Modified Centroid of Root Projection Method for Determining the Center of Resistance of a Tooth

Abstract

Abstract Center of resistance (CR) has been widely accepted in dentistry as a reference point for controlling tooth moment, which depends on the direction of loading and the morphology of the periodontal ligament (PDL). In clinical practice, dentists estimate the location of CR based on the morphology of the root of teeth, which may lead to a misestimation of orthodontic treatment. A quick method was proposed to efficiently determine the CR by identifying the centroid of the root projection (CRP), according to the orthodontic force. However, the original CRP method was limited to single-rooted teeth and it did not provide a strategy for handling the overlapping roots projection of multi-rooted teeth. To address this issue, we expanded the CRP method to accommodate multi-rooted teeth by applying the weighted average method. We further validated the modified CRP method using finite element simulation (FEA) for both single-rooted and multi-rooted teeth considering mesial-distal and buccal-lingual force directions. The evaluation of displacement distribution along the projection direction allowed us to assess translation and rotation movements, which confirmed that the centroid of root projection can accurately serve as the CR for the multi-rooted teeth. Additionally, we observed heterogeneous stress distributions in the multi-rooted teeth. Considering the well-acknowledged bone remodeling effect in response to local stress states, this indicated that the comprehensive indexes beyond the CR are desired for evaluating or controlling the tooth movement.