The morphology of root fusion in Chinese adults (I). Grades, types, location and distribution

Abstract

The purpose of the present study was to investigate the morphology, extent, and distribution of root fusions in 1st and 2nd permanent molars in a Chinese population. The sample consisted of 158 maxillary and 151 mandibular extracted 1st and 2nd molars. Root fusion in molars was assessed by direct viewing and measuring the length of the root and root trunk with stereoscopic microscopy. Root fusion was graded by the extent of fusion and the number of affected surfaces. The main results were as follows: (1) the majority of root fusions affected upper and lower 2nd molars (39.7% and 28.1%, respectively); (2) the prevalence of maxillary roots with 1, 2 and 3 fusions was 55.2%, 31.3% and 13.4% respectively, and most of the root fusions affected the maxillary 2nd molars (65.7%); (3) the majority of mandibular root fusions affected the 2nd molars (89.2%), and were of grade III (48.7%); (4) in order of decreased prevalence, the grades of root fusion in 2nd molars were grades III, II and I; whereas in 1st molars they were grades I, II and III; (5) there were 44 (41.5%) and 19 (51.4%) complete root fusions (grade III) among 106 fused roots in maxillary molars and 37 fused roots in mandibular molars, respectively.