786Angle Orthodontist, Vol 76, No 5, 2006 DOI: 10.2319/080405-263

Original Article

Mandibular Growth during Adolescence

Aisha Souza Gomesa; Eduardo Martinelli Limab

ABSTRACTObjective: To evaluate the mandibular growth of whites according to Fishman’s method.Materials and Methods: Eighty-five subjects, 9 to 18 years of age, were selected from the filesof the Department of Orthodontics, Pontificia Universidade Catolica do Rio Grande do Sul, PortoAlegre, Brazil. Patients were evaluated at two time points. At T1, they had a lateral head film anda hand-wrist radiograph and at T2, a lateral head film. The interval between T1 and T2 was 5 to24 months. Subjects presented a Class I or II skeletal pattern and were divided into three groupsaccording to Fishman’s method: group I, in an accelerating growth velocity phase; group II, inpeak of growth velocity phase; and group III, in decelerating growth velocity phase. The cepha-lograms were manually traced and cephalometric points digitalized into DentoFacial Planner Plus2.0. The absolute growth amount was adjusted to obtain an annual growth rate (mm/y). The annualgrowth rate was compared between sexes, between individuals with Class I or II skeletal patterns,and among the three groups.Results: Mandibular annual growth rate in puberty was 2.16 mm for the mandibular body length,3.16 mm for the ramus height, and 4.31 mm for the mandibular length. The results did not showsignificant differences between sexes, skeletal patterns, and groups, although there was a ten-dency for growth acceleration in group II.Conclusions: There is great individual variation in mandibular linear growth.

KEY WORDS: Skeletal maturation; Mandibular growth

INTRODUCTION

Research on facial growth and development is es-sential in orthodontics for a state-of-the-art diagnosis,prevention, interception, and correction of malocclu-sions. A knowledge of these events will improve treat-ment planning because most orthodontic treatmentstake place during growth.1 The growth and develop-ment events must be correlated with the maturationallevel of each individual to identify the residual growthand the subject’s skeletal pattern and to decide on aproper treatment plan. The chronological age is not

a Private Practice, Departamento de Ortodontia, PontificiaUniversidade Catolica do Rio Grande do Sul, Porto Alegre, RS,Brazil.

b Department Head, Departamento de Ortodontia, PontificiaUniversidade Catolica do Rio Grande do Sul, Porto Alegre, RS,Brazil.

Corresponding author: Dr. Aisha Souza Gomes, Departa-mento de Ortodontia, Pontificia Universidade Catolica do RioGrande do Sul, Porto Alegre, RS, Brazil. R. Ulisses/cabral 255/4, Porto Alegre, Rio Grande do Sul 91330-520, Brazil(e-mail: aishagomes@hotmail.com)

Accepted: October 2005. Submitted: August 2005.� 2006 by The EH Angle Education and Research Foundation,Inc.

adequate to compare different subjects because mostpeople show a discrepancy between chronologicalage and maturational events.2 Among several matu-rational indicators, skeletal development appears to bequite a simple and accurate one. Bone age is deter-mined by radiographs, relating the appearance anddevelopment of certain bones with the maturationalstages.3–6

This knowledge is useful to obtain a more specificdiagnosis.7 Treatment modalities such as rapid palatalexpansion, protraction mask, extraoral traction, andother orthopedic devices will obtain better resultswhen applied in certain developmental phases.4 Dur-ing adolescence the treatment cooperation usually isbetter and the skeletal changes are enhanced, leadingto a shorter treatment time.8–10

Considerable attention is paid to the mandibulargrowth because it is reported that this bone enlargesthe most during adolescence.11,12 It is common sensethat the lower jaw grows in a posterior-superior direc-tion resulting in an anterior-inferior displacement.13,14

Hunter15 in 1771, as well as Humphry16 in 1866, dem-onstrated that mandibular sagittal growth is due toposterior deposition and anterior resorption in the ra-mus. Although the mandibular growth sites and direc-

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Figure 1. Cephalometric tracing, cephalometric landmarks, and lin-ear measurements.

tion are well established, the presence of growthspurts is still controversial. Some authors agree thatmost individuals experience mandibular growthspurts,5,17–19 whereas others state that the growthspurts are common but not universal.20,21 Moore et al22

believe that mandibular growth spurts may occur, butnot in a uniform amount and duration.

The aim of this study is to determine mandibulargrowth velocity in white subjects during adolescence.Furthermore, it is intended to compare mandibulargrowth velocity among different stages of adolescence(accelerating, peak, or decelerating phase).

MATERIALS AND METHODS

The sample was composed of 85 white adolescentorthodontic patients, between 9 and 18 years of age(46 females and 39 males), residents of Porto Alegre,previously treated at Pontificia Universidade Catolicado Rio Grande do Sul (PUCRS), Brazil. The criteria forsample selection demanded ANB angle between 0�and 6�. In this manner, subjects with skeletal Class IIIand severe skeletal Class II were excluded. Further-more, patients should not have any missing teeth orsyndromes, cleft lip or palate, or any kind of pathology,and they should not use any type of medication thatcould affect growth.

