occlusal plane leveling.
Figure 11. Depth of COS at pre- and post-treatment
51
SUCCESS OF OB REDUCTION
Table 2. Change in OB from pre- to post-treatment and significance from paired t-test
The average incisal overlap in this sample treated with IncognitoTM at pre- and post-
treatment was 5.80 mm (SD: 1.26 mm, range: 4.00 to 8.70 mm) and 2.91 mm (SD: 0.86
mm, range: 1.00 to 5.00 mm) respectively, equating to an average amount of OB reduc
tion of -2.89 mm (SD: 1.27 mm, range: -5.40 to -0.9 mm). This change was found to be
statistically significant (p<0.001) and reflected a substantial improvement in the anterior
OB relationship.
Figure 12. OB at pre-treatment and post-treatment
52
DENTAL MOVEMENTS CONTRIBUTING TO COS LEVELING AND OB REDUCTION
Mandible:
Intrusion vs. Extrusion
Table 3. Changes in mandibular incisor, premolar and molar distances to Mandibular Plane from pre- to post-treatment and significance from paired t-tests
The mandibular incisor, measured from the centroid, demonstrated an average intrusion
of -0.92 mm (SD: 0.87, range: -2.60 to 0.80 mm) which was found to be statistically
significant (p<0.001). Only 3 patients in the entire sample exhibited the opposite effect
of extrusion.
The mandibular first premolar showed an average extrusion of 0.85 mm (SD: 0.91 mm,
range: -0.70 to 3.30 mm) which was statistically significant (p<0.001).
The mandibular first molar demonstrated an average extrusion of 0.50 mm (SD: 0.89
mm, range: -1.10 to 2.90 mm) which was found to be statistically significant (p<0.05).
However, 9/34 cases actually experienced intrusion at this site.
53
Figure 13. Mandibular incisor, premolar and molar distances to Mandibular Plane at pre- and post-treatment
Table 4. Differences in mandibular incisor intrusion versus premolar and molar extrusion and significance from paired t-tests
The mean difference between mandibular incisor intrusion at the centroid and
mandibular premolar and molar extrusion was 0.07 mm (SD: 1.48, range: -2.50 to 3.10
mm) and 0.42 mm (SD: 1.40, -2.70 to 3.60 mm) respectively. Both of these differences
were found to be highly variable, and neither were statistically significant.
54
Relative Intrusion vs. Relative Extrusion
Table 5. Changes in mandibular incisor and molar mean inclination relative to Mandibular Plane from pre- to post-treatment and significance from paired t-tests
The mandibular incisor demonstrated an average degree of proclination of 6.86O (SD:
5.51O, range: -4.9 to 17.3O) which was significant (p<0.001), but highly variable. Only 4
cases experienced retroclination.
The mandibular molar showed an average distal tipping of -1.20O (SD: 2.66O; range: -6.6
to 4.5O) which was significant (p <0.05), but highly variable.
55
Maxilla:
Intrusion vs. Extrusion
Table 6. Changes in maxillary incisor and molar mean distances to Palatal Plane from pre- to post-treatment and significance from paired t-tests
The maxillary incisor, measured from the centroid, demonstrated an average intrusion
of 0.09 mm (SD: 0.99, range: -1.90 to 1.8 mm), which was not statistically significant,
and highly variable.
The maxillary molar demonstrated an average extrusion of 0.19 mm (SD: 1.06 mm,
range: -0.80 to 1.30 mm), which was not statistically significant.
56
Relative Intrusion vs. Relative Extrusion
Table 7. Changes in maxillary incisor and molar mean inclination relative to Palatal Plane from pre- to post-treatment and significance from paired t-tests
The maxillary incisor showed an average proclination of 2.61O (SD: 5.82O, range: -13.4 to
15.2O, p<0.05) which was statistically significant, yet extremely variable.
The maxillary molar showed an average degree of mesial tipping of only 0.42O (SD:
2.92O, range: -5.1 to 7.8O) which was not statistically significant, but highly variable.
Figure 14. Inclination of maxillary and mandibular incisors at pre- and post-treatment
57
MANDIBULAR ROTATION
Table 8. Changes in Y-axis angle, Mandibular Plane angle, and Face Height Ratio from pre- to post-treatment and significance from paired t-tests
The Y-axis angle measured at pre-treatment had a mean value of 56.5O (SD: 3.85, range:
49.6 to 68.9O). This angle showed a small but statistically significant increase after
treatment of 0.48O (SD: 1.05O, range: -2.7 to 2.2O, p<0.05).
The Cranial Base Plane (S-N) to Mandibular Plane (Go-Gn) angle measured at pre-
treatment had an average value of 27.3O (SD: 5.19O, range: 19.1 to 36.8O). This angle
also showed a small but statistically significant increase after treatment of 0.52O on
average (SD: 1.12O, range: -1.5 to 3.7O, p<0.05).
The Face Height Ratio (N-ANS/ANS-Me) measured at pre-treatment was an average of
0.82 (SD: 0.06, range: 0.70 to 0.99). Following treatment, the ratio demonstrated a small
but statistically significant decrease of -0.01 on average (SD: 0.02, range: -0.04 to 0.04,
p<0.01).
58
All of the above findings suggest that some degree of mandibular rotation was
experienced, with the average subject demonstrating rotation in a downward and
backward direction.
59
OTHER CEPHALOMETRIC MEASUREMENTS
Table 9. Changes in angles SNA, SNB, and ANB from pre- to post-treatment and significance from paired t-tests
No statistically significant differences were calculated from pre- to post-treatment for
the following cephalometric measurements investigated (but not already mentioned) in
this study: SNA (O), SNB (O), ANB (O).
60
POTENTIALLY CONFOUNDING FACTORS
Table 10. Tabulation of several potential confounding patient/treatment factors
Further, more complex statistical analyses could not be performed to uncover the
potential effects of several additional patient and/or treatment factors mentioned
above. This is due to the fact that the sample size was not large enough to permit
reliable analysis using appropriate statistical tests.
However, it was possible to make some inferences about the effect of some of these
factors with the use of visual box plots. Since all of the subjects presented with crowding
and only a small percentage (20% of the sample) were considered to be of the
hypodivergent facial category, the effect of just the remaining two factors: use of a
posterior bite opening prop and use of posterior inter-arch elastics, were examined.
(NB. A posterior bite opening prop was considered to be any removable or fixed
auxillary device used in the posterior dentition such as a posterior bite block, occlusal
build-ups, IncognitoTM bracket enhanced occlusal bite pads, etc. Posterior inter-arch
61
elastics were considered to be any use of inter-arch elastics that included mandibular
molar or premolar teeth that extended to any maxillary teeth).
Figure 15. Effects of posterior inter-arch elastics and posterior bite opening props on mandibular first molar extrusion
The box plot shown above demonstrates the effects of the two variables on the
mandibular molar. In subjects who wore elastics (EL+) but did not use a posterior bite
opening prop (PBB-), the greatest amount of mean molar extrusion occurred.
Contrastingly, in subjects who did not wear elastics (EL-) but did use a posterior bite
62
opening prop (PBB+), the least amount of mean molar extrusion took place. In subjects
who wore neither elastics nor posterior bite opening prop (EL- /PBB-) or both elastics
and posterior bite opening prop (EL+/PBB+) the amounts of mean molar extrusion were
found to be somewhere in the middle. As would be expected in the latter group, the
range of mandibular molar extrusion varied quite widely as would be expected since it
would be dependent on the variable length of time elastics were worn versus the length
of time the bite prop was used in each subject.
