[Morphological study on growth process of primary dentition having distal step of the terminal plane. 2. Individual growth].

Abstract

In order to analyze individual growth, 10 cases which contained longitudinal data and materials were chosen out of the 32 cases with bilateral distal step that were used in the study of Part I. The control group comprised the same twelve cases that were used in Part I. Observations of plaster models were made on the eruption age and eruption sequence of the first maxillary and mandibular permanent molars and incisors, the mesiodistal crown diameter, the interdental spaces in the primary dentition, and individual growth of the maxillary intercanine width. Cephalometric analysis was made on linear and angular items in which a significant difference between the two groups was found in the study Part I: Growth on the Average. Growth patterns were classified according to profilograms. The relationship between the terminal planes and analyzed items was also discussed. The results were as follows: 1. Individual growth data obtained from plaster models 1) Concerning the eruption age of the permanent teeth, the first maxillary molars of the examined group erupted in 5.84 years on the average. In cases of the control group, 6.42 years was the average. There was a significant difference between the two groups. The maxillary and mandibular central incisors of the examined group tended to erupt slightly earlier than the control group. 2) Concerning the eruption sequence of the permanent teeth, the first maxillary molars or the mandibular central incisors erupted earliest in the examined group, and the first mandibular molars or the mandibular central incisors in the control group. 2. Individual growth data obtained from cephalometrics 1) Concerning skeletal patterns, the examined group showed a significantly larger increase of the lower facial height (NF-Me) than the control group in the period from eruption of the first molars to eruption of the maxillary central incisors. In this period, 8 out of 10 cases of the examined group and 3 out of 12 cases of the control group showed the maximal growth change. 2) Concerning denture patterns, the maxillary incisor height (Ul-NF) increased markedly in the period from eruption of the first molars to eruption of the maxillary central incisors. This was found in 8 cases of the examined group and 4 cases of the control group.(ABSTRACT TRUNCATED AT 400 WORDS)