The subjects had a Class I (49 individuals) or ClassII (36 individuals) skeletal pattern. The patients hadundergone minor orthodontic problems such as pos-terior crossbites, anterior open bite, and mild to me-dium crowding and were treated with removable ex-pansion devices with or without a palatal grid, Nancelingual appliances, and, in 13 cases, fixed edgewiseappliance.

Each patient was observed at two time points. Thefirst evaluation (T1) included a lateral head film and ahand-wrist radiograph and the second evaluation (T2),a lateral head film. The interval between T1 and T2ranged from 5 to 24 months. The lateral head filmswere manually traced by one examiner, and the ceph-alometric points were digitalized into the DentofacialPlanner Plus Software (DFP Plus 2.0) for cephalo-metric measurements.

This study used the following cephalometric land-marks: Nasion (N), point A (A), point B (B), Condylion(Co), Gonion (Go), and Gnathion (Gn). ANB angle wasused for the determination of skeletal facial type. Thethree linear measurements for the determination ofmandibular growth were mandibular body length (dis-tance between Go and Gn), mandibular ramus height(distance between Co and Go), and mandibular length(distance between Co and Gn) (Figure 1).

The hand-wrist films were evaluated by the sameexaminer and classified according to Fishman’s meth-

od into 11 stages. This method was elected becauseit is very clear and easy to apply and it focuses onskeletal maturational index during adolescence.

The absolute growth amount was obtained by sub-tracting the T1 values from T2 values. Absolute growthamounts were divided by the number of months be-tween the two evaluations and multiplied by 12 to es-tablish an annual growth rate (mm/y).

The subjects were divided according to their bonematuration level into group I (accelerating phase orFishman stage 1–3), group II (peak of growth velocityphase or Fishman stage 4–7), and group III (deceler-ating phase or Fishman stage 8–11). Table 1 showsthe sample division according to sex, maturationalstage, and skeletal pattern. The annual growth ratewas compared between sexes, between individualswith skeletal Class I or II, and between the threegroups.

Intraexaminer study error was made with 12 lateralfilms that were randomly chosen and were retraced bythe same examiner 45 days after the first cephalo-metric tracing. For the statistical analysis, the Stu-dent’s t-test (95%), Mann-Whitney test, and Kruskall-Wallis test (SPSS 10.0) were used. This study protocolwas approved by the Research and Ethics Depart-ment, Faculty of Dentistry, PUCRS, Brazil.

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Table 1. Sample Distribution

Variable f %

Maturational stage

Accelerating phase 50 58.8Peak of growth velocity 22 25.9Deccelarating phase 13 15.3Total 85 100.0

Sex

Female 46 54.1Male 39 45.9Total 85 100.0

Skeletal pattern

Class I 49 57.6Class II 36 42.4Total 85 100.0

Table 2. Intraexaminer Error Study (n � 12)

Measurement n Mean SD P

Mandibular body length (A) 12 71.34 4.44 .10Mandibular body length (B) 12 71.11 4.50

Mandibular ramus height (A) 12 47.56 4.04 .34Mandibular ramus height (B) 12 47.71 3.93

Mandibular length (A) 12 108.07 5.32 .23Mandibular length (B) 12 107.84 5.48

Table 3. Means, Standard Deviation, and Mann-Whitney TestComparing Mandibular Annual Growth Rates (mm/y) Between Skel-etal Class I and II Individuals (n � 85)

MeasurementSkeletalPattern Mean SD P

Mandibular body length Class I 2.31 2.14 .20Class II 1.96 2.77

Mandibular ramus height Class I 2.78 2.88 .17Class II 3.62 3.27

Mandibular length Class I 3.84 2.50 .18Class II 4.84 3.37

Table 4. Means, Standard Deviation, and Mann-Whitney TestComparing Mandibular Annual Growth Rates (mm/y) Between Sex-es (n � 85)

Measurement Sex Mean SD P

Mandibular body length Female 2.34 2.72 .76Male 1.95 2.00

Mandibular ramus height Female 3.18 3.41 .50Male 3.08 2.63

Mandibular length Female 4.23 2.64 .79Male 4.30 3.25

Table 5. Whole Sample Means of Mandibular Annual GrowthRates (mm/y) (n � 85)

Measurement Mean

Mandibular body length 2.16Mandibular ramus height 3.16Mandibular length 4.31

Table 6. Means, Standard Deviation, and Kruskall-Wallis TestComparing Mandibular Annual Growth Rates (mm/y) Between theThree Groups (n � 85)

Measurement Groups Mean SD P

Mandibular body length Group I 2.05 2.65 .20Group II 2.64 2.24Group III 1.81 1.66

Mandibular ramus height Group I 3.14 2.99 .78Group II 3.01 2.41Group III 3.34 4.34

Mandibular length Group I 4.02 2.69 .53Group II 5.01 3.44Group III 3.92 2.84

RESULTS

The results are shown in Tables 2 through 6. Theintraexaminer error study (Table 2) did not show sta-tistically significant differences between the first and

the second measurements in the cephalograms (P �.05). None of the linear measurements had a differ-ence greater than 1 mm.

