Cranial-Base Morphology in Children with Class III Malocclusion

Novel prediction models for pharyngeal-airway volume based on the cranial-base and midsagittal cross-sectional area of the airway in the pharyngeal region: A cephalometric and magnetic resonance imaging study

OBJECTIVE

The objective of the study was to elucidate the association between cranial base (Bjork-Jarabak analysis), midsagittal cross-sectional area of the airway in the pharyngeal region (MCSA-PR) data and pharyngeal-airway volume (PAV) and develop a model that could help clinicians predict PAV using two-dimensional (2D) data (Bjork polygon and MCSA-PR).

MATERIALS AND METHODS

Pre-treatment lateral cephalometric radiographs and magnetic resonance imaging (MRI) scans of 82 women were categorized into three anteroposterior skeletal groups based on ANB angle: Class I (n = 29), 1.5° ≤ ANB≤5.1°; Class II (n = 26), ANB >5.1°; Class III (n = 27), ANB <1.5°. The Bjork polygon, MCSA-PR data from cephalograms and PAV data from MRI scans were examined. Intergroup comparisons were performed using the Kruskal-Wallis test and one-way analysis of variance (ANOVA), with pairwise comparisons conducted using the Bonferroni-corrected Mann-Whitney U-test for the Kruskal-Wallis test and Bonferroni-corrected multiple comparison test for one-way ANOVA. Forward multiple linear regression was used to create model equations for predicting PAV.

RESULTS

MCSA-PR and anterior (N-S) and posterior (S-Ar) cranial-base lengths were positively correlated with the PAV. We developed four models; three operated at the group level, and one encompassed the entire sample. Notably, all models could effectively explain the variance in the PAV data. The model for the Class I group was the strongest (adjusted R2 = 0.77).

CONCLUSION

Our findings indicate the remarkable potential of the MCSA-PR, N-S and Bjork sum angles (BSA) as predictors of the PAV and the relevance of 2D cephalometric and cranial-base parameters in predicting the three-dimensional (3D) pharyngeal-airway size.

Comparison of the transverse cranial base dimension in different craniofacial skeletal relationships: A cone-beam computed tomography study

Background/purpose

In comparing the cranial base's size, most cephalometric studies focused on the length and angle in the anteroposterior direction. However, investigating the anterior, middle, and posterior cranial base's transverse dimensions is challenging. This study aimed to investigate the transverse dimensions of the cranial base in different craniofacial skeletal patterns and sexes using cone-beam computed tomography (CBCT).

Materials and methods

A total of 210 adults (105 males and 105 females), including three different skeletal relationships, were included in the study. The cranial base dimensions were measured on a three-dimensional image structure rendered by CBCT. Statistical methods included the Kappa statistic for analysis of consistency and reproducibility and the independent t-test for differences in cranial base dimensions between sexes. A general linear model (GLM) was used to compare the transverse size of the cranial base among skeletal Class I, II, and III groups. The Pearson correlation coefficient explored the correlation among the cranial base dimensions.

Results

The cranial base dimensions did not differ significantly between skeletal Class I, II, and III. The more prominent cranial base size was found in males than females, except for the crista galli length (CGL) and cribriform ethmoid plate width (CEPW). The cranial base dimensions did not differ significantly between different skeletal relationships. Most dimensions have significant correlations in the middle and the posterior cranial base.

Conclusion

The cranial base's transverse dimensions in Taiwanese adults show no significant differences between craniofacial skeletal relationships. In the middle and posterior cranial base, transverse measurements reveal significant sexual dimorphism.

Cranial base measurements in different anteroposterior skeletal relationships using Bjork-Jarabak analysis

OBJECTIVES

To assess the linear and angular cranial base measurements (Bjork polygon) in different anteroposterior (AP) skeletal relationships using Bjork-Jarabak analysis.