63
ACCURACY OF S-N MEASUREMENT FOR CEPHALOMETRIC CALIBRATION
Table 11. Mean and absolute differences in measurements for S-N and S-Ba from pre- to post-treatment and significance from paired t-tests for 21 subjects with scales on both cephalograms
For the 21 cases that possessed scales on both pre- and post-treatment cephalograms,
paired t-tests showed that measurements for S-N and S-Ba were not significantly
different across time periods. This indicated that measurements made between these
landmarks were in fact stable over the treatment time, and therefore were reliable to
use for calibration of the cephalograms where one of the pre- or post-treatment images
was lacking a scale. The absolute difference reflected the positive difference between
the measurements taken at the two time points without a sense of direction. For the
sample of 13 subjects with one missing scale, calibration by using S-N was further
validated by confirming that the output measurements for S-Ba had an error only as
great as the mean absolute difference plus one standard deviation. According to the
above table, if the S-N measurement was accurately reproduced, then the output S-Ba
measurements should all have fallen within 1.149 mm of S-Ba measurement on the
partner cephalogram with a scale. This requirement was met for all 13 cases for which
this procedure was done.
64
ERROR STUDY
The intraclass correlation coefficient (ICC) and the Dahlberg’s statistic were calculated to
determine the intra-examiner reproducibility of cephalometric measurements. The ICC
ranged from 0.871 to 0.994, and the Dahlberg’s statistic ranged from 0.024 to 0.251. All
of these calculations suggested excellent reliability.
Table 12. Tests for intra-examiner reliability of cephalometric measurements
65
A second intraclass correlation coefficient (ICC) calculation was performed to assess the
inter-examiner reliability of cephalometric measurements. The ICC ranged from 0.833 to
0.980, suggesting excellent agreement between the investigator and second
orthodontist.
Table 13. Test for inter-examiner reliability of cephalometric measurements
66
VII. DISCUSSION
Leveling of the occlusal plane is an essential stage in orthodontic treatment. In patients
with a deep OB and an excessive COS, this task can be particularly challenging. A
number of studies have been carried out to elucidate the way in which a given appliance
or technique alters the dentition in order to achieve occlusal leveling and concomitant
OB correction. To date, no publications have investigated how leveling of a deep curve
of Spee occurs during treatment with IncognitoTM, a contemporary esthetic lingual
bracket-archwire system.
This retrospective cephalometric analysis examined the radiographic images of 34 adult
subjects with a pre-treatment deep OB and excessive COS treated with IncognitoTM. Pre-
treatment records were compared to post-treatment records to evaluate the capability
of the lingual appliance system to achieve occlusal leveling and OB correction as well as
the particular dental movements produced during this process.
The results showed that in this sample of adults patients treated with IncognitoTM, a
considerable amount of leveling of the mandibular occlusal plane was achieved. The
average depth of the COS was reduced from 1.78 mm to only 0.37 mm, equating to an
improvement by 79%, a finding that was highly statistically significant (p<0.001).
When comparing this measurement of the COS depth to other studies, it is important to
keep in mind the reference points used to define the COS line and the point of greatest
67
depth. In this study, the COS line was drawn from the mesiobuccal cusp tip of the
mandibular first molar to the tip of the most extruded incisor, and the deepest point of
the curve was measured from the cusp tip of the mandibular first premolar. These
reference points were selected to standardize the methods of measurement for all
subjects, and to allow comparison of the results with a recent COS study that used
similar landmarks (Bernstein et al., 2007). However, the depth of COS measurements
might appear to be underestimated in comparison with studies that may have used the
distobuccal cusp tip of the mandibular second molar, since often this reference point
would have been further in height from the most intruded premolar.
The findings of this study showed that the deep OB present in this sample prior to
treatment with IncognitoTM was successfully reduced from 5.80 mm to 2.90 mm, a
finding that was statistically significant (p<0.001).
Leveling and OB correction were accomplished via a combination of dental movements,
including a relatively greater amount of incisor intrusion (0.92 mm) than premolar (0.85
mm) and molar (0.50 mm) extrusion. Although the statistical comparison of intrusion
versus extrusion was not significant, the findings appear to be similar to the Fujita
lingual bracket and mushroom archwire study by Hong et al. (2001) and the segmented
archwire study by Weiland et al. (1996), but only in that all of these studies
demonstrated a relatively greater amount of incisor intrusion than molar extrusion. But,
when the actual quantity of incisor intrusion was taken into consideration, the 0.92 mm
68
of intrusion experienced in this sample treated with IncognitoTM was actually more
similar to the amount typically produced by a labial continuous archwire. Studies that
have investigated labial continuous archwire leveling techniques have demonstrated
incisor intrusions close to 1.00 mm (Weiland et al., 1996; Bernstein, 2007). Whereas, a
meta-analysis found that the combined mean estimate for incisor intrusion from labial
segmental techniques was 1.90 mm (range 1.22-2.57 mm) (Ng et al., 2005).
A possible reason to account for the fact that the amount of incisor intrusion was not as
impressive as was expected might include the fact that a greater amount of incisor
intrusion was not required. This pertains to cases where 1) sufficient OB and leveling
was accomplished early, and therefore there was no need for continued intrusion, or 2)
molar extrusion was actually more desirable. An inherent limitation to most studies
(including this one) examining incisor intrusion, is that maximum intrusion is not always
desirable. Because of this fact, intrusion is likely underestimated more often then not,
unless the sample includes a population of patients where maximum incisor intrusion is
identified as a treatment objective. Another rationale to explain why intrusion was not
as great as theorized, includes the fact that the anterior bite plane or turbo effect of the
maxillary incisor brackets on the mandibular incisors might not have been present in all
cases. It was documented that nearly 40% of subjects received some means of bite
opening from the posterior dentition. This would have eliminated any such anterior bite
plane effect from the maxillary brackets and any additive intrusive forces it would have
delivered to the mandibular incisors. Similarly, if a subject initiated treatment with a
69
large enough anterior overjet relationship (24% of the sample was noted to start with an
overjet of 5 mm or greater), or if early alignment created an increase in the overjet, it is
possible that the mandibular teeth may not have been in contact with the maxillary
brackets for the entire duration of treatment.
Regardless, the amount of incisor intrusion from pre- to post-treatment was found to be
statistically significant and was assumed to be a valid figure due to the accurate method
utilized in this study to measure true intrusion. Actual intrusion can only be proven
when the point of the center of resistance of the incisor has been intruded (Rebellato,
1995). Ideally a point in the center of the root, namely the ‘centroid’, should be used as
a point of reference to measure the amount of intrusion (Burstone, 1977). A recent
systematic review and meta-analysis of true incisor intrusion rejected 19 studies that
met initial selection criteria due to the fact that they did not evaluate intrusion using the
centroid of the incisor (Ng et al., 2005). This is because using the incisor edge or apex as
a reference point might create a false perception of intrusion if the incisor experienced a
change in inclination during treatment. Most often, some proclination would take place
and would lead to an overestimation of the amount of intrusion.
Perhaps one of the most surprising and unanticipated findings in this study was the
degree of incisor proclination (and relative intrusion) experienced in these subjects
treated with IncognitoTM. Both the maxillary and mandibular incisors experienced an
average proclination of 2.61O (p <0.05) and 6.86O (p <0.001) respectively. Such a
70
considerable degree of proclination might possibly have been the most significant
contributing factor to leveling of the occlusal plane and OB correction in some cases.
