ORTHOGNATHIC SURGERY

By HARDIK LALAKIYA3RD YEAR PG

CONTENTSWHAT IS ORTHOGNATHIC SURGERY

GOALS OF ORTHOGNATHIC SURGERY

ENVELOPE OF DISCREPANCY

TIMING OF ORTHOGNATHIC SURGERIES

WHY ORTHOGNATHIC SURGERY

INDICATIONS

PATIENT EVALUATION

CEPHALOMETRICS {COGS} ANALYSIS

MODEL SURGERY

CLASSIFICATION OF DENTOFACIAL DEFORMITIES

DISTRACTION OSTEOGENESIS

LATEST NAVIGATION BASED ORTHOGNATHIC SURGERY

REFERENCES

Patient

Orthodontist

Oral Surgeon

WHAT IS ORTHOGNATHIC SURGERY?• To correct conditions of the jaw and face related to structure, growth,

sleep apnea, TMJ disorders, malocclusion problems owing to skeletal disharmonies, or other orthodontic problems that cannot be easily treated with braces.

• Originally coined by Harold Hargis, it is also used in treatment of congenital conditions like cleft palate. Bones can be cut and re-aligned, then held in place with either screws or plates. Orthognathic surgery can also be referred to as corrective jaw surgery.

GOALS OF ORTHOGNATHIC /ORTHODONTIC TREATMENT OBJECTIVES – F.R.E.S.H.

• 1) F UNCTION 5) E conomic

• 2) R eliable 6) S tability

• 3) R ealistic 7) S atisfaction

• 4) E sthetics 8) H ealth

ENVELOPE OF DISCREPANCY

Orthodontics

Orthodontics + Growth

Modifications

Orthognathic Surgery

Open Journal of Stomatology, 2014, 4, 184-196

• Keep in mind that the envelope of discrepancy outlines the limits of hard tissue change toward ideal occlusion, other limits due to the major goals of treatment do not apply.

• In fact, soft tissue limitations not reflected in the envelope of discrepancy often are a major factor in the decision for orthodontic or surgical-orthodontic treatment.

• Measuring millimeter distances to the ideal condylar position for normal function is problematic, and measuring distances from ideal esthetics is impossible

•

WHY ORTHOGNATHIC SURGERY?1.When orthodontic treatment alone cannot correct a

problem. 2.To improve jaw function. 3.To enhance the long term orthodontic result (stability). 4.Reduction in overall treatment time. 5.Change in facial appearance. 6.Improved breathing. 7.Improved speech. 8.Improvement in jaw pain.

INDICATIONS • Congenital anomalies

• Excessively large or small jaw dimensions in adults (in one or more planes)

• Marked asymmetric jaw growth

• Anatomic limitations, which hinder the orthodontic tooth movement

• Corticotomy to hasten the orthodontic movements.

INTRODUCTIONSuccessful treatment of the orthognathic surgical patient is dependent on careful diagnosis

Cephalometrics can be an aid in the diagnosis of skeletal and dental problems and a tool for simulating surgery and orthodontics by the use of acetate overlays (Tracing sheets).

PATIENT EVALUATION Patient concerns

Past medical historySociopsychologic Evaluation

Facial evaluation - Frontal - Lateral

Nose evaluation Oral Examination TMJ evaluation Dental Model Analysis Radiographic evaluation

Cephalometric evaluation

ESTHETIC FACIAL EVALUATION• Patient position: The patient should sit upright in a

straight-backed chair with the examiner seated directly opposite at eye level.

• Patients head in examined in two positions• Natural head position• With the Frankfort horizontal plane and pupillary plane

parallel to the floor.

• Once the head oriented properly, the mandibular condyles should be seated in glenoid fossae with the teeth lightly touching. And in centric relation and occlusion

• Analysis in 2 views:1. Front face analysis2. Profile / lateral face analysis

•Frontal Analysis

FRONT FACE ANALYSISFormTransverse dimensions(rule of fifths)

Symmetry Vertical relationships

Upper thirdMiddle thirdLower third

Lips

FORM• Facial height : Bizygomatic width

• MALES - 1.35:1• FEMALES – 1.3 : 1

• Bigonial width : 30% less than bizygomatic width

TRANSVERSE DIMENSIONS

RULE OF FIFTHS• Face divided into five parts, each width approx

the width of the eye.• In the middle fifth, the width of the fifth should

approximate the distance between the inner margins of the irides of the eyes.

• The alae of the nose should coincide with these lines.

FACIAL SYMMETRY

• Glabella• Nasal Bridge• Nasal tip• Filtrum of upper lip• Dental Midlines• Pogonion

VERTICAL RELATIONSHIP

• Face divided into three equal parts:• Trichion to Glabella• Glabella to Subnasale• Subnasale to Menton

UPPER THIRD

• May be masked by hairstyle.• Look out for craniofacial

deformities

MIDDLE THIRD• Glabella to Subnasale• Sclera should not be seen

above or below the iris in relaxed state.

