Three-dimensional analysis of hard palate in Down syndrome subjects

Aim: Down syndrome (DS) is the most frequent chromosomal aberration in man, with a prevalence of about 40,000 affected people in Italy, resulting from complete or partial trisomy of chromosome 21. Several peculiar maxillofacial features have been described in DS subjects, but quantitative assessments of hard tissue palatal features in subjects are still scanty (1) and no data concerning Italian DS people do exist. The purpose of the study was to collect data on palatal size and shape in DS subjects focusing on the major determinants of the hard palate modifications, whether only the Down syndrome or some other variables. Both the dental formula and the ethnicity were thus considered. Materials and Methods: Hard tissue palatal shape and dimensions in 41 Italian DS subjects (29 men, 12 women) were analyzed and compared to normal reference data (15 men, 13 women). Palatal landmarks were digitized with a 3D computerised electromagnetic instrument and their coordinates were used to construct a mathematical equation of palatal shape, independent of dimensions (2, 3). Palatal length, slope, width, maximum palatal height in both sagittal and frontal plane were measured and two percentage ratios (maximum height to width and width to length) were obtained. Results: All average dimensions were reduced in DS subjects without any significant sex difference except for palatal height in the sagittal plane (larger in males). The height to width ratio increased in Down syndrome individuals, while width to length ratio was similar. In the sagittal plane the curves of DS and normal subjects within each sex were nearly superimposable; in the frontal plane Down individuals showed a higher palate than healthy subjects, particularly females. To assess the influence of posterior teeth on palatal morphology, DS males were then divided in two groups (eight totally edentulous and 21 partially dentate) and compared to normal subjects by analysis of variance. Global F values were significant for all variables. Partial comparisons showed significant smaller measures in edentulous versus dentate DS males (not width) and versus normal subjects (not slope). All parameters but slope and height in the frontal plane were larger in reference than in partially dentate DS males. Shape modifications were larger in edentulous subjects with a flattening of palatal curves; all ratios were significantly reduced. Conclusions: Trisomy of chromosome 21 seems to alter the normal palatal size and shape in Italian subjects, although further analyses may involve a larger group. Quantitative data on palatal features could be useful for clinicians when planning dental rehabilitation of DS patients, providing a reference to construct suitable prosthetic devices with improved oral health and dental care.