Contrarily, it was hypothesized that IncognitoTM would have improved torque control
due to the lingual point of force application closer to the center of resistance, and
therefore less of a tendency for intrusive forces to cause proclination. Though this
theory might still hold true, several explanations can attempt to explain why it did not
hold up in this study. It could be that the orthodontists chose in some cases to have the
patient remain in a round archwire without cinching for an extended period of time
during treatment, rather than cinching early or stepping up to a large dimension
rectangular wire that may have better maintained torque control. The recommended
archwire sequence for the IncognitoTM system begins with a 0.014” nickel-titanium (NiTi)
for several months during initial alignment before advancing to a 0.016 x 0.022” NiTi,
followed later by a 0.018 x 0.025” NiTi which fills the entire bracket slot and would
possess the greatest degree of torque control (Wiechmann, 2002). Perhaps, it could
have been that in some cases, mandibular incisor proclination was actually desired
either to upright initially retroclined teeth (38% of the sample was noted to have a
mandibular incisor inclination of 900 or less prior to treatment) or to allow for
compensation of an excessive overjet or Class II malocclusion especially in a non-
growing adult patient (35% of the sample started with a Class II malocclusion). Finally,
since all cases were treated non-extraction and 100% were reported to be crowded, it
would be expected that in order to level and align the dentition some proclination
would be inevitable. This relates to the fact that leveling the COS is known to cause a
71
decrease in arch perimeter (Braun, 1992). Complex mathematical equations to describe
the actual amount of arch perimeter lost due to occlusal plane leveling have even been
proposed by several authors. Baldridge suggested a ratio of Y = 0.488 X - 0.51 where Y is
the arch length differential from pre- to post-treatment and X is the combination of the
maximum depths of the COS on both the right and left sides (Baldridge, 1969). In
another study, Garcia found a ratio of Y = 0.657 X + 1.34 (Garcia, 1985). More simply, a
general rule of thumb for approximating the loss of arch circumference experienced is
that every millimeter of COS depth requires an equal millimeter of arch circumference
to level (Proffit et al., 1986). The implications of excessive incisor proclination on long-
term retention in this sample is something that should be taken into consideration. A
large degree of proclination can upset the functional equilibrium between the teeth and
soft tissues, and after orthodontic appliances are removed, lip pressure can lead to
relapse in the form of incisor uprighting (Kinzel et al., 2002; Proffit, 2007). However, if
the incisors were initially retroclined, as was noted in 38% of this sample, the opposing
argument can be made that retention might be enhanced in those patients now that
teeth were aligned over basal bone (Proffit, 2007).
Where the results of leveling in this sample treated with IncognitoTM differ slightly from
leveling using a labial continuous archwire technique is at the molar and premolar.
Weiland et al. (1996) showed that a labial continuous archwire technique produced an
average of 1.3 mm of molar extrusion (p <0.001). Bernstein et al. (2007) examined both
the molar and the premolar changes during COS leveling and found average extrusions
72
of 0.61 mm (p <0.0001) and 1.26 mm (p <0.0001) respectively. However, in this study,
the average amount of molar and premolar extrusion experienced during leveling with
IncognitoTM equated to only 0.50 mm (p <0.01) and 0.85 mm (p <0.001) respectively.
Though this posterior dental extrusion during treatment in this sample with IncognitoTM
appears to be less in comparison to a labial continuous archwire technique, it is
questionable whether this small amount is truly clinically significant. Statistical
significance of a difference between dental movements experienced during leveling
with a lingual continuous archwire versus a labial continuous archwire could not be
carried out since this investigation did not include its own labial control group.
However, an attempt to explain why mandibular posterior dental extrusion appeared to
be slightly less in this sample treated with IncognitoTM includes the theory that in
subjects who had some means of posterior bite opening, molar extrusion may have
been inhibited due to the additive intrusive forces experienced at the molars upon
biting, thereby bring down the calculated average molar extrusion. The same effect
would have occurred if the original treatment objective for a given patient was to
prevent molar extrusion, and the orthodontist used a posterior bite block to impede
molar eruption. Or, it could be that in this sample, a lingual continuous archwire was
more efficient at achieving incisor intrusion and proclination, without a large amount of
molar and premolar extrusion.
Dental movements experienced during orthodontic treatment can translate to changes
experienced at other regions of the craniofacial apparatus. Of particular interest in this
73
study was the effect of vertical molar dental movements on mandibular jaw rotation. A
side effect such as this is important as it can alter a patient’s vertical and horizontal
facial proportions. For example, in a long-faced individual, it would be an unfavourable
effect to have molar extrusion leading to down and backward rotation of the mandible,
as it would worsen the face height proportions. The results of this study indicated that
the mandibular rotation experienced in this sample treated with IncognitoTM was in fact
significant (p <0.05) even though only 0.53O (SD: 1.12O) of backward rotation was seen
on average. The significance most likely reflected the fact that many subjects
experienced some degree or rotation, but that this rotation was highly variable. This
suggests that a lingual continuous archwire may have no obvious direct effect on
mandibular rotation, but rather that tooth movement and other craniofacial
relationships can be influenced by additional treatment or patient variables.
This retrospective cephalometric analysis on leveling of the COS and deep OB correction
in patients treated with IncognitoTM included several limitations that should be
discussed:
The study was limited to investigate only those subjects that were submitted
voluntarily by orthodontists invited to contribute cases. To submit a case
required that the orthodontist had taken both pre- and post- treatment lateral
cephalometric records. Perhaps one of the greatest barriers to the collection of
records was the fact that many orthodontists were no longer acquiring post-
74
treatment lateral cephalograms in an effort to reduce radiation exposure to the
patient.
Although the philosophy of the IncognitoTM lingual bracket-archwire system is
that complete customization of the appliance should ultimately save the
orthodontist from the need to deliver manual adjustments (eg. all necessary
archwire bends are already included in the archwire) there are still a number of
treatment decisions driven by the orthodontist that would more than likely differ
from practitioner to practitioner. This factor introduces heterogeneity into the
sample, especially given that the sample size was relatively small. Ideally, the
sample should have come from a single orthodontist with sufficient clinical
expertise and experience in treating with the IncognitoTM appliance.
Because this study based all measurements and results from cephalograms, the
well recognized limitations related to cephalometric analysis had to be taken into
consideration. Some of the major components contributing to error in
orthodontic cephalometric analyses are related to quality of the image, patient
head positioning, superimposition of bilateral structures, image magnification,
and most importantly landmark identification (Baumrind and Frantz, 1971;
Midtgard et al., 1974; Houston et al., 1986; Battagel, 1993; Lamichane, 2009).
Each of these sources of error were minimized as much as possible by accepting
only high quality images with good positional symmetry, properly calibrating to
control for gross magnification errors, eliminating cephalograms with no means
of calibration, and performing statistical error tests to confirm the reliability of
75
the investigator’s cephalometric measurements. Despite these measures, a
cephalometric radiograph is a two-dimensional representation of what is truly a
three-dimensional object, and therefore some degree of minor error will have
inevitably been present. Also, because some of the lateral cephalograms
included in the study were conventional radiographs while others were CBCTs,
comparability of the two types of image modalities was essential to ensure
accurate results. A number of recent studies have confirmed that common
angular and linear lateral cephalometric measurements were not statistically
different when obtained from conventional radiographs compared to orthogonal
and/or perspective projection CBCT reconstructed images (Kumar et al., 2008;
Lamichane et al., 2009; Oz et al., 2001; Chang et al., 2011; Liedke et al., 2012).
