Thermal Behaviour of Teeth With Internal Root Resorption During Obturation and Enhancing Thermal Simulations: A Finite-Element Analysis.

Abstract

<h4>Introduction and aims</h4>This study evaluated heat transfer to the periodontal ligament (PDL) of simulated teeth with internal root resorption (IRR) cavities of varying diameters during thermoplasticized obturation.<h4>Methods</h4>Three-dimensional finite-element tooth models with IRR cavities of diameters 3, 3.5, 4, and 4.5 mm were constructed based on microcomputed scanning tomography of a maxillary central incisor tooth. Four digital models (V/3, V/3.5/, V/4, and V/4.5) were reconstructed with vascularized PDL layer and bone, and one without PDL vascularity (nonvascular/4.5) was also created to evaluate the effect of blood flow. Root canals were obturated using a simulated continuous wave of compaction technique. Additional simulations were conducted to evaluate the Effects of incorrect heat-carrier angulation at (200°C and 300°C) and backpacking with reduced gutta-percha temperature (100°C) on PDL heat transfer in the largest resorptive model were also simulated. Heat transfer to PDL was calculated to determine whether it exceeded the critical temperature.<h4>Results</h4>PDL temperatures remained below 47°C threshold during the downpack across all resorption models. In the backfill phase, PDL temperature in models with 4 and 4.5 mm diameter IRR cavities exceeded the critical level with thermoplasticized gutta-percha at 200°C. The vascularized model consistently registered lower PDL temperature than its nonvascularized counterpart.<h4>Conclusions</h4>Based on our findings, backfilling gutta-percha heated to 200°C in large IRR cavities may cause high temperature rise in the PDL. Therefore, when treating IRR cases, the size of the resorptive cavity should be considered, and treatment strategies that minimize heat generation are preferred.<h4>Clinical relevance</h4>Large IRR cavities can lead to harmful heat transfer to the PDL during heat-dependent obturation techniques. Clinicians should consider cavity size and use proper heat-minimizing measures to prevent PDL damage, especially during backfilling with high-temperature gutta-percha.