MATERIALS AND METHODS

Pretreatment lateral cephalograms of 288 (146 women, 142 men, mean ages 21.24 ± 2.72 years and 22.94 ± 3.28 years, respectively) adult patients were divided into Class I, II, and III skeletal relationships according to their ANB angle. Linear and angular measurements of Bjork polygon were measured and compared among different skeletal relationships. Analysis of variance was performed to detect the differences among groups. Independent-sample t-test was used to detect differences between men and women.

RESULTS

The Class II skeletal relationship has a significantly larger saddle angle than Class III does (P < .05), whereas Class III has a significantly larger gonial angle than Class II does (P < .05). The articular angle and sum of Bjork polygon angles were not significantly different among groups (P > .05). Anterior (N-S) and posterior (S-Ar) cranial base lengths were similar in the different AP skeletal relationships (P > .05). The ramal height and body of the mandible length were significantly larger in Class III compared with Class I and II (P < .05). Women had a significantly larger articular angle than men did (P < .05), although men had significantly larger linear measurements of Bjork polygon than women did (P < .05).

CONCLUSIONS

The Class III skeletal relationship has a smaller saddle angle and larger mandibular length and gonial angle. Men have a larger cranial base and mandibular linear measurements and a smaller articular angle compared with women.

Volumetric Analysis of the Jaws in Skeletal Class I and III Patients with Different Facial Divergence Using CBCT Imaging

Aim

The main objective was to evaluate any possible maxillary or mandibular volumetric difference between hyperdivergent skeletal Class III (CIII), normodivergent skeletal CIII, hypodivergent skeletal CIII, and normodivergent skeletal Class I (CI) patients using cone-beam computed tomography (CBCT) images. Also, the secondary objective was to investigate any possible correlation between CBCT-derived lateral cephalometric variables and the mandibular and maxillary volumes (MdV and MxV, respectively).

Materials and Methods

80 CBCT images of patients between 18 and 32 years of age were taken with one CBCT imaging device (Scanora 3D®, Soredex, Tuusula, Finland). The sample consisted of four groups: 20 hypodivergent skeletal CIII (11 males and 9 females), 20 normodivergent skeletal CIII (7 males and 13 females), 20 hyperdivergent skeletal CIII (8 males and 12 females), and 20 normodivergent skeletal CI (5 males and 15 females). The volumes of both jaws and the ratio of MxV/MdV were obtained using Mimics™ 19 software (Materialise, NV, Belgium), and 2D variables were obtained from CBCT-derived lateral cephalogram using AudaxCeph™ software (Orthodontic software suite, Ljubljana, Slovenia). One-way ANOVA test and Kruskal–Wallis analysis were employed to detect any possible significant difference between the volumetric variables, whereas Pearson's and Spearman's correlation coefficients were calculated to detect any possible relationship between the 2D variables and the volumetric measurements.

Results

There were no statistically significant differences in the maxillary volume or maxillary/mandibular ratio between the four groups (p=0.081 and 0.432, respectively). There was a significant difference in MdV between CIII hypodivergent (higher mean) and CIII hyperdivergent (p=0.039). There were some correlations between the MdV and 2D variables in the four studied groups especially in the posterior facial height (S-Go) and the facial depth (N-Go). There were some weaker correlations between the MxV and some 2D variables in the CIII hypodivergent and hyperdivergent groups.

Conclusions

The mandibular volume of the Class III hypodivergent patient was significantly greater than that of the Class III hyperdivergent patients. Correlations between the maxillary or mandibular volumes were found with some of the 2D variables. The volume of both jaws increased when the maxillofacial complex moved toward a horizontal growth pattern.

Three-Dimensional Analysis of the Skull Base of Individuals With Cleft Lip and Palate

AIMS

Identify variations of skull base measurements in individuals with dentofacial deformities associated or not with cleft lip and palate and compare the results with individuals without dentofacial deformities.