Due to the small sample size of the study, statistical analysis was limited to
perform only paired t-tests. Complex analyses to elucidate the effect of multiple
potentially confounding factors (such as use of posterior bite blocks, elastic
wear, facial growth pattern, crowding, treating orthodontist, cinching of wires,
etc.) could not reliably be carried out in such a way to provide significant
findings.
Finally, there was no inclusion of a labial continuous archwire control group,
therefore statistical testing for significant differences between lingual continuous
archwire and labial continuous archwire techniques for COS leveling and deep
OB correction could not be calculated.
76
Given these limitations, this study would most appropriately be defined as an
exploratory analysis. Future investigations related to this topic could be improved in the
following ways:
The study design should be prospective, to allow for more specific patient
selection and to ensure that all treatment records, especially post-treatment
cephalograms are obtained.
Particular characteristics of the subject, details about the treatment, and record
of the original treatment objectives should be collected to allow for proper
analysis and control of these variables. Alternatively, the sample of subjects
should be selected in such a way that confounding variables are minimized to
enhance homogeneity of the study sample.
The same radiographic machine should be used to acquire all lateral
cephalometric images to ensure that there is a consistent degree of divergence
of x-ray beams, and therefore same degree of magnification to be corrected.
Cases should be treated by a single experienced orthodontist in order to avoid
the variability introduced by different practitioners.
In order to compare the dental movements and other maxillo-mandibular effects
during leveling between an IncognitoTM lingual continuous archwire technique, a
labial control group matched for OB and COS depth should be included in the
sample.
77
Finally and most importantly, a much larger sample size would allow for more
complex statistical analyses capable of exploring the effects of potentially
confounding factors.
Leveling of the occlusal plane is an essential component of nearly every orthodontic
treatment case. It is necessary as a part of the traditional goals to achieve ideal anterior
OB and overjet relationships, proper posterior intercuspation, and an overall result that
is both functional and esthetically appealing. With the knowledge of how a particular
orthodontic appliance or technique causes actions and reactions of teeth and other
facial components, the orthodontist is more equipped to maintain control of the
treatment, enhance or offset side effects and deliver predictable and desirable tooth
movements. In this sample of 34 adult subjects with a deep OB and excessive COS,
treatment with IncognitoTM led to successful OB reduction and occlusal plane leveling. If
incisor intrusion is desirable, it would be wise to avoid the use of a posterior bite
opening prop to encourage maximum effects of the anterior bite plane or turbo effect
of the maxillary lingual brackets. However if molar extrusion and resultant mandibular
rotation is undesirable, than the use of a posterior bite opening prop might be in the
patient’s best interest. If incisor proclination is not favourable, then the archwires could
be cinched to avoid this side effect.
78
VIII. CONCLUSIONS
1. Significant occlusal plane leveling and OB reduction was achieved in this sample
of 34 adult subjects with a deep OB and excessive COS treated with IncognitoTM.
2. Leveling of the COS and reduction of the deep OB was accomplished by
statistically significant changes in the dentition including: mandibular incisor
intrusion, mandibular premolar and molar extrusion, and a considerable but
variable degree of both maxillary and mandibular incisor proclination.
3. The amount of mandibular incisor intrusion was greater than, but not
significantly different than, the amount of mandibular molar or premolar
extrusion.
79
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86
Appendix 1 – Abbreviations/Acronyms AVG: Average CBCT: Cone beam computed tomography COS: Curve of Spee DICOM: Digital Imaging and Communications in Medicine DFP: Dentofacial Planner EL: Elastics FH: Frankfort Horizontal Plane FHR: Face height ratio JPEG: Joint Photographic Experts Group MP: Mandibular Plane OB: Overbite PBB: Posterior bite block/prop PP: Palatal Plane SE: Standard Error SD: Standard deviation SPSS: Statistical Package for the Social Sciences
87
Appendix 2 – Lateral Cephalometric Landmark Definitions Landmark Definition
N Nasion: the most anterior point of the frontonasal suture
Or Orbitale: the lowest point on the inferior margin of the orbit
PNS Posterior Nasal Spine: the most posterior point on the bony hard palate
ANS Anterior Nasal Spine: the most anterior point on the maxilla at the level of the palate
A “A” point (Subspinale): the deepest point on the anterior contour of the maxilla
U1 Incisal tip of the most extruded maxillary incisor
U1C Centroid of the most extruded maxillary incisor (the midpoint between the tip and apex,
determined by DFP)
U6 Mesial cusp tip of the maxillary first molar
L1 Incisal tip of the most extruded mandibular incisor
L1C Centroid of the most extruded mandibular incisor (the midpoint between the tip and apex, determined by DFP)
L4 Cusp tip of the mandibular first premolar
L6 Mesial cusp tip of the mandibular first molar
B “B” point (Supramentale): the deepest point on the anterior contour of the mandible
Pg Pogonion: the most anterior point on the contour of the chin
Gn Gnathion: the most anterior inferior point in the lateral shadow of the chin; midpoint between Pogonion and Menton on the contour of the chin
Me Menton: the most inferior point on the mandibular symphysis
Go Gonion: the most posterior inferior point at the angle of the mandible
Po Porion: the midpoint of the upper contour of the external auditory canal
Ba Basion: the lowest point on the anterior margin of the foramen magnum at the base of the clivus
S Sella: the midpoint of the cavity of sella turcica
88
Appendix 3 – Questionnaire
1. Did the patient wear elastics during their treatment? If so, please indicate the
teeth included in elastic wear.
2. Did the patient require a posterior bite-opening prop?
3. Did the patient present with a crowded or spaced mandibular dentition prior to
treatment?
