Influence of autoclave sterilization procedures on the cyclic fatigue resistance of heat-treated nickel-titanium instruments: a systematic review

Objectives@#This systematic review evaluated the influence of autoclave sterilization procedures on the cyclic fatigue resistance of heat-treated nickel-titanium (NiTi) instruments. @*Materials and Methods@#A systematic search without restrictions was conducted in the following electronic databases: PubMed, Scopus, Web of Science, ScienceDirect, Cochrane, and Open Grey. The hand search was also performed in the main endodontic journals. The eligible studies were submitted to the methodological assessment and data extraction. @*Results@#From 203 abstracts, a total of 10 articles matched the eligible criteria. After reading the full articles, 2 were excluded because of the absence of the heat-treated instruments in the experimental design and 3 due to the lack of a control group using heat-treated instruments without autoclave sterilization. From the 5 included studies, 1 presented a low risk of bias, 3 presented moderate and 1 high risk. It was observed heterogeneous findings in the included studies, with autoclave sterilization cycles increasing, decreasing or not affecting the cyclic fatigue life of heat-treated NiTi instruments. However, the retrieved studies evaluating the cyclic fatigue resistance of endodontic instruments presented different protocols and assessing outcomes, this variability makes the findings less comparable within and also between groups and preclude the establishment of an unbiased scientific evidence base. @*Conclusions@#Considering the little scientific evidence and considerable risk of bias, it is still possible to conclude that autoclave sterilization procedures appear to influence the cyclic fatigue resistance of heat-treated NiTi instruments.

Micro-computed tomographic evaluation of canal retreatments performed by undergraduate students using different techniques

OBJECTIVES: This study evaluated the amount of remaining root canal filling materials after retreatment procedures performed by undergraduate students using manual, rotary, and reciprocating techniques through micro-computed tomographic analysis. The incidence of instrument fracture and the instrumentation time were also evaluated. MATERIALS AND METHODS: Thirty maxillary single rooted teeth were prepared with Reciproc R25 files and filled with gutta-percha and AH Plus sealer by the continuous wave of condensation technique. Then, the specimens were assigned to 3 groups (n = 10), according to the retreatment technique used: manual, rotary, and reciprocating groups, which used K-file, Mtwo retreatment file, and Reciproc file, respectively. Retreatments were performed by undergraduate students. The sample was scanned after root canal filling and retreatment procedures, and the images of the canals were examined to quantify the amount of remaining filling material. The incidence of instrument fracture and the instrumentation time were recorded. RESULTS: Remaining filling material was observed in all specimens regardless of the technique used. The mean volume of remaining material was significantly lower in the Reciproc group than in the manual K-file and Mtwo retreatment groups (p < 0.05). The time required to achieve a satisfactory removal of canal filling material and refinement was significantly lower in the Mtwo retreatment and Reciproc groups (p < 0.05) when compared to the manual K-file group. No instrument fracture was observed in any of the groups. CONCLUSIONS: Reciproc was the most effective instrument in the removal of canal fillings after retreatments performed by undergraduate students.

Comparison of canal transportation in simulated curved canals prepared with ProTaper Universal and ProTaper Gold systems

OBJECTIVES: The purpose of this study was to assess the ability of ProTaper Gold (PTG, Dentsply Maillefer) in maintaining the original profile of root canal anatomy. For that, ProTaper Universal (PTU, Dentsply Maillefer) was used as reference techniques for comparison. MATERIALS AND METHODS: Twenty simulated curved canals manufactured in clear resin blocks were randomly assigned to 2 groups (n = 10) according to the system used for canal instrumentation: PTU and PTG groups, upto F2 files (25/0.08). Color stereomicroscopic images from each block were taken exactly at the same position before and after instrumentation. All image processing and data analysis were performed with an open source program (FIJI). Evaluation of canal transportation was obtained for two independent canal regions: straight and curved levels. Student's t test was used with a cut-off for significance set at alpha = 5%. RESULTS: Instrumentation systems significantly influenced canal transportation (p < 0.0001). A significant interaction between instrumentation system and root canal level (p < 0.0001) was found. PTU and PTG systems produced similar canal transportation at the straight part, while PTG system resulted in lower canal transportation than PTU system at the curved part. Canal transportation was higher at the curved canal portion (p < 0.0001). CONCLUSIONS: PTG system produced overall less canal transportation in the curved portion when compared to PTU system.

Comparison of canal transportation in simulated curved canals prepared with ProTaper Universal and ProTaper Gold systems

OBJECTIVES: The purpose of this study was to assess the ability of ProTaper Gold (PTG, Dentsply Maillefer) in maintaining the original profile of root canal anatomy. For that, ProTaper Universal (PTU, Dentsply Maillefer) was used as reference techniques for comparison. MATERIALS AND METHODS: Twenty simulated curved canals manufactured in clear resin blocks were randomly assigned to 2 groups (n = 10) according to the system used for canal instrumentation: PTU and PTG groups, upto F2 files (25/0.08). Color stereomicroscopic images from each block were taken exactly at the same position before and after instrumentation. All image processing and data analysis were performed with an open source program (FIJI). Evaluation of canal transportation was obtained for two independent canal regions: straight and curved levels. Student's t test was used with a cut-off for significance set at alpha = 5%. RESULTS: Instrumentation systems significantly influenced canal transportation (p < 0.0001). A significant interaction between instrumentation system and root canal level (p < 0.0001) was found. PTU and PTG systems produced similar canal transportation at the straight part, while PTG system resulted in lower canal transportation than PTU system at the curved part. Canal transportation was higher at the curved canal portion (p < 0.0001). CONCLUSIONS: PTG system produced overall less canal transportation in the curved portion when compared to PTU system.