– In mid face deficiency, sclera seen below iris

LOWER THIRD OF FACE

• Middle third: Lower third= 5:6• Upper lip length:

– Males=22+/-2 mm– Females=2o+/-2 mm

• Detect and evaluate any midline shifts.

• Chin: symmetry, vertical relation and shape. 1/3

1/31/3

2/3

CHEEKBONE-NASAL BASE-LIP CONTOUR

• CC- Cheekbone area• a- zygomatic arch• b- middle area• c- subpupillary area

• MxP- Maxillary Point-• Most medial point on the

curve.• Nb-LC-Nasal Base-Upper lip

contour

OCCLUSAL CANT

LIPS• Extremely critical to overall esthetics. • Lip symmetry should be evaluated.• Asymmetry caused by

• eg, cleft lip, • facial nerve dysfunction, • underlying dentoskeletal asymmetry• scarring due to previous trauma• congenital unilateral microsomia or

macrosomia).

• The lower lip generally exhibits 25% more vermilion than the upper lip, and the lips should be 0 to 3 mm apart in repose.

• In patients with closed bites, the lips and tooth-lips relation should be evaluated with the lips relaxed and the jaws moved apart until the lips just part (closed bites may be due to maxillary vertical deficiency or severe deep bites).

• Accentuation of Cupid's bow of the upper lip may lead to exposure of only the maxillary central incisors

AVERAGE VALUES IN THE EVALUATION FROM FRONTAL

VIEW1.Forehead, eyes, orbits and nose are evaluated for

symmetry, size and deformity.2.Normal intercanthal distance 32 ± 3 mm for whites

35 ± 3 mm blacks 3.Normal interpupillary distances 65 ± 3 mm.4.The inter canthal distance, alar base width and

palpebral tissue width should all be equal.

5. Width of nasal dorsum should be one half the intercanthal distance and width of the nasal lobules should be 2/3rd the intercanthal distance.

6. A vertical line through the medical canthus and perpendicular to the pupillary line should fall on the alar bases ± 2 mm.

7. The upper lip length is measured from sabnasale to upper lip stomion (22 ± 2 mm for males and 20 ± 2 mm for females).

8. A normal upper tooth – to lip relationship exposes 2.5 ± 1.5 mm of incisal edge to lips.

9. The facial midline, nasal midline, lip midline dental midline all should be in line and face should be reasonably symmetric, vertical and transversely.

10. During smiling the vermilion of the upper lip should fall at the cervicogingival margin with no more than 1 to 2 mm of exposed gingival. The amount of upper lip elevation may be affected by

i. Anteroposterior positioning of maxilla and mandible ii. Amount of overjet/overbite iii. Angulation of the anterior dentition iv. Occlussal plane angulationv. Clinical crown length vi. Neuromuscular function.

11. The distance from glabella to subnasale and subnasale to menton should be approximately in a 1:1 ration, providing that the upper lip length is normal.

12. The length of the upper lip should be 1/3rd the length of the lower facial third, which is lower lip stomion to soft tissue menton should be twice the vertical dimension of the upper tip, provided that the upper lip is normal in length.

•Lateral/profile analysis

PROFILE / LATERAL FACE ANALYSIS

• Upper third of the face• Middle third of the face.

– Nose– Cheeks/Zygomatic projection– Paranasal areas

• Lower third of the face– Lips

• Upper lip length• Inter labial gap

– Labio-mental Fold– Nasolabial angle– Chin

• Mentalis habit– Chin-Throat area

• Submental volume• Mandibular angle pattern

• Static & dynamic information

• Natural head position• Incisor exposure with relaxed

lip• Lip insufficiency• Facial volume• Smile line• Hyperactive metalis• Tongue position

UPPER THIRD OF THE FACE

• The supraorbital rims normally project 5 to 10 mm beyond the most anterior projection of the globe of the eye.

• Check for • Frontal bossing• supraorbital hypoplasia• Exophthalmos• Enophthalmos.

MIDDLE THIRD OF THE FACE

• Middle third of the face includes

–Nose–Cheeks/Zygomatic projection

–Paranasal areas

THE NOSE

Evaluation

• Scars, soft tissue thickness and evidence of previous surgeries noted

• includes functional and esthetic examination of internal as well as nasal structures

NOSE

• Dorsum • Normal• Convex• Concave.

• The projection of the nasal bridge should be anterior to the globes (5 to 8 mm).

• The appearance of the nasal tip is evaluated for the presence of a supratip break and for tip definition and projection .