89
Appendix 4 – Example of DFP lateral cephalometric tracing and measurements
90
Appendix 5: Cephalometric measurements at pre- and post-treatment, differences and significance from paired t-tests
ID
SNA (O) pre
SNA (O)
post
SNA (O) diff
SNB (O) pre
SNB (O)
post
SNB (O) diff
ANB (O) pre
ANB (O)
post
ANB (O) diff
GHU 85.8 86.3 0.5 84.8 84.8 0 1 1.5 0.5 GHR 79.8 78.8 -1 78.2 78.8 0.6 1.6 0 -1.6 GXI 78.3 79.4 1.1 74.7 74.9 0.2 3.6 4.5 0.9 HBR 81.4 81.1 -0.3 74.7 74 -0.7 6.8 7.1 0.3 HCA 80.5 79 -1.5 76.2 75.3 -0.9 4.3 3.7 -0.6 HCR 80.4 82.1 1.7 79.2 79 -0.2 1.3 3.1 1.8 HDU 88.5 87.9 -0.6 84.6 84 -0.6 3.9 3.9 0 HGA 86 86.7 0.7 83.9 83.8 -0.1 2.2 2.9 0.7 HMO 79.9 80.4 0.5 77.8 78 0.2 1.9 2.4 0.5 HNE 78.6 78.9 0.3 77.6 77.2 -0.4 1 1.7 0.7 HAS 84.7 81.7 -3 78 75.3 -2.7 6.7 6.5 -0.2 HSC 89.5 90.3 0.8 87.1 87.5 0.4 2.4 2.8 0.4 HST 83.5 83.5 0 77.5 77.8 0.3 6.1 5.7 -0.4 HTH 80.1 80.9 0.8 78.9 79.5 0.6 1.2 1.4 0.2 KCO 82.2 82.9 0.7 79 79.1 0.1 3.1 3.8 0.7 PCK 75.6 76.2 0.6 72.8 72.9 0.1 2.8 3.4 0.6 PJH 79.3 79.7 0.4 78 78.7 0.7 1.4 1 -0.4 PMW 81.8 82 0.2 79.9 79.1 -0.8 1.9 2.9 1 PSF 87 88 1 84.8 85.3 0.5 2.2 2.7 0.5 PTP 85.4 85.8 0.4 82.1 83.5 1.4 3.3 2.3 -1 WBI 89.7 90.1 0.4 84.3 84.2 -0.1 5.5 5.9 0.4 WCA 83.3 82.9 -0.4 79.5 79 -0.5 3.8 3.9 0.1 WJO 83.2 82.6 -0.6 81.7 81.5 -0.2 1.5 1.1 -0.4 WKE 79.8 81.4 1.6 76.2 78.4 2.2 3.7 3 -0.7 WKL 83.3 83.1 -0.2 79.3 80.2 0.9 4 2.9 -1.1 WME 83.1 83.9 0.8 82.6 81.7 -0.9 0.5 2.2 1.7 WMU 86.6 85.5 -1.1 81.2 81.7 0.5 5.3 3.8 -1.5 WPA 78.8 78.2 -0.6 76.2 75.6 -0.6 2.6 2.6 0 WPR 83.2 83.3 0.1 82.7 82.6 -0.1 0.4 0.8 0.4 WRA 87.4 87.9 0.5 82.6 82.7 0.1 4.7 5.3 0.6 WRO 81.4 80.2 -1.2 76.8 76.1 -0.7 4.6 4.1 -0.5 WSH 82.4 82.9 0.5 79 78.4 -0.6 3.4 4.6 1.2 WSO 85.6 85.1 -0.5 84.9 83.9 -1 0.7 1.2 0.5 WVO 81 81 0 77.3 76.5 -0.8 3.7 4.5 0.8
AVG 82.86 82.93 0.08 79.82 79.73 -0.09 3.03 3.21 0.18 SD 3.43 3.47 0.94 3.51 3.63 0.84 1.77 1.68 0.80 P - - NS - - NS - - NS
91
ID
Y-Axis (O) pre
Y-Axis (O)
post
Y-Axis (O) diff
SNtoMP (O) pre
SNtoMP (O)
post
SNtoMP (O) diff
U1toPP (O) pre
U1toPP (O)
post
U1toPP (O) diff
GHU 53.4 53.3 -0.1 20.1 22.3 2.2 118.2 113.6 -4.6 GHR 58.8 58.8 0 23.2 25.8 2.6 101.8 103.4 1.6 GXI 68.9 69.7 0.8 21 21.8 0.8 104.8 105.9 1.1 HBR 60.6 61.7 1.1 36.6 37.4 0.8 95.5 106.1 10.6 HCA 57.6 59.1 1.5 36.8 38.1 1.3 97.1 105.3 8.2 HCR 56.8 57.8 1 26.6 28.3 1.7 106.9 108.8 1.9 HDU 58 58 0 31.9 31.7 -0.2 108.2 116.8 8.6 HGA 52.6 52.6 0 20.8 21 0.2 99.4 99.1 -0.3 HMO 55.7 56.7 1 22.9 23.8 0.9 98 103.4 5.4 HNE 52.8 53.4 0.6 27.2 27 -0.2 100.7 108.7 8 HAS 65.3 62.6 -2.7 33.9 37.6 3.7 92.2 101.4 9.2 HSC 57.2 57 -0.2 16.2 16.8 0.6 101.1 107 5.9 HST 60.8 60.9 0.1 33.4 33.4 0 100.7 106.2 5.5 HTH 58.4 58.1 -0.3 29.9 29.9 0 100.9 107.9 7 KCO 53.8 54.1 0.3 28.9 28.5 -0.4 100.7 98.2 -2.5 PCK 56.9 56 -0.9 32.2 32.7 0.5 98.2 105.3 7.1 PJH 55.7 56.7 1 24.1 24.4 0.3 101.2 109.4 8.2 PMW 56.8 59 2.2 29 30.1 1.1 112.1 113.5 1.4 PSF 52 52.2 0.2 25.1 25.1 0 104.6 104 -0.6 PTP 56.1 56 -0.1 26.4 24.9 -1.5 106.6 104.4 -2.2 WBI 55.7 57.6 1.9 24.8 26.9 2.1 108.2 107.1 -1.1 WCA 59.6 58.5 -1.1 25.5 25.3 -0.2 109.4 108.4 -1 WJO 56.1 56.1 0 30.1 29.2 -0.9 104.6 105.8 1.2 WKE 56 56.5 0.5 33.5 34.1 0.6 104.3 101.9 -2.4 WKL 49.6 49.7 0.1 26.2 25.7 -0.5 100.1 107.7 7.6 WME 54.7 55.5 0.8 28.2 29 0.8 113 104.8 -8.2 WMU 50.2 53.2 3 27.6 25.6 -2 112 114.3 2.3 WPA 57 57.4 0.4 23.3 23.8 0.5 95.5 110.7 15.2 WPR 56 58.1 2.1 25.4 25.6 0.2 100.8 106.8 6 WRA 52.8 53.6 0.8 19.1 19.2 0.1 122.2 108.8 -13.4 WRO 55.1 55.3 0.2 27.6 27.8 0.2 112.6 115.2 2.6 WSH 58.4 59.5 1.1 35.8 36.6 0.8 94.5 99.4 4.9 WSO 53.3 53.1 -0.2 22.1 23.9 1.8 122.5 117.2 -5.3 WVO 59.8 61.3 1.5 31.9 31.9 0 101.2 102 0.8 AVG 56.54 57.03 0.49 27.27 27.8 0.53 104.41 107.01 2.61 SD 3.85 3.71 1.05 5.19 5.28 1.12 7.478 4.85 5.82 P - - <0.05 - - <0.05 - - <0.05
92
ID
U1toPP (mm) pre
U1toPP (mm) post
U1toPP (mm) diff
U1CtoPP (mm) pre
U1CtoPP (mm) post
U1CtoPP (mm) diff
U6toPP (O) pre
