Modeling longitudinal mandibular growth: percentiles for gnathion from 6 to 15 years of age in girls

An open-source, three-dimensional growth model of the mandible

The available reference data for the mandible and mandibular growth consists primarily of two-dimensional linear or angular measurements. The aim of this study was to create the first open-source, three-dimensional statistical shape model of the mandible that spans the complete growth period. Computed tomography scans of 678 mandibles from children and young adults between 0 and 22 years old were included in the model. The mandibles were segmented using a semi-automatic or automatic (artificial intelligence-based) segmentation method. Point correspondence among the samples was achieved by rigid registration, followed by non-rigid registration of a symmetrical template onto each sample. The registration process was validated with adequate results. Principal component analysis was used to gain insight in the variation within the dataset and to investigate age-related changes and sexual dimorphism. The presented growth model is accessible globally and free-of-charge for scientists, physicians and forensic investigators for any kind of purpose deemed suitable. The versatility of the model opens up new possibilities in the fields of oral and maxillofacial surgery, forensic sciences or biological anthropology. In clinical settings, the model may aid diagnostic decision-making, treatment planning and treatment evaluation.

Validation of Machine Learning Models for Craniofacial Growth Prediction

This study identified the most accurate model for predicting longitudinal craniofacial growth in a Japanese population using statistical methods and machine learning. Longitudinal lateral cephalometric radiographs were collected from 59 children (27 boys and 32 girls) with no history of orthodontic treatment. Multiple regression analysis, least absolute shrinkage and selection operator, radial basis function network, multilayer perceptron, and gradient-boosted decision tree were used. The independent variables included 26 coordinated values of skeletal landmarks, 13 linear skeletal parameters, and 17 angular skeletal parameters in children ages 6 to 12 years. The dependent variables were the values of the 26 coordinated skeletal landmarks, 13 skeletal linear parameters, and 17 skeletal angular parameters at 13 years of age. The difference between the predicted and actual measured values was calculated using the root-mean-square error. The prediction model for craniofacial growth using the least absolute shrinkage and selection operator had the smallest average error for all values of skeletal landmarks, linear parameters, and angular parameters. The highest prediction accuracies when predicting skeletal linear and angular parameters for 13-year-olds were 97.87% and 94.45%, respectively. This model incorporates several independent variables and is useful for future orthodontic treatment because it can predict individual growth.

A three-dimensional statistical shape model of the growing mandible

Mandibular growth and morphology are important topics in the field of oral and maxillofacial surgery. For diagnostic and planning purposes, a normative database or statistical shape model of the growing mandible can be of great benefit. A collection of 874 cadaveric children’s mandibles with dental age between 1 and 12 years old were digitized using computed tomography scanning and reconstructed to three-dimensional models. Point correspondence was achieved using iterative closest point and coherent point drift algorithms. Principal component analysis (PCA) was applied to find the main modes of variation in the data set. The average mandible was presented, along with the first ten PCA modes. The first mode explained 78% of the total variance; combining the first ten modes accumulated to 95% of the total variance. The first mode was strongly correlated with age and hence, with natural growth. This is the largest study on three-dimensional mandibular shape and development conducted thus far. The main limitation is that the samples lack information such as gender and cause of death. Clinical application of the model first requires validation with contemporary samples.

Is securing normal dentofacial development an indication for tonsil surgery in children? A systematic review and meta-analysis

OBJECTIVE

Tonsil surgeries are common operations in the field of paediatric otorhinolaryngology. Often, the indication for these operations is hypertrophied tonsils. Paediatric sleep-disordered breathing and mouth-breathing are conventional situations caused by the hypertrophied tonsils. Both of these are further associated with dentofacial development alterations. Securing normal dentofacial development, or restoring it, is often used as an indication for tonsil surgery. In this review and meta-analysis, we assessed the contemporary literature to clarify whether tonsil surgery has an effect on dentofacial development in children.

METHODS

Studies with children aged 3-10 years who underwent tonsil surgery and were compared to non-operated controls using dentofacial parameters were included to the review. Search strategies were planned for specific databases. The Newcastle-Ottawa scale was used to assess the risk of bias. A meta-analysis was performed when the data was methodologically homogenous enough to be pooled.

RESULTS

The inclusion criteria for the review were fulfilled in 8 studies. The overall quality of the individual studies was judged to be moderate at best. The data were methodologically homogenous enough to be pooled for the meta-analysis in only 2 studies. The results of the meta-analysis revealed that tonsil surgery has a positive effect on the growth direction of the mandible (p < 0.001).

