Micro-computed tomographic evaluation of the shaping ability of four instrumentation systems in curved root canals.

AIM: To compare the shaping ability of four instrumentation systems in curved molar root canals, using computerized microtomography (micro-CT). METHODOLOGY: Forty mesial roots of mandibular molars were submitted first to radiographic examination to determine their curvature and then to a micro-CT scan to analyse other initial morphological characteristics. The specimens were distributed into four experimental groups, according to the endodontic instrumentation system used (n = 10): Group R, Reciproc; Group PTN, ProTaper Next; Group WOG, WaveOne Gold; Group PDL, ProDesign Logic. After root canal instrumentation, the specimens were submitted to a second micro-CT scan, and the pre- and postoperative data were examined to evaluate the following parameters: volume of dentine removed (DR), increase in root canal volume (VI), untouched root canal surface area (UA), volume of accumulated hard tissue debris (AD) and structure model index (SMI). The data observed for these parameters after instrumentation were analysed using generalized linear models. R software was used for the analyses, and the level of significance adopted was 5%. RESULTS: There were no significant differences among the instrumentation systems regarding the DR, VI, UA and AD parameters (P > 0.05). PTN and WOG systems were associated with greater increases in SMI than the PDL system (P < 0.05). CONCLUSIONS: The four systems evaluated were similar regarding the parameters analysed, with the exception of the SMI, with the rate of variation of this parameter being greater after using the PTN and WOG systems than after using the PDL system. These results indicate that the four systems perform similarly in terms of their shaping ability, but that the PTN and WOG systems produced more rounded preparations than the PDL system.

Counterclockwise or clockwise reciprocating motion for oval root canal preparation: a micro-CT analysis.

AIM: To evaluate oval root canal preparation using one or two instruments in counterclockwise or clockwise reciprocating motion. METHODOLOGY: The radiographic diameter of mandibular human incisors was evaluated, and oval canals were selected (2 ≤ Diameter Ratio ≤ 4). Fifty-seven teeth were assigned to root canal preparation (n = 19): Reciproc 40 (R40) in a counterclockwise reciprocating motion; Mtwo size 40, .06 taper (M 40.06) in a clockwise reciprocating motion or Mtwo size 20, .06 taper and size 40, .06 taper (M 20/40.06) in a clockwise reciprocating motion. Mtwo instruments were coupled to an ENDO DUAL motor, turning 150° clockwise and 30° counterclockwise. Scanning was performed before and after root canal preparation using a SkyScan 1176 micro-computed tomography. Volume, percentage of debris and percentage of uninstrumented surface were analysed in the entire root canal and in each third of the canal. Data were compared using anova and Tukey's tests or Kruskal-Wallis and Dunn tests. RESULTS: The Reciproc and Mtwo systems using different kinematics were associated with a similar increase in root canal volume. Additionally, both system had similar percentage of uninstrumented surface (P > 0.05). Mtwo size 20, .06 taper and size 40, .06 taper was associated with significantly lower debris (P < 0.05) in the middle third (0.56%) when compared to R40 (1.31%) and M size 40, .06 taper (1.54%). CONCLUSIONS: The conventional reciprocation motion for R40 and the clockwise reciprocation motion for Mtwo resulted in similar root canal preparations. Less remaining debris was present in the middle third when two instruments with different diameters were used.

Effect of finishing instrumentation using NiTi hand files on volume, surface area and uninstrumented surfaces in C-shaped root canal systems.

AIM: To assess the effect of 90°-oscillatory instrumentation with hand files on several morphological parameters (volume, surface area and uninstrumented surface) in C-shaped root canals after instrumentation using a single-file reciprocation system (Reciproc; VDW, Munich, Germany) and a Self-Adjusting File System (SAF; ReDent Nova, Ra'anana, Israel). METHODOLOGY: Twenty mandibular second molars with C-shaped canals and C1 canal configurations were divided into two groups (n = 10) and instrumented with Reciproc and SAF instruments. A size 30 NiTi hand K-file attached to a 90°-oscillatory motion handpiece was used as final instrumentation in both groups. The specimens were scanned using micro-computed tomography after all procedures. Volume, surface area increase and uninstrumented root canal surface were analysed using CTAn software (Bruker-microCT, Kontich, Belgium). Also, the uninstrumented root canal surface was calculated for each canal third. All values were compared between groups using the Mann-Whitney test and within groups using the Wilcoxon's signed-rank test. RESULTS: Instrumentation with Reciproc significantly increased canal volume compared with instrumentation with SAF. Additionally, the canal volumes were significantly increased after 90°-oscillatory instrumentation (between and within group comparison; (P < 0.05)). Regarding the increase in surface area after all instrumentation protocols, statistical analysis only revealed significant differences in the within groups comparison (P < 0.05). Reciproc and SAF instrumentation yielded an uninstrumented root canal surface of 28% and 34%, respectively, which was not significantly different (P > 0.05). Final oscillatory instrumentation significantly reduced the uninstrumented root canal surface from 28% to 9% (Reciproc) and from 34% to 15% (SAF; P < 0.05). The apical and middle thirds exhibited larger uninstrumented root canal surfaces after the first instrumentation that was significantly reduced after oscillatory instrumentation (P < 0.05). CONCLUSIONS: The Reciproc and SAF system were associated with similar morphological parameters after instrumentation of mandibular second molars with C-shaped canals except for a higher canal volume increase in the Reciproc group compared to the SAF. Furthermore, the final use of 90°-oscillatory instrumentation using NiTi hand files significantly decreased the uninstrumented canal walls that remained after Reciproc and SAF instrumentation.