U6toPP (O)
post
U6toPP (O) diff
GHU 25.9 25.9 0 15.4 15 -0.4 85 84.3 -0.7 GHR 31.7 30.9 -0.8 19.4 18.7 -0.7 85.2 86.8 1.6 GXI 28.2 28.2 0 16.3 16.3 0 82.8 84.1 1.3 HBR 29.8 29.8 0 17.5 18 0.5 83.6 82.5 -1.1 HCA 31.3 32.9 1.6 20.1 21.9 1.8 74.7 75.5 0.8 HCR 26.7 26.9 0.2 15 15.5 0.5 82 81.5 -0.5 HDU 30.3 30.9 0.6 18.4 20.1 1.7 81.8 85.8 4 HGA 26.2 27 0.8 15.4 16 0.6 88.1 87.3 -0.8 HMO 30.4 31.2 0.8 17.5 19.1 1.6 84.7 82.5 -2.2 HNE 26.5 26.8 0.3 15.6 16.4 0.8 84.4 84 -0.4 HAS 29.9 29.9 0 18.2 18.4 0.2 79 78.3 -0.7 HSC 28.1 27.7 -0.4 15.9 15.8 -0.1 89.7 86.9 -2.8 HST 31.7 31.7 0 19 19.5 0.5 90.2 90 -0.2 HTH 26.9 27.7 0.8 15.7 16.5 0.8 79.5 76.8 -2.7 KCO 26.8 26.4 -0.4 14.7 14.9 0.2 81.6 80.9 -0.7 PCK 25.6 25 -0.6 14.5 14 -0.5 77.6 85.4 7.8 PJH 25.9 25.9 0 14.6 14.9 0.3 84.4 85.4 1 PMW 25.5 25.7 0.2 14.7 14.7 0 88.6 90.3 1.7 PSF 28.7 28.2 -0.5 16.5 16.1 -0.4 84.6 86.4 1.8 PTP 30.4 30.9 0.5 18.7 18.2 -0.5 83.5 90.1 6.6 WBI 29.9 30.7 0.8 18 18.7 0.7 85.7 81.7 -4 WCA 30.9 30.4 -0.5 19.9 19.5 -0.4 84.1 84.5 0.4 WJO 30.5 28.8 -1.7 18.9 17 -1.9 87.5 88.8 1.3 WKE 27.7 27.3 -0.4 17.4 16.6 -0.8 71.6 78.7 7.1 WKL 28.1 26 -2.1 16.2 14.7 -1.5 86.5 84.3 -2.2 WME 27.2 28 0.8 17.1 17.3 0.2 83.2 82.5 -0.7 WMU 25.9 26.8 0.9 15 16.3 1.3 86.1 84.2 -1.9 WPA 27.7 25.8 -1.9 15.2 14.1 -1.1 88.2 90.7 2.5 WPR 28.6 28.4 -0.2 17.1 16.5 -0.6 80.4 78.2 -2.2 WRA 22.4 21.7 -0.7 13.2 11.4 -1.8 89.7 92.1 2.4 WRO 27 25 -2 15.5 14.3 -1.2 84.8 83.3 -1.5 WSH 30 28.4 -1.6 18.2 16.8 -1.4 83.9 78.8 -5.1 WSO 26.9 27.9 1 17.4 17.7 0.3 85.1 86.6 1.5 WVO 32.5 30.6 -1.9 20.8 19 -1.8 77.6 80.6 3 AVG 28.29 28.1 -0.19 16.85 16.76 -0.09 83.69 84.11 0.42 SD 2.28 2.40 0.97 1.88 2.13 1.00 4.21 4.19 2.93 P - - NS - - NS - - NS
93
ID
U6toPP (mm) pre
U6toPP (mm) post
U6toPP (mm) diff
L1toMP (O) pre
L1toMP (O)
post
L1toMP (O) diff
L1toMP (mm) pre
L1toMP (mm) post
L1toMP (mm) diff
GHU 21 21 0 90 93.9 3.9 40.3 39 -1.3 GHR 26 26.5 0.5 84.3 94.7 10.4 39.7 38.8 -0.9 GXI 22.6 23.4 0.8 108.6 116.5 7.9 42 40.6 -1.4 HBR 22 23.1 1.1 91.1 104.2 13.1 38.8 38.6 -0.2 HCA 22.9 24.2 1.3 91.5 102.1 10.6 35 34.2 -0.8 HCR 20.6 20.5 -0.1 93.6 103.8 10.2 35.3 34.9 -0.4 HDU 26.5 26.8 0.3 87.5 82.6 -4.9 42.6 41.1 -1.5 HGA 22 23 1 94.6 98.2 3.6 35.6 35.4 -0.2 HMO 24 24.6 0.6 89.9 104.5 14.6 39.2 38.1 -1.1 HNE 20.8 21 0.2 87.5 94.9 7.4 29.9 29.1 -0.8 HAS 21.6 21.1 -0.5 96.6 104 7.4 38.6 36.4 -2.2 HSC 24.8 24.5 -0.3 91.9 104.5 12.6 39.9 39.1 -0.8 HST 27.4 28.6 1.2 91.5 99.5 8 45.6 44.1 -1.5 HTH 22.1 22.8 0.7 82.5 96 13.5 33.3 32.7 -0.6 KCO 15.5 20.2 4.7 81.6 98.9 17.3 34.5 34.7 0.2 PCK 20.5 20.6 0.1 88.6 91.1 2.5 29.2 29.6 0.4 PJH 22.2 23.3 1.1 92.4 96.4 4 35.4 35.4 0 PMW 23.2 22.5 -0.7 102.9 100 -2.9 36.7 35.3 -1.4 PSF 24.2 24.3 0.1 84.3 87.7 3.4 35.5 33.9 -1.6 PTP 24.7 23.9 -0.8 95 98.1 3.1 38.1 36.3 -1.8 WBI 23.4 24.1 0.7 102.8 105.8 3 36.4 35.8 -0.6 WCA 25.5 25.4 -0.1 100.8 109.4 8.6 36.2 34.4 -1.8 WJO 24.1 23.8 -0.3 87.4 96.4 9 38.7 38.5 -0.2 WKE 21.5 20.7 -0.8 98 95.9 -2.1 37 34.3 -2.7 WKL 22.3 21.6 -0.7 91.9 104.2 12.3 34.4 33 -1.4 WME 23.5 22.9 -0.6 90.3 92.1 1.8 36.8 33.6 -3.2 WMU 23.4 23.4 0 98.4 108.8 10.4 40.4 38.2 -2.2 WPA 21.1 20.1 -1 84.6 101.4 16.8 39 37.4 -1.6 WPR 22.9 23.4 0.5 85.1 91.7 6.6 37.7 38 0.3 WRA 19.6 19.9 0.3 109 107.4 -1.6 36 32.9 -3.1 WRO 20.9 20.4 -0.5 101.4 109.6 8.2 35.7 32.8 -2.9 WSH 22.7 21.4 -1.3 76.9 84.7 7.8 34.4 35 0.6 WSO 24.7 24.4 -0.3 98.9 101 2.1 35.3 33.5 -1.8 WVO 25.9 25.1 -0.8 98 102.8 4.8 38.4 36.9 -1.5 AVG 22.83 23.01 0.19 92.63 99.49 6.86 37.11 35.93 -1.188 SD 2.29 2.12 1.06 7.56 7.36 5.51 3.28 3.15 1.00 P - - NS - - <0.001 - - <0.001
94
ID
L1CtoMP (mm) pre
L1CtoMP (mm) post
L1CtoMP (mm) diff
L6toMP (O) pre
L6toMP (O)
post
L6toMP (O) diff
L6toMP (mm) pre
L6toMP (mm) post
L6toMP (mm) diff
