Comparison of Different Retreatment Techniques: a Radiographical In-Vitro Analysis

Introduction: Despite the high success of endodontic treatment, failure occurs, mainly, because of poor disinfection achieved during it or reinfection of the root canal system, after its conclusion. To restore oral health it's often necessary a non-surgical endodontic retreatment. Objective: The aim of this study was to compare the efficacy of rotary and reciprocating techniques for removing filling material from root canals, using a radiographic method. A system - OneShape (Micro-Mega, France) was intentionally included for the first time in a retreatment research. Material and Methods: 80 single root teeth were instrumented with hand k-files up to size 30 according to a crown-down and step-back techniques and filled with gutta-percha and an epoxy resin-based sealer using Tagger's hybrid technique. Teeth were divided into four groups (n=20): Reciproc®(R) (VDW, Germany), WaveOne®(WO) (Dentsply Sirona, Switzerland) ProTaper Universal Retreatment®(PTR) (Dentsply Sirona, Switzerland), and One Shape®(OS) (Micro-Mega, France). All teeth were radiographed, using a paralleling angle technique with digital Image Plate Plus size 2 (Dental Durr, Germany) and a film positioner holder before and after filling material removal. The total area of the initial filling material and the remaining one was measured using the analysis software Adobe Photoshop CC 2017® in order to calculate the percentage of removed material. Data were compared using D'Agostino & Pearson, Krusskal-Wallis & Dunns and t-Student tests at 5 % significance level. Results: No significant statistical differences between groups were found; however, the WO group showed higher values of reduction, followed by R, PTR and OS, respectively. Discussion: The major goal in non-surgical endodontic retreatment is to obtain disinfection of the root canal system. In order to achieve that purpose, an effective filling material removal is necessary. Although there is disagreement between different studies, in the past two years, regarding the final results, a large number of them placed WO as the most effective. It should be noted that many systems, when designed for instrumentation, are, often, in clinical practice, used for the purpose of filling material removal. Conclusions: None of the tested systems were able to completely remove the filling material; reciprocating systems proved to be more efficient than continuous rotary systems: nevertheless, without significance differences between them. Clinical relevance: This study provided consistent information on filling material removal capacity of One Shape, a system never tested in this purpose. Considering that all tested systems were safe, One Shape may be an alternative for endodontic retreatment as, in spite of poor performance, that difference was not significant to the others systems tested. Additionally, a supplementary approach with a finishing instrument or an ultra-sound system may enhance filling material removal. Sponsorship: Micro-Mega, France; Dentsply Sirona, Switzerland and VDW, Germany. Keywords: Endodontics, retreatment, gutta-percha removal, reciprocating files, continuous rotation files, OneShape