A comparison of cranial base growth in Class I and Class II skeletal patterns

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.

Midface hypoplasia in syndromic craniosynostosis: predicting craniofacial growth via a novel regression model from anatomical morphometric analysis

Midface hypoplasia in syndromic craniosynostosis (SC) may lead to serious respiratory issues. The aim of this study was to analyse the morphometric correlation between midface and cranial base parameters in paediatric SC patients in order to formulate predictive regression models. The computed tomography scans of 18 SC patients and 20 control were imported into Materialise Mimics Medical version 21.0 software for the measurement of multiple craniofacial landmarks and correlation analysis. The results showed a strong correlation of anterior cranial base (SN), posterior cranial base (SBa), and total cranial base (NBa) (r = 0.935) to maxilla length and width (ZMR-ZML) (r = 0.864). The model of NBa = - 1.554 + 1.021(SN) + 0.753(SBa) with R2 = 0.875 is proposed to demonstrate the development of the cranial base that causes a certain degree of midface hypoplasia in SC patients. The formula is supported using a prediction model of ZMR-ZML = 5.762 + 0.920(NBa), with R2 = 0.746. The mean absolute difference and standard deviation between the predicted and true NBa and ZMR-ZML were 2.08 ± 1.50 mm and 3.11 ± 2.32 mm, respectively. The skeletal growth estimation models provide valuable foundation for further analysis and potential clinical application.

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.

Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation

OBJECTIVE

This study compared mandibular growth in children, aged 7 to 12 years, with Class II malocclusion and normal occlusion, between the following stages of cervical vertebrae maturation: initiation (I), acceleration (A), transition (T).

MATERIAL AND METHODS

A total of 148 lateral cephalograms (78 males, 70 females) of Class II malocclusion patients, and 60 lateral cephalograms (30 males, 30 females) of normal occlusion patients were included. The following linear cephalometric measurements were performed: Co-Gn (effective mandibular length), Co-Go (ramus height), and Go-Gn (length of mandibular body). Mean values of increments between stages (I-A, A-T, I-T) were obtained for each group and gender. Results were compared using the Student t-test, and a significance level of 0.05% was adopted.

RESULTS

Females group: A-T interval presented a greater increment in Co-Go in the Class II group, which was not significant for the I-T interval, with numerically smaller increments in Co-Gn and Go-Gn, without statistical significance. Males group: intervals I-A, A-T and I-T showed numerically smaller growth increments in the Class II group, with statistical significance for Co-Gn in I-A (p=0.001) and I-T (p=0.003). Comparing genders of the Class II group, Co-Go was higher in males (p=0.002) and I-T interval (p=0.031). In the Normal Occlusion group, the male gender had the greatest Co-Gn (p=0.038) for the I-A interval. In A-T and I-T, Co-Go in males was higher, with statistical significance (p=0.000 and p=0.002, respectively).

CONCLUSION

Growth phenomenon affects the mandibular dimensions regardless of the character of the malocclusion, with a tendency to be smaller in the presence of Class II malocclusion.

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.

Cranial base parameters in adults with skeletal class I and class II skeletal pattern

OBJECTIVE:

Cranial base parameters exhibit wide variations. This study evaluated cranial base morphological characteristics of class II and class I malocclusions to identify risk factors for class II skeletal malocclusions.

METHODS:

In this cross-sectional study, we recruited 30 class I adults and 30 class II adults and collected their lateral cephalograms. The cranial base length was calculated by measuring the base of the skull by determining the length of sella-to-nasion, basion to pterygomaxillary fissure, and pterygomaxillary fissure to point A. The cranial base angle was measured by the angle formed by the basion, sella, and nasion, and the base of the angle, which connects the basion and nasion, was measured.

RESULTS:

The independent t-test for combined values showed no significant differences in one angular and five linear measures between groups. However, one angular measurement was positively correlated when men and women in class I and class II groups were analyzed separately.

