Persistence of deciduous molars in subjects with agenesis of the second premolars

The purpose of the present study was to investigate persistent primary seco nd molars in a group of young people in their late twenties with agenesis o f one or two second premolars. In 1982-83 it was decided, in connection with the orthodontic evaluation of 25 patients, to allow 35 primary molars (one or two in each patient) to re main in situ. All patients had mixed dentitions and agenesis of one or two premolars. The primary teeth were generally in good condition, although roo t resorption and infra-occlusion (compensated by occlusal composite onlays) occurred. In 1997, 18 of the 25 patients with a total of 26 retained primary molars w ere reexamined, comprising a clinical examination for exfoliation, extracti on, loosening, and ankylosis, and a radiographic examination for root resor ption, tooth morphology (crown and root), and alveolar bone contour. The examination showed that the degree of root resorption was unaltered in 20 of the 26 primary molars. In the permanent dentitions, where these prima ry molars persisted, there were no morphological deviations. Three of the s ix remaining primary molars had been extracted and three showed extensive r esorption. In three of the 26 primary molars the infra-occlusion had worsen ed. The present study shows that persistence of primary second molars in subjec ts with agenesis of one or two premolars, and normal morphology of the perm anent dentition can be an acceptable, semi-permanent solution for the patie nt. Whether this could also be an acceptable long-term solution will be sho wn by follow-up studies.