- Email: [email protected]
Natural changes of the maxillary first molars in adolescents with skeletal Class II malocclusion
ORIGINAL ARTICLE
Natural changes of the maxillary first molars in adolescents with skeletal Class II malocclusion Fernando Lima Martinelli,a Antonio Carlos de Oliveira Ruellas,b Eduardo Martinelli de Lima,c and Ana Maria Bolognesed Rio de Janeiro and Porto Alegre, Brazil Introduction: The objective of this study was to evaluate natural changes in maxillary posterior alveolar height (MPAH) and axial inclination of the maxillary first molars (AIMFM) in subjects with Class II malocclusion to determine the validity of predictive equations. Methods: Longitudinal records of 30 untreated white subjects (13 girls, 17 boys) with skeletal Class II malocclusion were collected at ages 9, 12, 14, and 16 years. They had participated in the Burlington Growth Centre study, and cephalograms were analyzed with Dentofacial Planner Plus software (version 2.0, Dentofacial Planner, Toronto, Ontario, Canada). Serial means were compared with the Bonferroni post-hoc test (P \0.05). Predictive equations were obtained and studied with the analysis of agreement. Results: Gradually, means of MPAH had statistical increments with sexual dimorphism from 14 to 16 years of age. A distal mean of AIMFM was found at 9 years of age that decreased significantly during growth, with sexual dimorphism between the ages of 9 and 12 years. Changes in AIMFM varied among subjects in distinct stages. Values of MPAH were predicted with high validity at intervals of 3 years or longer, whereas estimations for AIMFM were unreliable. Conclusions: In this study group, there was significant alveolar growth, with a natural tendency to upright the distal inclination at the maxillary first molars. (Am J Orthod Dentofacial Orthop 2010;137:775-81)
C
lass II malocclusions have been successfully corrected with headgear appliances,1-7 mandibular advancers,8-11 and premolar extractions.12-15 Each approach is indicated for specific conditions of this malocclusion.12,14-16 In severe cases, treatment results are improved with orthognathic surgery.17 During puberty, headgears have shown results with orthopedic effects,3,6 controlled by the vector of forces.18,19 However, undesirable extrusion or distal tipping of the maxillary first molars has also been noted after treatment with cervical headgear2,20 and other appliances.21 Natural
a
Postgraduate student, Department of Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. b Professor, Department of Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. c Professor, Department of Orthodontics, Pontifıcia Universidade Cato´lica do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil. d Chairman, Department of Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. This study was made possible by material from the Burlington Growth Centre, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada; supported by funds provided by National Health Grant from Canada (605-7-299) for data collection), Province of Ontario Grant (PR 33) for duplicating, and a Varsity Fund grant from the University of Toronto for housing and collection. The authors report no commercial, proprietary, or financial interest in the products or companies described in this article. Reprint requests to: Fernando Lima Martinelli, Rua Mariante, 239/306, Porto Alegre, RS, Brazil 90430-181; e-mail, [email protected]. Submitted, January 2008; revised and accepted, June 2008. 0889-5406/$36.00 Copyright Ó 2010 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2008.06.037
growth changes of the maxillary first molars indicate that these aspects are not completely caused by mechanics.11,22-24 After the resorption of the deciduous dental roots, significant remodeling of the alveolar process occurs, and new alveolar bone is formed to support the newly erupted teeth.25 Increments of maxillary posterior alveolar height are reported in early and late stages of pubertal growth,22 with its magnitude varying proportionally in different facial types.26 Moreover, changes in the axial inclination of maxillary first molars can occur with alveolar growth, even if no mesial inclination of these molars is noted in patients with maxillary protrusion on both alveolar and basal bones.27 In this scenario, the vertical height of the maxillary molars has been analyzed to predict changes in the mandibular plane26; the intermolar angle is also used with other references to predict mandibular rotation.24 The importance of the maxillary molars’ height and axial inclination in the variations of the mandibular plane has been recognized.20,24,26 However, the contribution of physiologic and mechanical factors to the severity of undesirable results needs to be investigated.12 Rarely are growth changes considered in the analysis of molar tipping or extrusion after treatment. In 1957, Klein4 suggested an urgent need for serial investigation of untreated Class II subjects to evaluate growth increments per year, because of differences in the times of treatment. Therefore, the following 775
776
Martinelli et al
American Journal of Orthodontics and Dentofacial Orthopedics June 2010
Fig 2. The planes, lines and angles studied on cephalograms: the palatal plane (PP), anterior nasal spine (ANS) to posterior nasal spine (PNS); the distance, PP to the tip of the mesiobuccal cusp of the first maxillary molar (tcMFM), PP-tcMFM (MPAH); the angle formed between PP and the long axis of the maxillary first molar (axMFM), PP-axMFM (AIMFM).
Fig 1. Cephalometric references used to characterize the skeletal Class II malocclusion: the angle ANB ( ) and the unit difference CoGn-CoSn (mm).
questions should be answered. How much vertical growth can be expected in maxillary posterior alveolar height? What is the natural pattern of changes in the axial inclination of the maxillary first molars? Is the stage of growth important in the variability of changes? The objectives of this study were to answer these questions and determine predictive equations for natural changes and their validity. MATERIAL AND METHODS
Thirty untreated white subjects (13 girls, 17 boys) with Class II malocclusion, who had normal development of the dentition with no missing permanent teeth and no evident metabolic diseases, were selected from the files of the Burlington Growth Centre. Serial records comprised lateral cephalograms and clinical remarks at ages 9, 12, 14, and 16 years. Skeletal maturation was assessed on hand-wrist radiographs according to the standards of Greulich and Pyle.28 Differences between chronologic and skeletal ages did not exceed 2 years in either direction. After the cephalograms were manually traced, landmarks were digitized and studied with Dentofacial Planner Plus software (version 2.0, Dentofacial Software, Toronto, Ontario, Canada). Subjects were included in this study if skeletal Class II malocclusion was characterized at age 12 years, as
follows: ANB angle equal to or above 5 or a linear difference between the mandibular length (condylion to gnathion, CoGn) and the middle third of the face (condylion to subnasale, CoSn) equal to or less than 20 mm (Fig 1).29 The palatal plane (PP) was located, and a perpendicular line was traced (Fig 2) from there to the tip of the mesiobuccal cusp of the maxillary left first molar (tcMFM). The distance between PP and tcMFM (PP-tcMFM), and the axial inclination of this molar (axMFM) in relation to the PP (PP-axMFM) were both measured (Fig 2). The analysis of intraexaminer error was made as previously described, corroborating the reliability of the measurements.29 By measuring PP-tcMFM (millimeters) and PPaxMFM (degrees) at ages 9, 12, 14, and 16 years, means of maxillary posterior alveolar height (MPAH) and axial inclination of the maxillary first molar (AIMFM) were obtained, respectively. Growth changes were calculated by the difference between values measured in later and earlier ages. Serial measurements of MPAH and AIMFM were correlated, and the derived regressive equations were used to predict growth changes in distinct stages. A second equation was obtained to simplify the predictions, when the intercept point was arbitrarily defined as zero (a 5 0). Statistical analysis
Means of serial ages and consecutive changes of growth were analyzed separately, by using analysis of variance (ANOVA) with the Bonferroni post-hoc test6 (P \0.05). Sexual dimorphism was evaluated with the Student t test (P \0.01). Predicted means for corresponding ages were compared with each other and with the actual mean by using 1-way ANOVA (P \0.05). Squared multiple correlation (R2), mean of
Martinelli et al
American Journal of Orthodontics and Dentofacial Orthopedics Volume 137, Number 6
Table I.
Means of MPAH and AIMFM at the various
ages 9 years
12 years
MPAH (mm) PP-tcMFM 17.8 6 1.9a 20.0 6 2.2b Girls 17.7 6 1.4 20.1 6 1.9 Boys 17.9 6 2.2 19.8 6 2.5 AIMFM ( ) PP-axMFM 102.4 6 5.3e 99.1 6 5.6f Girls 103.8 6 5.2 97.8 6 6.9 Boys 101.4 6 5.3 100.0 6 4.5
14 years
Changes in MPAH and AIMFM in consecutive stages of growth
Table II.