CONCLUSION:

Male patients with class II patterns exhibited larger cranial base angles than did those with class I patterns. Our study suggested that cranial base features have a minimal role in the development of class II malocclusions.

Relationship between vertical components of maxillary molar and craniofacial frame in normal occlusion: cephalometric calibration on the vertical axis of coordinates

Objective

The aim of this study was to evaluate the correlation between the vertical position of maxillary first molar and vertical skeletal measurements in lateral cephalograms by using new linear measurements on the vertical axis of coordinates with calibration.

Methods

The vertical position of maxillary first molar (U6-SN), and the conventionally used variables (ConV) and the newly derived linear variables (NwLin) for vertical skeletal patterns were measured in the lateral cephalograms of 103 Korean adults with normal occlusions. Pearson correlation analyses and multiple linear regression analyses were performed with and without calibration using the anterior and posterior cranial base (ACB and PCB, respectively) lengths to identify variables related to U6-SN.

Results

The PCB-calibrated statistics showed the best power of explanation. ConV indicating skeletal hyperdivergency was significantly correlated with U6-SN. Six NwLin regarding the position of palatal plane were positively correlated with U6-SN. Each multiple linear regression analysis generated a two-variable model sella and nasion to palatal plane. Among the three models, the PCB-calibrated model yielded highest adjusted R² value, 0.880.

Conclusions

U6-SN could be determined by the vertical position of the maxilla, which could then be used to plan the amount of molar intrusion and estimate its clinical stability. Cephalometric calibration on the vertical axis of coordinates by using PCB for vertical linear measurements could strengthen the analysis itself.

Cephalometric Evaluation of Anterior Cranial Base Slope in Patients with Skeletal Class I Malocclusion with Low or High SNA and SNB Angles

Objective

In the cephalometric analyses, it is observed that both SNA and SNB angles are higher or lower than normal for some skeletal Class I patients. The aim of this study was to assess the correlation between low or high SNA, SNB angles, and anterior cranial base (ACB) slope.

Methods

One hundred and seventeen skeletal Class I patients (45 males with a mean age of 14.5 years, 72 females with a mean age of 14.4 years) were evaluated in three groups. Group 1(n=40): Control group, individuals with normal SNA(82°±2°), and SNB(80°±2°) values. Group 2 (n=37): Patients with SNA>84° and SNB >82°, Group 3 (n=40): Patients with both SNA and SNB values lower than 78°. On the cephalometric radiographs, three angulars (SN/FH; anterior cranial base, Ba-S/FH; posterior cranial base, SN-Ba; total cranial base) and seven linear (S-FH, N-FH, Δ, Ba-S, Ba-N, Ba-A, Ba-B) measurements were performed to analyze the vertical and horizontal positions of the S and N points and thereby the ACB slope. One-way ANOVA and Kruskal Wallis tests were used for statistical analysis.

Results

The ACB slope was observed to be relatively flatter in Group 2, and steeper in Group 3 (p<0.05). The location of the S and N points in the sagittal plane did not significantly affect the SNA and SNB. However, the vertical position of the S and N points was a factor determining the inclination of the ACB, therefore the SNA and SNB.

Conclusion

ACB slope directly affected SNA and SNB measurements. ACB might lead to misleading results when used as a reference plane.

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.

Maxillary and mandibular contribution to the establishment of class II malocclusion in an adult Lebanese population

INTRODUCTION

The main aim of this study was to describe the contribution of the maxilla and the mandible to the establishment of a Class II skeletal malocclusion in an adult Lebanese population. Secondary aims were to detect the presence of sex-based dimorphism and to study the influence of the vertical dimension on the Class II skeletal pattern.

MATERIAL AND METHOD

A sample of 90 adults in skeletal Class II was recruited and equally distributed according to sex and vertical typology. The study describes the skeletal and dentoalveolar cephalometric characteristics of the Class II sample, essentially according to Coben's cephalometric analysis.

