Authors : Jayaprakash PK, Kumari S, Verma SK, Chauhan AK, Kumar M
DOI : 10.18231/j.jco.2018.001
Volume : 2
Issue : 1
Year : 2018
Page No : 1-10
Purpose: Maxillary central incisor teeth present morphological variations in different malocclusions. The collum angles of maxillary central incisors in Class II, division 2 and Class III malocclusions are significantly higher than the other groups of malocclusions. The higher prevalence of root resorption seen in central incisors with increased column angle after orthodontic treatment, warranted the need to study the stress patterns over these teeth during intrusion. In this study, FEM has been used to evaluate and compare the effect of normal bracket and inverted bracket positioning on stress distribution in PDL and root displacement of maxillary central incisors with 11° collum angles during application of intrusion force.
Methods: FEM models of maxillary central incisor with normal collum angle (6°) and a high collum angle (11°)–representing the class II division 2 teeth were modeled. MBT prescription brackets were used to study the effect of positive or negative (invertion of bracket) torque on maxillary central incisors with high column angle. Each of the samples was loaded with intrusive force (0.5 N) perpendicular to the ideal position of bracket. The results were compared with the maxillary central incisor with normal column angle bonded with positive torque (+17°) MBT bracket.
Results: The calculated stress in the inverted bracket model was lesser and extended over a smaller area, as compared to normally positioned bracket in the teeth with increased collum angle. Also, better intrusion was achieved as compared to the conventional bracket placement which exerts positive torque resulting in root impingement frequently seen with such teeth.
Conclusion: The results of this study warn against the use of high positive torque prescription brackets , for Angle Class II division 2 subjects with increased collum angle. The orthodontic treatment must be tailored with respect to the biologic variations presented by the individual
patient.
Keywords: Class II Div 2 Malocclusion, Root Resorption, FEM,Torque.