16 years
21.4 6 2.5c 22.7 6 2.6d 21.7 6 2.5 22.3 6 2.2 21.3 6 2.6 23.0 6 2.9 96.3 6 6.0g 94.4 6 6.1h 96.5 6 8.1 94.7 6 7.7 96.1 6 4.0 94.1 6 4.9
777
9-12 y
12-14 y
14-16 y
9-16 y
MPAH (mm) PP-tcMFM 2.2 6 1.3a 1.5 6 1.3a 1.2 6 1.3a 4.9 6 1.6b Girls 2.5 6 1.1 1.5 6 1.2 0.6 6 0.9* 4.6 6 1.2 Boys 1.9 6 1.4 1.4 6 1.4 1.7 6 1.4* 5.1 6 1.9 AIMFM ( ) PP-axMFM –3.4 6 5.7c –2.8 6 4.3d –1.9 6 3.8e –8.1 6 6.1f Girls –6.0 6 4.5* –1.3 6 5.1 –1.8 6 5.0 –9.1 6 5.7 Boys –1.4 6 5.9* –3.9 6 3.2 –1.9 6 2.7 –7.3 6 6.4
a \ b, c, and d; d . b (P \0.05). e . g and h; f . h (P \0.05). There was no sexual dimorphism (P \0.01).
b . a (P \0.05). f . c, d, and e; c . d (P \0.05). *Sexual dimorphism (P \0.01).
error, and coefficient of accuracy were calculated for predictions.30 The subjects’ increasing MPAH and the frequency of each pattern of changes on AIMFM were assessed in consecutive stages of growth.31 Changes of MPAH were classified as incremental, if the difference between the ending and starting values was greater than 0.2 mm; or nonincremental, if this difference was equal to 0 6 0.2 mm. The pattern of changes in AIMFM was defined as mesial tipping, if angle PP-axMFM decreased from the starting to ending age (#0.5 ); or distal tipping, if this value increased along the stage of growth (.0.5 ). A subject’s overall change in AIMFM was considered in each stage when the difference was 0 6 0.5 . Predicted changes were also classified into the same criteria and the agreement between agreement between predicted and actual changes was analyzed in both variables, MPAH and AIMFM. In this analysis, the validity of the predictions was determined by the level of confidence, considered high if agreement was equal or greater than 90%.31
years were statistically greater than in the stage between 12 and 14 years (Table II). Correlations were strong for MPAH (Table III), and the equations showed high values of R2 (0.58-0.76), low means of error, and low coefficients of accuracy (Table III). The overall correlation of AIMFM was fairly weak, contrasting with higher values in later stages (Table IV). Predictions for AIMFM showed high means of error and weak R2 values; these were higher from 14 to 16 years of age (Table IV). Nevertheless, there were no statistical differences when we compared the predicted means with the actual values of MPAH and AIMFM (P .0.05). Although incremental changes were found in all 30 subjects, half had 1 stage without natural increases (Table V): 3 boys between ages 9 and 12 years, 4 boys and 2 girls from 12 to 14 years, and 4 girls and 2 boys between 14 and 16 years. The frequency of increasing MPAH was high in 3-year intervals or longer periods of growth (Table V). Agreement between the predicted and actual changes on MPAH was high from 9 years to 12, 14, and 16 years of age. It was also high between ages 12 and 16 years (Table V). When a nonincremental stage was experienced, increases in MPAH were predicted with equations (Table V). Overall changes on AIMFM showed a high frequency of mesial tipping contrasting with a low percentage found in shorter stages (Table VI). One period without natural changes in AIMFM was identified in 3 subjects, whose overall pattern was mesial tipping. Agreement between predicted and actual changes in AIMFM was high only for the overall period (Table VI).
RESULTS
Means of MPAH and AIMFM at ages 9, 12, 14, and 16 years were calculated; there was no sexual dimorphism (Table I). Significant increases in MPAH were noted in intervals of 3 years or longer (Table I). Overall growth was statistically greater than in shorter stages (Table II), and incremental changes were greater in boys from 14 to 16 years of age (Table II). Four years of growth were necessary to identify statistical difference between means of AIMFM in serial ages (Table I). The maxillary first molars had distal crown inclinations at age 9 years with a tendency to upright gradually until age 16 (Table I). Overall changes in AIMFM were greater than in shorter stages, and sexual dimorphism was noted from 9 to 12 years of age (Table II). Natural changes in AIMFM from 9 to 12
DISCUSSION
Merrifield and Cross20 stated that an orthodontic technique without headgear is like a ship without a rudder. Cervical headgear provides a favorable component
778
Martinelli et al
American Journal of Orthodontics and Dentofacial Orthopedics June 2010
Table III. Correlations between serial values of MPAH, derived regressive equations with respective squared multiple correlations (R2), predicted means, means of error, and coefficients of accuracy Correlation
Regressive equation
R2
Predicted mean (mm)
Mean of error (mm)
Coefficient of accuracy (mm)
9-12
.82
9-14
.77
12-14
.87
9-16
.79
12-16
.86
14-16
.87
Y 5 0.98X 1 2.5 Y0 5 1.12X Y 5 1.05X 1 2.75 Y0 5 1.2X Y 5 0.99X 1 1.7 Y0 5 1.07X Y 5 1.11X 1 2.8 Y0 5 1.27X Y 5 1.003X 1 2.6 Y0 5 1.13X Y 5 0.89X 1 3.4 Y0 5 1.056X
.67 .65 .59 .58 .75 .74 .63 .61 .73 .72 .76 .74
20.0 1 1.8 20.0 1 2.1 21.5 1 2.0 21.4 1 2.2 21.5 1 2.2 21.4 1 2.4 22.6 1 2.1 22.6 1 2.4 22.6 1 2.2 22.6 1 2.5 22.5 1 2.3 22.6 1 2.7
0.0 1 1.3 0.0 1 1.3 0.0 1 1.6 0.1 1 1.6 0.0 1 1.3 0.1 1 1.3 0.1 1 1.6 0.1 1 1.6 0.1 1 1.3 0.1 1 1.4 0.2 1 1.3 0.0 1 1.3
.065 .065 .075 .079 .061 .065 .075 .075 .062 .066 .067 .058
Stage of growth (y)
Y, prediction of MPAH; Yo, simplified prediction of MPAH; X, starting value of MPAH to the prediction. Table IV. Correlations among values of AIMFM, regressive equations with respective squared multiple correlations (R2), predicted means, means of error, and coefficients of accuracy Correlation
Regressive equation
R2
Predicted mean ( )
Mean of error ( )
Coefficient of accuracy ( )
9-12
.45
9-14
.44
12-14
.73
9-16
.44
12-16
.76
14-16
.80
Y 5 0.48X 1 49.8 Y0 5 0.96X Y 5 0.49X 1 45.5 Y0 5 0.94X Y 5 0.77X 1 19.7 Y0 5 0.97X Y 5 0.5X 1 42.4 Y0 5 0.92X Y 5 0.83X 1 12.0 Y0 5 0.95X Y 5 0.83X 1 14.9 Y0 5 0.98X
.20 –.004 .19 .04 .53 .49 .19 .06 .58 .57 .65 .62
99.0 1 2.6 98.3 1 5.1 95.7 1 2.6 96.3 1 5.0 96.0 1 4.3 96.1 1 5.5 93.6 1 2.7 94.2 1 4.9 94.2 1 4.7 94.1 1 5.4 94.8 1 5.0 94.3 1 5.8
–0.1 1 5.0 –0.7 1 5.6 –0.6 1 5.4 0.0 1 5.9 –0.3 1 4.1 0.2 1 4.2 –0.8 1 5.5 –0.1 1 5.9 –0.2 1 4.0 –0.3 1 4.0 0.4 1 3.6 0.0 1 3.8
–.052 –.064 –.063 .061 –.046 –.046 –.067 –.064 –.045 –.046 .042 .040
Stage of growth (y)
Y, prediction of AIMFM; Yo, simplified prediction of AIMFM; X, starting value of AIMFM to the prediction.