RESULTS

The total effective depth of the cranial base and the anterior cranial base angle (SN-BaH) were both greater in the Class II sample. In females, the effective depth of the maxilla (Ptm-A) was larger than normal while SNB was smaller. The parameters describing the size and shape of the body of the mandible were significantly different from those of normal subjects. The upper incisors were in a retrusive position, while the axis of the lower incisors was located normally. The mandibular molars had a more distal sagittal position. Hyperdivergent subjects had more significant posterior alveolar growth, a more retrusive mandibular position and smaller mandibular dimensions than the other two vertical sub-groups.

CONCLUSION

The cranial base contributes to the establishment of a Class II malocclusion, and mandibular retrusion cannot be considered as a characteristic shared by all skeletal Class II subjects. Lessening of the absolute length of the mandibular body is the second most frequent etiological factor noted in the Class II sample studied. Most individuals in skeletal Class II have an associated dental Class II malocclusion, and the vertical dimension has an influence on the Class II skeletal pattern.

Posterior cranial base natural growth and development: A systematic review

OBJECTIVE

To provide a synthesis of the published studies evaluating the natural growth and development of the human posterior cranial base (S-Ba).

MATERIALS AND METHODS

The search was performed on MEDLINE, Embase, PubMed, and all EBM Reviews electronic databases. In addition, reference lists of the included studies were hand-searched. Articles were included if they analyzed posterior cranial-base growth in humans specifically. Study selection, data extraction, and risk of bias assessment were completed in duplicate. A meta-analysis was not justified.

RESULTS

Finally, 23 published studies were selected: 5 cross-sectional and 18 cohort studies. Articles were published between 1955 and 2015, and all were published in English. The sample sizes varied between 20 and 397 individuals and consisted of craniofacial measurements from either living or deceased human skulls. Validity of the measurements was not determined in any of the studies, while six papers reported some form of reliability assessment. All the articles included multiple time points within the same population or data from multiple age groups. Growth of S-Ba was generally agreed to be from spheno-occipital synchondrosis growth. Basion displaced downward and backward and sella turcica moved downward and backward during craniofacial growth. Timing of cessation of S-Ba growth was not conclusive due to limited identified evidence.

CONCLUSIONS

Current evidence suggests that S-Ba is not totally stable, as its dimensions change throughout craniofacial growth and a minor dimensional change is observed even in late adulthood.

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.

Morphological configuration of the cranial base among children aged 8 to 12 years

BACKGROUND

Cranial base is used as reference structure to determine the skeletal type in cephalometric analysis. The purpose was to assess the cranial base length on lateral cephalic radiographs of children between 8 and 12 and compare these measurements with baseline studies in order to evaluate the relationship between the length and the cranial base angle, articular angle, gonial angle and skeletal type.

METHODS

A Cross-sectional study in 149 children aged 8-12 years, originally from Aburrá Valley, who had lateral cephalic radiographs and consented to participate in this study. The variables studied included: age, sex, sella-nasion, sella-nasion-articular, sella-nasion-basion, articular-gonion-menton, gonion-menton, sella-nasion-point B, sella-nasion-point A y point A-nasion-point B. These variables were digitally measured through i-dixel 2 digital software. One-way ANOVA was used to determine mean values and mean value differences. The values obtained were compared with previous studies. A p value <0.05 was considered significant.

RESULTS

Cranial base lengths are smaller in each age and sex group, with differences exceeding 10 mm for measurement, compared both with the study by Riolo (Michigan) and the study carried out in Damasco (Antioquia). No relation was found between the skeletal type and the anterior cranial base length, the sella angle and the cranial base angle. Also, no relation was found between the gonial angle and sella angle or the cranial base angle.

CONCLUSION

The cranial base varies from one population to another. Accordingly, compared to other studies it is shorter for the assessed sample.

Evaluating condylar position in different skeletal malocclusion patterns: A cephalometric study

Context

The cranial base and variations in its morphology affect the anterior-posterior positioning of jaws causing changes in the glenoid fossa and condylar position.

