Felipe Gonçalves Belladonna

Lack of Causal Relationship between Dentinal Microcracks and Root Canal Preparation with Reciprocation Systems

INTRODUCTION This study aimed to evaluate the frequency of dentinal microcracks observed after root canal preparation with 2 reciprocating and a conventional full-sequence rotary system using micro-computed tomographic analysis. METHODS Thirty mesial roots of mandibular molars presenting a type II Vertucci canal configuration were scanned at an isotropic resolution of 14.16 μm. The sample was randomly assigned to 3 experimental groups (n = 10) according to the system used for the root canal preparation: group A-Reciproc (VDW, Munich, Germany), group B-WaveOne (Dentsply Maillefer, Baillagues, Switzerland), and group C-BioRaCe (FKG Dentaire, La-Chaux-de-Fonds, Switzerland). Second and third scans were taken after the root canals were prepared with instruments sizes 25 and 40, respectively. Then, pre- and postoperative cross-section images of the roots (N = 65,340) were screened to identify the presence of dentinal defects. RESULTS Dentinal microcracks were observed in 8.72% (n = 5697), 11.01% (n = 7197), and 7.91% (n = 5169) of the cross-sections from groups A (Reciproc), B (WaveOne), and C (BioRaCe), respectively. All dentinal defects identified in the postoperative cross-sections were also observed in the corresponding preoperative images. CONCLUSIONS No causal relationship between dentinal microcrack formation and canal preparation procedures with Reciproc, WaveOne, and BioRaCe systems was observed.

Micro-computed Tomographic Assessment on the Effect of ProTaper Next and Twisted File Adaptive Systems on Dentinal Cracks.

INTRODUCTION The aim of the present study was to evaluate the frequency of dentinal microcracks observed after root canal preparation with ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland) and Twisted File Adaptive (TFA; SybronEndo, Orange, CA) systems through micro-computed tomographic analysis. METHODS Twenty moderately curved mesial roots of mandibular molars presenting a type II Vertucci canal configuration were randomly assigned to 2 experimental groups (n = 10) according to the system used for the root canal preparation: PTN or TFA systems. The specimens were scanned through high-resolution micro-computed tomographic imaging before and after root canal preparation. Afterward, pre- and postoperative cross-sectional images of the mesial roots (N = 25,820) were screened to identify the presence of dentinal defects. RESULTS Dentinal microcracks were observed in 38.72% (n = 5150) and 30.27% (n = 3790) of the cross-sectional images in the PTN and TFA groups, respectively. All dentinal defects identified in the postoperative scans were already present in the corresponding preoperative images. CONCLUSIONS Root canal preparation with PTN and TFA systems did not induce the formation of new dentinal microcracks.

Blue Thermomechanical Treatment Optimizes Fatigue Resistance and Flexibility of the Reciproc Files

Introduction: The aim of the present study was to evaluate the influence of Blue thermal treatment on the bending resistance and cyclic fatigue of conventional M‐Wire Reciproc files (VDW, Munich, Germany). The roughness pattern and the microhardness of the files were also assessed. Methods: Flexibility of standard Reciproc R25 files and the corresponding Blue prototypes was determined by 45° bending tests according to the ISO 3630‐1 specification. Instruments were also subjected to cyclic fatigue resistance, measuring the time to fracture in an artificial stainless steel canal with a 60° angle and a 5‐mm radius of curvature. The fracture surface of all fragments was examined with a scanning electron microscope. The roughness of the working parts was quantified by using a profilometer, and the microhardness test was performed using the Vickers hardness tester. Results were statistically analyzed using the Student t test with a level of significance set at P < .05. Results: Reciproc Blue instruments presented a significantly longer cyclic fatigue life and significantly lower bending resistance than the original Reciproc instrument (P < .05). Regarding the roughness pattern, there was no significant difference between Reciproc Blue and the original Reciproc instruments (P > .05), whereas Reciproc Blue revealed significantly lower microhardness than the original Reciproc instrument (P < .05). Conclusions: Reciproc Blue nickel‐titanium showed improved all‐around performance when compared with conventional M‐Wire superelastic nickel‐titanium, demonstrating improved flexibility and fatigue resistance, and reduced microhardness while maintaining similar characteristics of the surface. HighlightsSo far, Blue thermal treatment was not assessed regarding cyclic fatigue and other mechanical features.Reciproc Blue showed overall improved performances when compared with conventional Reciproc, demonstrating improved flexibility and fatigue resistance, and reduced microhardness while maintaining similar characteristics of the surface.

