Abstract
Objectives: This study reports the efficacy of two solvent mixtures on the dissolution of gutta-percha and AH Plus sealer, together with the cytotoxicity. Methods: Methyl ethyl ketone (MEK), orange oil, tetrachloroethylene, MEK/tetrachloroethylene (1:1), MEK/orange oil (1:1), and chloroform (control) were tested. Twelve groups (n = 15) of standardized stainless-steel molds filled with softened gutta-percha cones and twelve (n = 15) filled with AH Plus were immersed in the corresponding mixture or individual solvent, in an ultrasonic bath, for either 2 or 5 min. The effect of the solvents was assessed qualitatively by a topographical analysis (scanning electron microscopy) and chemical analysis (Fourier transform infrared spectroscopy), and quantitatively by a weight loss and viscoelastic property (dynamic mechanical analysis) evaluation. The cytotoxicity was assessed on MG63 human osteoblastic cells. Results: The mixtures did not show the formation of new compounds. Both presented significantly higher efficacies compared to their individual solvents, suggesting a synergistic effect. Their dissolution efficacy was similar to that of chloroform, showing high cytocompatibility. Conclusions: The proposed strategy, incorporating ultrasound agitation and profiting from the synergy of adequate solvents, might enhance root canal cleanliness allowing a single-step procedure to dissolve gutta-percha and the sealer remnants, while assuring cytocompatibility with the periapical tissues.
Highlights
The prevalence of apical periodontitis is highly correlated with poorly endodontically treated teeth, persisting or emerging as post-treatment apical periodontitis [1,2]
Gutta-percha is considered easy to remove, it can persist with sealer remnants entrapped in the dentine structure
We reported a new dissolution approach, using a non-traditional endodontic solvent—methyl ethyl ketone (MEK), potentiated by ultrasonic agitation (UA), that seemed an excellent alternative to chloroform in the dissolution of epoxy resin-based sealers (AH Plus) [14]
Summary
The prevalence of apical periodontitis is highly correlated with poorly endodontically treated teeth, persisting or emerging as post-treatment apical periodontitis [1,2]. Nonsurgical root canal retreatment is often the first choice to manage secondary endodontic infections. The success of this procedure requires the effective cleaning and subsequent prevention of reinfection, which is only achieved after the complete removal of the old filling materials [3,4]. Gutta-percha does not adhere to the canal walls, and a sealer is recommended in obturation procedures. Gutta-percha is considered easy to remove, it can persist with sealer remnants entrapped in the dentine structure. Materials 2020, 13, 3237 after retreatment, independently of the filling technique [5]. Micro-CT studies showed that a complete removal of the filling materials is almost impossible, even with the development of new instruments and techniques [6]
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