• It is important to distinguish between a dorsal hump and a turned down tip, since the implications for treatment are entirely different.

• The possible effect of maxillary surgery on the nose should be kept in mind when evaluating the proportions of the base of the nose

AVERAGE PARAMETERS

FOR THE NOSE The nasal dorsal length should fill most of the middle

3rd of face. No more than 1/3rd of vertical length of nares should

be visible from the frontal view. The normal nasolabial angle ranges from 90 ± 105º. The normal nasal projection angle is 34º for females,

36º for males.

The collumella should extend 3 to 4 mm below the lateral alar rims.

The distance from the base of he nose to anterior extent of the nares, and that from the anterior aspects of the nares to tip of the nose should be 2:1 ratio

Intranasal examination done to find out any septal deviation, any existing airway obstruction, hypertrophied turbinates, nasal polyps, nasopharyngeal adenoids.

CHEEKS

• The globes generally project 0 to 2 mm ahead of the infraorbital rims, while the lateral orbital rims lie 8 to 12 mm behind the most anterior projection of the globes

The cheeks should exhibit a general convexity from cheek bone apex to the commissure of the mouth.

This line starts just anterior to the ear, extending forward through the cheekbone, then anteroinferiorly over the

maxilla adjacent to the alar base of the nose, and ending lateral to the commissure of the mouth

Cheekbone-nasal base-lip curve contour

LOWER THIRD OF THE FACE

• Examination includes • Lips • Labiomental fold• Nasolabial angle• Chin• Chin-throat area

LIPS

• The protrusion, retrusion, and soft tissue thickness of each lip is evaluated with the lips in repose.

• The upper lip usually projects slightly anterior to the lower lip.

• The lips positions relate to the underlying dental position, such as maxillary dental protrusion or lack of upper lip support caused by, for example,

• Class II, division 2 malocclusion • excessive orthodontic retraction of maxillary incisors.

• An individual with an excessive increase in lower lip vermilion and a deep labiomental fold often also has a Class II, division 1 malocclusion.

• The subnasale-pogonion line, also called the lower facial plane, is an important guide in assessing the lip position and planning orthodontic and surgical positioning of the incisors, as well as surgical positioning of the chin.

• The upper lip should be 1-3 mm ahead of this line • The lower lip 1-2 mm ahead of this line.

• Extractions followed by retraction of incisors behind the subnasale pogonion line should be avoided.

LABIOMENTAL FOLD• The lower lip-chin contour should have

a gentle S-curve, with a lower lip-chin angle of at least 130 degrees.

• The angle is often acute in cases of Class II mandibular anteroposterior deficiency because of impingement of the maxillary incisor on the lower lip or macrogenia.

• The angle is flattened in individuals with microgenia or lower lip tension caused by Class III malocclusion.

Nasolabial angle

NASOLABIAL ANGLE

• The nasolabial angle, which is measured between the inclination of the columella and the upper lip , should be in the range of 85 to 105 degrees.

• In females a slightly larger angle is acceptable, while a smaller angle is considered esthetically pleasing in males.

• Surgical or orthodontic re traction of maxillary incisors should be avoided in individuals with large nasolabial angles.

• Where crowding necessitates tooth extraction, the nasolabial angle should influence the deci sion to extract first versus second premolars.

• Surgical repositioning of the maxilla also affects the nasolabial angle. In general, the maxilla should never be moved posteriorly, especially in combination with superior repositioning.

• This surgical movement leads to loss of lip support, increase in nasolabial angle, increase in nasal projection, and flattening of the nasal base.

CHIN

• The chin should, however, be evaluated in all three dimensions. The width of the chin should be assessed in relation to the overall facial shape.

• A narrow chin often has a knobby appearance, and if surgical advancement of the chin is planned, widening of the chin should be contemplated.

• The labiomental fold, chin shape, relation to the dental midline, symmetry, and cant of the lower border should be considered

CHIN-THROAT AREA• The presence of a "double" chin and adipose tis sue should

be noted. The chin-throat angle (normally 110 degrees) provides chin definition.

• The distance from the neck-throat angle to the soft tissue pogonion should be approximately 42 mm.

• These observations are pertinent when considering mandibular setback or advancement procedures, genioplasty (advancement or reduction), or submental liposuction.

Chin throat angle

AVERAGE VALUES IN THE PROFILE / LATERAL FACE ANALYSIS

Most valuable in assessing vertical and anteroposterior problems of the jaws:

1.The distance form glabella to subnasale and from subnasale to soft tissue menton should be in a 1:1 ratio if the upper lip length is normal.

2.With the maxilla in normal AP position and the upper lip in normal thickness, ideal chin projection is 3 ± 3 mm posterior to a line through subnasale that is perpendicular to a clinical Frankfort horizontal.