There was no difference in mandibular growth be-tween Class I and II skeletal pattern individuals (Table3) and there was no significant difference between thesexes (Table 4).

Table 5 shows the mean growth velocity among thethree groups for each measurement. The mandibularannual growth rate in the adolescence phase was 2.16mm for the mandibular body length, 3.16 mm for theramus height, and 4.31 mm for the mandibular length.From Table 6, it is clear that the greatest mandibulargrowth velocity for two of the three measurements(mandibular body length and mandibular length) oc-curred in group II, although the amount was not statis-tically different from the other two groups. In the man-dibular length, the annual growth difference betweengroups II and III was greater than 1 mm.

DISCUSSION

Mandibular growth has been widely studied, espe-cially because of the late-adolescent growth spurt.11,12

From this study, it is clear that the mandibular growthamount is not significantly different in the various pu-bertal phases but that there is an accelerating tenden-cy in group II, especially for mandibular length andmandibular body length. A possible explanation for thestatistical results is the intense individual variation,which was noticed in this study once it was apparentthat the standard deviation values were larger than themeans. This individual variation has been reported byother authors.3,23–26 It should also be considered that

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11 individuals of group 1 were studied for more than18 months and they probably have changed their mat-urational stage.

The sample studied in this research comprisedwhite residents of Porto Alegre, Brazil. Southern Bra-zilian population is mainly composed of Portuguese,German, and Italian descents and could be represen-tative of a white population. Patients had undergoneminor orthodontic treatment, and some of them wereeven treated with fixed appliances. Such therapies donot influence linear mandibular growth. Only mandib-ular position could be affected, but that was not stud-ied here. Therefore, the results concerning mandibularbody length (Go-Gn), mandibular ramus height (Co-Go), and mandibular length (co-Gn) are reliable.

Among the linear measurements, ramus height pre-sented less variation in annual growth rates. It rangedfrom a lower value of 3.01 mm in group II to a highervalue of 3.34 mm in group III. Lima27 found rates of2.06 mm in males and 1.42 mm in females. However,subjects of that study were not classified according tomaturational stages.

The mandibular length showed an annual rate of3.92 mm for group III, which represented individuals inthe decelerating phase according to Fishman7. Forgroup I, which included subjects at the acceleratingphase, annual rates were similar, reaching 4.02 mm.The greatest velocity of growth for mandibular length(5.01 mm) occurred in group II, where individuals wereat the peak of growth velocity. No statistical differenc-es between groups were found for annual growthrates, but group II did present greater growth (close toone mm) than groups I and III, and this should be con-sidered in treatment planning.

Sato et al28 found that, in Japanese girls from 8 to18 years of age, the mandibular length measured fromcondylion to gnathion increased 17.84 mm. If thisamount was divided by 10 to obtain an annual rate, itwould be 1.78 mm/y. It has to be considered that inthis study rates were much higher because of the factthat the individuals in this study were at puberty,whereas in the Sato and coworkers report, the sub-jects were observed since childhood and it is expectedthat more growth will occur in our subjects since it wasduring puberty.

Mandibular body length showed lower annual ratesof 1.81 and 2.05 mm for groups III and I, respectively.In group II (peak of growth), the annual rates reached2.64 mm. The values found by Lima27 at a supposedpuberty (12 to 16 years in males and 9 to 14 years infemales) did not exceed 1.49 mm for females and 1.86mm for males. Different results may be due to differentsamples because Lima studied Canadian individualsover a different time intervals between evaluations, ie,2 years.

These results are really difficult to compare with theones presented in the literature because there areseveral methodological differences among them. Moststudies do not classify their samples by maturationalindicators enhancing the growth differences regardingmaturational levels. Probably, most differences amongthe results of the studies presented in the literature arebecause of different methodologies such as the ceph-alometric points used, cephalometric tracing tech-nique, sample standardization, and the tendency toselect samples by chronological age instead of matu-rational indicators.

The results of this study suggest that mandibularlinear growth does not differ among skeletal Class I orII subjects, in agreement with other previous stud-ies.29–34 It also suggests that there is no difference be-tween sexes, enhancing the fact that classifying theindividuals by their skeletal stage will diminish or eveneliminate the sex differences. It is important to restatethat although there was no statistical difference be-tween the annual growth rates, the higher valuesfound in the peak of velocity (group II) should bestrongly considered in treatment planning. New stud-ies should be carried out with a larger number of sub-jects, especially for individuals in the deceleratingphase of growth (group III).

CONCLUSIONS

• The mandibular annual growth rate in the adoles-cence phase was 2.16 mm for the mandibular bodylength, 3.16 mm for the ramus height, and 4.31 mmfor the mandibular length.

• There is great individual variation in mandibular lin-ear growth.

• There are no differences in mandibular linear growthbetween sexes when individuals are considered astheir maturational stages.

• The greatest rates occurred in the subjects in thepeak of pubertal growth velocity, except for the ra-mus height, although there were no significant dif-ferences among the groups.

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