[A comparison of growth and development of the dental arch, alveolar process, and palate in the lateral segment determined with reference to dental age and chronological age, particularly on the period of premolar eruption].

The purpose of this study is to observe and compare growth and development in the dental arch, the alveolar process, and the palate in reference to dental age, which is based on tooth emergence, and chronological age. Subjects consisted of serial dental casts taken at two-month intervals from 40 children (20 males and 20 females) with normal occlusion in permanent dentition. In terms of dental age, observations were made for a total of two years, one year before and one year after the tooth emergence of first premolar and second premolar. In terms of chronological age, observations were made for a total of two years, one year before and one year after the average age of tooth emergence of first premolars and second premolars in this sample of children. Results and Conclusions. Comparisons between growth changes in the dental arch, the alveolar process, and the palate on dental and chronological age showed some regions in which growth patterns were similar and others in which growth patterns were different. The differences between both growth patterns from two ages were classified into two groups according to the tooth which caused the difference: those produced by the tooth used as a standard for dental age and those produced by teeth other than that used as a dental-age standard. 1) Differences resulting from the influence of the tooth used as a dental-age standard In regions of the tooth used as a dental-age standard, differences occurred in growth patterns on both kinds of age in practically all measured items. In regions adjacent to that of the tooth used as a dental-age standard, the differences were observed in growth patterns of the alveolar process and the palate but not in those of the dental arch. The differences were the most pronounced in the regions of dental-age-standard teeth than in the adjacent regions. The majority of the differences caused by teeth used as standards for dental age were thought to have been the results from the influence of eruption. No growth-pattern differences were observable in regions more than two teeth away from the tooth used as a dental-age standard. 2) Differences resulting from the influences of teeth other than that used as a dental-age standard Using the emergence time of a certain tooth as a dental-age standard, the emergence times of other teeth lead to be come together in some degree.(ABSTRACT TRUNCATED AT 400 WORDS)