3.The morphologic characteristics and relationships of the nose, lips, cheeks and chin are evaluated.

4. The length of the upper lip should be 1/3rd the length of lower facial height (third). Lower lip stomion to soft tissue menton should be twice the vertical dimension of the upper lip if the upper lip is normal in length.

5. Upper lip suprabasale should be 1 to 3 mm anterior to subnasale

6. A line perpendicular to Frankfort horizontal and tangent to the globe should fall on the infraorbital soft tissues within 2 mm.

• Cephalometrics for orthognathic surgery burstone 1978 april Journ. of oral surg

• Quadrilateral analysis- By Di-paolo AJO-DO 1984 Dec

• Proportionate mesh analysis AJO 1987 JUN

•More recent venture into Cephalometric treatment planning and predictions has been VIDEOIMAGING

COGS – CEPHALOMETRICS FOR ORTHOGNATHIC SURGERY

• Developed at university of Connecticut

• Based on a system from Indiana University and further developed by additions at Connecticut

PLANE OF REFERENCE FOR COMPARISON

• A constructed plane called Horizontal Plane which is surrogate Frankfort Horizontal plane constructed by drawing a line 70 from SN plane

• Most measurements will be made from projections either parallel or perpendicular to the Horizontal Plane

COGS

Chosen landmarks and measurements can be altered by various surgical procedures.

The appraisal includes all facial bones and a cranial base reference.

Rectilinear measurements can be readily transferred to a study cast for mock surgery.

H-P lineBaseline for comparison of most data

Constructed planeBy drawing a line 7 ° to SN

Cranial Base

Ar-N:length of the cranial baseIt is not an absolute value,Proportionate value , so that can becorrelated with mandibular ,maxillary lengthsMean value is 50 ± 3

1) PTM – N Males = 52.8 +/- 4.1 mm females= 50.9 +/- 3.0 mmIndicates-the position of Posterior border of maxilla in relation to NasionIncreases – more posterior position of maxillaDecreases- anterior position of maxilla

3.Ar-PTM : --Measure horizontal distance b/tpoterior aspects of mandible &maxilla.The greater the distance,the more themandible will lie posteriorly to maxillaMales=37.1 ± 2 mmFemales = 32.8 ± 1.9 mm

B. HORIZONTAL SKELETAL PROFILE

1. N-A-Pg = angle of skeletal facial convexity -- Measurement doesn’t indicate if due to maxilla or mandible + angle-convex face - angle –concave face Mean : Males : 3.9 ± 0.4 ° females: 2.6 ± 5.1 °

A perpendicular to HP drawn through N. The inferior anatomic point is horizontally measured

in relation to the superior structure, with + being anterior and – being

posterior.

2.N-A : horizontal position of A is measured to this Perpendicular .

measurement describes the horizontal position of

Apical Base of the maxilla in relation to N ---to determine if anterior part of maxilla is

protrusive or retrusive. Mean : males= 0.0 ± 3.7mm ; females = -2.0 ±

3.7 mm

3.N-B : horizontal position of B is measured to this Perpendicular

Indicates: apical base of mandible in relation to nasion.

males= -5.3 ± 6.7 mm ; females= -6.9 ± 4.3 mm

4.N-Pg : prominence of chin This describes the position of chin in

relation to nasion. MEAN: MALES = -4.3 ± 8.5 mm ; females = -6.5 ±

5.1

Horizontal Measurements

Diagnosis of:• Horizontal maxillary hypolasia/hyperplasia• Horizontal mandibular hypo/hyperplasia• Horizontal genial hypo/hyperplasia

Used in planning of treatments:• Augmentation /reduction genioplasty• Ant mandibular horizontal advancement or reduction

• Total mandibular horizontal advancement or reduction

Vertical Measurements

• c. Vertical skeletal dysplasia 1. middle 1/3 facial ht (N-ANS) ╧ HP Anterior components males= 54.7+/- 3.2mm females= 50 +/- 2.4mm Indicates any increase or decrease in middle facial third height

2. lower 1/3 facial ( ANS- Gn ) ╧ HP males = 68.6 +/- 3.8mm

females= 61.3 +/- 3.3mm Indicates – increased or decreased anterior lower facial third

height

3. posterior maxillary ht- PNS- N Value-50.6 +/- 2.2 mm --- length of perpendicular line from HP intersecting PNSIndicates- Increase or decrease posterior maxillary height

4. MP-HP angle = relates the posterior facial divergence with respect to anterior facial height.

Indicates – increase or decreased posterior facial divergence.

Helps in Diagnosis of:• anterior , posterior or total vertical maxillary hyperplasia or hypoplasia.

• clockwise or counterclockwise rotations of maxilla and the mandible.