Aims

To evaluate the condylar position in patients with different skeletal sagittal malocclusion patterns.

Materials and Methods

Pretreatment lateral cephalometric radiographs of 112 subjects (both males and females) were categorized into three classes (Class I, Class II, Class III) based on their ANB angulation and studied for N-S-Ar (saddle angle), S-Ar-Go (articular angle), S-Ar (posterior cranial base length).

Statistical Analysis

Shapiro-Wilk test was done to check for normality of the distribution of values. Groups were evaluated using parametric tests (one-way ANOVA). Significance for all tests was predetermined asP< 0.05.

Results

N-S-Ar and S-Ar-Go and also S-Ar did not vary significantly in all the three classes. N-S-Ar and S-Ar-Go angles have shown a significant negative correlation in all the three classes.

Conclusions

There is no significant difference in condylar position in different skeletal malocclusion patterns. N-S-Ar and S-Ar-Go angles show a negative correlation in any skeletal malocclusion pattern.

Craniofacial cephalometric morphology in 8-year-old children with operated sagittal synostosis

OBJECTIVES

To evaluate cephalometrically craniofacial morphology in children with operated sagittal synostosis and to compare the findings with age- and sex-matched controls.

SETTING AND SAMPLE POPULATION

Forty-two children (37 boys) with operated primary sagittal synostosis were compared retrospectively with age- and sex-matched controls from lateral cephalograms taken at a mean age of 8.1 (range 7.0-8.9) years.

MATERIAL AND METHODS

The operations had been performed between the ages of 2 months and 6.3 years at three Finnish hospitals. The surgical methods included strip craniectomy, pi-plasty and cranial vault expansion. A paired Student's t-test and Pearson's correlation analysis were used in the statistical analyses.

RESULTS

Children with operated sagittal synostosis had wide cranial base angles and their mandibles were retrognathic with labially inclined lower incisors relative to the controls. Age at craniosynostosis operation did not correlate with the cranial base angle.

CONCLUSION

This study suggests that children with operated sagittal synostosis have minor distinctive morphological features in the cranial base and mandible. Orthodontic evaluation of craniofacial growth is recommended.

The relationship between the cranial base and jaw base in a Chinese population

Introduction

The cranial base plays an important role in determining how the mandible and maxilla relate to each other. This study assessed the relationship between the cranial base and jaw base in a Chinese population.

Methods

This study involved 83 subjects (male: 27; female: 56; age: 18.4 ± 4.2 SD years) from Hong Kong, who were classified into 3 sagittal discrepancy groups on the basis of their ANB angle. A cephalometric analysis of the angular and linear measurements of their cranial and jaw bases was carried out. The morphological characteristics of the cranial and jaw bases in the three groups were compared and assessments were made as to whether a relationship existed between the cranial base and the jaw base discrepancy.

Results

Significant differences were found in the cranial base angles of the three groups. Skeletal Class II cases presented with a larger NSBa, whereas skeletal Class III cases presented with a smaller NSBa (P < 0.001). In the linear measurement, skeletal Class III cases presented with a shorter NBa than skeletal Class I and II cases (P < 0.01). There was a correlation between the cranial base angle NSBa and the SNB for the whole sample, (r = -0.523, P < 0.001). Furthermore, correlations between SBaFH and Wits (r = -0.594, P < 0.001) and SBaFH and maxillary length (r = -0.616, P < 0.001) were more obvious in the skeletal Class III cases.

Conclusions

The cranial base appears to have a certain correlation with the jaw base relationship in a southern Chinese population. The correlation between cranial base and jaw base tends to be closer in skeletal Class III cases.

Permutation method for evaluating topographic craniofacial correlations

INTRODUCTION

Correlations between cephalometric measurements are frequently assumed to represent biologic associations. However, a significant portion of such correlations might arise from purely geometric dependencies, when measurements share common landmarks. Analytic calculation of this topographic component is difficult. The purpose of this study was to propose a permutation method for evaluating the topographic component of cephalometric correlations.