of distal force for approaching Class II patients,5,6,19 despite extrusion and distal crown tipping can be produced in the maxillary first molars.20 Variation of the mandibular plane is an important factor in the quality of results,20 and it has been associated with such effects.6,20,26 Regarding possible mechanics to correct Class II malocclusions, Tweed12 argued that the fault lies in our inability to master the potentialities of orthodontic mechanisms. Comprehension of growth is relevant to improve this ability, especially for skeletal Class II patients during puberty.4,11,21-23,32,33 As growth changes in untreated cases are recognized, the natural development of craniofacial aspects could be further preserved along the approach. Once the immutability of the maxilla has been challenged, parameters of natural changes in MPAH and AIMFM were determined with the reference of the PP (Tables I and II).4 Even though the predictions of growth were
hypothetical,34 the findings were consistent35 that gradual increments of growth can be expected on posterior alveolar height (Tables I and II), and that the maxillary first molars generally have distal inclinations in younger patients, changing naturally to upright positions (Tables I and II). The vertical alveolar growth previously reported was confirmed in our findings.11,22,32 Significant increases in MPAH were noted in intervals of ages equal to or longer than 3 years (Table I). The overall increase in MPAH was the greatest mean, whereas changes in shorter stages were not statistically different (Table II). This suggests that vertical alveolar growth is a long-term process of incremental changes in alveolar height that develops slowly and gradually. Otherwise, MPAH might not show a natural increase during short periods (Table V), especially in boys at younger ages and girls at later stages. Thus, discrepant means of
Martinelli et al
American Journal of Orthodontics and Dentofacial Orthopedics Volume 137, Number 6
779
Analysis of agreement between predicted and actual changes of MPAH
Table VI. Analysis of agreement between predicted and actual growth changes on AIMFM
Stage of growth prediction (y)
Stage of growth prediction (y)
Table V.
9-12 Agreed Disagreed Actual frequency 9-14 Agreed Disagreed Actual frequency 12-14 Agreed Disagreed Actual frequency 9-16 Agreed Disagreed Actual frequency 12-16 Agreed Disagreed Actual frequency 14-16 Agreed Disagreed Actual frequency
Growth changes Incremental
Nonincremental
Agreement (prediction / actual)
27 27 (90%)
3 3 (10%)
27 (90%) 3 (10%) 30 (100%)
30 30 (100%)
0%
30 (100%) 0% 30 (100%)
24 24 (80%)
6 6 (20%)
24 (80%) 6 (20%) 30 (100%)
30 30 (100%)
0%
30 (100%) 0% 100%
30 30 (100%)
0%
30 (100%) 0% 30 (100%)
24 24 (80%)
6 6 (20%)
24 (80%) 6 (20%) 30 (100%)
9-12 Agreed Disagreed Actual frequency 9-14 Agreed Disagreed Actual frequency 12-14 Agreed Disagreed Actual frequency 9-16 Agreed Disagreed Actual frequency 12-16 Agreed Disagreed Actual frequency 14-16 Agreed Disagreed Actual frequency
Pattern of changes Mesial tipping
Distal tipping
Agreement (prediction / actual)
21 1 22 (73%)
1 7 8 (27%)
22 (73%) 8 (27%) 30 (100%)
26 26 (87%)
4 4 (13%)
26 (87%) 4 (13%) 30 (100%)
23 23 (77%)
7 7 (23%)
23 (77%) 7 (23%) 30 (100%)
27 27 (90%)
3 3 (10%)
27 (90%) 3 (10%) 30 (100%)
26 26 (87%)
4 4 (13%)
26 (87%) 4 (13%) 30 (100%)
18 4 22 (73%)
8 8 (27%)
18 (60%) 12 (40%) 30 (100%)
High level of confidence $90%.
High level of confidence $90%.
alveolar growth in the literature can be explained, since studies are conducted with longer or shorter periods of growth.11,22 Skeletal maturation23 and vertical facial pattern26 have been associated with the variability of changes. Isaacson et al26 stated that MPAH is increased in patients with a high mandibular plane. Even though subjects with low, average, and high mandibular planes were included in this study, the influence of vertical pattern on the variability of MPAH could not be assessed. Favorably, strong correlations were found (Table III), indicating that the higher the starting height of the maxillary molars, the greater the expectation of increments. If high MPAH is shown in subjects with a high mandibular plane, greater incremental changes can be expected.26 Conversely, this behavior might not be observed at upper anterior alveolar height, because of the weaker correlations reported elsewhere.32 Furthermore, these parameters might be misleading in boys with low MPAH at early ages and in girls with high molar height after 14 years of age. Depending on the treatment objectives, the starting MPAH (Table I) and sexual dimorphism (Table II) are important for determining the timing of treatment in
skeletal Class II patients. Decisions concerning the point of extraoral traction are based on the proportion of molar extrusion and intrusion and alveolar growth desired for each patient.18,19 Minimal physiologic recovery was reported after cervical headgear therapy during growth with small forces applied over an average period of 2 years 8 months.36 In patients with long faces, alveolar growth should be maximized and maxillary molar extrusion minimized.26 Therefore, combined extraoral traction must be considered.7 The use of parietal headgear for a long period might improve the goal of molar intrusion, but using it in later stages is reasonable only for boys (Table II).19 Patients with high posterior alveolar height are more favorable for molar intrusion because greater increments are expected (Table III). In Class II patients with low maxillary posterior height, this expectation is weaker (Table III). Hence, natural changes need to be managed slowly and gradually over a longer time to maximize the growth potential (Table II). Extrapolating these findings, we can assume that 2-phase treatment with cervical headgear is favorable for alveolar growth, mainly in girls with deep bite and low mandibular plane.37 Obviously, the suggestions for clinical benefits resulting
780
Martinelli et al
from the management of maxillary alveolar growth should be evaluated in further studies. Generally, the maxillary first molars showed distal crown inclinations at 9 years of age, with a tendency to upright gradually until age 16 (Table II). Although molar crown tipping varied among subjects (Tables II and VI), measurements of AIMFM were between 113.7 and 85.1 , denoting distal or vertical inclination. These findings were corroborated by Henry,27 who found no mesial inclination of the maxillary first molars of Class II patients. Therefore, the distal inclination noted in the maxillary first molars after using headgear2,7,18,20 or other mechanisms21 seems to be compatible with this population. Hypothetical contributions of AIMFM to the severity of undesirable results could not be ascertained, because growth changes in AIMFM were not constant (Tables II, IV, and VI). Conversely, Skieller et al24 postulated the importance of the intermolar angle to predict mandibular rotation, which was weak in a mixed sample including treated patients.38 Significant molar crown tipping was observed in longer periods (Tables I and II), suggesting that this natural aspect can be expected until 16 years of age or in later posttreatment evaluations. This agrees with the finding of Badell,7 who reported a strong tendency to upright the maxillary molars after the headgear period. The squared multiple correlation coefficient (R2), varying between 0 and 1, indicates the fraction of changes that can be explained by natural growth.24 However, the strong R2 predictions of MPAH (Table III), from 12 to 14 and 14 to 16 years, were not confirmed in the analysis of agreement (Table V). Between ages 14 and 16 years, sexual dimorphism was observed in the statistics (Table II) and in agreement (Table V), indicating the reliability of this method only for boys. Values of R2, mean of error, coefficient of accuracy (Table III), and agreement (Table V) demonstrated the highest level of validity in estimating MPAH from 12 to 16 years old. Predictions of MPAH had high validity in assessing periods of 3 years or longer (Table V) in white skeletal Class II subjects, whose starting value did not exceed 1 SD from the corresponding mean (Table I).34 Although incremental changes were predicted in every situation (Table V), the pattern of errors was unsystematic when growth changes actually occurred.35 Logically, limitations in the accuracy of predictions are likely, as observed in growth intervals of 2 years (Table V).34 The risk of errors is reduced if the method is selected according to demographic characteristics,39 type of malocclusion, skeletal maturation,22 age, sexual dimorphism, and initial value of the predicted variable.34 Thames et al40 reported a statistical difference between predicted and actual changes on this
American Journal of Orthodontics and Dentofacial Orthopedics June 2010
variable; this disagrees with our study, in which another design was used. The agreement of 90% between the predicted and actual overall changes on AIMFM (Table VI) suggested high validity of the methods. However, the lack of accuracy shown by the R2 values (Table IV) associated with low agreement in other stages (Table VI) suggested a bias. In addition, the high R2 value found in later stages (Table IV) was not corroborated by the analysis of agreement (Table VI). Not only the amounts of change (Table IV), but also the pattern of molar tipping (Table VI) were unpredictable. Further investigations are necessary to determine factors beyond growth that influence changes in AIMFM. The pattern of tissue remodeling in alveolar bone does not involve classic Harvesian remodeling, because of the influence of the dental roots, unique forces in the oral cavity, and the continuous accommodation of Sharpey’s fibers.25 Thus, the possibility of a biologic adaptation in the alveolar bone during mechanical stimulation cannot be totally disregarded.5,20 Natural increments in MPAH were gradual, indicating that slower orthodontic treatment might take more advantage of growth in skeletal Class II patients.41 No statistically significant orthopedic change is produced with combined traction headgear worn for a relatively short period of growth.7 Perhaps wearing headgear with a lower total force for a longer period of growth would improve treatment goals.7 Predictive equations for MPAH are recommended to analyze mechanical extrusion and intrusion of the maxillary molars over a 3-year period. CONCLUSIONS
In untreated white adolescents with skeletal Class II malocclusion, orthodontists can expect (1) gradual maxillary posterior alveolar growth without important periods of change, (2) greater increases of MPAH in boys from 14 to 16 years of age, (3) a distal crown AIMFM at the age of 9 years tending to upright naturally, and (4) marked variability of natural changes in AIMFM between patients. The equations were valid to evaluate growth increments on MPAH during a 3-year period or longer. REFERENCES 1. Elder J, Tuenge R. Cephalometric and histologic changes produced by extraoral high-pull traction to the maxilla in Macaca mulatta. Am J Orthod 1974;66:599-617. 2. Hubbard G, Nanda RS, Currier G. A cephalometric evaluation of nonextraction cervical headgear treatment in Class II malocclusion. Angle Orthod 1994;64:359-70. 3. Melsen B. Effects of cervical anchorage during and after treatment: an implant study. Am J Orthod 1978;73:526-40.