VERTICAL DENTAL DYSPALSIA• Anterior component: Anterior maxillary height : upper1-NF • Mean value- 27.5 + 1.7 mm

perpendicular distance from incisal edge of upper incisor to NF is measured

indicates - Increased or decreased upper anterior dental height

Anterior mandibular height : lower1 – MPMean value- 40.8 + 1.8 mm

a perpendicular line is dropped from the edge of lower incisor to MPIndicated – increase or decrease lower anterior facial height.

• Posterior conponent: Posterior maxillary height :Upper 6 – NFMean value- 23.0 + 1.3 mm perpendicular line is dropped from tip of mesiobuccal cusp of upper

first molar to NFIndicates – Increased or decreased upper posterior dental heights

Posterior mandibular height : Lower 6 – MPMean value- 32.1 + 1.9 mm• Perpendicular line is dropped from mesiobuccal cusp of lower first molar

to MP• indicates – increased or decreased lower posterior dental height

Maxilla and Mandible

1. PNS- ANS: Total Effective Length of Maxilla With ANS-N And PNS-N Males = 57.7 ± 2.5 Mm Females =52.6 ± 3.5mm

2. Ar- Go ( Linear): Length of Mandibular RamusMales= 52±4.2 Mm Females =46.8±2.5mm Variation in ramal height can be a causative factor for skeletal open

bite or deep bite.

3. Go- Pg (Linear): Length of Mandibular BodyMales = 83.7±4.6mm Females = 74.3±5.8mm

. B- Pg : Prominence of chin relation to mandibular Denture base

males = 8.9 ± 1.7mm; female = 7.2 ± 1.9mm By comparing with N-Pg distance chin prominence relation to face

5. Ar- Go- Gn ( gonial angle)Mean value is 122 + 6.9 mmGonail angle also contributes to skeletal open or deepbite

Diagnosis of:• variations in ramus height that effect open

bite or deep bite• increased dimension of mandibular body

length• acute or obtuse Go angles• assesment of chin prominence • prominence of chin related to mandibular

denture base.• by relating to N-Pog asses the prominence of

the chin in relation to the face.

ASSESSMENT OF DENTAL ANOMALIES

• OP : line drawn from the buccal groove of both first permanent molars through a point 1mm apical to the incisal edge of the central incisor in each arch

1.OP angle: upper- HP,OP lower – HPmales= 6.2 ± 5.1mm females =7.1 ± 2.5mm

Increased OP-HP is associated with skeletal open bite lip incompetence and increased anterior facial height.

Decreased OP – HP is associated with skeletal deep bite decrease anterior facial height and lip reduncy.

2.A-B: measuring the distance between projection of point A and Point B on OP

This gives us relationship between maxillary and mandibular apical bases in relation to OP

relationship of maxillary and mandibular apical base to OPmales= -1.1±2.0mm females = -0.4 ± 2.5mm

Diagnosis of:• Increased OP-HP :skeletal open bite,lip

incompetence,increased facial hieght,retrognathia

• Decreased OP-HP:

• A-B: large A-B with point B posterior to point A ,mandibular denture discrepancy that predisposes to class II malocclusion.

3. upper incisor – NF angle done by intersecting a line passing through the tip of incisal edge through the root tip of upper incisor and NF line

males = 111.0 ±4.7° females = 112.5± 5.3°Gives us the inclination of upper incisors in relation to palatal plane

4. lower incisor - MP angle intersecting a line joining the incisal edge of lower incisors passing through its root tip and MP

males = 95.9 ± 5.2° females = 95.9 ± 5.7mm

Indicates inclination of lower incisor in relation to MP

CEPHALOMETRIC LANDMARKS

CEPHALOMETRIC LANDMARKS• Glabella(G)- the most prominent point in the

midsagittal plane of the forehead.

• Columella (Cm)- The most anterior point on the columella of the nose.

• Subnasale(Sn)- the point at which the nasal septum merges with the upper cutaneous lip in the mid sagittal plane.

• labrale superius (Ls)-a Point indicating the mucocutaneous border of the upper lip.

• Stomion superius(Stms)- the lowermost point on the vermilion of the upper lip.

• Stomion inferius (Stm)- the uppermost point on the vermilion of the lower lip.

• labrale inferius (Li)- a Point indicating the mucocutaneous border of the lower lip.

• Soft tissue pogonion (Pg’): The most anterior point on soft tissue chin.

• Soft tissue gnathion (Gn’). The constructed midpoint between soft tissue Pogonion and soft tissue menton. and can be located at the intersection of subnasale to soft tissue pogonion line and the line from C to Me’.

• Mentolabial sulcus(Si)- the point of greatest concavity in the midline between lower lip(Li) and chin(Pg’).

