Longitudinal growth changes in subjects with deepbite

Introduction

This study was a cephalometric evaluation of the growth changes in untreated subjects with deepbite at 4 time points during their developmental ages (from the early mixed dentition to the permanent dentition, and from the prepubertal phase to young adulthood).

Methods

A sample of 29 subjects with deepbite (overbite >4.5 mm) was followed longitudinally from about 9 through about 18 years of age. Dentofacial changes at 4 times, defined by the cervical vertebral maturation method, were analyzed on lateral cephalograms. Nonparametric statistical analysis was used for comparisons.

Results

Overbite improved on average by 1.3 mm between the first and last measurements; it worsened significantly during the prepubertal period, but it improved significantly at the pubertal growth spurt. From the prepubertal ages through young adulthood, overbite improved in 83% of the subjects and self-corrected in 62% of the subjects. Improvements in overbite were related to the initial amount of maxillary incisor proclination. The significant improvement in overbite during the adolescent growth spurt depended on the amount of vertical growth of the mandibular ramus and the eruption of the mandibular molars.

Conclusions

Subjects with deepbite showed worsened occlusal conditions during the prepubertal and mixed dentition phases, but had significant improvements thereafter. Improvements in overbite cannot be predicted on the basis of skeletal vertical relationships. These results provide useful indications for appropriate orthodontic treatment timing for an increased overbite.

Deepbite is an occlusal condition characterized by an excessive vertical overbite. The increased depth of the bite at the incisor level can be associated with skeletal hypodivergence, otherwise called short-face syndrome or low-angle disharmony. Deepbite is a frequent problem, especially in patients with Class II malocclusions. About 50% of non-Hispanic white adolescents in the United States have an overbite greater than 4 mm, and over 10% of them have an overbite greater than 6 mm. Reported unfavorable consequences of an untreated deepbite include increased anterior crowding, maxillary dental flaring, and associated periodontal sequelae. Increased overbite has been regarded as a possible cause of severe interference with lateral and anterior mandibular movements in mastication and temporomandibular joint problems.

Despite the high prevalence of increased overbites in the general population, few authors have analyzed changes in the depth of the bite during growth. A series of studies has described the development of “normal overbite” and its variations during the mixed and permanent dentitions, sometimes with analysis of small subsamples of subjects showing increased overbite at different age periods. Only Bergersen attempted an extensive study on the changes in overbite from 8 to 20 years of age. He classified the sample into subjects with increased overbite (>3 mm) and normal or decreased overbite (≤3 mm). General trends observed in this study for the increased overbite group were that 80% of the overbites greater than 3 mm at 8 years still exceeded 3 mm by adulthood, and overbite increased during the exchange of incisors and deciduous molars from 8 to 11 years of age, whereas it decreased during eruption of the second and third molars between 13 and 20 years of age. The study by Bergersen, however, was semilongitudinal, because the subjects were not the same at all developmental ages. Moreover, the investigation focused on changes in overbite in general and not on changes in deepbite in particular. Finally, no appraisal of individual skeletal maturity concurrent with the changes in overbite was performed, although this aspect is vital to longitudinal studies of growing subjects.

Occlusal changes in postadolescent subjects with Class II Division 1 deepbite malocclusion were investigated by Feldmann et al. This study was carried out on dental casts only, and it failed to find any significant worsening of the deepbites in the examined period. A 25-year follow-up study of an Icelandic population showed that, from adolescence to midadulthood, about 50% of the deepbite subjects showed improvement in overbite. These epidemiologic observations were made only from clinical examinations.

The aim of our study was to provide a cephalometric evaluation of the growth changes in untreated subjects with deepbite at 4 time points during the developmental ages (early mixed dentition to permanent dentition, and prepubertal phases to young adulthood). The main features of this investigation were a specific focus on growth changes of untreated subjects with deepbite at the initial observation (overbite >4.5 mm); a longitudinal study, with the same subjects evaluated at 4 time points; and the use of a biologic indicator of individual skeletal maturity at all developmental periods.

