Primary Rugae Research Articles

Morphological study of the palatal rugae in Japanese. I. Bilateral differences in the regressive evolution of the palatal rugae.

The bilateral differences in the type, number, form and distribution of the palatal rugae were studied in 410 maxillary dental casts of Japanese adults to investigate whether the regressiveevolution of the rugae proceeds more, in the right or left side of the palate.1.There was no bilateral difference in the mean number of the primary rugae. However, in the mean number of all the rugae including the primary, secondary and fragmentary rugae, the regressiveevolution progressed more in the right side.2.The distinct postero-anterior changes in the direction, shape, origin and papillate rugae of the primary rugae indicated that the rugae degenerated from the posterior part of the hard palate.(1) The right rugae of which the direction distinctly inclined backward, degenerated more thanthe left.(2) The bilateral differences in the shape and origin were observed only on the posterior rugae. The right rugae degenerated more in the shape, but in the origin the left rugae degenerated more.(3) There was no bilateral difference in the papillate rugae, but the regressive evolution was considered to extend to the first rugae because the papillate rugae were observed in the first rugae at the higher frequency of34-40%.From the above view, the clear bilateral differences were found in the morphology of the palatal rugae. The results showed that the regressive evolution of the rugae in both sides does not proceed at the same time, but proceeded more in the right side than in the left.

Relationship of first primary palatine rugae to the maxillary canines in man.

Fifty dentate maxillary casts, obtained from thirty-four males and sixteen females, were mounted in the three-dimensional co-ordinate system of a contour meter. A transverse line of reference (x-axis) was drawn through the distal contact points of the maxillary canines, at a right angle to the y-axis which passed through the contact points of the maxillary central incisors. Relative to the canine-to-canine baseline, the locations of the lateral borders of the right and left first primary rugae were determined. The rugae were distributed on both the anterior and posterior sides of the baseline, and the anterior and posterior distances from the baseline were on the average about 1 mm. The age of the subjects, ranging from 12 to 52 years, appeared to be unrelated to the frequencies of anteriorly and posteriorly positioned rugae. Right and left first primary rugae, located on the anterior side of the baseline, showed a minute asymmetry in their topography. By contrast, there was topographical symmetry when the rugae were located on the posterior side of the baseline.