CONCLUSIONS

There is modest evidence that suggests that tonsil surgery has a positive effect on the dentofacial development in children with hypertrophied tonsils. Securing normal dentofacial development should be one component, but not the only one, when the indications for tonsil surgery in children are considered.

Quantification of mandibular sexual dimorphism during adolescence

The present study investigates how sexual dimorphism in the human mandible develops in three-dimensionally during adolescence. A cross-sectional sample of mandibular meshes of 268 males and 386 females, aged between 8.5 and 19.5 years of age, were derived from cone beam computed tomography and were analysed using geometric morphometric methods. Growth trajectories of the mandible in males and females were modelled separately using a recently developed non-linear kernel regression framework. Growth rate and direction at a dense array of points all over the mandibular surface were visualized within each group and compared between groups. We found that mandibular sexual dimorphism already exists at 9 years of age, but this is mostly in size not in shape. The differential growth rate and duration between the sexes during pubertal growth largely explained by adult sexual dimorphism: the growth direction in both males and females is similar but the male mandible changed more quickly and over a longer period than the female mandible, where the growth rate peaked and declined earlier. This results in increasing dimorphism in form, which is evident in both size and shape. The development of dimorphic features, concentrated in the chin and ramus, were further visualized. The dense morphometric approach provides detailed three-dimensional quantitative assessment of the development of sexual dimorphism of the mandible.

Geometric morphometric analysis of craniofacial growth between the ages of 12 and 14 in normal humans

Aim

There is great variation of growth among individuals. The question whether patients with different skeletal discrepancies grow differently is biologically interesting but also important in designing clinical trials. The aim of the present study was to evaluate whether growth direction depends on the initial craniofacial pattern.

Subjects and method

The sample consisted of 350 lateral cephalograms of 175 subjects (91 females and 84 males) followed during normal growth without any orthodontic treatment. The examined ages were 12 (T1) and 14 (T2) years. The cephalograms were obtained from the American Association of Orthodontists Foundation (AAOF) Craniofacial Growth Legacy Collection (Burlington, Fels, Iowa, and Oregon growth studies). We digitally traced 15 curves on each cephalogram, comprehensively covering the craniofacial skeleton, and located 127 points on the curves, 117 of which were sliding semilandmarks and 10 fixed. Procrustes alignment, principal component analysis and two-block partial least squares analysis were performed, after sliding the semilandmarks to minimize bending energy.

Results

The first 10 principal components (PCs) described approximately 71 per cent of the total shape variance. PC1 was related to shape variance in the vertical direction (low/high angle skeletal pattern) and PC2 was mainly related to shape variance in the anteroposterior direction (Class II/Class III pattern). PC3 was mainly related to the shape variance of the mandibular angle. All subjects shared a similar growth trajectory in shape space. We did not find any correlation between the initial shape and the magnitude of shape change between T1 and T2, but males showed a greater shape change than females. The direction of shape change was moderately correlated to the initial shape (RV coefficient: 0.14, P < 0.001).

Conclusions

The initial shape of the craniofacial complex covaried weakly with the direction of shape change during growth.

Variation in timing, duration, intensity, and direction of adolescent growth in the mandible, maxilla, and cranial base: the Fels longitudinal study

There is considerable individual variation in the timing, duration, and intensity of growth that occurs in the craniofacial complex during childhood and adolescence. The purpose of this article is to describe the extent of this variation between traits and between individuals within the Fels Longitudinal Study (FLS). Polynomial multilevel models were used to estimate the ages of onset, peak velocity, and cessation of adolescent growth, the time between these ages, the amount of growth between these ages, and peak velocity. This was done at both the group and individual levels for standard cephalometric measurements of the lengths of the mandible, maxilla, and cranial base, the gonial angle, and the saddle angle. Data are from 293 untreated boys and girls age 4-24 years in the FLS. The timing of the adolescent growth spurt was, in general, not significantly different between the mandible and the maxilla, with each having an earlier age of onset, later age of peak velocity, and later age of cessation of growth as compared to the cranial base length. Compared to lengths, angles had in general later ages of onset, peak velocity, and cessation of growth. Accurate characterization of the ontogenetic trajectories of the traits in the craniofacial complex is critical for both clinicians seeking to optimize treatment timing and anatomists interested in examining heterochrony.

Vertical craniofacial growth changes in French-Canadians between 10 and 15 years of age

INTRODUCTION

Because of limited available reference data, this study described the vertical growth changes that occur in untreated adolescents 10 to 15 years of age and evaluated the validity of measurements commonly used to classify patients' vertical growth tendencies.

