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Background/Purpose: Canal instrumentation with rotary nickel-titanium (NiTi) instruments might weaken the dentinal wall. This study aims to investigate the apical root cracks during canal instrumentation with new reciprocatory system and comparing it with the conventional rotary systems by using optical coherencetomography (OCT) scans. Materials and methods: Twenty mandibular incisors were selected and divided into two groups that are instrumented using S-One pro (S-one) and ProTaper Universal (PTU) systems. OCT scans were taken immediately after canal instrumentation with file #25, #30 and #40. Each cross-sectional reconstructed image of 1, 2 and 3 mm from the apex was examined, root cracks were scored, and dentin thickness was measured at 12 sites. Our null hypothesis was that there would be no difference in root cracks formation between different file systems used.

Objectives: To compare the effectiveness of different sealer cleaning methods on bonding of a self-etch adhesive to root canal sealer-contaminated dentine. Methods: Forty-nine extracted molars were divided into seven groups. Dentine surfaces were exposed and contaminated with a thin layer of epoxy resin-based sealer (AH Plus (AHP)) or zinc oxide eugenol-based sealer (Pulp Canal Sealer (PCS)). Three cleaning protocols were examined: dry cotton pellet, 70% ethanol-saturated cotton pellet and a surfactant-based cleaner (ZirClean (ZC), Bisco, US). Uncontaminated dentine served as control. The dentine surfaces were bonded with a two-step self-etch adhesive and restored with resin composite. Bond strength testing was performed using a micro-tensile approach. Results: Tensile bond strength for uncontaminated dentine control was 46.4±7.3 MPa; bond strength decreased significantly for the dry cotton group (29.6±4.2 MPa for AHP, 24.7±4.7 MPa for PCS, p<0.05). Both ethanol and ZC restored bonding performance after cleaning, with no significant difference from the control. Significantly lower mTBS was observed for the ZOE/ethanol subgroup (38.9±5.1 MPa). Conclusions: Zirclean decontaminates root canal sealer-smeared dentine surfaces effectively and restores the bonding performance of a self-etch adhesive to dentine. Clinical significance: The surfactant-based ZirClean Cleaner, originally designed for cleaning zirconia surfaces prior to adhesive bonding, may be used as for cleaning dentine that has been contaminated with unset root canal sealers after root canal treatment to restore the bonding strength of a self-etch adhesive to sealer-contaminated dentine.

Background: One of the factors that most negatively affect the endodontic instrumentation process in primary teeth are the presence of extruded debris in the periapical region. Therefore, different techniques have been evaluated to reach an answer to the question regarding which root canal preparation method produces the least amount of debris extrusion. Objectives: The main objective of this study was to assess the amount of debris extrusion as well as irrigation associated with 3 different instrumentation techniques: a rotary system (PROTAPER NEXT – PTN),a new reciprocating system (S-ONE pro – SO) and hand K-files. Material and methods: Forty-eight primary mandibular molars with a single distal canal were selected and randomly divided into 3 groups (n = 16). Three different techniques were used for the canal instrumentation of each group, comprising PTN, WO and hand K-files. Pre-weighed Eppendorf tubes were usedfor the collection of debris extrusion, then stored in an incubator at 70°C for 5 days. A one-way analysisof variance (ANOVA) test was used for data analysis, followed by Tukey’s post hoc test. Results: Statistically significant differences were found while comparing the PTN and SO systems with the hand files. Both PTN and SO showed less debris extrusion toward the periapical tissues than the hand files. Still, no statistically significant differences were seen between the PTN and SO groups. Conclusions: Generally, debris extrusion occurred in all of the 3 experimental groups. The PTN and SOsystems showed the least debris extrusion as compared to the hand files during the root canal instrumentation of the primary teeth, and for these reasons along with the shorter operating time, it may be concluded that using rotary and reciprocating systems rather than manual files is highly advisable. However, a clinical assessment is suggested.