• Soft tissue Menton (Me’). The most inferior point on the contour of the soft tissue chin; found by dropping a perpendicular from horizontal plane through menton.

• Cervical point (C)- the innermost point between the submental area and the neck located at the intersection of lines drawn tangent to the neck and submental area.

•Angle of facial convexity•Lower neck face angle•Lower vertical height-depth ratio

•Anteroposterior maxillary & mandibular measurements•Vertical facial height proportionality

• Facial convexity angle – by G-Sn line and Sn-Pg’ line• Standard value – 12 + 4 • Any Increase or decrease in this value indicates convex or concave profile

• Maxillary prognathism- distance between sn and a line perpendicular to HP passing through glabella gives maxillary prognathism

• Negative no. indicates retrognathism

•Mandibular prognathism - Distance between Pg and a line perpendicular to hp passing through G gives mandibular prognathism.

•Vertical height ratio:- ratio between G-Sn and Sn-Me’ • Increased ratio suggest increased middle third height

Lower face throat angle: it is the angle formed by intersection of Sn-Gn’ and Gn’- C

This angle affects treatment planning to correct anterio posterior facial dysplasia

• Lower face vertical height depth ratio :- It is obtained by diving Sn-Gn’ distance with C-Gn’

• - - larger than 1 value indicate patient has relatively short neck.

• Nasolabial angle:- Formed by intersection of Cm-Sn line and Sn-LS line

• Lower than normal nasolabial angle suggests proclination of upper incisors or anterior maxillary base

• Higher than normal nasolabial angle suggest retroclination of upper incisors or anterior maxillary base.

•Upper lip Protrusion : - It is perpendicular distance between Ls- Sn-pg’line .

• Lower lip protrusion :- It is perpendicular distance between Li to Sn-pg’ line .

• Mentolabial sulcus depth :- It is perpendicular distance between deepest point on the Mentolabial sulcus to Li - Pg’ line.

• --- The depth of sulcus is affected by various factors which are – flared lower incisors, flaccid lower lip tone, extruded upper incisors causing rolling of lower lip and prominence of lip.

• Vertical Lip : Chin Ratio- it is ratio between Sn-stms and stmi - Me’

• Whenever the value decreases vertical reduction genioplasty should be considered

• Maxillary incisor exposure :- It is obtained by measuring the distance between tip of upper central incisor and stms

• Increased incisor exposure would be may be due to vertical maxillary excess

Or short upper lip.

• Interlabial Gap :- It’s the distance between Stms and stmi • Pt with vertical maxillary excess tend to have a large interlabial gap and

lip incompetence.

MODEL SURGERY

•Model surgery simulates actual surgery, in the dental arch models of the patient. It gives the three dimensional understanding of the post operative relationship of the jaws.

MAJOR AIMS OF THE MODEL SURGERY

1.To get the definite idea about the extent of bone / arch advancement or reduction required in the surgery.

2.To get a post-operative relationship of the jaws, dentition and occlusion.

3.To decide about the post-surgical orthodontic treatment.

4.As a vehicle for fabrication of splints for stabilization after surgery.

ARMAMENTARIUM:

• 1) A fret saw and fine blades (size M2) or a 10cm (4 inch) fine fiber or metal cutting disc mounted on a lathe.

• 2) Hand-piece and motor.• 3) A steel fissure bur.• 4) A plaster bur or an Ash acrylic cutter pear.• 5) Surgical scalpel blades, NO.10 or 20.• 6) Plaster knife, Spatula, 15 cm(6 inch) rubber bowl.

• Bunsen burner, spirit lamp,or soldering iron.

• 8) Wax knife and carver.

• 9) Soft ribbon wax, hard modeling and sticky wax.

• 10) 15cm (6inch)flexible ruler.

• 11) Spring dividers(15cm /6 inch)

• 12) Plane line hinge articulator, and face bow.

DIAGNOSTIC SET-UP

• A diagnostic set up is employed to be sure that it will be possible to get the teeth to fit together if a given orthodontic treatment plan is employed.

Diagnostic pre-orthodontic set-up showing the proposed extractions and tooth movements.

Method: Individually remove the tooth from the dental cast and reset the tooth in soft wax so that their alignment and interdigitation can be observed.

METHODS OF MODEL SURGERY:

•Simple method

•Anatomically oriented model surgery.

ANATOMICALLY ORIENTED MODEL SURGERY

• In complex cases, especially where multiple bimaxillary movements are required, it is essential to use a more refined technique such as the following variant of a popular “North American method”

TECHNIQUE:

• In this technique, in addition to the impressions and sqash bite, a face-bow recording is taken

• The working models are anatomically trimmed and articulated on the semi adjustable articulator using the face-bow recording and then the standard squash bite

2. Horizontal and vertical reference lines are drawn on the mounting plaster to register the post-operative position of each maxillary and mandibular segments before surgery.

