Optimal Loading Conditions for Controlled Movement of Anterior Teeth in Sliding Mechanics

Abstract

Objective: To determine optimal loading conditions such as height of retraction force on the power arm and its position on the archwire in sliding mechanics. Materials and Methods: A 3D finite element method (FEM) was used to simulate en masse anterior teeth retraction in sliding mechanics. The degree of labiolingual tipping of the maxillary central incisor was calculated when the retraction force was applied to different heights of a power arm set mesial or distal to the canine. Results: When the power arm was placed mesial to the canine, at the level of 0 mm (bracket slot level), uncontrolled lingual crown tipping of the incisor was observed and the anterior segment of the archwire was deformed downward. At a power arm height of 5.5 mm, bodily movement was produced and the archwire was less deformed. When the power arm height exceeded 5.5 mm, the anterior segment of the archwire was raised upward and lingual root tipping occurred. When the power arm was placed distal to the canine, lingual crown tipping was observed up to a level of 11.2 mm. Conclusions: Placement of the power arm of an archwire between the lateral incisor and canine enables orthodontists to maintain better control of the anterior teeth in sliding mechanics. Both the biomechanical principles associated with the tooth's center of resistance and the deformation of the archwire should be taken into consideration for predicting and planning orthodontic tooth movement.

Evaluating the effects of consolidation on intrusion and retraction using temporary anchorage devices—a FEM study

“…Bilateral implants will be angulated to 30° to the long axis of the occlusal plane. The anterior retraction hook is placed between the canine and lateral brackets [31] at a 9-mm height [30, 32], (Fig. 1).…”

En-masse Retraction of the Maxillary Anterior Teeth by Applying Force from Four Different Levels – A Finite Element Study

“…Here tipping occurred because the point of force application was below the center of resistance. The center of resistance of the six anterior teeth was estimated to be halfway\between the center of resistance of the four incisors and canines(red dot in figure) [5,14,20] as told by Melsen, Hyo-Sang Park and others i.e. 13.5 mm apical and 14.0mm posterior to the incisal edge of the upper central incisor.…”

“…Force of 150gms/side was used as it is within the physiologic limits for enmasse retraction as told by Rickets and others [1,6,14,19,20].…”

“…Studies were done by changing the height of retraction hook in anterior region [14] and by changing the position of implants in mesiodistal direction in posterior region [15], but till now studies have not been done by changing vertical levels of point of force application in the posterior region by keeping the anterior point of force application constant and its effect on anterior teeth during space closure.…”

“…High, Medium, Low pull Implants and from a conventional Molar hook and also to quantify the retraction and intrusion components of force during retraction with implants. Here a force of 150gm/side was applied [1,6,14,19,20].…”