The relationship between cranial base and maxillo-facial morphology in Egyptian children

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.

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.