METHODS

The sample consisted of 228 subjects (119 boys, 109 girls) between 10 and 15 years of age with normal occlusions or malocclusions who had lateral cephalograms (n = 1303) taken annually. Based on 6 landmarks, 3 angles (PPA, MPA, PP/MPA) and 2 proportions (PFH:AFH and UFH:LFH) were calculated. To reduce errors, each subject's growth curve was estimated by using multilevel modeling procedures, and the estimated values were analyzed.

RESULTS

Growth changes between 10 and 15 years for each of the 5 measurements followed relatively simple (linear or quadratic) polynomial models. On average, PPA and PFH:AFH increased, and MPA and PP/MPA decreased. The UFH:LFH ratio increased during the first few years and then decreased. MPA, PP/MPA, and PFH:AFH showed moderately high intercorrelations; PPA displayed moderate to moderately low correlations with UFH:LFH; UFH:LFH showed a moderate correlation with PP/MPA. Approximately 75% to 86% of the subjects classified as hyperdivergent or hypodivergent at 10 years maintained their classification. Subjects classified as hyperdivergent at 15 years of age showed significantly greater growth changes than did those classified within normal limits, who, in turn, showed greater changes than did the hypodivergent subjects.

CONCLUSIONS

Measurements typically used to classify vertical growth tendencies changed significantly during adolescence, with boys generally showing greater changes than girls. Although MPA, PFH:AFH, and PP/MPA measured the same phenotypic attribute, PPA and UFH:LFH were relatively independent of the other 3 measurements. Most subjects maintained their vertical facial types, but some worsened, and others improved.

How does tooth eruption relate to vertical mandibular growth displacement?

INTRODUCTION

Our objectives were to investigate the eruptive patterns of the mandibular teeth and assess their associations with mandibular growth displacements.

METHODS

Cephalograms for a mixed-longitudinal sample of 124 French-Canadian girls were evaluated between 10 and 15 years of age. Vertical mandibular displacement and mandibular eruption were evaluated by using cranial and mandibular superimpositions, respectively. Multilevel modeling procedures were used to estimate each subject's growth change over time. Stepwise multiple regressions were used to determine the amount and relative magnitudes of variations in mandibular eruption explained by mandibular growth displacement, controlling for vertical maxillary tooth movements.

RESULTS

Cubic polynomial models explained between 91% and 98% of the variations in eruption and vertical growth displacement. All curves showed acceleration of eruption until approximately 12 years of age, after which eruption decelerated. The eruption of the mandibular teeth demonstrated greater relative variability than did vertical mandibular growth displacements. Independent of the overall movements of the maxillary molars, inferior mandibular growth displacement explained approximately 54% of the variation in mandibular molar eruption between 10.5 and 14.5 years of age.

CONCLUSIONS

Inferior mandibular growth displacement and dental eruption followed similar patterns of change during adolescence. Based on their associations and the differences in variability identified, mandibular eruption appears to compensate for or adapt to growth displacements.

Age-dependant cephalometric standards as determined by multilevel modeling

INTRODUCTION

The purpose of this study was to evaluate the feasibility of constructing age-dependant cephalometric standards for white subjects by using 3 data sets.

METHODS

The data sets were the samples from the Fels Longitudinal Study (United States), the Michigan Growth Study (United States), and the Nijmegen Growth Study (The Netherlands). The 3 mixed-longitudinal samples provided data for 218 girls and 231 boys between 9 and 14 years of age and were compared based on 4 cephalometric angles: SNA, SNB, ANB, and SN/GoMe. Curve-fitting and statistical comparisons were performed with multilevel modeling procedures.

RESULTS

All 4 angles showed linear changes over time. SNA and SNB increased, whereas ANB and SN/GoMe decreased. Based on paired-sample comparisons, the samples displayed statistically significant (P <0.05) differences for 50% of the growth velocities and 8% to 17% of the intercepts (size of the angle at 11 years). The SNA and SNB angles showed small and inconsistent differences across the samples. The ANB angle for the Fels boys decreased less than in the other 2 samples. The Nijmegen and Fels girls had the greatest and the least decreases, respectively, in the SN/GoMe angle. Most sample differences decreased over time.

CONCLUSIONS

Based on the growth differences identified, we concluded that sagittal and vertical jaw relationships have different patterns of growth in different samples of white subjects; indiscriminate pooling of data, to create age-dependant cephalometric standards for white subjects is not recommended.

