Comparative study of palatal rugae shape in two samples of Egyptian and Saudi children

This study was performed to investigate differences in the shape of the individual palatal rugae in two population samples of Arabian children from Egypt and Saudi Arabia, and develop discriminant function to identify the populations based on rugae shape. A total of 152 stone casts (80 from Egyptian and 72 from Saudi children), equally distributed between genders aged 6-8 years were examined for rugae shape (straight, wavy, curved, circular, unification and cross-link) and their incidence was recorded. Association between rugae shape and gender as well as rugae shape and population were tested using chi-square and discriminant function analyses using SPSS 13 statistical package. Curved and wavy were the most prevalent rugae shape in both groups, followed by straight rugae. Circular, converged and diverged unifications were few in number, while cross-link rugae were not observed in Saudi children. No significant gender differences were observed. Chi-square analysis for association between rugae shape and population groups showed significant differences in curved, wavy, cross-link, converged and diverged unification. Three rugae shapes; wavy, diverging unification and cross-link contributed to the discriminant function which enabled population identification. It was concluded that palatal rugae shape revealed significant differences between the two Egyptian and Saudi populations and also confirmed previous reports of lack of gender dimorphism. Discriminant function analysis allowed differentiation of the populations and it is inferred that discrete variables such as rugae shape are better suited for that purpose than continuous variables such as rugae length.