American Journal of Orthodontics and Dentofacial Orthopedics Volume 137, Number 6
4. Klein P. An evaluation of cervical traction on the maxilla and the upper first permanent molars. Angle Orthod 1957;27:61-8. 5. Kloehn S. Guiding alveolar growth and eruption of teeth to reduce treatment time and produce a more balanced face. Angle Orthod 1947;17:10-33. 6. Lima Filho R, Lima A, De Oliveira Ruellas AC. Longitudinal study of anteroposterior and vertical maxillary changes in skeletal Class II patients treated with Kloehn cervical headgear. Am J Orthod Dentofacial Orthop 2003;73:187-93. 7. Badell M. An evaluation of extraoral combined high-pull traction and cervical traction to the maxilla. Am J Orthod 1976;69:431-46. 8. Voudouris J, Woodside D, Altuna G, Kuftinec M, Angelopoulos G, Bourque P. Condyle-fossa modifications and muscle interactions during Herbst treatment, part 1. New technological methods. Am J Orthod Dentofacial Orthop 2003;123:604-13. 9. Voudouris J, Woodside D, Altuna G, Angelopoulos G, Bourque P, Lacouture C. Condyle-fossa modifications and muscle interactions during Herbst treatment, part 2. Results and conclusions. Am J Orthod Dentofacial Orthop 2003;124:13-29. 10. Vargervik K, Harvold EP. Response to activator treatment in Class II malocclusions. Am J Orthod 1985;88:242-51. 11. Almeida M, Henriques J, Almeida R, Almeida-Pedrin R, Ursi W. Treatment effects produced by the bionator appliance. Comparison with an untreated Class II sample. Eur J Orthod 2004;26:65-72. 12. Tweed C. The application of the principles of the egdewise arch in the treatment of Class II, division 1, malocclusion: part II. Angle Orthod 1936;6:255-7. ˚ rtun J, Joondeph D, Little R. Long-term stability of 13. Fidler B, A Angle Class II, Division 1 malocclusions with successful occlusal results at end of active treatment. Am J Orthod Dentofacial Orthop 1995;107:276-85. 14. Jarabak J, Fizzell J. Technique and treatment with the light-wire appliances. St Louis: Mosby; 1963. 15. Bishara S, Cummins D, Zaher A. Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment. Am J Orthod Dentofacial Orthop 1997;111:18-27. 16. Rosenblum R. Class II malocclusion: mandibular retrusion or maxillary protrusion. Angle Orthod 1995;65:49-62. 17. Bailey L, Proffit W, White R. Assessment of patients for orthognathic surgery. Semin Orthod 1999;5:209-22. 18. Armstrong M. Controlling the magnitude, direction and duration of extraoral force. Am J Orthod 1971;59:217-43. 19. Oosthuizen L, Dijkman J, Evans W. A mechanical appraisal of the Kloehn extraoral assembly. Angle Orthod 1973;43:221-32. 20. Merrifield L, Cross J. Directional forces. Am J Orthod 1970;57: 435-64. 21. Bussick T, McNamara J. Dentoalveolar and skeletal changes associated with the pendulum appliance. Am J Orthod Dentofacial Orthop 2000;117:333-43. 22. Arat Z, Ru¨bendu¨z M. Changes in dentoalveolar and facial heights during early and late growth periods: a longitudinal study. Angle Orthod 2005;75:69-74.
Martinelli et al
781
¨ zdiler E, Ru¨bendu¨z M, Erdogan B. Cranifacial 23. Arat Z, Ko¨klu¨ A, O growth and skeletal maturation: a mixed longitudinal study. Eur J Orthod 2001;23:355-61. 24. Skieller V, Bjork A, Linde-Hansen T. Prediction of mandibular growth rotation evaluated from a longitudinal implant sample. Am J Orthod 1984;86:359-70. 25. Sodek J, McKee M. Molecular and cellular biology of alveolar bone. Periodontol 2000;24:99-126. 26. Isaacson J, Isaacson R, Speidel T, Worms F. Extreme variation in vertical facial growth and associated variation in skeletal and dental relations. Angle Orthod 1971;41:219-29. 27. Henry RG. A classification of Class II, division 1 malocclusion. Angle Orthod 1957;27:83-92. 28. Greulich W, Pyle S. Radiographic atlas of skeletal development of hand and wrist. Stanford, Calif: Stanford University Press; 1959. 29. Hoffelder L, de Lima E, Martinelli F, Bolognese A. Soft-tissue changes during facial growth in skeletal Class II individuals. Am J Orthod Dentofacial Orthop 2007;131:490-5. 30. Martinelli F, Lima EM, Rocha R, Tirre-Araujo M. Prediction of lower permanent canine and premolars width by correlation methods. Angle Orthod 2005;75:805-8. 31. Luiz R, Costa A, Nadanovsky P. Epidemiologia e bioestatıstica na pesquisa odontolo´gica, Sa˜o Paulo, Brazil: Editora Atheneu; 2005. 32. Naumann S, Behrents R, Buschang P. Vertical components of overbite change: a mathematical model. Am J Orthod Dentofacial Orthop 2000;117:486-95. 33. Schudy F. Vertical growth versus anteroposterior growth as related to function and treatment. Angle Orthod 1964;34:75-93. 34. Moyers R, Johnston L, Rao C, Tanner J, Woodside D. Seminar 2. Prediction of cranio-facial growth. In: Moyers R, Krogman W, editors. Cranio-facial growth in man. New York: Pergamon Press; 1971. p. 293-313. 35. Collett T. Evidence, judgment, and the clinical decision: an argument for evidence-based orthodontics. Am J Orthod Dentofacial Orthop 2008;133:190-4. 36. Wieslander L, Buck D. Physiologic recovery after cervical traction therapy. Am J Orthod 1974;66:294-301. 37. Gianelly A. One-phase versus two-phase treatment. Am J Orthod Dentofacial Orthop 1995;108:556-9. 38. Lee RS, Daniel FJ, Swartz M, Baumrind S, Korn EL. Assessment of a method for the prediction of mandibular rotation. Am J Orthod Dentofacial Orthop 1987;91:395-402. 39. Bishara S, Jakobsen J, Abdallah E, Fernandez A. Comparisons of mesiodistal and buccolingual crown dimensions of the permanent teeth in three populations from Egypt, Mexico, and the United States. Am J Orthod Dentofacial Orthop 1989;96: 416-22. 40. Thames T, Sinclair P, Alexander R. The accuracy of computerized growth prediction in Class II high-angle cases. Am J Orthod 1985; 87:398-405. 41. Joondeph D. Retention and relapse. In: Graber T, Vanarsdall R, editors. Orthodontics: current principles and techniques. St Louis: Mosby; 1994.