Development and testing of multilevel models for longitudinal craniofacial growth prediction

INTRODUCTION

The aims of this study were to (1) develop longitudinal growth curves that would allow individual variations to be accurately modeled and (2) use these models to predict craniofacial growth changes in children with varying amounts of longitudinal data available.

METHODS

Based on a sample of 159 girls (994 cephalograms) and 128 boys (947 cephalograms), multilevel population models were derived. Polynomial models of the population's growth curve were derived for the measurements MPA, Me-X, Me-theta, Me-Y, and Me-R. Angular and horizontal measures (MPA, Me-X, and Me-theta) were described by simpler, second-order models, and vertical measures (Me-Y and Me-R) were described by more complex, fifth-order models.

RESULTS

Decreases in MPA during childhood and increases in Me-theta during adolescence could be explained by the relative contributions of the horizontal (Me-X) and vertical (Me-Y) movements of menton. There was greater anterior movement of menton during childhood and greater inferior movement during the adolescent growth spurt. By using varying numbers of longitudinal cephalograms between 6 and 10 years of age, the models were used to predict subjects' craniofacial growth changes from ages 10 to 15. Based on correlations, root mean squared error, and percent accuracy, individual growth predictions for the various measures were found to be highly accurate on an independent subsample drawn from the larger sample and on an independent validation sample. Correlations between predicted and actual values on the sample used to develop the models ranged from 0.81 to 0.95. Accuracy was best for the measurements that changed the most during the prediction period (Me-Y and Me-R), with accuracies between 83% and 90%. More longitudinal data did not increase the predictive accuracy for all measurements. The models that were least accurate (Me-X, MPA, and Me-theta) showed the greatest improvement in prediction accuracy with more longitudinal data. These improvements ranged from 1.6% to 15%.

CONCLUSIONS

Longitudinal growth curves based on multilevel procedures can accurately describe population and individual growth curves, and 5-year predictions with this method are highly accurate and externally valid.

Midsagittal facial soft-tissue growth of French Canadian adolescents

This study examines changes in 12 midline soft-tissue thicknesses from the forehead, nose, lip, and chin regions in girls and boys from 10 to 16 years of age. The soft-tissue changes are compared to changes in two hard-tissue distances (sella-nasion and nasion-menton). The subjects are from a mixed-longitudinal sample studied at the Montreal Human Growth Research Center in the 1960s and 1970s. Total sample size is 242 (from lateral cephalographs of 124 males and 118 females), with numbers varying by age and measurement. For hard-tissues, boys show clearly defined adolescent spurts, while girls display small velocity increases indicative of only very minor spurts. Forehead tissue thicknesses for both sexes change little and show no demonstrable growth spurts. For the nose and philtrum region, which have the greatest absolute soft-tissue growth changes, both boys and girls show adolescent spurts. Peak velocities are attained between 13 and 14 years in boys and between 11.9 and 12.5 years in girls. Boys appear to have small adolescent spurts for upper (13.7 years) and perhaps lower lip thicknesses. Neither sex displays clear evidence for adolescent spurts in the chin region.

Postsurgical growth changes in the mandible of adolescents with vertical maxillary excess growth pattern

This case-control study investigates the effects of superior maxillary repositioning by LeFort I osteotomy on adolescent mandibular growth. A total of 15 growing patients (average age, 12.8 years) with vertical maxillary excess who had undergone maxillary surgery were compared with matched untreated control subjects. Lateral cephalograms were evaluated and superimposed to describe the presurgical (1.6 years), surgical, and postsurgical (4.0 years) changes. During the presurgical period, comparisons of traditional measures and mandibular modeling changes showed no significant differences between the 2 groups. During surgery, the maxilla was impacted approximately 3 mm anteriorly and 1 mm posteriorly, which caused a 3.2 degrees autorotation of the mandible. During the postsurgical period, there was no change in the vertical growth pattern of the surgical patients, with the vertical facial heights increasing the same as the control subjects and the mandible rotating backwards. Although there was no inhibition of mandibular growth in the patients postsurgically, there was a decrease in horizontal maxillary growth compared with control subjects. There were clear postsurgical changes in the mandibular modeling and condylar growth, which were indicative of adaptive compensations for surgical mandibular repositioning and autorotation. It is concluded that early maxillary impaction does not normalize or inhibit the vertical maxillary excess growth pattern; mandibular modeling and condylar growth undergo adaptive changes in response to repositioning.

