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Assessment of Stress and Strain in Alveolar Bone during Upper Midline Diastema Closure using Finite Element Method
ZC30-ZC33
Correspondence
Dr. Sonal K Javali,
C/o Kiran S Javali, #37, 11th Main Vasant Nagar, Bengaluru-560052, Karnataka, India.
E-mail: sonaljavali@gmail.com
Introduction: Application of orthodontic forces to a tooth is characterised by extensive macroscopic and microscopic changes during remodelling which occurs in the Periodontal Ligament (PDL), alveolar bone and gingiva. This occurs mainly due to the local stresses and strains subjected on the supporting tissues. As direct measurement of these parameters is almost impossible, Finite Element Method (FEM) is an effective method for calculating stress and strain distribution on the alveolar bone.
Aim: To assess the stress and strain distribution in the cortical and cancellous bone around maxillary central incisors during the process of diastema closure with a constant force using FEM.
Materials and Methods: A three-dimensional computer model of anterior segment of the maxilla simulated from a CBCT scan was reproduced using MIMICS software and they had varying width of midline diastema of 4 mm, 3 mm and 2 mm. Each tooth was designed with a bracket on the labial surface and a 0.019×0.025 orthodontic stainless steel wire. A 1.5 N of force was applied on the labial surface of the brackets. Stresses and strains around the two central incisors on the alveolar bone were calculated.
Results: In the cortical bone, maximum compressive stress (Von-Mises stress) was concentrated at the mesial side and tensile stress (principle stress) on the distal side near the cervical region of the central incisors in all the 3 models. Maximum stress was seen in the 2mm midline diastema model. In the cancellous bone, both these stresses were concentrated along the roots of central incisor cavity more towards the middle of the tooth in all the 3 models. In the longitudinal section, stress and strain was more concentrated at the cervical region gradually decreasing as they reached apex of the tooth in cortical bone and in the cancellous bone maximum stress was observed in the middle third.
Conclusion: Stresses in the cortical bone increases when the diastema gap is small while strain in cancellous bone increases when the midline diastema width is large. The stresses in cancellous bone remain constant in all the 3 models. Graphically the strains were more concentrated near cervical region of the teeth in both the cortical and in cancellous bone maximum stress was observed in the middle third.