Natural changes of the maxillary first molars in adolescents with skeletal Class II malocclusion Fernando Lima Martinelli,a Antonio Carlos de Oliveira Ruellas,b Eduardo Martinelli de Lima,c and Ana Maria Bolognesed Rio de Janeiro and Porto Alegre, Brazil Introduction: The objective of this study was to evaluate natural changes in maxillary posterior alveolar height (MPAH) and axial inclination of the maxillary first molars (AIMFM) in subjects with Class II malocclusion to determine the validity of predictive equations. Methods: Longitudinal records of 30 untreated white subjects (13 girls, 17 boys) with skeletal Class II malocclusion were collected at ages 9, 12, 14, and 16 years. They had participated in the Burlington Growth Centre study, and cephalograms were analyzed with Dentofacial Planner Plus software (version 2.0, Dentofacial Planner, Toronto, Ontario, Canada). Serial means were compared with the Bonferroni post-hoc test (P \0.05). Predictive equations were obtained and studied with the analysis of agreement. Results: Gradually, means of MPAH had statistical increments with sexual dimorphism from 14 to 16 years of age. A distal mean of AIMFM was found at 9 years of age that decreased significantly during growth, with sexual dimorphism between the ages of 9 and 12 years. Changes in AIMFM varied among subjects in distinct stages. Values of MPAH were predicted with high validity at intervals of 3 years or longer, whereas estimations for AIMFM were unreliable. Conclusions: In this study group, there was significant alveolar growth, with a natural tendency to upright the distal inclination at the maxillary first molars. (Am J Orthod Dentofacial Orthop 2010;137:775-81)
C
lass II malocclusions have been successfully corrected with headgear appliances,1-7 mandibular advancers,8-11 and premolar extractions.12-15 Each approach is indicated for specific conditions of this malocclusion.12,14-16 In severe cases, treatment results are improved with orthognathic surgery.17 During puberty, headgears have shown results with orthopedic effects,3,6 controlled by the vector of forces.18,19 However, undesirable extrusion or distal tipping of the maxillary first molars has also been noted after treatment with cervical headgear2,20 and other appliances.21 Natural
a
Postgraduate student, Department of Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. b Professor, Department of Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. c Professor, Department of Orthodontics, Pontifıcia Universidade Cato´lica do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil. d Chairman, Department of Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. This study was made possible by material from the Burlington Growth Centre, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada; supported by funds provided by National Health Grant from Canada (605-7-299) for data collection), Province of Ontario Grant (PR 33) for duplicating, and a Varsity Fund grant from the University of Toronto for housing and collection. The authors report no commercial, proprietary, or financial interest in the products or companies described in this article. Reprint requests to: Fernando Lima Martinelli, Rua Mariante, 239/306, Porto Alegre, RS, Brazil 90430-181; e-mail, [email protected]. Submitted, January 2008; revised and accepted, June 2008. 0889-5406/$36.00 Copyright Ó 2010 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2008.06.037
growth changes of the maxillary first molars indicate that these aspects are not completely caused by mechanics.11,22-24 After the resorption of the deciduous dental roots, significant remodeling of the alveolar process occurs, and new alveolar bone is formed to support the newly erupted teeth.25 Increments of maxillary posterior alveolar height are reported in early and late stages of pubertal growth,22 with its magnitude varying proportionally in different facial types.26 Moreover, changes in the axial inclination of maxillary first molars can occur with alveolar growth, even if no mesial inclination of these molars is noted in patients with maxillary protrusion on both alveolar and basal bones.27 In this scenario, the vertical height of the maxillary molars has been analyzed to predict changes in the mandibular plane26; the intermolar angle is also used with other references to predict mandibular rotation.24 The importance of the maxillary molars’ height and axial inclination in the variations of the mandibular plane has been recognized.20,24,26 However, the contribution of physiologic and mechanical factors to the severity of undesirable results needs to be investigated.12 Rarely are growth changes considered in the analysis of molar tipping or extrusion after treatment. In 1957, Klein4 suggested an urgent need for serial investigation of untreated Class II subjects to evaluate growth increments per year, because of differences in the times of treatment. Therefore, the following 775
776
Martinelli et al
American Journal of Orthodontics and Dentofacial Orthopedics June 2010
Fig 2. The planes, lines and angles studied on cephalograms: the palatal plane (PP), anterior nasal spine (ANS) to posterior nasal spine (PNS); the distance, PP to the tip of the mesiobuccal cusp of the first maxillary molar (tcMFM), PP-tcMFM (MPAH); the angle formed between PP and the long axis of the maxillary first molar (axMFM), PP-axMFM (AIMFM).
Fig 1. Cephalometric references used to characterize the skeletal Class II malocclusion: the angle ANB ( ) and the unit difference CoGn-CoSn (mm).
questions should be answered. How much vertical growth can be expected in maxillary posterior alveolar height? What is the natural pattern of changes in the axial inclination of the maxillary first molars? Is the stage of growth important in the variability of changes? The objectives of this study were to answer these questions and determine predictive equations for natural changes and their validity. MATERIAL AND METHODS
Thirty untreated white subjects (13 girls, 17 boys) with Class II malocclusion, who had normal development of the dentition with no missing permanent teeth and no evident metabolic diseases, were selected from the files of the Burlington Growth Centre. Serial records comprised lateral cephalograms and clinical remarks at ages 9, 12, 14, and 16 years. Skeletal maturation was assessed on hand-wrist radiographs according to the standards of Greulich and Pyle.28 Differences between chronologic and skeletal ages did not exceed 2 years in either direction. After the cephalograms were manually traced, landmarks were digitized and studied with Dentofacial Planner Plus software (version 2.0, Dentofacial Software, Toronto, Ontario, Canada). Subjects were included in this study if skeletal Class II malocclusion was characterized at age 12 years, as
follows: ANB angle equal to or above 5 or a linear difference between the mandibular length (condylion to gnathion, CoGn) and the middle third of the face (condylion to subnasale, CoSn) equal to or less than 20 mm (Fig 1).29 The palatal plane (PP) was located, and a perpendicular line was traced (Fig 2) from there to the tip of the mesiobuccal cusp of the maxillary left first molar (tcMFM). The distance between PP and tcMFM (PP-tcMFM), and the axial inclination of this molar (axMFM) in relation to the PP (PP-axMFM) were both measured (Fig 2). The analysis of intraexaminer error was made as previously described, corroborating the reliability of the measurements.29 By measuring PP-tcMFM (millimeters) and PPaxMFM (degrees) at ages 9, 12, 14, and 16 years, means of maxillary posterior alveolar height (MPAH) and axial inclination of the maxillary first molar (AIMFM) were obtained, respectively. Growth changes were calculated by the difference between values measured in later and earlier ages. Serial measurements of MPAH and AIMFM were correlated, and the derived regressive equations were used to predict growth changes in distinct stages. A second equation was obtained to simplify the predictions, when the intercept point was arbitrarily defined as zero (a 5 0). Statistical analysis
Means of serial ages and consecutive changes of growth were analyzed separately, by using analysis of variance (ANOVA) with the Bonferroni post-hoc test6 (P \0.05). Sexual dimorphism was evaluated with the Student t test (P \0.01). Predicted means for corresponding ages were compared with each other and with the actual mean by using 1-way ANOVA (P \0.05). Squared multiple correlation (R2), mean of
Martinelli et al
American Journal of Orthodontics and Dentofacial Orthopedics Volume 137, Number 6
Table I.
Means of MPAH and AIMFM at the various
ages 9 years
12 years
MPAH (mm) PP-tcMFM 17.8 6 1.9a 20.0 6 2.2b Girls 17.7 6 1.4 20.1 6 1.9 Boys 17.9 6 2.2 19.8 6 2.5 AIMFM ( ) PP-axMFM 102.4 6 5.3e 99.1 6 5.6f Girls 103.8 6 5.2 97.8 6 6.9 Boys 101.4 6 5.3 100.0 6 4.5
14 years
Changes in MPAH and AIMFM in consecutive stages of growth
Table II.
