OBJECTIVE: To determine the forces and moments delivered to a maxillary central incisor during rotation with aligners when a simulated occlusal force generated during swallowing acts on the appliance. MATERIALS AND METHODS: Five identical appliances were manufactured from four different starting materials (Erkodur 0.8 mm and 1.0 mm; Biolon 0.75 mm and 1.0 mm). An upper central incisor fixed in a measuring device was rotated around its central axis in 0.5-degree steps up to ±10 degrees with the appliance fixed in place. An occlusal force of 30 N generated during swallowing was simulated with a weight positioned on the appliance. For statistical analysis, the moments Tz (rotation) and forces Fz (intrusion) at a deflection of ±0.34 mm to the incisor edge (±5 degrees rotation) were tested. Means and standard deviations for Tz and median and 25% and 75% quartiles for Fz were calculated. An analysis of variance was performed. RESULTS: The simulated occlusal force increased the measured intrusive force Fz (maximum with a weight, -3.7 N [-3.7, -2.4]; minimum without a weight, -1.3 N [-1.4, -1.1]) and the rotary moment Tz (maximum with a weight, -50.8 Nmm [±0.8]; minimum without a weight, 18.2 Nmm [±0.9]) significantly in all cases (P < .01). This was found for all materials measured and for both directions of rotation. CONCLUSION: During rotation with aligners, a simulated occlusal force increases the intrusive force and the rotary moment. The biological adverse side effects of these phenomena remain unclear, especially in patients with periods of bruxism.
OBJECTIVE: To determine the forces and moments delivered to a maxillary central incisor during rotation with aligners when a simulated occlusal force generated during swallowing acts on the appliance. MATERIALS AND METHODS: Five identical appliances were manufactured from four different starting materials (Erkodur 0.8 mm and 1.0 mm; Biolon 0.75 mm and 1.0 mm). An upper central incisor fixed in a measuring device was rotated around its central axis in 0.5-degree steps up to ±10 degrees with the appliance fixed in place. An occlusal force of 30 N generated during swallowing was simulated with a weight positioned on the appliance. For statistical analysis, the moments Tz (rotation) and forces Fz (intrusion) at a deflection of ±0.34 mm to the incisor edge (±5 degrees rotation) were tested. Means and standard deviations for Tz and median and 25% and 75% quartiles for Fz were calculated. An analysis of variance was performed. RESULTS: The simulated occlusal force increased the measured intrusive force Fz (maximum with a weight, -3.7 N [-3.7, -2.4]; minimum without a weight, -1.3 N [-1.4, -1.1]) and the rotary moment Tz (maximum with a weight, -50.8 Nmm [±0.8]; minimum without a weight, 18.2 Nmm [±0.9]) significantly in all cases (P < .01). This was found for all materials measured and for both directions of rotation. CONCLUSION: During rotation with aligners, a simulated occlusal force increases the intrusive force and the rotary moment. The biological adverse side effects of these phenomena remain unclear, especially in patients with periods of bruxism.
Authors: Laura J Barbagallo; Allan S Jones; Peter Petocz; M Ali Darendeliler Journal: Am J Orthod Dentofacial Orthop Date: 2008-02 Impact factor: 2.650