Material and methods

The files of the University of Michigan Growth Study (n = 706) and the Denver Child Growth Study (n = 155) were searched for longitudinal records of orthodontically untreated subjects with deepbite malocclusions. Lateral cephalograms of good quality at 4 consecutive developmental intervals corresponding to the different stages in cervical vertebral maturation (CS1-CS6) had to be available for all selected subjects.

The first observation (T1) corresponded to CS1 (prepubertal); the second observation (T2) corresponded to CS3 (beginning of puberty); the third observation (T3) corresponded to either CS4 or CS5 (postpubertal); and the fourth observation (T4) corresponded to a developmental period that was at least 1 year after the appearance of CS6 (young adulthood). Longitudinal records for all subjects, therefore, covered the entire circumpubertal period from prepubertal through young adult stages of skeletal development. All subjects were of European-American ancestry (white) and had no craniofacial abnormalities or tooth anomalies in number or eruption (eg, supernumeraries, congenitally missing teeth, or impacted canines).

Subjects with deepbite malocclusion were diagnosed according to an overbite greater than 4.5 mm. This value agrees with an average value for the definition of increased overbite in the literature. The sample consisted of 29 subjects (15 boys, 14 girls). Their mean age at T1 was 9 years 2 months ± 11 months, with all subjects in the early mixed dentition; at T2, it was 12 years 4 months ± 10 months, with subjects in the late mixed and early permanent dentitions; at T3, it was 15 years 2 months ± 11 months, with all subjects in the permanent dentition; and at T4, it was 17 years 8 months ± 11 months, with all subjects having permanent dentition. There were 13 subjects with Class I occlusion, 8 with Class II Division 1 malocclusion, and 8 with Class II Division 2 malocclusion.

Cephalograms were traced by 1 investigator (L.F.) and then verified for landmark location, anatomic contours, and tracing superimpositions by a second (T.B.). Any disagreements were resolved by retracing the landmark or structure to the satisfaction of both observers. A customized digitization regimen and analysis provided by Viewbox (version 3.1, dHAL Software, Kifissia, Greece) was used for all cephalograms examined in this study. The customized cephalometric analysis containing measurements from the analyses of Steiner, Jacobson, Ricketts, and McNamara was used, generating 29 variables—9 angular, 19 linear, and 1 ratio—for each tracing.

All sets of cephalograms were traced at the same time. Fiducial markers were placed in the maxilla and the mandible on the first tracing and then transferred to the second, third, and fourth tracings in each subject’s cephalometric series, based on superimposition of internal maxillary or mandibular structures. The maxillae were superimposed along the palatal plane by registering on the bony internal details of the maxilla superior to the incisors, and the superior and inferior surfaces of the hard palate. Fiducial markers were placed in the anterior and posterior part of the maxilla along the palatal plane. This superimposition described the movement of the maxillary dentition relative to the maxilla. The mandibles were superimposed posteriorly on the outline of the mandibular canal. Anteriorly, they were superimposed on the anterior contour of the chin and the bony structures of the symphysis. A fiducial marker was placed in the center of the symphysis and another in the body of the mandible near the gonial angle. These superimpositions facilitated measuring the movement of the mandibular dentition relative to the mandible.

The magnifications of the 2 data sets were different, with the lateral cephalograms from the University of Michigan Growth Study having a magnification of 12.1% and those from the Denver Child Growth Study having a magnification of 4%. Therefore, the lateral cephalograms from the 2 growth studies were corrected to match an 8% enlargement factor.

Before the analysis of the lateral cephalograms, the power of the study when assessing cumulative occlusal changes and skeletal changes at the 4 times, respectively, was calculated (SigmaStat version 3.5, Systat Software, Point Richmond, Calif). For the occlusal changes, on the basis of the average change in overbite (0.6 mm) and the standard deviation (1.1 mm) in untreated subjects from early adolescence to adulthood in previous studies, the power of this study with a sample of 29 subjects was 0.81 at α = 0.05. For the skeletal changes, on the basis of the average change in inclination of the mandibular plane to the palatal plane (3.2°) and the standard deviation (4.4°) in untreated subjects from early adolescence to adulthood in a previous study, the power of this study with a sample of 34 subjects was 0.97 at α = 0.05.