GHU 29 27.8 -1.2 81.1 79.1 -2 31.7 31.9 0.2 GHR 28.8 27.8 -1 82.7 78.5 -4.2 32.2 32.7 0.5 GXI 31.8 30.9 -0.9 86.8 84 -2.8 36.1 37.5 1.4 HBR 28 28 0 69.7 74.2 4.5 31.1 31.4 0.3 HCA 25.1 24.9 -0.2 81.1 78.6 -2.5 27 27.8 0.8 HCR 25.1 24.8 -0.3 80.8 78.7 -2.1 28.8 28.9 0.1 HDU 31.1 30.5 -0.6 77.1 72.6 -4.5 30.4 31 0.6 HGA 25.5 25.1 -0.4 79.3 81.2 1.9 28.9 29.7 0.8 HMO 28.4 28.2 -0.2 82.5 83 0.5 30.9 33.8 2.9 HNE 19.7 19.3 -0.4 80.4 80 -0.4 23.7 23.8 0.1 HAS 29 27.5 -1.5 77.3 75.4 -1.9 29.1 29 -0.1 HSC 29.2 28.5 -0.7 78.4 77 -1.4 33.5 33.9 0.4 HST 34.6 33.3 -1.3 77.7 77.3 -0.4 37.4 36.7 -0.7 HTH 24.3 23.8 -0.5 81.5 79.8 -1.7 27.7 28.3 0.6 KCO 24.2 24.4 0.2 81.5 83.9 2.4 28.6 29.2 0.6 PCK 20 20.4 0.4 81.2 78.7 -2.5 22.2 24.1 1.9 PJH 25.2 24.9 -0.3 92.3 85.7 -6.6 28 29.9 1.9 PMW 25.8 24.4 -1.4 76.8 72.6 -4.2 27.7 28.5 0.8 PSF 24.9 23.5 -1.4 72.8 74.2 1.4 27.5 27.2 -0.3 PTP 27.6 26 -1.6 78.1 77.9 -0.2 29.5 30.3 0.8 WBI 25.4 25 -0.4 75.3 78.4 3.1 28.3 27.2 -1.1 WCA 24.5 23.3 -1.2 82 78.4 -3.6 28.2 28.7 0.5 WJO 28.3 28.2 -0.1 73.1 77.2 4.1 32 32.7 0.7 WKE 26.9 24.3 -2.6 77.4 78.1 0.7 27.6 27.8 0.2 WKL 24.7 23.6 -1.1 85 78.6 -6.4 26.6 28.3 1.7 WME 26.2 23.5 -2.7 80.1 76.6 -3.5 28.8 27.9 -0.9 WMU 29.8 28.2 -1.6 82 80.5 -1.5 32 32.3 0.3 WPA 27.5 27.2 -0.3 80.5 81.2 0.7 33.4 33 -0.4 WPR 27.8 27.2 -0.6 81.7 79.5 -2.2 30.2 30.5 0.3 WRA 26 23.4 -2.6 77.2 75.1 -2.1 28.9 29 0.1 WRO 26 23.5 -2.5 90.2 87.7 -2.5 28.8 28.6 -0.2 WSH 23.3 24.1 0.8 74.1 72.9 -1.2 26.7 26.5 -0.2 WSO 25.3 23.7 -1.6 78.3 79.6 1.3 27.1 29.6 2.5 WVO 28.3 26.7 -1.6 75.7 74.6 -1.1 29.4 29.3 -0.1 AVG 26.69 25.76 -0.92 79.76 78.55 -1.20 29.41 29.91 0.5 SD 3.00 2.89 0.87 4.59 3.59 2.67 3.04 3.00 0.89 P - - <0.001 - - <0.05 - - <0.01
95
ID
L4toCOS (mm) pre
L4toCOS (mm) post
L4toCOS (mm) diff
L4toMP (mm) pre
L4toMP (mm) post
L4toMP (mm) diff
UFH (mm) pre
UFH (mm) post
UFH (mm) diff
GHU 2.1 0.7 -1.4 33.8 34.9 1.1 54.2 54 0.2 GHR 1.7 0.1 -1.6 35.1 35.5 0.4 50.1 50.1 0 GXI 1.6 -0.1 -1.7 37.6 39.1 1.5 56.8 56.7 0.1 HBR 1.5 0.4 -1.1 34.2 35 0.8 52.9 53.2 -0.3 HCA 1.6 0.8 -0.8 30.2 29.6 -0.6 50.6 51 -0.4 HCR 1.6 0.1 -1.5 30.9 32 1.1 48.5 48.4 0.1 HDU 1.6 1 -0.6 34.8 34.9 0.1 60.3 60.3 0 HGA 1.7 0.7 -1 30.9 31.8 0.9 50.5 50.9 -0.4 HMO 1.6 0.3 -1.3 32.9 35.6 2.7 55.3 55.7 -0.4 HNE 1.6 0.9 -0.7 25.4 25.6 0.2 53.8 53.5 0.3 HAS 1.7 -0.3 -2 32.5 32.9 0.4 51.6 51.2 0.4 HSC 1.9 0.6 -1.3 35.3 36.1 0.8 51.8 51.9 -0.1 HST 1.5 0.1 -1.4 41.5 40.8 -0.7 57 56.9 0.1 HTH 1.5 0.7 -0.8 28.3 29.2 0.9 50 49.1 0.9 KCO 1.7 1 -0.7 29.8 30.9 1.1 51.7 51.3 0.4 PCK 2.1 0.6 -1.5 24.7 27 2.3 49.3 49.8 -0.5 PJH 2.9 1.1 -1.8 28.6 31.9 3.3 54.8 55.1 -0.3 PMW 1.5 -0.4 -1.9 31.5 32.2 0.7 53.3 54.2 -0.9 PSF 1.5 0.7 -0.8 30.7 30.1 -0.6 47.7 47 0.7 PTP 1.6 0 -1.6 32.9 33.6 0.7 53.7 52.4 1.3 WBI 1.6 0 -1.6 31 31.6 0.6 48.2 48.5 -0.3 WCA 1.7 -0.1 -1.8 31 31.8 0.8 51.1 51.1 0 WJO 1.5 0.6 -0.9 34.2 35.6 1.4 54.9 54.5 0.4 WKE 2.4 0.7 -1.7 28.6 29.7 1.1 51.1 50.2 0.9 WKL 2.9 -0.1 -3 28.3 30.9 2.6 47.1 47.4 -0.3 WME 2.3 0.2 -2.1 31.1 30.7 -0.4 50.5 50 0.5 WMU 1.7 0 -1.7 34.7 35.4 0.7 51.9 51.3 0.6 WPA 1.7 0.8 -0.9 34.8 35 0.2 52.4 52.5 -0.1 WPR 1.8 0.5 -1.3 32.6 34.1 1.5 55.7 56.1 -0.4 WRA 1.5 0.1 -1.4 31.2 31.1 -0.1 50.5 50.1 0.4 WRO 1.8 0 -1.8 29.7 30.7 1 52.1 53.2 -1.1 WSH 1.9 0.5 -1.4 28.8 30.2 1.4 53.6 53 0.6 WSO 1.9 0.5 -1.4 29 29.6 0.6 53.3 54.4 -1.1 WVO 1.5 0 -1.5 32.7 33.2 0.5 49.4 49.5 -0.1 AVG 1.79 0.37 -1.41 31.74 32.60 0.85 52.23 52.19 0.04 SD 0.36 0.41 0.49 3.33 3.17 0.91 2.89 2.97 0.55 P - - <0.001 - - <0.001 - - NS
96
ID
LFH (mm) pre
LFH (mm) post
LFH (mm) diff
FHR
pre
FHR
post
FHR