METHODS AND RESULTS

The individuals were categorized into three different groups: dentofacial deformity without cleft malformation, dentofacial deformity associated with cleft lip and palate, and without facial deformity. The inclusion criteria were individuals over 18 years of age, without any intervention involving facial bones or structures of interest for the study and field of view encompassing from the glabella to the hyoid bone. Poor quality CT scans or lack of adequate medical records were considered exclusion criteria. In the analysis by computerized tomography using the Dolphin Imaging Software, the length determined by the Ba-S and S-N lines was evaluated, as well as the Ba-S-N angle formed by landmarks.

RESULTS

The length of S-N was not statistically different between the groups, the Ba-S length and the Ba-S-N angle demonstrated statistical difference.

CONCLUSION

There was statistically significant difference in the morphometry of the (Ba-S) between groups (FS) and (C). This suggests that the standard values for cephalometric analyzes involving these structures, especially to determine the treatment planning, should be used with caution.

A case of extreme skeletal class III Malocclusion beyond the envelope of discrepancy, managed effectively by a modified ortho-surgical protocol

Correction of severe anteroposterior skeletal discrepancy, as described in this case of Extreme Skeletal Class III Malocclusion, can be challenging and fraught with difficulties. Conventional, single stage Bi-jaw Orthognathic surgery, with pre-and post-surgical orthodontics is associated with drawbacks such as risk of relapse and an unsatisfactory outcome, with persisting occlusal discrepancies and skeletal abnormalities, especially when the magnitude of skeletal correction is large. Excessive mandibular setback restricts tongue space, narrows the posterior airway and pharyngeal spaces, and is prone to relapse from the forward pterygomasseteric pull; while large maxillary advancements are accompanied by wound dehiscence, bone exposure and delayed union at the site of pterygomaxillary disjunction, and risk of relapse due to backward palatopharyngeal pull. Bi-jaw surgeries invariably involve considerable blood loss and prolonged operating time with its attendant anaesthetic risks. These drawbacks may be obviated by employing a two staged protocol of Bi-jaw surgeries allowing a minimum time period of 3 months to elapse between them, which allows the oral and maxillofacial musculature to adapt itself to the new jaw position following the first surgery, thus creating a better and more stable environment for the succeeding one. This reduces the chance of relapse thereafter, and produces more effective and stable long term results. The intervening time period also allows for observation of the repositioned jaw and arch relations achieved, and scrutiny for any positional changes in this post-surgical phase, which thereby allows modifications in the planned surgery of the next jaw, thereby achieving the most ideal final outcome.

[A computerized tomography study of morphological and positional features of basicranial bones in patients with different facial types]

BACKGROUND

There is a lack of a comprehensive theory about how cranium base influences the development of facial skull morphology. Due to up-to-date tomography technologies, it is possible to get more reliable information about position of basicranial bones.

OBJECTIVE

Aim of this research is to analyze anatomical and morphological features of sphenoid and vomer and their interrelationship in patients with different facial types of the skull.

MATERIAL AND METHODS

Cone beam computed tomography (CBCT or CT) results of 120 adult patients were examined. The sample was divided into three groups depending on the facial type: mesocephalic, brachycephalic and dolichocephalic, and each group was further divided by three, depending on the skeletal class: I, II and III. Proportions, shape and positioning of sphenoid and vomer were studied on frontal and sagittal planes. Proportions of sphenoid and vomer were calculated using "A/B" formula. Shape of the bones was described with angles: Va, N-S-PSO, SSE-S-PSO. Position of vomer posterior surface was identified by angles: VSa and VSBa.

RESULTS

The results of CBCT analysis suggest that there are differences between groups with different facial types and different skeletal classes in shape and proportions of sphenoid body and sinus, as well as in shape and position of the vomer. The greatest difference is registered on the sagittal planes of CBCT between groups with brachycephalic and dolichocephalic facial types.

CONCLUSION

Basicranial bones differ in shape, proportions and position between people with different facial types and different skeletal classes.