Two sets of parallel horizontal lines A/A and B/B are drawn on the upper and lower models. These are easily done by rotating the detached model with the felt pen

•The B lines should be just clear of the apices of the teeth, and not less than 15mm from the A lines. The actual distance between the A and B lines is then recorded on the plaster. These lines will be used to plan the vertical movements.

3. Three vertical lines VC, VB, VM are drawn from upper base line (A) to the lower baseline (A) on each buccal segment.

These lines pass through the buccal surfaces of the upper cuspid, bicuspid and the distal cusp of the last upper molar tooth., and they are extended to their occluding partners.

These will help to indicate the anteroposterior movements achieved by the model surgery.

Upper and lower midlines are also drawn.

Marked models with the recorded distances.

4. The vertical distances from the buccal cusp tips of the three reference teeth to their A base lines are recorded to help calculate any vertical movements.

Transverse changes are recorded by the inter-canine and inter-molar distances measured across the palate and recorded by taking reference points on the canine tips and the mesiobuccal cusp of the first molars.

Cuspal reference points are used for transverse changes.

When all the reference lines have been drawn and the measurements completed, the osteotomy lines are drawn between A and B lines to correspond with the bone cuts.

The plaster mounting assembly is then sectioned at the

osteotomy sites with a saw or large abrasive disc and the whole arch or segments are repositioned in the planned post-operative position

Interrupted line is the proposed osteotomy site.

osteotomy lines

After making the horizontal cut, rotate the dental midline on the model to match the facial midline on the mounting plaster.

This will rotate the model VB and VM on the deviated side forwards and the contra-lateral side VB and VM lines backwards.Carefully mark their new positions.

Additional forward movements are then measured from these new verticalreferences

Maxilla is reassembled with the wax after the osteotomy cuts. Mandible closes in to the intermediate occusal relationship. Intermediate wafer is made at this stage.

Lower segmental set-down of 3mm is carried out with the forward slide of 5mm to correct the interarch occlusal relationship.

Anterior view: models showing the upper midline split to widen the intercanine width and the lower anterior set-down.

CLASSIFICATION OF DENTOFACIAL

DEFORMITIES• I-According to jaw involved -maxilla -mandible -combination of both

• II- ACCORDING TO PLANE - TRANSVERSE - VERTICAL - ANTEROPOSTERIOR

• ALSO CLASSIFIED AS- - SKELETAL CLASS I - SKELETAL CLASS II - SKELETAL CLASS III

CLASS I DENTOFACIAL DEFORMITIES

• CLASS I VERTICAL MAXILLARY EXCESS

• CLASS I VERTICAL MAXILLARY EXCESS WITH OPEN BITE

CLASS II DENTOFACIAL DEFORMITIES

• CLASS II DENTOFACIAL DEFORMITIES SECONDARY TO MANDIBULAR DEFICIENCY

• CLASS II DENTOFACIAL DEFORMITIES SECONDARY TO VERTICAL MAXILLARY EXCESS

• CLASS II DENTOFACIAL DEFORMITIES SECONDARY TO VERTICAL MAXILLARY EXCESS AND MANDIBULAR DEFICIENCY

• CLASS II DENTOFACIAL DEFORMITIES WITH OPEN BITE

CLASS III DENTOFACIAL DEFORMITIES

- CLASS III DENTOFACIAL DEFORMITIES SECONDARY TO MANDIBULAR PROGNATHISM

- CLASS III DENTOFACIAL DEFORMITIES SECONDARY TO MAXILLARY DEFICIENCY

A-P VERTICAL TRANSVERSE- CLASS III DENTOFACIAL DEFORMITIES SECONDARY TO

MAXILLARY DEFICIENCY AND MANDIBULAR PROGNATHISM- CLASS III DENTOFACIAL DEFORMITIES WITH OPEN BITE

CONDITIONS COMMON TO CL I, CL II AND CL III DEFORMITIES

• TRANSVERSE MAXILLO-MANDIBULAR DISCREPANCIES

• BIMAXILLARY PROTRUSION CLASS I CLASS II CLASS III

TYPES OF SURGERY• 1 MANDIBULAR SURGERY

• 2 MAXILLARY SURGERY

• 3 COMBINATION OF BOTH

MANDIBULAR SURGERY• 1 RAMUS OSTEOTOMY

• 2 BODY OSTEOTOMY

• 3 COMBINATION OF BOTH

• 4 SUB APICAL OSTEOTOMY

• 5 GENIOPLASTY PROCEDURES

RAMUS OSTEOTOMY• 1 OSTEOTOMY IN THE CONDYLAR NECK• 2 VERTICAL OSTEOTOMY• 3 VERTICAL OBLIQUE OSTEOTOMY• 4 INVERTED ‘L’ OSTEOTOMY• 5 SAGITTAL SPLIT OSTEOTOMY• 6 HORIZONTAL OSTEOTOMY IN THE RAMUS