16 years
21.4 6 2.5c 22.7 6 2.6d 21.7 6 2.5 22.3 6 2.2 21.3 6 2.6 23.0 6 2.9 96.3 6 6.0g 94.4 6 6.1h 96.5 6 8.1 94.7 6 7.7 96.1 6 4.0 94.1 6 4.9
777
9-12 y
12-14 y
14-16 y
9-16 y
MPAH (mm) PP-tcMFM 2.2 6 1.3a 1.5 6 1.3a 1.2 6 1.3a 4.9 6 1.6b Girls 2.5 6 1.1 1.5 6 1.2 0.6 6 0.9* 4.6 6 1.2 Boys 1.9 6 1.4 1.4 6 1.4 1.7 6 1.4* 5.1 6 1.9 AIMFM ( ) PP-axMFM –3.4 6 5.7c –2.8 6 4.3d –1.9 6 3.8e –8.1 6 6.1f Girls –6.0 6 4.5* –1.3 6 5.1 –1.8 6 5.0 –9.1 6 5.7 Boys –1.4 6 5.9* –3.9 6 3.2 –1.9 6 2.7 –7.3 6 6.4
a \ b, c, and d; d . b (P \0.05). e . g and h; f . h (P \0.05). There was no sexual dimorphism (P \0.01).
b . a (P \0.05). f . c, d, and e; c . d (P \0.05). *Sexual dimorphism (P \0.01).
error, and coefficient of accuracy were calculated for predictions.30 The subjects’ increasing MPAH and the frequency of each pattern of changes on AIMFM were assessed in consecutive stages of growth.31 Changes of MPAH were classified as incremental, if the difference between the ending and starting values was greater than 0.2 mm; or nonincremental, if this difference was equal to 0 6 0.2 mm. The pattern of changes in AIMFM was defined as mesial tipping, if angle PP-axMFM decreased from the starting to ending age (#0.5 ); or distal tipping, if this value increased along the stage of growth (.0.5 ). A subject’s overall change in AIMFM was considered in each stage when the difference was 0 6 0.5 . Predicted changes were also classified into the same criteria and the agreement between agreement between predicted and actual changes was analyzed in both variables, MPAH and AIMFM. In this analysis, the validity of the predictions was determined by the level of confidence, considered high if agreement was equal or greater than 90%.31
years were statistically greater than in the stage between 12 and 14 years (Table II). Correlations were strong for MPAH (Table III), and the equations showed high values of R2 (0.58-0.76), low means of error, and low coefficients of accuracy (Table III). The overall correlation of AIMFM was fairly weak, contrasting with higher values in later stages (Table IV). Predictions for AIMFM showed high means of error and weak R2 values; these were higher from 14 to 16 years of age (Table IV). Nevertheless, there were no statistical differences when we compared the predicted means with the actual values of MPAH and AIMFM (P .0.05). Although incremental changes were found in all 30 subjects, half had 1 stage without natural increases (Table V): 3 boys between ages 9 and 12 years, 4 boys and 2 girls from 12 to 14 years, and 4 girls and 2 boys between 14 and 16 years. The frequency of increasing MPAH was high in 3-year intervals or longer periods of growth (Table V). Agreement between the predicted and actual changes on MPAH was high from 9 years to 12, 14, and 16 years of age. It was also high between ages 12 and 16 years (Table V). When a nonincremental stage was experienced, increases in MPAH were predicted with equations (Table V). Overall changes on AIMFM showed a high frequency of mesial tipping contrasting with a low percentage found in shorter stages (Table VI). One period without natural changes in AIMFM was identified in 3 subjects, whose overall pattern was mesial tipping. Agreement between predicted and actual changes in AIMFM was high only for the overall period (Table VI).
RESULTS
Means of MPAH and AIMFM at ages 9, 12, 14, and 16 years were calculated; there was no sexual dimorphism (Table I). Significant increases in MPAH were noted in intervals of 3 years or longer (Table I). Overall growth was statistically greater than in shorter stages (Table II), and incremental changes were greater in boys from 14 to 16 years of age (Table II). Four years of growth were necessary to identify statistical difference between means of AIMFM in serial ages (Table I). The maxillary first molars had distal crown inclinations at age 9 years with a tendency to upright gradually until age 16 (Table I). Overall changes in AIMFM were greater than in shorter stages, and sexual dimorphism was noted from 9 to 12 years of age (Table II). Natural changes in AIMFM from 9 to 12
DISCUSSION
Merrifield and Cross20 stated that an orthodontic technique without headgear is like a ship without a rudder. Cervical headgear provides a favorable component
778
Martinelli et al
American Journal of Orthodontics and Dentofacial Orthopedics June 2010
Table III. Correlations between serial values of MPAH, derived regressive equations with respective squared multiple correlations (R2), predicted means, means of error, and coefficients of accuracy Correlation
Regressive equation
R2
Predicted mean (mm)
Mean of error (mm)
Coefficient of accuracy (mm)
9-12
.82
9-14
.77
12-14
.87
9-16
.79
12-16
.86
14-16
.87
Y 5 0.98X 1 2.5 Y0 5 1.12X Y 5 1.05X 1 2.75 Y0 5 1.2X Y 5 0.99X 1 1.7 Y0 5 1.07X Y 5 1.11X 1 2.8 Y0 5 1.27X Y 5 1.003X 1 2.6 Y0 5 1.13X Y 5 0.89X 1 3.4 Y0 5 1.056X
.67 .65 .59 .58 .75 .74 .63 .61 .73 .72 .76 .74
20.0 1 1.8 20.0 1 2.1 21.5 1 2.0 21.4 1 2.2 21.5 1 2.2 21.4 1 2.4 22.6 1 2.1 22.6 1 2.4 22.6 1 2.2 22.6 1 2.5 22.5 1 2.3 22.6 1 2.7
0.0 1 1.3 0.0 1 1.3 0.0 1 1.6 0.1 1 1.6 0.0 1 1.3 0.1 1 1.3 0.1 1 1.6 0.1 1 1.6 0.1 1 1.3 0.1 1 1.4 0.2 1 1.3 0.0 1 1.3
.065 .065 .075 .079 .061 .065 .075 .075 .062 .066 .067 .058
Stage of growth (y)
Y, prediction of MPAH; Yo, simplified prediction of MPAH; X, starting value of MPAH to the prediction. Table IV. Correlations among values of AIMFM, regressive equations with respective squared multiple correlations (R2), predicted means, means of error, and coefficients of accuracy Correlation
Regressive equation
R2
Predicted mean ( )
Mean of error ( )
Coefficient of accuracy ( )
9-12
.45
9-14
.44
12-14
.73
9-16
.44
12-16
.76
14-16
.80
Y 5 0.48X 1 49.8 Y0 5 0.96X Y 5 0.49X 1 45.5 Y0 5 0.94X Y 5 0.77X 1 19.7 Y0 5 0.97X Y 5 0.5X 1 42.4 Y0 5 0.92X Y 5 0.83X 1 12.0 Y0 5 0.95X Y 5 0.83X 1 14.9 Y0 5 0.98X
.20 –.004 .19 .04 .53 .49 .19 .06 .58 .57 .65 .62
99.0 1 2.6 98.3 1 5.1 95.7 1 2.6 96.3 1 5.0 96.0 1 4.3 96.1 1 5.5 93.6 1 2.7 94.2 1 4.9 94.2 1 4.7 94.1 1 5.4 94.8 1 5.0 94.3 1 5.8
–0.1 1 5.0 –0.7 1 5.6 –0.6 1 5.4 0.0 1 5.9 –0.3 1 4.1 0.2 1 4.2 –0.8 1 5.5 –0.1 1 5.9 –0.2 1 4.0 –0.3 1 4.0 0.4 1 3.6 0.0 1 3.8
–.052 –.064 –.063 .061 –.046 –.046 –.067 –.064 –.045 –.046 .042 .040
Stage of growth (y)
Y, prediction of AIMFM; Yo, simplified prediction of AIMFM; X, starting value of AIMFM to the prediction.
