Moment to force ratio, center of rotation and force levels: A finite element study predicting their interdependency for simulated orthodontic loading regimens

• Published in: Journal of Indian Orthodontic Society 2016-07, Vol.50 (3), p.139-144
• Main Authors: Mamatha, J, Raju, Aravind, Hegde, Nikhilanand, Reddy, Vinay, Chandrashekar, B, Vani, J
• Format: Article
• Language: English
• Subjects: Forces (Physics); Ligaments; Orthodontics; Physiological aspects
• ISSN: 0301-5742; 0974-9098
• DOI: 10.1177/0974909820160302

Objective: The objective of this study is to determine the relationship between the moment to force ratio applied at brackets and to evaluate different force level, the actual load transfer across the periodontal ligament (PDL) leading to different types of tooth movement. Materials and Methods: A segment of a mandible containing the canine and the first premolar obtained from autopsy was scanned with micro-computed tomography, and a finite element (FE) model was generated. In a series of FE analyses simulating teeth subjected to various orthodontic loading regimens, the influences of the male/female ratio and the force magnitude were examined. Results: By applying a range of values of male/female, different types of tooth movement were generated, although the classic prescription of the male/female ratio suggested in the literature could not be confirmed. Due to the nonlinear behavior of the PDL, loading modes with a constant male/female ratio, yet varying the force magnitude, resulted in different types of tooth movement. Conclusions: The material properties of the PDL, the morphology of the root, and the alveolar bone are patient specific. Therefore, the male/female values generally advocated to obtain orthodontic tooth movement should be used only as guidelines. To be effective and accurate, the force system selected for a specific tooth movement must be monitored and the outcome compared with the predicted tooth movement.