A longitudinal cephalometric study of incisor supra-eruption in young and adult rhesus monkeys (Macaca mulatta).
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Supra-eruption was examined in 28 adult (N = 19 experimental and 9 control) and 12 juvenile monkeys (N = 7 experimental and 5 control). The experimental animals had a bite splint cemented to the posterior maxillary teeth which opened the bite inter-incisally by 15 mm and was worn continuously for 48 weeks. Lateral cephalograms were taken prior to the cementation and at 12-week intervals thereafter. Radio-opaque bone implants placed in the basal bone of the jaws served as fixed reference points from which to assess the vertical and horizontal components of central incisor movement. Significantly greater movement of both upper and lower incisors towards the occlusal plane occurred in the experimental animals of both age groups over the 48 weeks when compared to the same aged controls (p less than 0.01). Mean vertical movement ranged from 4 mm (about 40% of crown length) in the juvenile upper incisors to 1.5 mm (15%) in the adult lower incisors. The overall pattern of movement of upper and lower incisors in the experimental juveniles differed from that in the controls only in the vertical component (p less than 0.01), indicating that the supra-eruptive response was superimposed on the antero-occlusally directed tooth movement and alveolar growth that normally occurs in rhesus monkeys of this age. In contrast to the more evenly distributed response found in the juveniles, the majority of the supra-eruptive response occurred during the first 12 weeks in the experimental adults.(ABSTRACT TRUNCATED AT 250 WORDS)
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