A total of 42 lateral cephalograms randomly chosen from all observations were retraced and redigitized to calculate the method error with Dahlberg’s formula. The errors for linear measurements ranged from 0.2 (overjet) to 0.8 mm (Pg to nasion perpendicular); the errors for angular measurements varied from 0.4° (ANB) to 1.4° (L1 to mandibular plane).

The assessment of the stages in cervical vertebral maturation on the lateral cephalograms for each subject was performed by 1 investigator (T.B.) and verified by a second (L.F.). Any disagreements were resolved to the satisfaction of both observers.

Statistical analysis

Descriptive statistics for the dentoskeletal measurements in the deepbite sample at all 4 observation periods were calculated, and also for the between-stage changes (T1-T2, T2-T3, T3-T4, and the overall T1-T4). The Kolmogorov-Smirnov test showed lack of normality of distribution for several measurements used in the study. Comparisons of the values of the cephalometric variables at the 4 time periods were carried out with nonparametric statistics with the Friedman test (analysis of variance [ANOVA] on ranks for repeated measures) followed by Tukey post-hoc tests (SigmaStat software).

The prevalence rates for the following changes in overbite (variable OVB) were calculated at T2, T3, and T4 with respect to the values at T1, and they were expressed in terms of numbers of subjects showing changes during specific time intervals (T1-T2, T1-T3, and T1-T4): improvement in OVB equal to or greater than −1.5 mm (more negative change); improvement in OVB equal to or greater than −0.5 mm (more negative change); and worsening of OVB equal to or greater than +0.5 mm (more positive change).

The prevalence rates of subjects showing correction of deepbite at T2, T3, and T4 were calculated. Correction of deepbite was assessed when the OVB value was smaller than 4 mm at that time point.

Logistic regression on the cephalometric variables at T1 with the value of OVB at T4 (classified as “self-corrected” when OVB was <4 mm vs “not corrected,” when OVB was still >4 mm) as the dependent variable was performed (stepwise method, with P to enter <0.05 and P to remove >0.1). The aim was to identify T1 predictive variables for favorable or unfavorable outcomes in OVB.

A multiple linear regression analysis was performed with the T2 to T3 changes in OVB as the dependent variable and the T2 to T3 changes in vertical dentoskeletal mandibular parameters as the independent variables (FH to mandibular plane, S-Go/N-Me, Co-Go, and L6 vertical). The goal of this analysis was to evaluate whether the changes in overbite at the pubertal growth spurt were related to changes in mandibular structures. It is known that dentoskeletal mandibular components can be affected significantly by growth changes at puberty.

Logistic regression and multiple linear regression analyses were carried out with statistical software (version 17.0, SPSS, Chicago, Ill).

Results

Descriptive statistics for the cephalometric measurements at the 4 observation periods are reported in Table I , along with the statistical comparisons among the stages. No significant growth changes were detected in the cranial base angle.

