Torque Control Of Incisors Research Articles

Creative biomechanics for complex cases

Orthodontic biomechanics play a crucial role in achieving successful outcomes, especially in complex cases requiring precise control of tooth movements. This article explores force system analysis based on the moments and forces around the center of resistance and emphasizes traditional and contemporary approaches in orthodontic biomechanics, focusing on key tooth movements such as bite opening, space closure, retraction, protraction, intrusion, and extrusion.In complex borderline cases involving nonsurgical treatment, this article addresses the significance of total arch distalization for maximum retraction, total arch intrusion for vertical control, total arch extrusion for enhancing maxillary incisor display, lever arm mechanics for achieving incisor torque control, and total arch protraction for improving the maxillary incisor show.Patient-specific factors, efficient biomechanics, and a comprehensive understanding of the limitations of treatment modalities are emphasized in pursuit of optimal orthodontic outcomes.

The treatment of severe class II division 2 patients with deep overbites and gummy smiles using lingual appliances: a case series

Abstract The treatment of Class II division 2 patients with palatally inclined upper incisors using lingual appliances is generally challenging due to difficulties in achieving upper incisor torque control. The present case series aims to describe a simple method combining lingual appliances and mini-screws for the non-surgical management of two severe Class II division 2 patients presenting with deep overbites and gummy smiles. The treatment plans involved initial bite opening and upper incisor torque recovery, followed by distalisation of the entire upper arch using mini-screw anchorage. In one case, additional anterior labial mini-screws were necessary to assist incisor intrusion and complete upper arch levelling. Favourable treatment results suggest that lingual appliances, when combined with mini-screws and pre-torqued arch wires, may offer an effective approach for the non-surgical management of severe Class II division 2 patients with deep overbites and gummy smiles.

Three-dimensional finite element study on the effects of maxillary anterior two-step retraction and en-masse retraction with clear aligners

Objective: To investigate the effects of two-step retraction and en-masse retraction on tooth movement pattern of anterior teeth and posterior anchorage with clear aligners using three-dimensional finite element analysis. Methods: A finite element model of maxillary first premolar extraction case undergoing clear aligner treatment was established based on maxillofacial cone-beam CT data of a 24-year-old adult male with individual normal occlusion, who visited Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine for impacted mandibular third molar in June, 2022. The initial tooth displacement of five anterior retraction protocols (two-step with canine retraction, two-step with incisor bodily retraction, two-step with incisor retraction-overtreatment, en-masse bodily retraction, and en-masse retraction-overtreatment) were evaluated. Results: Two step with canine retraction caused distal tipping of the canine and labial tipping of the incisors (0.18° for central incisor and 0.13° for lateral incisor). Two step with incisor retraction caused mesial tipping of the canine. In two step with bodily retraction protocol, uncontrolled lingual tipping was found in central incisor (0.29°) and lateral incisor (0.32°). In two-step with incisor retraction-overtreatment protocol, the movement pattern of the incisors didn't change, but the inclinations reduced to 0.21° and 0.18°. En-masse retraction caused distal tipping of the canine. In en-masse bodily retraction protocol, uncontrolled lingual tipping was also found in central incisor (0.19°) and lateral incisor (0.27°). In en-masse retraction-overtreatment protocol, the central incisor showed controlled lingual tipping (0.02°) and the lateral incisor showed palatal root movement (0.03° labial inclination). Posterior teeth exhibited mesial tipping in all five protocols. Conclusion: En-masse retraction with incisor overtreatment was beneficial to incisor torque control in clear aligner treatment.

Effects of force magnitude on torque control in the correction of bimaxillary protrusion with mass retraction.

OBJECTIVES:This study was designed to explore whether force magnitude would influence incisor torque control and the overall outcome in patients with bimaxillary protrusion who need mass incisor retraction.MATERIALS AND METHODS:Forty-one female patients (aged > 15 years) with bimaxillary protrusion requiring mass incisor retraction were selected. Two sliding mechanics were utilized, with the elastic group receiving a light force of ~100 g by wearing elastics and the power chain group receiving a moderate force of ~250 g by power chain. Lateral cephalograms obtained before and after treatment were traced and measured.RESULTS:Patients in both groups displayed maxillary protrusion with a similar skeletal class II tendency. A longer treatment time was found in the elastic group. No difference in the distance of incisor tip movement was observed between the two groups; however, a larger inclination of upper incisors was found in the elastic group, indicating less loss of torque. In addition, larger reduction in Sella-Nasion-A and A-Nasion-B angle was observed in the elastic group, which was accompanied by a larger ratio of upper lip retraction to upper incisor retraction as well as more upper lip retraction.CONCLUSIONS:Sliding mechanics with elastics to generate light forces can achieve better torque control with more reduction in skeletal and soft tissue protrusion.

Effectiveness of mini implants in three-dimensional control during retraction - a clinical study.

