Comparison of inclination and vertical changes between single-wire and double-wire retraction techniques in lingual orthodontics

Abstract

Objective: The Heat Induction Typodont System (HITS), used in some recent studies, has a distinct advantage over previous tooth movement simulation methods. This study aimed to compare inclination and vertical changes between the single-wire and double-wire techniques during en masse retraction with different lengths of lever arms in lingual orthodontics using an upgraded version of the HITS. Methods: Duet lingual brackets, which have two main slots, were used in this study. Forty samples were divided into four groups according to the length of the lever arm (3-mm or 6-mm hook) and the retraction wire (singlewire or double-wire). Four millimeters of en masse retraction was performed using lingual appliances. Thereafter, 3-dimensional-scanned images of the typodont were analyzed to measure inclination and vertical changes of the anterior teeth. Results: Incisor inclination presented more changes in the singlewire groups than in the double-wire groups. However, canine inclination did not differ between these groups. Regarding vertical changes, only the lateral incisors in the single-wire groups presented significantly larger values than did those in the double-wire groups. Combining the effect of hook lengths, among the four groups, the single-wire group with the 3-mm hook had the highest value, while the double-wire group with the 6-mm hook showed the least decrease in crown inclination and extrusion. Conclusions: The double-wire technique with an extended lever arm provided advantages over the single-wire technique with the same lever arm length in preventing torque loss and extrusion of the anterior teeth during en masse retraction in lingual orthodontics.

Biomechanical analysis of maxillary anterior teeth movements during different retracting methods with a lever arm miniscrew system in double‐slot lingual brackets: A finite element method study

“…Previous studies reported the use of a few specific techniques to reduce the unexpected bowing effect and preserve the arch shape of the anterior six teeth during retraction: the reciprocal force applied to both the buccal and lingual sides of the bilateral canines, that is, ‘double cable’ mechanics, 16 placing the lever arms at the distal side of the canines, 10 or using a straight lingual ribbon‐wise archwire 21 . In our study, we used the double‐slot lingual bracket system.…”