Table I
Descriptive statistics for cephalometric measurements at the 4 observation periods
Cephalometric measures
N = 29
T1 T2 T3 T4 Growth changes and statistical comparisons
Mean SD Mean SD Mean SD Mean SD T1-T2 prepubertal T2-T3 pubertal T3-T4 postpubertal T1-T4 overall
Cranial base
NSBa (°) 130.2 4.6 130.1 4.8 130.4 4.7 130.2 5.1 −0.2 0.4 −0.3 0.0
Maxillary skeletal
SNA (°) 80.6 2.7 82.0 3.1 81.9 3.4 82.2 3.1 1.4 −0.1 0.2 1.6
Pt A to nasion perp (mm) −0.3 3.1 1.1 3.1 0.9 3.7 0.1 3.8 1.4 −0.2 −0.8 0.4
Co-Pt A (mm) 83.8 3.6 89.1 4.0 92.8 4.1 93.5 4.8 5.3 3.7 0.8 9.8
Mandibular skeletal
SNB (°) 76.7 2.0 78.0 2.8 78.5 2.9 78.8 2.8 1.3 0.5 0.3 2.1
Pg to nasion perp (mm) −6.6 4.9 −3.6 4.9 −2.5 5.9 −3.6 6.5 3.0 1.1 −1.0 3.0
Co-Gn (mm) 105.9 3.9 111.6 4.0 121.2 5.0 122.9 5.4 5.9 9.6 1.7 17.4
Maxillary/mandibular
ANB (°) 3.9 1.8 4.0 1.6 3.5 2.1 3.4 2.1 0.1 −0.5 −0.1 −0.5
Wits (mm) 0.3 2.2 0.9 1.7 1.2 2.7 1.8 3.0 0.5 0.2 0.6 1.4
Max / mand diff (mm) 20.1 2.5 23.1 3.5 26.2 4.2 25.7 4.3 3.0 3.0 1.5 7.7
Vertical skeletal
FH to palatal plane (°) −2.2 3.2 −2.0 2.7 −1.2 3.0 −1.2 3.2 0.2 0.8 0.0 1.0
FH to mandibular plane (°) 23.3 3.6 21.6 4.2 19.9 4.0 19.5 4.1 −1.7 −1.7 −0.4 −3.8
Palatal pl. to mand. pl. (°) 21.1 4.2 19.5 3.4 18.7 4.1 18.3 4.1 −1.6 −0.9 −0.4 −2.8
N-ANS (mm) 48.8 2.4 52.7 2.6 55.7 3.1 55.7 3.0 3.9 2.9 0.0 6.9
ANS-Me (mm) 57.0 4.4 60.2 4.9 63.0 5.4 64.8 6.3 3.1 2.9 1.8 7.9
N-Me (mm) 106.5 5.3 113.7 5.5 119.8 7.1 121.8 8.0 7.2 6.0 2.1 15.2
S-Go (mm) 64.5 4.0 70.2 4.6 75.3 5.2 78.1 6.3 5.7 5.1 2.8 13.6
S-Go/N-Me (%) 65.5 0.03 66.8 0.04 68.0 0.04 69.3 0.04 1.3 1.2 1.3 3.8
Co-Go (mm) 51.6 2.9 56.2 3.7 60.9 3.6 63.6 4.6 4.5 4.8 2.6 12.0
ArGoiMe (°) 120.3 5.3 118.0 4.9 116.5 5.1 114.8 5.1 −2.3 −1.5 −1.7 −5.5
Interdental
Overjet (mm) 4.1 1.2 4.2 1.3 4.4 1.7 4.5 1.7 0.2 0.2 0.1 0.4
Overbite (mm) 5.5 0.6 6.3 0.8 4.6 1.2 4.2 1.0 0.8 −1.6 −0.4 −1.3
Molar relationship (mm) −0.4 1.6 0.3 1.4 0.6 1.7 0.6 1.6 0.8 0.3 0.0 1.1
Maxillary dentoalveolar
U1 to FH (°) 108.5 7.0 107.3 6.9 107.7 7.7 107.6 9.0 −1.2 0.4 −0.1 −0.9
U1 vertical (mm) 24.9 2.2 26.4 2.8 26.8 3.1 27.3 2.9 1.3 0.5 0.5 2.4
U6 vertical (mm) 17.6 1.8 19.7 1.9 21.9 2.3 23.1 2.7 2.2 2.3 1.2 5.5
Mandibular dentoalveolar
L1 to mandibular plane (°) 96.1 5.5 97.3 5.5 98.1 6.4 97.2 7.2 1.2 0.7 −0.8 1.1
L1 vertical (mm) 30.9 2.1 32.7 2.6 33.9 2.8 34.7 3.1 1.8 1.2 0.6 3.8
L6 vertical (mm) 21.4 1.4 24.3 2.1 25.9 2.7 27.2 3.0 2.9 1.6 1.3 5.8
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Apr 11, 2017 | Posted by in Orthodontics | Comments Off on Longitudinal growth changes in subjects with deepbite
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