Does the type of endodontic access influence in the cyclic fatigue resistance of reciprocating instruments?

INTRODUCTION: The aim of the present study was to compare the cyclic fatigue resistance of Reciproc R25 (R25) and Reciproc Blue R25 (R25B) instruments, after simulated clinical use in traditional (TradAC) and ultraconservative (UltraAC) endodontic access cavities. METHODS: Forty mandibular molars were randomly assigned into the following groups, according to the type of access and instrument to be used: TradAC and R25, TradAC and R25B, UltraAC and R25, and UltraAC and R25B. Teeth were accessed accordingly, and the root canals were prepared using "RECIPROC ALL" kinematics. The cyclic fatigue resistance of the forty used instruments was obtained measuring the time to fracture in an artificial stainless-steel canal. Ten brand new R25 and R25B were used as control groups. The fracture surfaces and the side cutting edges of the instruments were examined with a scanning electron microscope. Data were statistically analyzed using one-way ANOVA and post hoc Tukey tests with a significance level of P < 0.05. RESULTS: R25B instruments showed significantly higher cyclic fatigue resistance than R25, regardless of the access cavity type (P < 0.05). No differences were observed in the cyclic fatigue resistance between instruments without simulated clinical use and used in TradAC (P > 0.05). R25 and R25B used in UltraAC showed significantly lower cyclic fatigue resistance compared with the instruments used in TradAC and without simulated clinical use (P < 0.05). CONCLUSIONS: R25B files showed improved cyclic fatigue resistance than R25. The use of R25B and R25 files in mandibular molars with UltraACs decreased their cyclic fatigue resistance, compared with TradAC. CLINICAL RELEVANCE: The use of Reciproc and Reciproc Blue files in mandibular molars with ultra-conservative endodontic access cavities reduced their cyclic fatigue resistance. Clinicians should be aware about the reduced cyclic fatigue resistance of these files when used in mandibular molars with UltraAC, due to the synergistic effect of access angulation and severe curvature induced in the endodontic files.

Efficacy of reciprocating and rotary techniques for removing filling material during root canal retreatment.

AIM: To compare the efficacy of reciprocating and rotary techniques with that of hand files for removing gutta-percha and sealer from root canals. METHODOLOGY: The root canals of fifty-four human extracted maxillary central incisors were cleaned and shaped using a crown-down technique to a size 40 and filled with gutta-percha and a zinc oxide-eugenol-based sealer using a lateral compaction technique. Teeth were divided into three groups according to the technique used for removing the root filling material: group I - Gates-Glidden burs and stainless steel hand files up to size 50; group II - rotary technique with NiTi Mtwo R files and additional Mtwo files to size 50, 0.04 taper; group III - reciprocating technique with the Reciproc instrument R50, size 50, 0.05 taper. Chloroform was used as a solvent in all groups. Teeth were then split longitudinally and photographed under 8× magnification. The images were transferred to a computer, and the total canal space and remaining filling material were quantified. The ratio of remaining filling material to root canal periphery was computed with the aid of Image Tool 3.0 software. The mean percentages of remaining filling material and time required to remove it were compared using the Kruskal-Wallis and Mann-Whitney tests (P < 0.05). RESULTS: The mean percentage of remaining filling material was significantly higher (P < 0.05) in group II, with Mtwo rotary files (12.17%), than in group I, with the hand file technique (7.19%), and group III, with Reciproc instruments (4.57%), which were statistically similar (P > 0.05). The time required to remove filling material was significantly shorter (P < 0.05) in group III (194 s), followed by group II (365 s) and group I (725 s) (P < 0.05). CONCLUSION: Remaining endodontic filling material was observed on the canal walls of all teeth regardless of the technique used. Hand files combined with Gates-Glidden burs (group I) and the reciprocating technique (group III) removed more filling material from the canal walls than the Mtwo R files. The reciprocating technique was the most rapid method for removing gutta-percha and sealer, followed by the rotary technique and the hand file technique.

Reciproc Endodontic File Surface Defects After Single Use: An SEM Analysis.

OBJECTIVE: The aim of this investigation was to detect defects that may occur to Reciproc endodontic files after a single use. MATERIALS AND METHODS: A sample of convenience of Reciproc files (VDW GmbH, Munich, Germany) that were used to prepare root canals of anterior or posterior teeth were collected. The files were divided equally into two groups: Group 1 (R25) files were used to prepare mesial root canals of 50 human permanent mandibular molars, and Group 2 (R40) included 50 files that were used to prepare permanent maxillary incisor teeth. Files were analyzed after single use by using a scanning electron microscope at X120 to detect changes in surface morphology. The data were statistically analyzed by using the χ2 test, and statistical significance was set at P < 0.05. RESULTS: A total of 96 Reciproc NiTi files were collected; of those, 67 (70%) were unaffected and 29 (30%) showed overall surface deformations. The types of deformation were blade disruption (22%), surface pitting (12%), and unwinding and tip deformation (1%). No microcracks were detected, and none of the studied files showed fracture. R40 was three times more likely to be deformed and showed blade disruption compared with R25 (P < 0.05). CONCLUSIONS: Reciproc rotary NiTi files show high resistance to deformation after a single use. Blade disruption was the most frequent defect occurring in both the small and large files.

Treatment of Necrotic Teeth Using Two Engine-Driven Systems and Patient's Postoperative Pain: A Double-Blind Clinical Trial.

INTRODUCTION: One of the most important reasons for postoperative pain is the extrusion of debris from the apical foramen during preparation and shaping of root canals. The aim of this clinical trial was to evaluate the severity of postoperative pain with the use of two different engine-driven NiTi systems. METHODS AND MATERIALS: Ninety mandibular molars were randomly divided into two groups (n=45), and root canal cleaning and shaping was done using either RaCe or Reciproc instruments. The severity of postoperative pain was determined with visual analogue scale (VAS) at 4-, 12-, 24-, 48- and 72 h and 1-week intervals and postoperative pain was compared between the two groups. The chi-squared test and repeated-measures analysis were used to compare the data between the two groups. RESULTS: Based on the results of the statistical analyses, the two groups were matched regarding the age and gender, with no significant differences. In addition, except for 4- and 24-h and 1-week intervals, postoperative pain was significantly less in the RaCe group compared to the Reciproc group (P<0.001). CONCLUSION: Based on the results of the present study, use of RaCe files for cleaning and shaping of root canals in necrotic mandibular molars resulted in less severe postoperative pain compared to Reciproc files.