Torquing an upper central incisor with aligners--acting forces and biomechanical principles

TY - JOUR

T1 - Torquing an upper central incisor with aligners--acting forces and biomechanical principles

AU - Hahn, Wolfram

AU - Zapf, Antonia

AU - Dathe, Henning

AU - Fialka-Fricke, Julia

AU - Fricke-Zech, Susanne

AU - Gruber, Rudolf

AU - Kubein-Meesenburg, Dietmar

AU - Sadat-Khonsari, Reza

PY - 2010/12

Y1 - 2010/12

N2 - The forces delivered by aligners during torquing have still not been investigated. The purpose of this study was to measure the forces delivered to an upper central incisor during torquing with three different materials of the same thickness, and to describe the biomechanical principles of torquing with aligners. Five identical appliances were manufactured from each of three materials, all with a thickness of 1.0 mm (Ideal Clear®, Erkodur®, and Biolon®). An upper central incisor, as part of the measuring device, was torqued in defined steps in the vestibular and palatal directions with the respective appliance in place. For statistical analysis, the resulting forces, Fx (forces acting in the palatal and facial directions) and Fz (intrusive force as a side-effect) at a displacement of ±0.15 and ±0.8 mm from the tooth at the gingival margin were calculated. The mean Fx forces for ±0.15 mm displacement ranged from -1.89 N [standard deviation (SD) 0.48] to 0.11 N (SD 0.1). The mean Fz forces were between -0.97 N (SD 0.57) and -0.07 N (SD 0.22). The highest intrusive forces were measured during palatal displacement of the measuring tooth. An influence of direction of displacement on the levels of force was observed, especially for Fz at the greater displacement of ±0.8 mm. In relation to the intended amount of root movement during torquing, aligners tend to 'lift up' and therefore no effective force couple can be established for further root control. The force delivery properties are also influenced by the material used and the shape of the tooth.

AB - The forces delivered by aligners during torquing have still not been investigated. The purpose of this study was to measure the forces delivered to an upper central incisor during torquing with three different materials of the same thickness, and to describe the biomechanical principles of torquing with aligners. Five identical appliances were manufactured from each of three materials, all with a thickness of 1.0 mm (Ideal Clear®, Erkodur®, and Biolon®). An upper central incisor, as part of the measuring device, was torqued in defined steps in the vestibular and palatal directions with the respective appliance in place. For statistical analysis, the resulting forces, Fx (forces acting in the palatal and facial directions) and Fz (intrusive force as a side-effect) at a displacement of ±0.15 and ±0.8 mm from the tooth at the gingival margin were calculated. The mean Fx forces for ±0.15 mm displacement ranged from -1.89 N [standard deviation (SD) 0.48] to 0.11 N (SD 0.1). The mean Fz forces were between -0.97 N (SD 0.57) and -0.07 N (SD 0.22). The highest intrusive forces were measured during palatal displacement of the measuring tooth. An influence of direction of displacement on the levels of force was observed, especially for Fz at the greater displacement of ±0.8 mm. In relation to the intended amount of root movement during torquing, aligners tend to 'lift up' and therefore no effective force couple can be established for further root control. The force delivery properties are also influenced by the material used and the shape of the tooth.

KW - Acrylic Resins

KW - Biomechanical Phenomena

KW - Dental Stress Analysis

KW - Humans

KW - Incisor

KW - Maxilla

KW - Orthodontic Appliance Design

KW - Orthodontic Appliances, Removable

KW - Statistics, Nonparametric

KW - Tooth Movement Techniques

KW - Torque

KW - Journal Article

U2 - 10.1093/ejo/cjq007

DO - 10.1093/ejo/cjq007

M3 - SCORING: Journal article

C2 - 20462912

VL - 32

SP - 607

EP - 613

JO - EUR J ORTHODONT

JF - EUR J ORTHODONT

SN - 0141-5387

IS - 6

ER -