"The relation between nasorespiratory function and dentofacial morphology"

Principles of Orthognathic Surgical Correction of Skeletal Anterior Open Bite

This article describes the principles of orthognathic surgical correction of skeletal anterior open bite (AOB), including a description of the aetiological factors involved in the development of predominantly skeletal AOBs, description of the presenting diagnostic features, the principles of treatment planning, orthodontic preparation, and postoperative requirements.

Second premolar agenesis is associated with mandibular form: a geometric morphometric analysis of mandibular cross-sections

The aim of this study was to compare mandibular form (i.e., size and shape) between patients with agenesis of the lower second premolar (P2) and a control group with no agenesis. Three hypotheses were tested: (H1) agenesis causes a change in mandibular morphology because of inadequate alveolar ridge development in the area of the missing tooth (mandibular plasticity); (H2) agenesis is caused by spatial limitations within the mandible (dental plasticity); and (H3) common genetic/epigenetic factors cause agenesis and affect mandibular form (pleiotropy). A geometric morphometric analysis was applied to cross-sectional images of computed tomography (CT) scans of three matched groups (n=50 each): (1) regularly erupted P2; (2) agenesis of P2 and the primary second molar in situ; and (3) agenesis of P2 and the primary second molar missing for >3 months. Cross-sections of the three areas of interest (first premolar, P2, first molar) were digitized with 23 landmarks and superimposed by a generalized Procrustes analysis. On average, the mandibular cross-sections were narrower and shorter in patients with P2 agenesis compared with that in the control group. Both agenesis groups featured a pronounced submandibular fossa. These differences extended at least one tooth beyond the agenesis-affected region. Taken together with the large interindividual variation that resulted in massively overlapping group distributions, these findings support genetic and/or epigenetic pleiotropy (H3) as the most likely origin of the observed covariation between mandibular form and odontogenesis. Clinically, reduced dimensions and greater variability of mandibular form, as well as a pronounced submandibular fossa, should be expected during the treatment planning of patients with P2 agenesis.

[Facial volumes and vertical facial type: a three dimensional comparative study]

INTRODUCTION

The purpose of this study was to compare the volume of facial cavities in untreated young subjects with long- and short-faces.

METHODS

Two groups of thirty subjects each, one with low (GoGn-SN < or = 28 degrees), and the other with high (GoGn-SN > or = 36 degrees) mandibular plane angles, ages between 18 to 30 years, were selected. For each subject, volumes of orbital, sinusal and buccal cavities were measured from CT scans with the AMIRA software. The statistical studies were performed using Kolmogorov-Smirnov, followed by Student "t" test (p < 0.05).

RESULTS

Results suggest that there is no statistically significant difference between the volume of facial cavities in long- and short-face subjects. Only the ratio of nasal cavity volume to the total volume is significantly smaller in the short-face group.

CONCLUSION

A compensatory phenomenon might exist between the three directions of growth to equilibrate an excess or deficit of the vertical dimension, thus maintaining constant the volume of facial cavities.

[Correlations between the volume of the sinuses and the facial bones and parameters of 3D cephalometry]

The goal of this work is to study, using a sample of 95 persons, the parameters of the 14 points of the 3D Treil cephalometric analysis and to compare them to the facial volumes of these subjects. The 3D parameters are described on three levels and for all three dimensions of space; they are also defined statistically for each class of occlusion, and indications are given for sagittal two-dimensional variables. The correlations between all these variables and facial bones and air cavity volumes are also analyzed. The antero-posterior and vertical variables showed more statistically significant relationships with volumes than with transverse parameters. It appears that a Class III occlusion is primarily related to the vertical and antero-posterior position of the mandible and its morphology and not to its size, while Class II Division 1 types are associated with increased size of the maxillary sinuses. It also appears that facial hyper-divergence is related to a decrease in the size of the maxilla and the mandible.