Orthodontists, thanks to their keen appreciation of facial morphology and their skills in making functional examinations, are ideally placed to detect breathing problems in their patients that can require an ENT assessment, with special attention paid to the evaluation of sleep patterns. After a site of obstruction, resulting from a soft tissue anomaly and/or a narrowing of the airway passage through bone, has been established, orthodontists may be called upon to undertake corrective treatment sometimes in conjunction with a surgical procedure.

This study determines deformations of the midface that contribute to a class III appearance, employing thin-plate spline analysis. A total of 135 lateral cephalographs of prepubertal children of European-American descent with either class III malocclusions or a class I molar occlusion were compared. The cephalographs were traced and checked, and 7 homologous landmarks of the midface were identified and digitised. The data sets were scaled to an equivalent size and subjected to Procrustes analysis. These statistical tests indicated significant differences (P<0.05) between the averaged class I and class III morphologies. Thin-plate spline analysis indicated that both affine and nonaffine transformations contribute towards the total spline for the averaged midfacial configuration. For nonaffine transformations, partial warp 3 had the highest magnitude, indicating the large scale deformations of the midfacial configuration. These deformations affected the palatal landmarks, and were associated with compression of the midfacial complex in the anteroposterior plane predominantly. Partial warp 4 produced some vertical compression of the posterior aspect of the midfacial complex whereas partial warps 1 and 2 indicated localised shape changes of the maxillary alveolus region. Large spatial-scale deformations therefore affect the midfacial complex in an anteroposterior axis, in combination with vertical compression and localised distortions. These deformations may represent a developmental diminution of the palatal complex anteroposteriorly that, allied with vertical shortening of midfacial height posteriorly, results in class III malocclusions with a retrusive midfacial profile.

To investigate the claim that the primate paranasal sinuses possess not a functional but a structural role associated with the skull architecture (Blaney, 1990), the relationship between the maxillary sinus and the skull architecture was studied ontogenetically in 30 skulls of male and female Japanese macaques (Macaca fuscata). Coronal CT scan series and computerised 3-dimensional images served to evaluate the maxillary sinus. The definitive hemispherical shape of the sinus was already achieved after the completion of the primary dentition. Sinus volume increased with a trend indicating positive allometry. When compared with an ontogenetic data set of orang-utan (Koppe et al. 1995), however, the growth rate of the maxillary sinus of M. fuscata was significantly less. The maxillary sinus both of male and female macaques enlarged according to a common growth pattern. However, no sexual dimorphism could be established for the maxillary sinus size. Although the volume of the right maxillary sinus was normally bigger than that of the left side, the results suggested that asymmetry in maxillary sinus volume is related neither to skull size nor sex. Whereas a correlation analysis showed close relationships between the maxillary sinus volume and external cranial dimensions, the partial correlation coefficients revealed that these relationships were highly influenced by skull size. Although it cannot be ruled out that the paranasal sinuses are to some extent linked to the skull architecture, this study does not support a solely structural role for these air cavities.