Occlusal development between primary and mixed dentitions: a 5-year longitudinal study.

Purpose The purpose of this study was to evaluate the variations in occlusal relationships and the influence of dental arch type and primate spaces on the development of primary and mixed dentition, including molar-canine relationship and anterior crowding, over a 5-year period. Methods One hundred twenty-eight children were examined in schools in Nova Friburgo, Rio de Janeiro, Brazil. Results There was a straight terminal plane development (ie, from mesial step to Class I and III, and from distal step to Class II). It was noted that a Class I canine relationship observed in the primary dentition was maintained in 91% of the cases during the mixed dentition presenting type 1 arch and primate spaces, whereas a Class III relationship developed into Class I. There was a modification in the negative overbite followed by mild to severe relationship and then by a moderate one in the mixed dentition, with a discrete increase in overjet compared to the primary dentition. It was verified a greater prevalence of Baume arch type I and primate spaces. As for the molar relation, there were no significant changes in the development from primary to mixed dentition, according to dental arch type and primate spaces. Lower arch crowding, however, was found in 29% of the children, even in the presence of arch type I and primate spaces. Conclusions The occlusal relationships in the mixed dentition were influenced and followed a pattern determined by the primary dentition. Arch type I and primate spaces favor both development of Class I malocclusion and the absence of upper arch crowding, although they do not appear to affect the molar relationship and lower arch crowding.