METHODS

The method consisted of creating a virtual sample of cephalometric tracings (landmark configurations) from the original biologic sample under investigation. Each novel landmark configuration was constructed by assigning coordinates to the cephalometric points; the coordinates of each point were taken randomly from the original sample, each from a potentially different subject. Correlation analysis was performed separately on both samples and the results compared. Biologic meaning was ascribed only when there was a significant difference in correlation values between the samples. Confidence intervals for assessing statistical significance were calculated by using a randomization approach. The method was tested on a sample of 170 radiographs to evaluate the correlation between cranial base angle (NSBa) and angles SNA and SNB, as well as between ANB angle and the Wits appraisal.

RESULTS

No biologic association was found between ANB and Wits, or between NSBa and SNA. The biologic correlation between NSBa and SNB was statistically significant but low (r(2) = 12%).

CONCLUSIONS

Topographic associations between cephalometric measurements are ubiquitous and difficult to assess. The proposed method enables evaluation of their relative strength without the need for analytic solutions.

Cranial base angulation in Brazilian patients seeking orthodontic treatment

The relationship between cranial base flexion and facial prognathism has been of interest to orthodontists, orthognathic maxillofacial surgeons, and plastic surgeons. This study aimed to identify the cranial base flexion of adults with anteroposterior skeletal disharmony. Because the sample was representing a mixed racial population, the authors performed an investigation to confirm an association with other researches performed in different parts of the world. The results revealed an increase in the cranial base flexion in cases diagnosed as class II skeletal pattern and reduction in the group with class III skeletal pattern. These findings suggested that the characteristics of the Brazilian cases did not differ from some other studies despite various influences of different ethnicities in that population.

A protocol for cranial base reference in cephalometric studies

Establishment of the cranial base references and the coordinate system is important for measurement of events occurring on the face. The literature suggests that the horizontal axis is obtained by tracing a line in clockwise direction at seven degrees from the Sella-Nasion line, and the vertical axis is perpendicular to this former axis passing through the Sella point. However, could this standardization better represent the angle between the Sella-Nasion line and Frankfort Horizontal Plane in a Brazilian population and be employed in cephalometric studies? Thus, the present study had two purposes: to identify the cranial base inclination in adult patients presenting with intermaxillary anteroposterior skeletal disharmony and to evaluate the reliability of a protocol to reproduce the cranial base reference. Lateral cephalograms of three different times were traced: T0) onset of orthodontic treatment and immediately before the orthognathic surgery, T1) six months after surgery, and T2) one year after surgery. The results displayed a mean cranial base inclination of 7.91 degrees. Variation of the intraindividual data allowed the conclusion that the protocol proposed by utilization of an individual template of the cranial base reference was effective for the exactness of measurements in cephalometric studies.

Thin-plate spline analysis of the cranial base in African, Asian and European populations and its relationship with different malocclusions

OBJECTIVES

To test the hypothesis that midline basicranial orientation and posterior cranial base length are discriminating factors between adults of different populations and its potential maxillo/mandibular disharmonies.

DESIGN

Twenty-nine 2D landmarks of the midline cranial base, the face and the mandible of dry skull X-rays from three major populations (45 Asians, 34 Africans, 64 Europeans) were digitized and analysed by geometric morphometrics. We used, first, MANOVA to test for mean shape differences between populations; then, principal components analysis (PCA) to assess the overall variation in the sample and finally, canonical variate analysis (CVA) with jack-knife validations (N=1000) to analyse the anatomical features that best distinguished among populations.