Accumulated hard tissue debris produced during reciprocating and rotary nickel-titanium canal preparation.

INTRODUCTION This study compared the amount of hard tissue debris produced after different apical enlargement with single-file reciprocating systems (WaveOne [Dentsply Maillefer, Baillaigues, Switzerland] and Reciproc [VDW, Munich, Germany]) and a conventional multifile rotary system (BioRaCe [FKG Dentaire, La-Chaux-de-Fonds, Switzerland]) using micro-computed tomographic imaging. METHODS Thirty moderately curved mesial roots of mandibular molars presenting 2 independent root canals were selected and scanned at an isotropic resolution of 14.16 μm. The sample was assigned to 3 groups (n = 10) with respect to the root length and degree of curvature of the mesial root according to the system used for the root canal preparation: Reciproc, WaveOne, and BioRaCe. Second and third scans were taken after the root canals were prepared up to ISO sizes 25 and 40, respectively. The matched images of the mesial canals, before and after preparation, were examined from the furcation level to the apex to evaluate the amount of hard tissue debris (%). Data were statistically compared using a general linear model for repeated-measures with a significance level set at 5%. RESULTS Instrumentation systems per se did not influence the amount of hard tissue accumulation (P > .05), whereas a significant reduction in the percentage of hard tissue debris was observed after sequential enlargement in all groups (P < .05). CONCLUSIONS None of the systems yielded root canals completely free from packed hard tissue debris. The increased final apical size resulted in significantly less debris accumulation for both reciprocating and rotary systems.

Reciprocating Versus Rotary Systems for Root Filling Removal: Assessment of the Apically Extruded Material

INTRODUCTION This study was designed to quantitatively evaluate the amount of apically extruded debris by comparing the ProTaper Universal Retreatment system (Dentsply Maillefer, Ballaigues, Switzerland) with 2 reciprocating single-file systems (Reciproc [VDW, Munich, Germany] and WaveOne [Dentsply Maillefer]) during endodontic retreatment. METHODS Forty-five mandibular premolars with a single canal were prepared with the ProTaper Universal system and then obturated. The specimens were divided into 3 groups (n = 15) according to the system used for filling removal: ProTaper Universal Retreatment system associated with the ProTaper Universal system (until file F4 40/0.06]), Reciproc system (Reciproc R40 [40/0.06]), and WaveOne system (WaveOne Large [40/0.08]). Sodium hypochlorite was used as an irrigant, and the apically extruded debris was collected in glass vials and then dried. The mean weight of debris was assessed with a microbalance and statistically analyzed using 1-way analysis of variance and post hoc Tukey multiple comparison tests (P < .05). RESULTS The ProTaper Universal Retreatment system produced significantly more debris compared with the Reciproc and WaveOne systems (P < .01). The reciprocating systems showed no significant difference between them (P > .05). CONCLUSIONS Under the conditions of the present study, all systems caused apical debris extrusion. Reciprocating systems were associated with less debris extrusion when compared with a conventional rotary retreatment system.

