Aplasia, supernumerary teeth and fused teeth in the primary dentition

abstract – Numerical variations and fusions in the primary dentition were studied among 4,564 children from 3 to 31/2 years of age. The results of the examination showed that aplasia occurs in 0.5%, hyperodontia in 0.5%, and fusions in 0.9%. Patients with aplasia in the primary dentition nearly always showed aplasia of the successors. In patients with unilateral aplasia in the primary dentition, aplasia of the contralateral permanent tooth was often found also. Most cases of hyperodontia occurred in the maxilla. Half the supernumerary teeth were maxillary lateral incisors, and they were often followed by hyperodontia in the permanent dentition, whereas cases with supernumerary central incisors were less often followed by hyperodontia in the permanent dentition. Where a mandibular lateral incisor and canine were fused, aplasia of the permanent lateral incisor was always found, whilst cases with fused incisors only rarely involved changes in the permanent dentition. Cases with gemination in the primary dentition were as a rule followed by normal conditions in the permanent dentition.