RESULTS

Significant mean shapes differences were shown between populations (P<0.001). CVA revealed two significant axes of discrimination (P<0.001). Jack-knife validation correctly identified 92% of 15,000 unknowns. In Africans the whole cranial base is rotated into a forward-downward position, while in Asians it is rotated in the opposite way. The Europeans occupied an intermediate position. African and Asian samples showed a maxillo/mandibular prognathism. African prognathism was produced by an anterior positioned maxilla, Asian prognathism by retruded anterior cranial base and increase of the posterior cranial base length. Europeans showed a trend towards retracted mandibles with relatively shorter posterior cranial bases.

CONCLUSIONS

The results supported the hypothesis that basicranial orientation and posterior cranial base length are valid factors to distinguish between geographic groups. The whole craniofacial configuration underlying a particular maxillo-facial disharmony must be considered in diagnosis, growth predictions and resulting treatment planning.

Soft-tissue changes during facial growth in skeletal Class II individuals

INTRODUCTION

In orthodontic treatment, a harmonious soft-tissue profile can be difficult to achieve; the thickness of the soft tissues can vary greatly, and changes with growth and treatment can be difficult to predict. The purpose of this study was to investigate changes in the thickness and the length of the soft tissues of the nose, upper and lower lips, and chin due to growth from 6 to 16 years of age.

METHODS

Cephalograms of 36 subjects (22 boys, 15 girls) with skeletal Class II malocclusions were analyzed. They participated in the Burlington Growth Study, and longitudinal records had been collected at ages 6, 9, 12, 14, and 16 years. The cephalograms were digitized and analyzed with Dentofacial Planner Plus (version 2.0; Dentofacial Software, Toronto, Ontario, Canada) software. Statistical analysis was performed with the nonparametric Friedman test, and comparisons among means were made with 1-way ANOVA software.

RESULTS

All structures showed some growth at all stages. The nose showed the greatest increases in thickness and length in both sexes. There was sexual dimorphism at 16 years, with higher values for boys. Upper lips tended to reduce in the girls. Upper lip length showed slight increases, and base of the upper lip showed small increases for both sexes. The lower lip had moderate increases in all measurements, and its thickness showed sexual dimorphism at almost all ages. The soft tissues of the chin increased in both thickness and length, with no sexual dimorphism.

Crescimento da base craniana nos diferentes tipos faciais nos relacionamentos maxilomandibulares ortopédicos de Classe I, II e III: Parte 2 (Crescimento médio de Ba-Na, CC-Na e CC-Ba)

OBJETIVO: este estudo retrospectivo avaliou o crescimento médio da base craniana nos diferentes tipos faciais e de relacionamentos maxilomandibulares ortopédicos.METODOLOGIA: uma amostra aleatória de 300 pacientes brasileiros leucodermas (131 do gênero masculino, 169 do gênero feminino), com idade média inicial de 10 anos e 2 meses (dentadura mista) e final de 14 anos e 8 meses (segundos molares em oclusão) e tempo médio de observação de 4 anos e 5 meses, foi selecionada em uma clínica particular, em São Paulo, Brasil. Havia 118 Classe I, 151 Classe II e 31 Classe III. Todas as 600 radiografias cefalométricas laterais foram obtidas no mesmo aparelho de raios-x. As análises de Ricketts e Schwarz modificadas por Faltin foram usadas. As medidas lineares (Ba-Na, CC-Na e CC-Ba) foram feitas manualmente pelo mesmo examinador em T1 e T2. Os relacionamentos foram estudados juntos e separadamente, considerando tipo facial e gênero. O teste t-pareado e ANOVA foram aplicados. RESULTADOS E CONCLUSÕES: o tipo facial retrovertido cresceu significantemente mais em CC-Na na Classe II, sendo a sua correção desfavorável no gênero feminino; com tendência favorável na Classe III e crescimento dentro do esperado na Classe I. O neutrovertido cresceu significantemente mais em CC-Na nas Classes I e II, sendo desfavorável na Classe II; com crescimento eqüitativo de CC-Na e CC-Ba na Classe III e levemente acima do esperado na Classe I. O provertido teve crescimento eqüitativo em todas as Classes, sendo significantemente favorável na Classe II mandibular; com tendência favorável na Classe III e crescimento médio acima do esperado na Classe I.

