Orthodontic traction of palatally impacted canines : a finite element analysis study

Abstract

Introduction: The treatment of impacted canines is most challenging because of undesirable side effects, demanding anchorage control, and remarkable increase in treatment duration. Accurate localization of palatally impacted canines and careful application of forces are keys to successful treatment. Reaction forces on adjacent teeth vary with the mechanical design of the appliances used. Aims: 1. Develop a scheme to determine the severity of palatally impacted canines (PIC) related to treatment objectives; 2. Determine the stresses on the impacted canine when subjected to initial force activation in various directions (buccal, vertical, and distal) and in relation to the severity of impaction; 3. Evaluate the stresses on adjacent teeth generated by different appliances. Design: The research comprised 2 major parts, a CBCT section in which the spatial position of PIC is evaluated along with the components contributing to its severity. The second section is the finite element analysis study in which stress on the impacted tooth is assessed in response to differently directed forces and different appliances. Methods: Part 1: 38 PIC were evaluated, derived from 28 CBCT scans of patients with a mean age of 16.06 years. Severity was based on an angle defined between the PIC axis and its projected virtual alignment within the arch virtual aligned canine (VAC). Measurements in axial, coronal, sagittal and panoramic CBCT sections were recorded and analyzed. Part 2: 21 scans that included 30 PIC’s were evaluated. A prototype 3D model was reconstructed and segmented into its anatomic components. The individual impacted canines were precisely positioned in the prototype model to portray their original position. Stresses in response to a distal, vertical and buccal force (1N) were evaluated at different levels of the root on the periodontal ligament of the PIC. Stress on adjacent teeth were also compared with different appliances. Statistics included analyses of variance for comparisons of variables, and regressi