[Secondary retention of permanent molars. I. Clinical, radiologic and histologic characterization]

The clinical, radiographical and histological aspects of secondary retention in permanent molars were studied in a group of 53 patients with 81 secondarily retained permanent molars. First molars turned out to be affected most frequently. The mean infraocclusion at the patients' first visit was 4.3 mm. After six months, infraocclusion had increased in adolescents. It seemed to be stable in adults. Tilting of adjacent teeth was observed in 39 cases of secondary retention. A solid, clear percussion sound and a partial absence of the periodontal ligament space on radiographs was only noted in less than 20% of the affected molars, while histological examination of 38 removed molars revealed that local areas of ankylosis were present in all cases. During a follow-up period of four years, six new cases of secondary retention were observed in the same population.