BODY OSTEOTOMY• 1 ANTERIOR BODY OSTEOTOMY

• 2 POSTERIOR BODY OSTEOTOMY

CONDYLAR NECK OSTEOTOMY

• GIVEN BY BERARD IN 1898• ADVANTAGES :• 1. SIMPLE TO PERFORM• 2. SHORTER OPERATING TIME• 3. SCARRING IS NEGLIGIBLE• 4. NO INJURY TO MANDIBULAR NERVE• 5. TEETH NOT SACRIFICED

VERTICAL OSTEOTOMY

GIVEN BY CALDWELL AND LETTERMAN IN 1954

CORRECTION OF PROGNATHISM MORE THAN 10 TO 12 MM.

VERTICAL OBLIQUE OSTEOTOMY• ALSO CALLED AS SUB CONDYLAR OSTEOTOMY OR SUB

CONDYLOTOMY • TWO TYPES :• 1 EXTRA ORAL • 2 INTRA ORAL• MODIFICATION OF VERTICAL OSTEOTOMY• EXTRA ORAL WAS GIVEN BY HINDS,ROBINSON AND THOMA IN 1957.• MODERATE PROGNATHISM CORRECTED

INTRA ORAL OBLIQUE OSTEOTOMY

• WAS GIVEN BY WINSTANLEY IN 1968

SAGITTAL SPLIT OSTEOTOMY• WAS GIVEN BY OBWEGESER IN 1957• WIDE VARIETY OF CHANGES AND MOVEMENT POSSIBLE• SURGICAL MODIFICATION OF TRAUMATIC FACTORS• MODIFIED BY DAL PONT• OTHER MODIFICATION DONE BY BELL AND SCHENDEL

INVERTED ‘L’ OSTEOTOMY

HORIZONTAL OSTEOTOMY OF RAMUS

• WAS GIVEN BY BLAIR IN 1907• MODIFIED BY KAZANZIAN IN 1941

BODY OSTEOTOMY

• ANTERIOR BODY OSTEOTOMY

• POSTERIOR BODY OSTEOTOMY

• GIVEN BY BLAIR IN 1907

DISTRACTION OSTEOGENESIS• Distraction osteogenesis is a technique that relies

on the normal healing process that occurs between controlled, surgically osteotomized bone segments.

• De novo bone lengthening occurs by gradual, controlled distraction. In contrast to traditional approaches, the soft tissue envelope (the skin, muscle, and neurovascular structures) is simultaneously expanded, which stabilizes the skeletal reconstruction.

• The technique today is an important part of the reconstructive surgeon's armamentarium.

A NEW SYSTEM FOR COMPUTER-AIDED PREOPERATIVE

PLANNING AND INTRAOPERATIVE NAVIGATION DURING

CORRECTIVE JAW SURGERY

A new system for computer-aided corrective surgery the jaws has been developed and introduced clinically and it combines 3D surgical planning with conventional dental occlusion planning.

TITB-00229-2005.R2

• The developed software allows simulating the surgical correction on virtual 3D models of the facial skeleton generated from CT scans.

• Surgery planning and simulation include dynamic cephalometry, semi-automatic mirroring, interactive cutting of bone and segment repositioning. By coupling the software with tracking system and with the help of a special registration

REFERENCES• 1) WIKIPEDIA : ORTHOGNATHIC SURGERY

• 2) ESSENTIALS OF ORTHOGNATHIC SURGERY 2ND EDITION – JOHAN P. REYNEKE

• 3) THE CURRENT CONCEPTS OF ORTHODONTIC DISCREPANCY STABILITY - OPEN JOURNAL OF STOMATOLOGY, 2014, 4, 184-196

• 4) Facial Aesthetics: 2. Clinical Assessment Dent Update 2008; 35: 159-170

• 5) SHRIDHAR PREMKUMAR – 2ND EDITION

• 6) A NEW SYSTEM FOR COMPUTER-AIDED PREOPERATIVE PLANNING AN INTRAOPERATIVE NAVIGATION DURING CORRECTIVE JAW SURGERY - THIS WORK WAS FUNDED BY THE SWISS NATIONAL CENTER OF COMPETENCE IN RESEARCH "COMPUTER AIDED AND IMAGE GUIDED MEDICAL INTERVENTIONS (CO-ME)", AND THE AO/ASIF FOUNDATION, DAVOS, SWITZERLAND. ASTERISK INDICATES CORRESPONDING AUTHOR.