[Effect on the development of permanent successors due to the extraction and non-extraction of infected deciduous teeth].

The purpose of this study was to clarify the effects on the eruption and root formation of the permanent successors of deciduous teeth affected by periapical periodontitis. Materials used were forty-one healthy infant dogs about two months old. Standardized X-ray films were taken every two weeks. The period of study ran from the age of ten weeks to twenty eight weeks until the roots of the permanent successors were completed. A total of 328 mandibular teeth were used and classified as P2 and P3 with their preceding deciduous teeth being Dp2 and Dp3. The following four groups were used in this experiment. 1) Extraction group with infected deciduous teeth: The infected deciduous teeth were extracted after being left for four weeks following pulpectomy. 2) Extraction group with healthy deciduous teeth: Healthy deciduous teeth were extracted from fourteen-week olds. 3) Left-alone group with infected deciduous teeth: After pulpectomy the infected deciduous teeth were left until they were shed naturally. 4) Healthy group (control): Untreated teeth were observed which represented the opposites of all the teeth examined in the previous three groups. A study was made of the changes in location, eruption and root formation of the permanent successors of deciduous teeth in affected with periapical periodontitis and the condition of eruption and root formation of the permanent successors. The result were as follows. 1. Appearance rate of periapical periodontitis: 1) DP2: Two weeks after pulpectomy, periapical periodontitis was observed in eleven out of twenty-one teeth (52.4%), and after four weeks in seventeen out of twenty-one teeth (81.0%). 2) Dp3: Two weeks after pulpectomy, periapical periodontitis was observed in eighteen out of twenty-one teeth (85.7%), and after four weeks in all of the experimental teeth. The appearance rate of periapical periodontitis in Dp3 was higher than in Dp2. 2. Eruption of permanent successors: 1) Extraction group with infected deciduous teeth: (1) The eruption of permanent successors was accelerated more than the other experimental groups. This tendency was stronger in P3 than in P2. (2) There were changes in location in the upper and lower directions of P2 before extraction of Dp2, in the lower direction for P3 before extraction of Dp3, and in the upper direction for P2 and P3 after extraction of Dp2 and Dp3. 2) Extraction group with healthy deciduous teeth: (1) Eruption of P2 appeared to be almost the same as the control group, but the eruption of P3 was delayed slightly at the eruption from the alveolar bone.(ABSTRACT TRUNCATED AT 400 WORDS)