Three-dimensional control throughout the orthodontic treatment is essential for uncompromised results. Mini screws introduced for orthodontic anchorage has given the clinician an option of absolute three dimensional control. The purpose of this study was to compare and measure the vertical control and torque control of incisors and molar during enmass retraction with titanium microimplants and conventional molar anchorage. Twenty patients were selected with extraction of all first premolars and bonded with 0.022″ slot MBT system. After aligning and leveling, all subjects were placed with 0.019″ X 0.025″ posted SS wire with standardized torquing curve. The 20 subjects were randomly divided into 2 groups consisting of 10 each (Group A & Group B). Group A subjects, implants were placed and Group B formed the control group. Retraction was carried out using NiTi closed coil springs. The assessment of the vertical and torque control of incisors and tipping and vertical control of molars was done by radiographic method using lateral cephalogram taken before and after retraction. The torque control of incisors, P11 value in group A and B indicated no significant difference. The molar tip, P12 value in group A indicated that there was distal tipping of molars while the P12 in group B indicated mesial tipping. On vertical plane P21, P22 and P23 values in Group A indicated that there was intrusion of incisors and molars while value in Group B indicated extrusion of incisors and molars. Three dimensional control is better in the implant group compared to the non implant group. Therefore the implant group definitely has citied advantages over conventional method.

Torque control of the maxillary incisors in lingual and labial orthodontics: A 3-dimensional finite element analysis

Lingual orthodontics has developed rapidly in recent years; however, research on torque control variance of the maxillary incisors in both lingual and labial orthodontics is still limited, especially studies with 3-dimensional finite element methods. Thorough understanding of the biomechanical differences of incisor torque control during lingual and labial orthodontic treatment is critical for the best results. A 3-dimensional finite element model of the maxilla and the maxillary incisors was made with 98,106 nodes, 71,944 10-node solid elements, and 5236 triangle shell units. Horizontal retraction force, vertical intrusive force, and lingual root torque were applied to simulate labial and lingual orthodontic treatment. Then the distribution of the stress-strain (maximum and minimum principal stresses; maximum and minimum principal strains) in the periodontal ligament, the total displacement, and the vector graph of displacement of the nodes of the maxillary central incisor were analyzed and compared between labial and lingual orthodontics. Loads of the same magnitude produced translation of the maxillary incisor in labial orthodontics but lingual crown tipping of the same tooth in lingual orthodontics. This suggests that loss of torque control of the maxillary incisors during retraction in extraction patients is more likely in lingual orthodontic treatment. Lingual orthodontics should not simply follow the clinical experience of the labial techniques but should increase lingual root torque, increase vertical intrusive force, and decrease horizontal retraction force properly to achieve the best orthodontic results.

Incisor torque control with fixed appliance

To evaluate the properties of orthodontic rectangular arch wires in torsion. To measure and analyze the torsional moments and angles of 0.46 mm x 0.63 mm rectangular orthodontic arch wires in single 0.022 inch bracket of the maxillary central incisor with a torsion measurement apparatus. (1) The torsional stiffness of stainless steel arch wires, Chinese nitinol arch wires, 7.0 mm vertical loop arch wires, 3.0 mm and 6.0 mm horizontal loop arch wires is 4.909, 1.325, 4.137, 3.448 and 3.024 Nmm per degree, respectively. (2) The arch wires will be twisted 19.143, 36.832, 19.851, 21.812 and 22.418 degrees; respectively to obtain optimal force. (3) Vertical and horizontal loop decreased the torsional stiffness of the rectangular stainless steel arch wire. The straight rectangular stainless steel arch wire is not well suitable for the torque control of the incisor. Loop design in arch wire is capable of decreasing torsional stiffness. The horizontal loop is more effective than vertical loop.

Moments with the edgewise appliance: Incisor torque control

Traditional edgewise orthodontic mechanics are significantly limited in their ability to provide incisor torque control because of the limitations of bracket-to-bracket mechanics and the poorly defined reciprocal actions inherently produced. Attempts to address this issue clinically have been largely empirical. The science of mechanics dictates that all incisor torque control mechanisms must act through one of two basic principles: the moment of a couple or the moment of a force. The torquing arch is a modification of the traditional edgewise system and employs the moment of a couple to achieve incisor torque control and precise definition of reciprocal effects. The torquing arch force system includes a large moment to rotate incisors in a crown facial/root lingual direction, and concurrent equilibrium forces to extrude incisors and intrude molars. Alternatively, the base arch uses the moment of a force to also rotate incisors in a crown facial/root lingual direction. The base arch, however, includes a large moment to rotate molars in a crown distal/root mesial direction, and concurrent equilibrium forces to intrude incisors and extrude molars. Depending on how they are employed, torquing arches and base arches may also rotate molars in a faciolingual direction, enhance or diminish posterior anchorage, and increase or conserve arch perimeter. Contemporary quality orthodontic care requires an awareness and control of all of the forces created by orthodontic appliances.