Hardness and penetration of gutta percha when exposed to two endodontic solvents
Purpose: Endodontic retreatment requires the removal of the obturation material from the root canal system. Gutta percha (GP), the most commonly employed obturation material, requires mechanical instrumentation coupled with a chemical adjunct to facilitate its removal. Xylene and Eucalyptus oil are recommended as endodontic solvents due to their dissolving capacity of GP. This study sought to test the changes in the hardness and penetrability of three types of GP (Conventional, Thermafil® and Guttacore™) when exposed to these solvents, utilizing distilled water as a control. Method and materials: Textural analysis was performed to determine the hardness by testing for rigidity, and the penetrability by testing for deformation energy and resilience. These properties were tested on 81 GP cones prior to, and following solvent exposure. For each outcome variable, results were tabulated by group. Between-group differences were assessed by means of a General Linear Model, with the outcome variable as the dependent variable and the solvent, GP type and solvent-GP type interaction as the independent variables. Results: A significant decrease in rigidity and deformation energy was observed across all groups. Resilience was observed to decrease with the thermoplastic GP, Thermafil and Guttacore, but increased with conventional GP. Thermoplastic GP was more amenable to a reduction in hardness and penetration when compared with Conventional GP. A greater reduction in the hardness of Thermafil was observed with Eucalyptus oil. Conventional GP was susceptible to a significant reduction in hardness with both solvents, however its penetrability may be reduced following exposure to Xylene. Guttacore was significantly altered by both solvents. Conclusions: Considering the toxicity profile of Xylene, and the biocompatibility and antimicrobial effects of Eucalyptol, Eucalyptus oil is recommended for use during endodontic retreatment.
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Dentistry. School of Oral Health Sciences, Faculty of Health Sciences, University of the Witwatersrand, South Africa Johannesburg, 2014