Integration of Cranial Base and Face in Growing Subject

Background: many papers investigate the role of the cranial base in facial development, but the results are not in agreement. This can be due to a difference between the central and lateral parts of the cranial base. The aim of the present study is to evaluate the relationship between the central and the lateral cranial base and the facial skeleton in pre-pubertal peak subjects and at the end of growth. Material/Methods: a total sample of 52 latero-lateral cranial teleradiographs were analyzed. To test the correlation between structures, the “Partial Least Square” analysis was performed. Geometric morphometric analysis were applied and partial least square analysis was used to test correlation. Integration was studied removing the effect of allometry. Results: facial skeleton has no significant relation with central cranial base. Facial skeleton has significant relationships with the lateral portion of the cranial base. This relationship is higher in the post-peak phase of growth. Conclusion: the Integration between facial structures and cranial base is significant. The Spatial orientation and shape of the facial structures are both influenced by cranial base. This is mainly due to the lateral portion of cranial base.

A Case of Extreme Skeletal Class III Malocclusion Beyond the Envelope of Discrepancy, Managed Effectively by a Modified Ortho-Surgical Protocol

Introduction

Correction of a severe anteroposterior skeletal discrepancy, as described in this case of extreme skeletal class III malocclusion, can be quite challenging and fraught with difficulties. Conventional, single-stage bi-jaw orthognathic surgery with pre-and post-surgical orthodontics is associated with drawbacks such as the risk of relapse and an unsatisfactory overall long-term outcome, with persisting occlusal discrepancies and skeletal abnormalities, especially when the magnitude of skeletal correction required is large. Excessive mandibular setback can restrict tongue space, cause narrowing of posterior airway and pharyngeal space, and be prone to relapse from the forward pterygomasseteric muscle pull, while large maxillary advancements are often accompanied by wound dehiscence and bone exposure at the site of pterygomaxillary disjunction, delayed union or malunion at the osteotomy and disjunction sites, and risk of relapse due to backward palatopharyngeal muscle pull. In addition, bi-jaw surgeries invariably involve an appreciable blood loss and a prolonged operating time with its attendant anaesthetic risks such as respiratory insufficiency.

Aim and Objectives

To develop an orthosurgical protocol wherein excessive skeletal discrepancy can be successfully managed, achieving the desired magnitude of correction, with little or no relapse. To assess its efficacy and superiority over the hitherto-employed single-stage bi-jaw procedures in the management of severe skeletal discrepancies.

Materials and Method

A two-staged, shorter 'single-jaw at a time' operative procedure with an intervening period of three months between the two surgical phases was employed.

Results

Drawbacks of conventional orthognathic surgery may be obviated by employing a two-staged protocol of bi-jaw surgeries allowing a minimum time period of 3 months to elapse between them. This period of time intervening between the maxillary advancement and mandibular setback allows the oral and maxillofacial musculature to adapt itself to the new jaw position following the first surgery, thus creating a better and more stable environment for the succeeding one, thereby reducing the chances of relapse thereafter, and producing more effective and stable long-term results. Moreover, the intervening time period also allows for observation of the repositioned jaw and arch relations achieved, and scrutiny for any positional changes in this post-surgical phase, which thereby allows modifications in the planned surgery of the next jaw, so as to achieve the most ideal final outcome following the second jaw surgery. A shorter operating time, reduced operator fatigue and less blood loss are other obvious advantages over the conventional bi-jaw procedures.

Conclusion

An effective and stable correction of the extreme class III skeletal deformity and malocclusion was achieved, with a dramatic enhancement of facial balance, symmetry and proportion in this patient, following a modified orthosurgical management protocol. The staged protocol of 'maxilla first and mandible after' orthognathic surgery with conventional pre- and post-surgical orthodontics helped in pushing the envelope of skeletal discrepancy correctable by orthognathic surgery, thereby achieving large quantum of jaw movements, with ideal and stable functional as well as aesthetic results. This is suggestive of its efficacy and superiority over the hitherto-employed single stage bi-jaw procedures in the management of severe skeletal discrepancies.