diff GHU 63.6 64.5 -0.9 0.85 0.84 -0.01 GHR 67.7 69.4 -1.7 0.74 0.72 -0.02 GXI 69.6 70.4 -0.8 0.82 0.81 -0.01 HBR 67.4 68.5 -1.1 0.79 0.78 -0.01 HCA 66.5 68.4 -1.9 0.76 0.75 -0.01 HCR 59.9 61.6 -1.7 0.81 0.79 -0.02 HDU 74 74.1 -0.1 0.82 0.81 -0.01 HGA 61.3 62.7 -1.4 0.82 0.81 -0.01 HMO 67 71.1 -4.1 0.82 0.78 -0.04 HNE 54.3 54.6 -0.3 0.99 0.98 -0.01 HAS 67.5 67 0.5 0.76 0.76 0 HSC 66 66.9 -0.9 0.78 0.78 0 HST 76.4 77.3 -0.9 0.75 0.74 -0.01 HTH 59.8 62.1 -2.3 0.84 0.79 -0.05 KCO 60.6 61.3 -0.7 0.85 0.84 -0.01 PCK 55.5 58 -2.5 0.89 0.86 -0.03 PJH 59.4 61.6 -2.2 0.92 0.9 -0.02 PMW 60.4 60.5 -0.1 0.89 0.9 0.01 PSF 63.4 64.6 -1.2 0.75 0.73 -0.02 PTP 67.2 67.5 -0.3 0.8 0.78 -0.02 WBI 63.4 64 -0.6 0.76 0.73 -0.03 WCA 66 66 0 0.77 0.77 0 WJO 69 69.2 -0.2 0.8 0.79 -0.01 WKE 62.9 64.2 -1.3 0.81 0.78 -0.03 WKL 59.7 59.2 0.5 0.79 0.8 0.01 WME 61.3 60.9 0.4 0.82 0.82 0 WMU 64.4 65.3 -0.9 0.8 0.79 -0.01 WPA 62.8 62.2 0.6 0.83 0.85 0.02 WPR 67.4 67.7 -0.3 0.83 0.83 0 WRA 55.9 56.7 -0.8 0.9 0.88 -0.02 WRO 59.4 57.8 1.6 0.88 0.92 0.04 WSH 64.9 65.9 -1 0.82 0.8 -0.02 WSO 60.8 62.7 -1.9 0.88 0.87 -0.01 WVO 70.2 69.3 0.9 0.7 0.71 0.01 AVG 63.99 64.8 -0.81 0.82 0.81 -0.01 SD 4.96 4.97 1.12 0.06 0.06 0.02 P - - <0.001 - - <0.01
97
Appendix 6: Mandibular incisor intrusion versus premolar and molar extrusion, and results from paired t-tests
ID
L1C intrusion
(mm)
L4 extrusion
(mm)
L6 extrusion
(mm) DIFF L1C-
L4 DIFF L1C-
L6 GHU 1.2 1.1 0.2 0.1 1 GHR 1 0.4 0.5 0.6 0.5 GXI 0.9 1.5 1.4 -0.6 -0.5 HBR 0 0.8 0.3 -0.8 -0.3 HCA 0.2 -0.6 0.8 0.8 -0.6 HCR 0.3 1.1 0.1 -0.8 0.2 HDU 0.6 0.1 0.6 0.5 0 HGA 0.4 0.9 0.8 -0.5 -0.4 HMO 0.2 2.7 2.9 -2.5 -2.7 HNE 0.4 0.2 0.1 0.2 0.3 HAS 1.5 0.4 -0.1 1.1 1.6 HSC 0.7 0.8 0.4 -0.1 0.3 HST 1.3 -0.7 -0.7 2 2 HTH 0.5 0.9 0.6 -0.4 -0.1 KCO -0.2 1.1 0.6 -1.3 -0.8 PCK -0.4 2.3 1.9 -2.7 -2.3 PJH 0.3 3.3 1.9 -3 -1.6 PMW 1.4 0.7 0.8 0.7 0.6 PSF 1.4 -0.6 -0.3 2 1.7 PTP 1.6 0.7 0.8 0.9 0.8 WBI 0.4 0.6 -1.1 -0.2 1.5 WCA 1.2 0.8 0.5 0.4 0.7 WJO 0.1 1.4 0.7 -1.3 -0.6 WKE 2.6 1.1 0.2 1.5 2.4 WKL 1.1 2.6 1.7 -1.5 -0.6 WME 2.7 -0.4 -0.9 3.1 3.6 WMU 1.6 0.7 0.3 0.9 1.3 WPA 0.3 0.2 -0.4 0.1 0.7 WPR 0.6 1.5 0.3 -0.9 0.3 WRA 2.6 -0.1 0.1 2.7 2.5 WRO 2.5 1 -0.2 1.5 2.7 WSH -0.8 1.4 -0.2 -2.2 -0.6 WSO 1.6 0.6 2.5 1 -0.9 WVO 1.6 0.5 -0.1 1.1 1.7 AVG 0.92 0.85 0.5 0.070 0.42 SD 0.87 0.91 0.89 1.48 1.40 P <0.001 <0.001 <0.01 NS NS
98
Appendix 7: Error study results – Intra-examiner reliability
99
Appendix 8: Error study results – Inter-examiner reliability
100
Appendix 9 – Calibration data and results: cephalograms with scales on both pre- and post-treatment images
Pre- and post-treatment measurements for S-N and S-B, significance from paired t-tests, and calculation of maximum error for S-B (AVG +/- 1SD):
ID
S-N (mm) pre
S-N (mm) post
S-N (mm) diff
S-N (mm)
absolute diff
S-B (mm) pre
S-B (mm) post
S-B (mm) diff
S-B (mm)
absolute diff
GHU 73 73.1 -0.1 0.1 50.3 50.4 -0.1 0.1 GHR 68.4 68.4 0 0 48.4 48.4 0 0 GXI 65.3 65.6 -0.3 0.3 46 45.5 0.5 0.5 HBR 71.8 71.8 0 0 44.2 45.1 -0.9 0.9 HCA 65.8 66.3 -0.5 0.5 42.6 41.8 0.8 0.8 HCR 66.8 66.6 0.2 0.2 44 44.3 -0.3 0.3 HDU 71.6 71 0.6 0.6 48.7 49.2 -0.5 0.5 HGA 72.5 73.3 -0.8 0.8 42.7 43 -0.3 0.3 HMO 76.4 76.5 -0.1 0.1 48.3 50.7 -2.4 2.4 HNE 73.4 72.9 0.5 0.5 45.9 46.2 -0.3 0.3 HAS 67.5 67.6 -0.1 0.1 38.7 39 -0.3 0.3 HSC 74.6 73.5 1.1 1.1 46.1 45.5 0.6 0.6 HST 69.7 70.1 -0.4 0.4 48.6 48.2 0.4 0.4 HTH 65.1 66.1 -1 1 42.6 41.9 0.7 0.7 KCO 67.3 68 -0.7 0.7 46.9 46.3 0.6 0.6 PCK 66.8 67 -0.2 0.2 42.3 43.4 -1.1 1.1 PJH 74.5 74.4 0.1 0.1 46.7 47.1 -0.4 0.4 PMW 67.8 67.5 0.3 0.3 45.3 45.7 -0.4 0.4 PSF 67.6 67.9 -0.3 0.3 43.6 45.2 -1.6 1.6 PTP 72 71.9 0.1 0.1 51.5 51.5 0 0 WSO 71 70.6 0.4 0.4 46.7 46.9 -0.2 0.2
AVG - - -0.057 0.371 - - -0.248 0.590 SD - - 0.493 0.318 - - 0.784 0.559 P - - NS - - - NS -
Max. Error - - - - - - - 1.150
101
Appendix 10 – Calibration data and results: Cephalograms
without a scale on one of pre- or post-treatment images after
Pre- and post-treatment measurements for S-B after calibration using S-N:
ID
S-B (mm) pre
S-B (mm) post
S-B (mm) diff
S-B (mm)
absolute diff
WBI 46.9 46 0.9 0.9 WCA 48.9 48 0.9 0.9 WJO 48.1 47.5 0.6 0.6 WKE 44.6 43.8 0.8 0.8 WKL 45 44.3 0.7 0.7 WME 39.4 40.3 -0.9 0.9 WMU 49.3 48.5 0.8 0.8 WPA 43 43.5 -0.5 0.5 WPR 56.9 55.9 1 1 WRA 45.3 46.1 -0.8 0.8 WRO 44.6 44.1 0.5 0.5 WSH 43.4 43.7 -0.3 0.3 WVO 46.2 45.4 0.8 0.8
AVG 47.0 45.9 0.346 0.731 SD 0.700 0.202 P - - NS -