Evaluation of Dental Changes in Maxilla With Tipback Mechanics

Objectives: The aim of this prospective study was to test the null hypothesis that there is no significant difference in the antero-posterior and vertical position of the maxillary incisors and antero-posterior position of the maxillary first molars with tipback mechanics (one couple force system)
Methods: Lateral cephalometric radiographs of 16 adolescent subjects (mean age 12.63 + 1.1 years, 7 males, 9 females) taken at T1 (before molar tipback), T2 (after molar tipback) and T3 (after molar root uprighting) were evaluated. Wilcoxon signed rank test was performed to test the significance at T1, T2 and T3. P-value of <0.05 was deemed to be statistically significant.
Results: The maxillary first molar distalized by 1.53mm (P < 0.00) with 6.65 (P < 0.00) degrees of distal tipping and extruded by 0.86mm (P < 0.00) at T2. At T3, first molar moved forward by 0.09mm, tipped mesially by 1.84 degrees and intruded by 0.12mm. Antero-posteriorly, at T2 the maxillary incisors flared labially by 0.4mm and the incisor root apex moved palatally by 1.19mm (P < 0.00). At T3, the upper incisors flared labially by 0.12mm and incisor root apex moved palatally by 1.5mm (P < 0.00). Angular change of 3.31° (P < 0.00) and 3.53° (P < 0.00) at T2 and T3 respectively were seen due to the palatal root movement of maxillary incisors. Vertically, the incisors intruded by 0.97mm (P < 0.00) at T2, but 0.56mm of intrusion was lost at T3.
Conclusions: Vertically and antero-posteriorly, there was no significant change in the maxillary incisor position, but significant amount of distalization of the maxillary molars was attained with tipback mechanics. Additionally, tipback mechanics resulted in significant expression of palatal root torque on the maxillary incisors.