Growth Changes of Incisors and Molars Position During Transition

Objective The purpose of the study was to investigate the longitudinal growth changes in tooth position of incisors and first molars from mixed dentition to early permanent dentition.Methods Two stages of the dental development of 20 subjects(6 males and 14 females)with normal occlusion were evaluated:stage Ⅰ,when the first molars and four incisors fully erupted;stage Ⅱ,period when the second molars fully erupted.The dental casts were photocopied.Two series of the dental casts were superimposed at the median palatal phane and the median ends of the third palatal rugae,and the changes of the incisors and first molars position were analyzed.Results For the boys,the left first molars in the upper and lower arch mesially moved 2.6mm,3.1 mm(P0.05)respectively.For the girls,the upper lateral incisors on left and right side moved labially 1.0 mm(P0.01),1.1mm(P0.05)respectively.The distance of the upper left lateral incisor to median palatal plane decreased 0.45mm(P0.001).The right first molars in the upper and lower arch mesially moved 2.0mm(P0.001),2.1mm(P0.05)respectively,while the left first molars in the upper and lower arch moved mesially 1.8mm,2.4mm(P0.001)respectively. Conclusions During teeth transition,little change wase noted in incisors position and transverse molars position.First molars significantly moved mesially and greater movement occurred in the lower.Mesial movement of the first molars was the main cause of arch depth decrease.