Skeletal open bite cranial base characteristics in young Latin-American individuals with class I, II and III malocclusions: An observational study

OBJECTIVE

This study aimed to compare cranial base linear and angular measurements between individuals with skeletal open bite and different sagittal skeletal relationships.

MATERIALS AND METHODS

This observational and cross-sectional study included 101 lateral radiographs of young Latin-American individuals with skeletal open bite that met the inclusion criteria and were collected from a private radiological centre. Three groups were formed. Groups 1, 2 and 3 included individuals with skeletal open bite (negative overbite and FMA>30°) and Class I (n=31), II (n=35) and III (n=35) sagittal skeletal relationship, respectively. The anterior and posterior cranial bases (SN and SBa), and cranial base angles (BaSN and ArSN) were measured. Groups were compared with one-way analysis of variance and post-hoc Scheffé tests. The influence of predictor variables on the cranial base were evaluated with linear regressions (α=0.05).

RESULTS

The cranial base angles were significantly smaller (approximately 3° to 5°) in the skeletal open bite Class III group (BaSN=127.97°± 5.86°, ArSN=120.19°±6.12°) when compared with the other groups. BaSN angle, Class I versus Class III (p<0.001) and Class II versus Class III (p<0.001). ArSN angle, Class I versus Class III (p=0.005) and Class II versus Class III (p=0.026). Multiple linear regressions showed that sex had a significant influence on both cranial base dimensions with men showing larger values than women.

CONCLUSIONS

Skeletal open bite Class III individuals show a smaller cranial base angle than Skeletal open bite Class I or II individuals.

Influence of the cranial base flexion on Class I, II and III malocclusions: a systematic review

Objective:

The aim of this study was to perform a systematic review on the morphological characteristics of the skull base (flexion, anterior length and posterior length) and the concomitant development of malocclusions, by comparing differences in dimorphism, ethnicity and age.

Methods:

The articles were selected by means of electronic search on BBO, MEDLINE and LILACS databases from 1966 to 2016. A qualitative evaluation of the methodologies used on the articles was also performed.

Results:

Although the literature on this topic is abundant, only 16 articles were selected for the present systematic review. The cranial base angle itself does not seem to play a significant role in the development of malocclusions. In fact, the cranial base angle is relatively stable at the ages of 5 to 15 years.

Conclusions:

A more obtuse angle at the skull base, in association or not with a greater anterior length of the cranial base, can contribute to the development of Class II division 1 malocclusions. On the other hand, a more acute angle at the skull base can contribute to a more anterior positioning of the mandible and to the development of Class III malocclusions.

Cranial base characteristics in anteroposterior malocclusions: A meta-analysis

OBJECTIVE

To investigate cranial base characteristics in malocclusions with sagittal discrepancies.

MATERIALS AND METHODS

An electronic search was performed in PubMed, Embase, Web of Science, and the Cochrane Library. A fixed- or random-effect model was applied to calculate weighted mean difference with 95% confidence intervals (CIs) according to statistical heterogeneity. Outcome measures were anterior, posterior, and total cranial base length and cranial base angle. Sensitivity analysis and publication bias were conducted.

RESULTS

Twenty studies that together included 1121 Class I, 1051 Class II, and 730 Class III cases qualified for the final analysis. Class III malocclusion demonstrated significantly reduced anterior (95% CI: -1.74, -0.53; P < .001 vs Class I; 95% CI: -3.30, -2.09; P < .001 vs Class II) and total cranial base length (95% CI: -3.33, -1.36; P < .001 vs Class I; 95% CI: -7.38, -4.05; P < .001 vs Class II). Further, Class II patients showed significantly greater anterior and total cranial base length than did Class I patients (95% CI: 0.51, 1.87; P < .001 for SN; 95% CI: 2.20, 3.30; P < .001 for NBa). Cranial base angle was significantly smaller in Class III than in Class I (95% CI: -3.14, -0.93; P < .001 for NSBa; 95% CI: -2.73, -0.68; P  =  .001 for NSAr) and Class II malocclusions (95% CI: -5.73, -1.06; P  =  .004 for NSBa; 95% CI: -6.11, -1.92; P < .001 for NSAr) and greater in Class II than in Class I malocclusions (95% CI: 1.38, 2.38; P < .001 for NSBa).

