Geometric morphometric evaluations of a randomized prospective split-mouth study on modes of ligation and reverse-curve mechanics.

OBJECTIVES: To evaluate tooth position after six and 9 months of orthodontics with conventional brackets on one side of the dentition and ligature-less brackets on the other. SETTING AND SAMPLE POPULATION: Orthodontic Division, Vienna Medical University. Twenty patients aged 22.5 +/- 5.7 years, symmetrical malocclusion and arch form, no premolar extraction. MATERIAL AND METHODS: Prospective split-mouth study, 0.022-inch SmartClip self-ligating brackets assigned randomly to the left or right dentition, conventional 0.018-inch brackets on the other side. 52 dental landmarks, digitized on plaster casts, represented dental arches at baseline (t0), 6 months and 9 months (t1, t2). During t0-t1, we used 0.016 and 0.014 x 0.025 inch superelastic wires, during t1-t2 connected reverse-curve hemiarch wires: 0.017 x 0.025 inch ss-titanium on the ligature-less side, and 0.016 x 0.022 inch Elgiloy multiloop wires on conventional brackets. Morphometric analyses were used to assess differences in dental arch shapes. RESULTS: Neither initial alignment nor the reverse-curve phase showed statistically significant differences between ligature-less and conventional brackets in moving teeth. CONCLUSION: Morphometric shape analyses corroborated current evidence that self-ligating brackets were no more effective than conventional brackets with steel ligatures after 6-month initial alignment. From months 6-9 treatment with ss-titanium reverse-curve wires on 0.022-inch ligature-less brackets resulted in similar tooth positions as accomplished by Elgiloy multiloop wires on 0.018-inch steel-ligature-tied brackets.