[Morphological study using Moiré patterns on the dental arch and palate of Japanese with normal occlusion]

Studies of the dental arch and the palate have progressed from two-dimensional to three-dimensional analysis. However, many points still need clarification in this field even though the fundamental structure of arch and palate have a common function in connection with mastication. The present study, using three-dimensional measurements of the palate, endeavors to clarify the differences in palatal morphology as these are affected by the changes in the dental arch morphology. Casts were made using 62 males between the ages of 20-25. Only those casts which were considered to represent normal occlusion of the upper dentition were selected for use in this study. Photographs of the casts were studied using the Moiré topographical method with a grid of 0.5 mm. Seven points were selected for measurement purposes (figs. 2 and 3). Based on these points, the seven distances were used in this study. Measuring of the palate was performed in the following manner: lines were drawn radially from the origin (F) to the most lingually protrusive point on the gingiva of each of the 12 teeth from the right first molar round to the first molar on the left side. The points of mergence by these lines with every second line (2 mm deep) of the Moiré pattern were fed into a digitizer. The results were summarized as follows: 1. The anterior, posterior and complete arch chords were 23.73 mm, 19.93 mm and 41.68 mm respectively. The anterior, posterior and complete arch lengths were 14.14 mm, 19.98 mm and 34.12 mm respectively. The anterior and posterior arch widths were 38.02 mm and 50.73 mm respectively. 2. As for the correlation coefficients, there was a correlation between the lengths and widths of the anterior portion, but not for the posterior. 3. The length from the origin (F) to the papilla incisiva was 25.4 mm, and the depth of the palate at the origin (F) was 13.4 mm on the average. 4. In the vertical cross section of the palate for each tooth, the slope line of the palate gradually increased from the incisors to the first molars, but the amount varied between the anterior and posterior portions of the maxillary dentition. Also, the line of the palate converged at one point about 11 mm from the origin (between lines 9 and 11 on the Moiré pattern). 5. In the horizontal cross section of the palate, the shape of the palate was almost semi-circular in the range of Moiré lines 9-11 with the origin at the center.(ABSTRACT TRUNCATED AT 400 WORDS)