CONCLUSIONS

This meta-analysis showed that anterior and total cranial base length and cranial base angle were significantly smaller in Class III malocclusion than in Class I and Class II malocclusions, and that they were greater in Class II subjects compared to controls.

A retrospective analysis of dentofacial deformities and orthognathic surgeries using the index of orthognathic functional treatment need (IOFTN)

OBJECTIVES

To assess the functional needs of orthognathic cases treated in Northampton General Hospital using the index of orthognathic functional treatment need (IOFTN).

MATERIALS AND METHODS

A retrospective study was conducted on 78 subjects (54 female and 24 males, 10-54 years, mean (SD) age=21.88 (6.98) years) who had orthognatic surgery in Northampton General Hospital or were in preparation for it (5 case). The sample represents a period between February 1997 and December 2014. The components of IOFTN and Dental Health Component (DHC) of the Index of Orthodontic Treatment Need (IOTN) as well as Malocclusion type were recorded.

RESULTS

Class III malocclusion/skeletal pattern was the most prevalent type (approximately 49%). There were 1, 36, 3, and 38 subjects with Class I, Class II Division I, Class II Division II, and Class III malocclusions, respectively. In terms of sagittal skeletal relationship, there were 2, 37, and 39 subjects with Class I, Class II, and Class III skeletal bases, respectively. The most prevalent IOFTN score in our sample was the 5.2 (29.5%), followed by 5.3 (15.5%), 4.2 (13%), 4.3 (11.5%). Overall, 92.3% were classified as in great and very great functional needs according to the IOFTN. Similarly, 84.6% scored as grade 4 or 5, according to the IOTN (DHC). The bimaxillary type osteotomy was the most prevalent type (61.5%).

CONCLUSIONS

Using IOFTN, 92.3% of our sample were classified as having great and very great functional needs. IOFTN is a simple and reliable tool to identify patients in need of orthognathic surgery and can be used in resource allocation for patients with highest functional needs.

Base of the skull morphology and Class III malocclusion in patients with unilateral cleft lip and palate

OBJECTIVE

The aim of the present study was to determine the morphological differences in the base of the skull of individuals with cleft lip and palate and Class III malocclusion in comparison to control groups with Class I and Class III malocclusion.

METHODS

A total of 89 individuals (males and females) aged between 5 and 27 years old (Class I, n = 32; Class III, n = 29; and Class III individuals with unilateral cleft lip and palate, n = 28) attending PUC-MG Dental Center and Cleft Lip/Palate Care Center of Baleia Hospital and PUC-MG (CENTRARE) were selected. Linear and angular measurements of the base of the skull, maxilla and mandible were performed and assessed by a single calibrated examiner by means of cephalometric radiographs. Statistical analysis involved ANCOVA and Bonferroni correction.

RESULTS

No significant differences with regard to the base of the skull were found between the control group (Class I) and individuals with cleft lip and palate (P > 0.017). The cleft lip/palate group differed from the Class III group only with regard to CI.Sp.Ba (P = 0.015). Individuals with cleft lip and palate had a significantly shorter maxillary length (Co-A) in comparison to the control group (P < 0.001). No significant differences were found in the mandible (Co-Gn) of the control group and individuals with cleft lip and palate (P = 1.000).

CONCLUSION

The present findings suggest that there are no significant differences in the base of the skull of individuals Class I or Class III and individuals with cleft lip and palate and Class III malocclusion.

