Evaluating anchorage and torque control in adolescent patients with Class II Division 1 malocclusion among 3 appliances

Abstract

Introduction

The objective of this study was to compare the differences in anchorage and torque control among the Tweed edgewise, Roth, and physiological anchorage Spee-wire systems (PASS) appliances (Zhejiang Xinya Technology Co, Ltd, Hangzhou, China).

Methods

A sample of 90 adolescent patients with Angle Class II Division 1 malocclusion (30 Tweed edgewise appliances, 30 Roth appliances, and 30 PASS appliances) with maximum anchorage requirements in the maxilla were collected for this study. The pretreatment baseline levels of the 3 groups were compared initially, and then the differences between the 3 appliances in anchorage and torque control were analyzed after superimposing the pretreatment and posttreatment lateral cephalograms and maxillary 3-dimensional (3D) digital models, respectively.

Results

There was no statistical difference in the pretreatment baseline levels of 3 groups, including gender, age, sagittal skeletal types (ANB), vertical skeletal types (SN-GoGn), anchorage requirements, and occlusal plane inclination (SN-OP). After superimposing the pretreatment and posttreatment lateral cephalograms and 3D digital models, respectively, no statistical differences were observed between the measurement results obtained from lateral cephalograms and 3D digital models. Among the measurement variables assessed in this study, statistical differences were observed in the mesial displacement of maxillary first molars, the incisor retraction, and the torque variation of maxillary central incisors among the 3 groups. Specifically, the Tweed group exhibited lower mesial displacement of maxillary first molars compared with the PASS and Roth groups. Furthermore, the Tweed group exhibited the greatest amount of incisor retraction and torque variation of maxillary central incisors, followed by the Roth group and then the PASS group. The remaining measurement variables for the 3 groups showed no statistical differences, including vertical variation of maxillary first molars and central incisors, torque variation of maxillary first molars and canines, mesiodistal inclination variation of maxillary first molars and canines, width variation between maxillary first molars, and width variation between maxillary canines.

Conclusions

Compared with contemporary preadjusted straight wire appliances, the Tweed edgewise appliance has superiority in molar anchorage control. In contrast, compared with the Roth appliances, the PASS appliances without any auxiliary anchorage devices could make full use of physiological anchorage to achieve adequate control of molar anchorage. Clinical orthodontists may need to pay extra attention to physiological anchorage. The difference in torque control varies depending on the respective characteristics of bracket designs.