A comparison of craniofacial Class I and Class II growth patterns

Longitudinal craniofacial databases, including the Fels Longitudinal Study, the Michigan Growth Study, and the Nijmegen (The Netherlands) Growth Study, were compared for a set of 12 craniofacial measurements on lateral skull cephalograms. The age ranges of the subjects were 7-14 years for females and 9-14 years for males. When we compared the normally distributed databases using multiple comparisons, a small sample test statistic t for differences between means of the databases showed few statistical differences. The databases were therefore pooled, and sex-specific Class I (ANB < 4 degrees), and Class II (ANB > or = 4 degrees) subsamples were analyzed with the same t test. The sizes of these subsamples ranged from 39 to 122 at the different ages. The findings showed that the Class II samples had greater SNA and SN-GoMe angles. Compared with the Class I group, shorter mandibles were found in the younger age groups of the Class II samples. No differences were found in mandibular length (Ar-Gn) and mandibular body length (Go-Gn) in the older Class II groups compared with the Class I groups. These findings indicate that the greater mandibular lengthening in the Class II groups might have contributed to successful Class II treatment in studies in which a Class I group was the control. Because of individual biological variability, the average Class I or Class II growth pattern might not be a realistic assumption or have clinical relevance for individual patients.

Clinical outcomes of Fränkel appliance therapy assessed with a counterpart analysis

To evaluate whether the Fränkel Regulator-II (FR-II) induced mandibular growth rotations relative to the nasomaxilla and the middle cranial fossae, cephalometric changes in 28 treated Brazilian children were compared with changes in 28 untreated Class II children and in 28 children with normal occlusion. According to Enlow's counterpart analysis, the 3 groups were not significantly different initially in ramus alignment or relative ramus vertical dimension. These jaw relationships were maintained in both untreated groups. In the treated group, all children had overjet reduction, with correction of the dental arch relationship in 26 of the 28, and there was a significant trend toward a more forward ramus alignment (P =.002) and increased ramus relative vertical dimension (P =.0002). These treatment-induced changes showed a negative correlation with ramus alignment; ie, greater improvement was more likely in children who had backward ramus alignment before treatment and whose Class II malocclusion had not already been intrinsically compensated. Changes in the treated children were similar to but greater than those in the normal children, and different from those in the untreated Class II group. The data suggest that studies of skeletal variations with counterpart analysis can show ramus remodeling compensations from treatment that are missed with conventional cephalometrics.

Role of cranial base flexure in developing sagittal jaw discrepancies

The aim of this longitudinal cephalometric study was to investigate skeletal features in patients with small and large cranial base angles. Two groups of untreated subjects were formed on the basis of a small and large cranial base angle N-S-Ar at the age of 5 years: the large cranial base angle group (n = 22) consisted of subjects with an N-S-Ar angle larger than 125 degrees (mean, 128.1 degrees ), and the small cranial base angle group (n = 20) included subjects with an N-S-Ar angle of less than 120 degrees (mean, 117.6 degrees ). Cephalometric data of the 2 groups were analyzed at subject ages 5 and 12 years. At both ages, the groups showed significant differences of the variables SNA, SNB, individualized ANB, and Y axis. The unadjusted ANB angle and the angle of convexity N-A-Pg were not significantly different between the 2 groups. According to the individualized norm of the ANB angle, subjects with a large cranial base angle in the primary dentition demonstrated a skeletal Class II tendency both at the initial observation and at the longitudinal follow-up. On the basis of cephalometric variables at 12 years of age, it was possible to classify 88.1% of the initial large and small cranial base angle individuals, indicating a constancy of the skeletal pattern during the longitudinal follow-up. The relationship between cranial base flexure and skeletal pattern of the jaws seems to be established before the age of 5 years.