Cranial-base morphology in adults with skeletal Class III malocclusion

INTRODUCTION

The objectives of this study were to clarify the characteristics of cranial-base morphology in adults with skeletal Class III malocclusion and investigate factors relating to the establishment of a skeletal Class III malocclusion.

METHODS

Initial lateral cephalograms of women were examined. Subjects with an ANB angle of 0° to 4°, normal overjet and overbite, and a Class I molar relationship were classified as Class I (n = 86). Those with an ANB angle less than -1°, a Wits appraisal less than 2 mm, a negative overjet, and a Class III molar relationship were the Class III group (n = 86) in this study. Angular, linear, and coordinate measurements were made. Multivariate analysis of variance and the Student t test were used to analyze significant differences between the 2 groups. Discriminant analysis, logistic regression analysis, and decision analysis were used to identify which cranial-base and maxillomandibular variables influenced the establishment of a skeletal Class III malocclusion.

RESULTS

The Class III group had smaller values for NSBa, SeSBa, FH-SSe, and FH-SBa. Sphenoidale and basion were more inferior and anterior than those of the Class I group. There was no difference in the anterior and posterior cranial-base lengths between the groups. Greater mandibular length was the first major characteristic in the Class III group, followed by smaller values for SeSBa and NSBa.

CONCLUSIONS

Cranial-base morphology in adults with a skeletal Class III malocclusion is different from that in a skeletal Class I malocclusion. Smaller cranial-base angles, steeper posterior cranial bases, more inferiorly positioned sphenoidale, and more anteriorly positioned basion are major characteristics of skeletal Class III malocclusions. These characteristics play important roles in the establishment of a skeletal Class III malocclusion.

Phenotypic diversity in white adults with moderate to severe Class III malocclusion

INTRODUCTION

Class III malocclusion is characterized by a composite of dentoskeletal patterns that lead to the forward positioning of the mandibular teeth in relation to the maxillary teeth and a concave profile. Environmental and genetic factors are associated with this condition, which affects 1% of the population in the United States and imposes significant esthetic and functional burdens on affected persons. The purpose of this study was to capture the phenotypic variation in a large sample of white adults with Class III malocclusion using multivariate reduction methods.

METHODS

Sixty-three lateral cephalometric variables were measured from the pretreatment records of 292 white subjects with Class II malocclusion (126 male, 166 female; ages, 16-57 years). Principal component analysis and cluster analysis were used to capture the phenotypic variation and identify the most homogeneous groups of subjects to reduce genetic heterogeneity.

RESULTS

Principal component analysis resulted in 6 principal components that accounted for 81.2% of the variation. The first 3 components represented variation in mandibular horizontal and vertical positions, maxillary horizontal position, and mandibular incisor angulation. The cluster model identified 5 distinct subphenotypes of Class III malocclusion.

CONCLUSIONS

A spectrum of phenotypic definitions was obtained replicating results of previous studies and supporting the validity of these phenotypic measures in future research of the genetic and environmental etiologies of Class III malocclusion.

Morphological integration between the cranial base and the face in children and adults

The primary aim of the present study was to assess morphological covariation between the face and the basicranium (midline and lateral), and to evaluate patterns of integration at two specific developmental stages. A group of 71 children (6-10 years) was compared with a group of 71 adults (20-35 years). Lateral cephalometric radiographs were digitized and a total of 28 landmarks were placed on three areas; the midline cranial base, the lateral cranial base and the face. Geometric morphometric methods were applied and partial least squares analysis was used to evaluate correlation between the three shape blocks. Morphological integration was tested both with and without removing the effect of allometry. In children, mainly the midline and, to a lesser extent, the lateral cranial base were moderately correlated to the face. In adults, the correlation between the face and the midline cranial base, which ceases development earlier than the lateral base, was reduced. However, the lateral cranial base retained and even strengthened its correlation to the face. This suggests that the duration of common developmental timing is an important factor that influences integration between craniofacial structures. However, despite the apparent switch of primary roles between the cranial bases during development, the patterns of integration remained stable, thereby supporting the role of genetics over function in the establishment and development of craniofacial shape.