Quantitative Transportation Assessment in Simulated Curved Canals Prepared with an Adaptive Movement System

INTRODUCTION The aim of this study was to evaluate the ability of the Twisted File Adaptive (TF Adaptive; SybronEndo, Orange, CA) system in maintaining the original profile of root canal anatomy. The ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland) and Twisted File (TF) (SybronEndo) systems were used as reference techniques for comparison. METHODS Thirty simulated curved root canals manufactured in clear resin blocks were randomly assigned to 3 groups (n = 10) according to the instrumentation system: TF in rotary motion, TF in TF Adaptive motion, and ProTaper Universal. 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 2 independent canal regions: straight and curved levels. Univariate analysis of variance and Tukey Honestly Significant Difference were used, and a cutoff for significance was set at alpha = 5%. RESULTS Instrumentation systems significantly influenced canal transportation (P = .000). A significant interaction between instrumentation system and root canal level (P = .000) was also found as follows: at the straight part, TF and TF Adaptive systems produced similar canal transportation, which was significantly lower than for the ProTaper Universal system; at the curved part, TF resulted in the lowest canal transportation followed by TF Adaptive and ProTaper Universal systems. Canal transportation was higher at the curved canal parts (P = .00). CONCLUSIONS The TF in rotary motion produced overall less canal transportation in the curved portion when compared with the others tested systems. The ProTaper Universal system showed the highest canal transportation.

Cyclic and Torsional Fatigue Resistance of XP-endo Shaper and TRUShape Instruments

Introduction: The purpose of this study was to evaluate the cyclic and torsional fatigue resistance of the XP‐endo Shaper (FKG Dentaire, La Chaux‐de‐Fonds, Switzerland) and TRUShape (Dentsply Tulsa Dental Specialties, Tulsa, OK) instruments. Methods: Twenty XP‐endo Shaper (30/0.01) instruments and 20 TRUShape (30/0.06v) instruments were used. Cyclic fatigue resistance was tested by measuring the number of cycles and time to fracture in an artificial stainless steel canal with a 60° angle and a 5‐mm radius of curvature (n = 10). The torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630‐1. The fracture surface of all fragments was examined with a scanning electron microscope. Results were statistically analyzed using the Student t test at a significance level of P < .05. Results: The XP‐endo Shaper instruments showed a significantly longer number of cycles to fracture and time to failure in seconds than the TRUShape instruments (P < .05). The XP‐endo Shaper also presented a lower maximum torque load (P < .05) but a significantly higher angular rotation to fracture than TRUShape (P < .05). Conclusions: The XP‐endo Shaper instruments showed a higher cyclic fatigue resistance and angle of rotation to fracture but lower torque to failure than TRUShape instruments. HighlightsCyclic and torsional fatigue resistance of the newly launched XP‐endo Shaper and TRUShape instruments was assessed.The XP‐endo Shaper instruments showed a significantly longer cyclic fatigue life than TRUShape instruments.The XP‐endo Shaper presented a lower maximum torque load but a higher angular rotation to fracture than TRUShape.

On the Causality Between Dentinal Defects and Root Canal Preparation: A Micro-CT Assessment

This study aimed to evaluate the cause-effect relationship between canal preparation with ProTaper Universal (PTU) system and dentinal defects formation using micro-computed tomography (micro-CT) analysis. Forty mesial canals of mandibular molars with a type II Vertuccis canal configuration were scanned at an isotropic resolution of 14.16 µm. The sample was assigned to an experimental (n = 30) and a control (n = 10) groups, and the mesial canals were prepared with PTU system up to F2 instrument. The specimens from the experimental group were scanned and the cross-section images of the mesial roots, before and after preparation, were screened to identify the presence of dentinal defects. In the control group, the specimens were sectioned perpendicularly to the long axis of the root into 1-mm-thick slices (n = 80) and examined under optical microscope. Once a dentinal defect was detected, the slice was scanned through micro-CT. In the experimental group, dentinal micro-cracks were observed in 4,828 slices (24.04%). In all cross-section images, dentinal defects identified in the postoperative images were already present in the corresponding preoperative image. In the control group, 13 out of 80 slices (16.25%) had at least one dentinal defect visualized under stereomicroscopy, which was identified after a further micro-CT scanning. Micro-CT showed reliability as similar as optical microscopy in detecting dentinal defects, adding the possibility of tracking the dentinal tissue, before and after canal preparation, and providing a clear visualization of micro-cracks. Root canal preparation with PTU system did not induce the formation of new dentinal defects.