Early treatment of vertical skeletal dysplasia: the hyperdivergent phenotype

This cephalometric study evaluated an early nonextraction treatment approach for patients with severe vertical skeletal dysplasia and maxillary transverse constriction. Thirty-eight patients, 8.2 years (+/- 1.2 years) of age, were treated for 1.3 years (+/- 0.3 years) with lip seal exercises, a bonded palatal expander appliance, and a banded lower Crozat/lip bumper. The bonded palatal expander functioned as a posterior bite-block and was fixed in place throughout treatment. Patients with poor masticatory muscle force (79%) wore a high-pull chincup 12 to 14 hours per day. A control group was matched for age, sex, and mandibular plane angle. Treatment changes for chincup and other patients were not significantly different. Overall, treatment significantly enhanced condylar growth, altered it to a more anterosuperior direction, and produced "true" forward mandibular rotation 2.7 times greater than control values. Posterior facial height increased significantly more in patients than in controls, and the maxillary molars showed relative intrusion. In treated patients, articular angle increased, gonial angle decreased, and the chin moved anteriorly twice as much as in controls. Treatment also led to increased overbite and decreased overjet. Maxillary and mandibular expansion did not cause the mandibular plane angle to increase. The 16 patients with openbite malocclusions exhibited a 2.7 mm increase in overbite and inhibition of growth in anterior lower facial height. The aggregate of individual changes demonstrates a net improvement, indicating this treatment approach may be suited for hyperdivergent patients with skeletal discrepancies in all 3 planes of space.

Cranial base growth for Dutch boys and girls: a multilevel approach

Growth of the cranial base in Dutch children who had undergone orthodontic treatment and children who had not is described and compared with the aid of multilevel statistical techniques. Growth changes of the cranial base (S-N, N-Ba, and S-Ba) were evaluated. The results pertain to a mixed longitudinal sample of 153 boys and 167 girls for S-N and 116 boys and 116 girls for N-Ba and S-Ba, 7 to 14 years of age. No significant difference could be demonstrated between subjects who had received orthodontic treatment and subjects who had not. The cranial base displayed sexual dimorphism in the timing and amount of growth. All dimensions measured in girls were significantly smaller than in boys (p < 0.05). No adolescent growth spurts were found in girls; boys showed adolescent growth spurts for S-N and N-Ba. Adolescent growth velocities were significantly greater for boys than for girls.

Longitudinal shape changes of the nasal dorsum

This investigation quantifies childhood and adolescent growth changes of the upper and lower nasal dorsum and evaluates various aspects of the persons' morphology that relate to shape changes of the dorsum. A longitudinal sample of 37 French-Canadian girls, each having cephalograms at 6, 10, and 14 years of age, was evaluated. The 6- to 10-year interval was chosen to represent childhood growth; the 10- to 14-year interval represented adolescent growth. The upper dorsum rotates upward and forward (counterclockwise) approximately 10 degrees between 6 to 14 years of age. The lower dorsum shows both downward and backward (clockwise) and upward and forward (counterclockwise) rotation average childhood and adolescent changes in angulation were not significant. The results clearly indicate that changes in the nasal dorsum are most closely related to angulation changes of the lower dorsum, particularly during adolescence. The lower dorsum rotates downward and backward in persons who show greater vertical and less horizontal growth changes. Rotational changes of the lower dorsum are most closely related with vertical changes at pronasale.

An inventory of United States and Canadian growth record sets: preliminary report

A listing and description of longitudinal craniofacial growth record sets currently extant on the North American continent is provided. An argument is made for the preservation of these resources and for the generation of a pooled or shared image base of duplicate craniofacial physical records. This is a preliminary report and is assumed to be incomplete. In an effort to improve our accuracy and completeness, we invite corrections and additions.

Mandibular rotation and angular remodeling during childhood and adolescence

Using the structural method of superimposition, childhood and adolescent rates of mandibular rotation and remodeling are described. The results pertain to a longitudinal sample of French-Canadian children, including 42 females with records at 6, 10, and 14 years of age and 39 males with records at 7, 11, and 15 years of age. There are no sex differences in rates of mandibular rotation and remodeling. Childhood rates of true rotation and angular remodeling are significantly greater than adolescent rates. Children whose first permanent molars had not erupted at the time of the first observation showed significantly greater rates of angular remodeling than children whose molars had already erupted. Over the eight year period, there were approximately 4.8 degrees of forward true rotation, between 5.2 and 6.4 degrees forward angular remodeling, and less than 1 degree of backward apparent rotation. During adolescence and the primary dentition stage, associations are strongest between true and apparent rotation. During the mixed dentition stage, true rotation is most closely correlated with angular remodeling. © 1992 Wiley-Liss, Inc.