Cranial base features in skeletal Class III patients

OBJECTIVE

To investigate the cranial base configuration in skeletal Class III patients to clarify the conflicting findings from literature.

MATERIALS AND METHODS

Initial lateral radiographs of 54 skeletal Class III patients and 54 matched controls (Class I, II/1, II/2) aged 14 to 24 years were analyzed retrospectively for 21 cephalometric basicranial variables and jaw lengths relative to anterior cranial base length.

RESULTS

In contrast to overall cranial base length, the anterior (N-S) and posterior (S-Ba, S-Ar) sections failed to show a significant reduction in Class III patients. The significantly more acute angles Ca-S-Ba and Se-S-Ba reflected increased cranial base flexure. Resulting anterior condylar displacement was shown by significant reduction of Se-S-Cd and Ar-Ca. Relative mandibular length was significantly increased.

CONCLUSIONS

Decreased basicranial angulation associated with Class III mandibular protrusion was clearly confirmed for skeletal Class III patients. Overall shortening of the cranial base apparently resulted from various minor alterations. The results are compatible with the deficient orthocephalization hypothesis of Class III morphogenesis. The basicranial-maxillary relationship in skeletal Class III remains unclear.

Correlated variation between the lateral basicranium and the face: A geometric morphometric study in different human groups

OBJECTIVES

The significance of the cranial base in the contribution of normal and pathologic facial patterns is uncertain. The aim of this study was to explore and compare patterns of morphological covariation between the face and the lateral basicranium (anterior and middle cranial fossae) with covariation patterns between the face and the midline cranial base.

DESIGN

We employed 2D geometric morphometrics and partial least squares analysis to quantify and compare correlation coefficient between principal variation patterns between basicranial and facial structures in lateral radiographs from 143 humans from Japan (N=45), Europe (N=65) and Africa (N=34).

RESULTS

In both comparisons basicranial patterns co-varied with dolichofacial and brachyfacial morphologies. The findings showed that the midline cranial base is not significantly correlated of common facial patterns (r=0.37, P=0.09). Instead, the lateral basicranium is significantly (P=0.000), and significantly higher (r=0.6) correlated with facial variation than is the midline cranial base.

CONCLUSIONS

The lateral basicranium may be of higher morphogenetic relevance for influencing facial variation than previously thought. This influence may be of clinical importance for the generation of skeletal class II or class III malocclusions. Further research should expand on geometric morphometric analysis of ontogenetic and clinical 3D data in order to advance in the understanding of these complex developmental relationships.

Treatment of Mandibular Prognathism

Mandibular prognathism (MP) or skeletal Class III malocclusion with a prognathic mandible is one of the most severe maxillofacial deformities. Facial growth modification can be an effective method of resolving skeletal Class III jaw discrepancies in growing children with dentofacial orthopedic appliances including the chincup, face mask, maxillary protraction combined with chincup traction and the Fränkel functional regulator III appliance. Orthognathic surgery in conjunction with orthodontic treatment is required for the correction of adult MP. The two most commonly applied surgical procedures to correct MP are sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy. Both procedures are suitable for patients in whom a desirable occlusal relationship can be obtained with a setback of the mandible, and each has its own advantages and disadvantages. In bilateral SSRO, the intentional ostectomy of the posterior part of the distal segment can offer long-term positioned stability. This may be attributable to reduction of tension in the pterygomasseteric sling that applies force in the posterior mandible. While various environmental factors have been found to contribute to the development of MP, heredity plays a substantial role. The relative contributions of genetic and environmental components in the etiology of MP are unclear. The recent identification of the genetic susceptibilities to MP constitutes the first step toward understanding the molecular pathogenesis of MP. Further studies in molecular biology are needed to identify the gene-environment interactions associated with the phenotypic diversity of MP and the heterogenic developmental mechanisms thought to be responsible for them.