Bending resistance and cyclic fatigue of a new heat-treated reciprocating instrument

The current study aimed to evaluate the bending resistance and the cyclic fatigue life of a new heat-treated reciprocating instrument (ProDesign R). Untreated ProDesign R, Reciproc R25, and WaveOne Primary instruments were used as reference instruments for comparison. The bending resistance was performed in ten instruments of each system by using a universal testing machine and a proper apparatus. The cyclic fatigue resistance was tested measuring the number of cycles to failure in an artificial stainless steel canal. Scanning electron microscopy analysis was performed to determine the mode of fracture and possible deformations at the helical shaft. Statistical analysis was performed by using parametric methods; one-way analysis of variance plus post hoc pair-wise Tukey test for multiple comparisons (p < 0.05). Untreated ProDesign R presented significantly higher bending resistance than the other tested systems (p < 0.05). No differences were observed between ProDesign R and Reciproc files regarding the bending resistance (p > 0.05). Moreover, ProDesign R revealed a significantly longer cyclic fatigue life (p < 0.05). In contrast, Untreated ProDesign R and WaveOne instruments presented significantly lower cyclic fatigue life than Reciproc (p < 0.05). The new heat-treated reciprocating instrument ProDesign R have higher cyclic fatigue resistance than Untreated ProDesign R, Reciproc, and WaveOne instruments. ProDesign R and Reciproc were significantly more flexible than Untreated ProDesign R and WaveOne files. SCANNING 38:837-841, 2016.

Micro–computed Tomography Assessment of Dentinal Micro-cracks after Root Canal Preparation with TRUShape and Self-adjusting File Systems

Introduction The aim of the present study was to evaluate the percentage frequency of dentinal micro‐cracks observed after root canal preparation with TRUShape and Self‐Adjusting File (SAF) systems by means of micro–computed tomography imaging analysis. A conventional full‐sequence rotary system (BioRace) and a single‐file reciprocation system (Reciproc) were used as reference techniques for comparison because of their known assertive cutting efficiency. Methods Forty anatomically matched mandibular incisors were selected, scanned at a resolution of 14.25 &mgr;m, and assigned to 4 experimental groups (n = 10), according to the preparation protocol: TRUShape, SAF, BioRace, and Reciproc systems. After the experimental procedures, the specimens were scanned again, and the registered preoperative and postoperative cross‐section images of the roots (n = 70,030) were screened to identify the presence of dentinal micro‐cracks. Results Overall, dentinal defects were observed in 28,790 cross‐section images (41.11%). In the TRUShape, SAF, BioRace, and Reciproc groups, dentinal micro‐cracks were visualized in 56.47% (n = 9842), 42.38% (n = 7450), 32.90% (n = 5826), and 32.77% (n = 5672) of the slices, respectively. All dentinal defects observed in the postoperative data sets were already present in the corresponding preoperative images. Conclusions None of the preparation systems induced the formation of new dentinal micro‐cracks. HighlightsThe frequency of dentinal micro‐cracks was evaluated after canal preparation with TRUShape and Self‐Adjusting File systems using micro‐CT analysis.Micro‐CT nondestructive technology provides the possibility to examine the dentinal tissue before any root canal procedure.Dentinal micro‐cracks were visualized in 56.47%, 42.38%, 32.90%, and 32.77% of the slices in the TRUShape, SAF, BioRace, and Reciproc groups, respectively.All dentinal defects observed in the postoperative data sets were already present in the corresponding preoperative images.None of the preparation systems induced the formation of new dentinal micro‐cracks.