of distal force for approaching Class II patients,5,6,19 despite extrusion and distal crown tipping can be produced in the maxillary first molars.20 Variation of the mandibular plane is an important factor in the quality of results,20 and it has been associated with such effects.6,20,26 Regarding possible mechanics to correct Class II malocclusions, Tweed12 argued that the fault lies in our inability to master the potentialities of orthodontic mechanisms. Comprehension of growth is relevant to improve this ability, especially for skeletal Class II patients during puberty.4,11,21-23,32,33 As growth changes in untreated cases are recognized, the natural development of craniofacial aspects could be further preserved along the approach. Once the immutability of the maxilla has been challenged, parameters of natural changes in MPAH and AIMFM were determined with the reference of the PP (Tables I and II).4 Even though the predictions of growth were
hypothetical,34 the findings were consistent35 that gradual increments of growth can be expected on posterior alveolar height (Tables I and II), and that the maxillary first molars generally have distal inclinations in younger patients, changing naturally to upright positions (Tables I and II). The vertical alveolar growth previously reported was confirmed in our findings.11,22,32 Significant increases in MPAH were noted in intervals of ages equal to or longer than 3 years (Table I). The overall increase in MPAH was the greatest mean, whereas changes in shorter stages were not statistically different (Table II). This suggests that vertical alveolar growth is a long-term process of incremental changes in alveolar height that develops slowly and gradually. Otherwise, MPAH might not show a natural increase during short periods (Table V), especially in boys at younger ages and girls at later stages. Thus, discrepant means of
Martinelli et al
American Journal of Orthodontics and Dentofacial Orthopedics Volume 137, Number 6
779
Analysis of agreement between predicted and actual changes of MPAH
Table VI. Analysis of agreement between predicted and actual growth changes on AIMFM
Stage of growth prediction (y)
Stage of growth prediction (y)
Table V.
9-12 Agreed Disagreed Actual frequency 9-14 Agreed Disagreed Actual frequency 12-14 Agreed Disagreed Actual frequency 9-16 Agreed Disagreed Actual frequency 12-16 Agreed Disagreed Actual frequency 14-16 Agreed Disagreed Actual frequency
Growth changes Incremental
Nonincremental
Agreement (prediction / actual)
27 27 (90%)
3 3 (10%)
27 (90%) 3 (10%) 30 (100%)
30 30 (100%)
0%
30 (100%) 0% 30 (100%)
24 24 (80%)
6 6 (20%)
24 (80%) 6 (20%) 30 (100%)
30 30 (100%)
0%
30 (100%) 0% 100%
30 30 (100%)
0%
30 (100%) 0% 30 (100%)
24 24 (80%)
6 6 (20%)
24 (80%) 6 (20%) 30 (100%)
9-12 Agreed Disagreed Actual frequency 9-14 Agreed Disagreed Actual frequency 12-14 Agreed Disagreed Actual frequency 9-16 Agreed Disagreed Actual frequency 12-16 Agreed Disagreed Actual frequency 14-16 Agreed Disagreed Actual frequency
Pattern of changes Mesial tipping
Distal tipping
Agreement (prediction / actual)
21 1 22 (73%)
1 7 8 (27%)
22 (73%) 8 (27%) 30 (100%)
26 26 (87%)
4 4 (13%)
26 (87%) 4 (13%) 30 (100%)
23 23 (77%)
7 7 (23%)
23 (77%) 7 (23%) 30 (100%)
27 27 (90%)
3 3 (10%)
27 (90%) 3 (10%) 30 (100%)
26 26 (87%)
4 4 (13%)
26 (87%) 4 (13%) 30 (100%)
18 4 22 (73%)
8 8 (27%)
18 (60%) 12 (40%) 30 (100%)
High level of confidence $90%.
High level of confidence $90%.
alveolar growth in the literature can be explained, since studies are conducted with longer or shorter periods of growth.11,22 Skeletal maturation23 and vertical facial pattern26 have been associated with the variability of changes. Isaacson et al26 stated that MPAH is increased in patients with a high mandibular plane. Even though subjects with low, average, and high mandibular planes were included in this study, the influence of vertical pattern on the variability of MPAH could not be assessed. Favorably, strong correlations were found (Table III), indicating that the higher the starting height of the maxillary molars, the greater the expectation of increments. If high MPAH is shown in subjects with a high mandibular plane, greater incremental changes can be expected.26 Conversely, this behavior might not be observed at upper anterior alveolar height, because of the weaker correlations reported elsewhere.32 Furthermore, these parameters might be misleading in boys with low MPAH at early ages and in girls with high molar height after 14 years of age. Depending on the treatment objectives, the starting MPAH (Table I) and sexual dimorphism (Table II) are important for determining the timing of treatment in
skeletal Class II patients. Decisions concerning the point of extraoral traction are based on the proportion of molar extrusion and intrusion and alveolar growth desired for each patient.18,19 Minimal physiologic recovery was reported after cervical headgear therapy during growth with small forces applied over an average period of 2 years 8 months.36 In patients with long faces, alveolar growth should be maximized and maxillary molar extrusion minimized.26 Therefore, combined extraoral traction must be considered.7 The use of parietal headgear for a long period might improve the goal of molar intrusion, but using it in later stages is reasonable only for boys (Table II).19 Patients with high posterior alveolar height are more favorable for molar intrusion because greater increments are expected (Table III). In Class II patients with low maxillary posterior height, this expectation is weaker (Table III). Hence, natural changes need to be managed slowly and gradually over a longer time to maximize the growth potential (Table II). Extrapolating these findings, we can assume that 2-phase treatment with cervical headgear is favorable for alveolar growth, mainly in girls with deep bite and low mandibular plane.37 Obviously, the suggestions for clinical benefits resulting
780
Martinelli et al
from the management of maxillary alveolar growth should be evaluated in further studies. Generally, the maxillary first molars showed distal crown inclinations at 9 years of age, with a tendency to upright gradually until age 16 (Table II). Although molar crown tipping varied among subjects (Tables II and VI), measurements of AIMFM were between 113.7 and 85.1 , denoting distal or vertical inclination. These findings were corroborated by Henry,27 who found no mesial inclination of the maxillary first molars of Class II patients. Therefore, the distal inclination noted in the maxillary first molars after using headgear2,7,18,20 or other mechanisms21 seems to be compatible with this population. Hypothetical contributions of AIMFM to the severity of undesirable results could not be ascertained, because growth changes in AIMFM were not constant (Tables II, IV, and VI). Conversely, Skieller et al24 postulated the importance of the intermolar angle to predict mandibular rotation, which was weak in a mixed sample including treated patients.38 Significant molar crown tipping was observed in longer periods (Tables I and II), suggesting that this natural aspect can be expected until 16 years of age or in later posttreatment evaluations. This agrees with the finding of Badell,7 who reported a strong tendency to upright the maxillary molars after the headgear period. The squared multiple correlation coefficient (R2), varying between 0 and 1, indicates the fraction of changes that can be explained by natural growth.24 However, the strong R2 predictions of MPAH (Table III), from 12 to 14 and 14 to 16 years, were not confirmed in the analysis of agreement (Table V). Between ages 14 and 16 years, sexual dimorphism was observed in the statistics (Table II) and in agreement (Table V), indicating the reliability of this method only for boys. Values of R2, mean of error, coefficient of accuracy (Table III), and agreement (Table V) demonstrated the highest level of validity in estimating MPAH from 12 to 16 years old. Predictions of MPAH had high validity in assessing periods of 3 years or longer (Table V) in white skeletal Class II subjects, whose starting value did not exceed 1 SD from the corresponding mean (Table I).34 Although incremental changes were predicted in every situation (Table V), the pattern of errors was unsystematic when growth changes actually occurred.35 Logically, limitations in the accuracy of predictions are likely, as observed in growth intervals of 2 years (Table V).34 The risk of errors is reduced if the method is selected according to demographic characteristics,39 type of malocclusion, skeletal maturation,22 age, sexual dimorphism, and initial value of the predicted variable.34 Thames et al40 reported a statistical difference between predicted and actual changes on this
American Journal of Orthodontics and Dentofacial Orthopedics June 2010
variable; this disagrees with our study, in which another design was used. The agreement of 90% between the predicted and actual overall changes on AIMFM (Table VI) suggested high validity of the methods. However, the lack of accuracy shown by the R2 values (Table IV) associated with low agreement in other stages (Table VI) suggested a bias. In addition, the high R2 value found in later stages (Table IV) was not corroborated by the analysis of agreement (Table VI). Not only the amounts of change (Table IV), but also the pattern of molar tipping (Table VI) were unpredictable. Further investigations are necessary to determine factors beyond growth that influence changes in AIMFM. The pattern of tissue remodeling in alveolar bone does not involve classic Harvesian remodeling, because of the influence of the dental roots, unique forces in the oral cavity, and the continuous accommodation of Sharpey’s fibers.25 Thus, the possibility of a biologic adaptation in the alveolar bone during mechanical stimulation cannot be totally disregarded.5,20 Natural increments in MPAH were gradual, indicating that slower orthodontic treatment might take more advantage of growth in skeletal Class II patients.41 No statistically significant orthopedic change is produced with combined traction headgear worn for a relatively short period of growth.7 Perhaps wearing headgear with a lower total force for a longer period of growth would improve treatment goals.7 Predictive equations for MPAH are recommended to analyze mechanical extrusion and intrusion of the maxillary molars over a 3-year period. CONCLUSIONS
In untreated white adolescents with skeletal Class II malocclusion, orthodontists can expect (1) gradual maxillary posterior alveolar growth without important periods of change, (2) greater increases of MPAH in boys from 14 to 16 years of age, (3) a distal crown AIMFM at the age of 9 years tending to upright naturally, and (4) marked variability of natural changes in AIMFM between patients. The equations were valid to evaluate growth increments on MPAH during a 3-year period or longer. REFERENCES 1. Elder J, Tuenge R. Cephalometric and histologic changes produced by extraoral high-pull traction to the maxilla in Macaca mulatta. Am J Orthod 1974;66:599-617. 2. Hubbard G, Nanda RS, Currier G. A cephalometric evaluation of nonextraction cervical headgear treatment in Class II malocclusion. Angle Orthod 1994;64:359-70. 3. Melsen B. Effects of cervical anchorage during and after treatment: an implant study. Am J Orthod 1978;73:526-40.
American Journal of Orthodontics and Dentofacial Orthopedics Volume 137, Number 6
4. Klein P. An evaluation of cervical traction on the maxilla and the upper first permanent molars. Angle Orthod 1957;27:61-8. 5. Kloehn S. Guiding alveolar growth and eruption of teeth to reduce treatment time and produce a more balanced face. Angle Orthod 1947;17:10-33. 6. Lima Filho R, Lima A, De Oliveira Ruellas AC. Longitudinal study of anteroposterior and vertical maxillary changes in skeletal Class II patients treated with Kloehn cervical headgear. Am J Orthod Dentofacial Orthop 2003;73:187-93. 7. Badell M. An evaluation of extraoral combined high-pull traction and cervical traction to the maxilla. Am J Orthod 1976;69:431-46. 8. Voudouris J, Woodside D, Altuna G, Kuftinec M, Angelopoulos G, Bourque P. Condyle-fossa modifications and muscle interactions during Herbst treatment, part 1. New technological methods. Am J Orthod Dentofacial Orthop 2003;123:604-13. 9. Voudouris J, Woodside D, Altuna G, Angelopoulos G, Bourque P, Lacouture C. Condyle-fossa modifications and muscle interactions during Herbst treatment, part 2. Results and conclusions. Am J Orthod Dentofacial Orthop 2003;124:13-29. 10. Vargervik K, Harvold EP. Response to activator treatment in Class II malocclusions. Am J Orthod 1985;88:242-51. 11. Almeida M, Henriques J, Almeida R, Almeida-Pedrin R, Ursi W. Treatment effects produced by the bionator appliance. Comparison with an untreated Class II sample. Eur J Orthod 2004;26:65-72. 12. Tweed C. The application of the principles of the egdewise arch in the treatment of Class II, division 1, malocclusion: part II. Angle Orthod 1936;6:255-7. ˚ rtun J, Joondeph D, Little R. Long-term stability of 13. Fidler B, A Angle Class II, Division 1 malocclusions with successful occlusal results at end of active treatment. Am J Orthod Dentofacial Orthop 1995;107:276-85. 14. Jarabak J, Fizzell J. Technique and treatment with the light-wire appliances. St Louis: Mosby; 1963. 15. Bishara S, Cummins D, Zaher A. Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment. Am J Orthod Dentofacial Orthop 1997;111:18-27. 16. Rosenblum R. Class II malocclusion: mandibular retrusion or maxillary protrusion. Angle Orthod 1995;65:49-62. 17. Bailey L, Proffit W, White R. Assessment of patients for orthognathic surgery. Semin Orthod 1999;5:209-22. 18. Armstrong M. Controlling the magnitude, direction and duration of extraoral force. Am J Orthod 1971;59:217-43. 19. Oosthuizen L, Dijkman J, Evans W. A mechanical appraisal of the Kloehn extraoral assembly. Angle Orthod 1973;43:221-32. 20. Merrifield L, Cross J. Directional forces. Am J Orthod 1970;57: 435-64. 21. Bussick T, McNamara J. Dentoalveolar and skeletal changes associated with the pendulum appliance. Am J Orthod Dentofacial Orthop 2000;117:333-43. 22. Arat Z, Ru¨bendu¨z M. Changes in dentoalveolar and facial heights during early and late growth periods: a longitudinal study. Angle Orthod 2005;75:69-74.
Martinelli et al
781
¨ zdiler E, Ru¨bendu¨z M, Erdogan B. Cranifacial 23. Arat Z, Ko¨klu¨ A, O growth and skeletal maturation: a mixed longitudinal study. Eur J Orthod 2001;23:355-61. 24. Skieller V, Bjork A, Linde-Hansen T. Prediction of mandibular growth rotation evaluated from a longitudinal implant sample. Am J Orthod 1984;86:359-70. 25. Sodek J, McKee M. Molecular and cellular biology of alveolar bone. Periodontol 2000;24:99-126. 26. Isaacson J, Isaacson R, Speidel T, Worms F. Extreme variation in vertical facial growth and associated variation in skeletal and dental relations. Angle Orthod 1971;41:219-29. 27. Henry RG. A classification of Class II, division 1 malocclusion. Angle Orthod 1957;27:83-92. 28. Greulich W, Pyle S. Radiographic atlas of skeletal development of hand and wrist. Stanford, Calif: Stanford University Press; 1959. 29. Hoffelder L, de Lima E, Martinelli F, Bolognese A. Soft-tissue changes during facial growth in skeletal Class II individuals. Am J Orthod Dentofacial Orthop 2007;131:490-5. 30. Martinelli F, Lima EM, Rocha R, Tirre-Araujo M. Prediction of lower permanent canine and premolars width by correlation methods. Angle Orthod 2005;75:805-8. 31. Luiz R, Costa A, Nadanovsky P. Epidemiologia e bioestatıstica na pesquisa odontolo´gica, Sa˜o Paulo, Brazil: Editora Atheneu; 2005. 32. Naumann S, Behrents R, Buschang P. Vertical components of overbite change: a mathematical model. Am J Orthod Dentofacial Orthop 2000;117:486-95. 33. Schudy F. Vertical growth versus anteroposterior growth as related to function and treatment. Angle Orthod 1964;34:75-93. 34. Moyers R, Johnston L, Rao C, Tanner J, Woodside D. Seminar 2. Prediction of cranio-facial growth. In: Moyers R, Krogman W, editors. Cranio-facial growth in man. New York: Pergamon Press; 1971. p. 293-313. 35. Collett T. Evidence, judgment, and the clinical decision: an argument for evidence-based orthodontics. Am J Orthod Dentofacial Orthop 2008;133:190-4. 36. Wieslander L, Buck D. Physiologic recovery after cervical traction therapy. Am J Orthod 1974;66:294-301. 37. Gianelly A. One-phase versus two-phase treatment. Am J Orthod Dentofacial Orthop 1995;108:556-9. 38. Lee RS, Daniel FJ, Swartz M, Baumrind S, Korn EL. Assessment of a method for the prediction of mandibular rotation. Am J Orthod Dentofacial Orthop 1987;91:395-402. 39. Bishara S, Jakobsen J, Abdallah E, Fernandez A. Comparisons of mesiodistal and buccolingual crown dimensions of the permanent teeth in three populations from Egypt, Mexico, and the United States. Am J Orthod Dentofacial Orthop 1989;96: 416-22. 40. Thames T, Sinclair P, Alexander R. The accuracy of computerized growth prediction in Class II high-angle cases. Am J Orthod 1985; 87:398-405. 41. Joondeph D. Retention and relapse. In: Graber T, Vanarsdall R, editors. Orthodontics: current principles and techniques. St Louis: Mosby; 1994.