Torsional Performance of ProTaper Gold Rotary Instruments during Shaping of Small Root Canals after 2 Different Glide Path Preparations

Analysis of Torque and Force Induced by Rotary Nickel-Titanium Instruments during Root Canal Preparation: A Systematic Review

The aim of this review was to provide a detailed literature analysis of torque and force generation during nickel-titanium rotary root canal instrumentation. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An electronic search was performed using in PubMed and in journals for articles published in English from 1987 to June 2020 on studies that investigated dynamic torque and force in vivo or in vitro. We assessed article titles and abstracts to remove duplicates, and the titles and abstracts of the remaining articles were screened for eligibility. Full texts were read to verify eligibility by considering predetermined inclusion and exclusion criteria. Fifty-two out of 4096 studies met the inclusion criteria, from which we identified 26 factors that influence torque or force generation. Factors associated with higher torque or force generation and supported by multiple studies with mostly consistent results included convex triangle cross-sectional design, regressive taper, short pitch length, large instrument size, small canal size, single-length preparation technique, long preparation time, deep insertion depth, low rate of insertion, continuous rotation (torque), reciprocating motion (force), lower rotational speed and conventional alloy. However, several factors are interrelated, which obscured the independent effect of each factor, and there was insufficient scientific evidence supporting the influence of some factors.

A laboratory study of the scouting ability of two reciprocating glide path instruments in mesial root canals of extracted mandibular molars

AIM

To evaluate in a laboratory setting the performance of two reciprocating glide path systems, WaveOne Gold Glider (WO) and R-Pilot (RP), to create a glide path in mesial root canals of mandibular molars and to assess the torsional resistance of instruments after performing the glide path.

METHODOLOGY

A total of 60 mesial root canals of extracted human mandibular molars were divided into two groups (n = 30) according to the glide path system to be used. The data from the volume of each canal, acquired by microcomputed tomography (micro-CT), were validated statistically for the anatomical pairing of the groups. Preparation time, frequency in gaining apical patency, plastic deformation rate of instruments, and canal transportation and centring ability were recorded and compared statistically. The torsional fatigue of the instruments after use was also evaluated. Data were analysed using Fisher's exact test and Mann-Whitney U-test with a 5% significance level.

RESULTS

No significant differences were found between groups regarding the time required to perform the glide path, the frequency distributions of the canals classified as patent and the instruments with plastic deformation after use (P > 0.05). No significant differences were found between groups regarding the degree of canal transportation and centring ability at the cervical, middle and apical thirds (P > 0.05). The RP groups had significantly greater maximum torsional strength values compared with the WO groups (P < 0.05). The used WO group had greater angular deflection to fracture when compared to the new WO group (P < 0.05). A significant difference was also found in the percentage of loss of angular deflection in a comparison of the WO group with the RP group (P < 0.05).

CONCLUSIONS

The WO and RP instruments performed the same in terms of preparation time, plastic deformation, gaining apical patency, degree of canal transportation and centring ability. The RP instruments had greater torsional strength, less angular deflection and lower percentage of loss in angular deflection than the WO. The used WO group had the greatest angular deflection values.

Effect of dentine cutting efficiency on the lateral force created by torque-controlled rotary instruments

AIM

To study the impact of dentine cutting efficiency of rotary instruments on the lateral force they create when instrumenting simulated root canals in bovine dentine.

METHODOLOGY

Lateral cutting efficiency of austenitic files (ProTaper Universal) was compared to that of counterparts of a reported identical geometrical design with a martensite phase component (ProTaper Gold) in bovine dentine disks (n = 6). Instrument shapes were studied using digital microscopy. The intracanal lateral force exerted by the two systems in simulated premolars (n = 9) made from bovine incisor roots containing a standardized narrow root canal of 16 mm length was monitored using a testing apparatus equipped with a torque-controlled endodontic motor/handpiece. Data were compared using parametric statistics, alpha error = 0.05.

RESULTS

The geometrical design of the two systems under investigation was found to be identical. The martensitic nickel-titanium rotary files had a significantly (t-test, P < 0.05) higher lateral cutting efficiency than austenitic counterparts. This difference, however, did not impact the lateral force that was created when instrumenting simulated premolar root canals. Furthermore, lateral force peaks were generated with the progressively tapered instruments under investigation towards the full working length. Even though a glide path was prepared, the first instrument in the full-length sequence (S1) created the highest lateral force (anova/Tukey's HSD, P < 0.05).

CONCLUSIONS

The current experimental set-up allows the study of the lateral force generated during root canal instrumentation. This force was not influenced by the dentine cutting efficiency of the instruments under investigation, but rather by their geometrical design.

Influence of Negotiation, Glide Path, and Preflaring Procedures on Root Canal Shaping-Terminology, Basic Concepts, and a Systematic Review

INTRODUCTION

Negotiation, glide path, and preflaring are essential steps in root canal shaping procedures. This report aimed to discuss the terminology, basic concepts, and clinical considerations of negotiation, glide path, and preflaring procedures and the influence of these steps on root canal shaping.

METHODS

This systematic review was undertaken following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol has been registered with the International Prospective Register of Systematic Reviews (number CRD42019127021). A comprehensive literature search was performed by 2 independent reviewers using a selected search strategy in 2 electronic databases (PubMed and Scopus) until January 28, 2019. A further search was performed manually in endodontic journals. Studies investigating or comparing at least 1 shaping property resulting from root canal instrumentation with a glide path or preflaring in human extracted teeth or clinical studies were included.

RESULTS

The literature shows that the definition of glide path and preflaring procedures remains controversial, which requires an elaboration in the American Association of Endodontists' Glossary of Endodontic Terms. After the removal of irrelevant and duplicated articles, 98 articles were included. The impact of glide path preparation and preflaring on working length determination, apical file size determination, canal transportation, separation of endodontic files, shaping time, dentinal microcrack formation, and extrusion of debris was discussed. Because of heterogeneity among the included studies, quantitative synthesis was not performed for most of the parameters.

CONCLUSIONS

An evidence-based guideline is needed to define and correlate the basic concepts and current applications of each step of contemporary advancements in root canal instruments. Glide path preparation reduces the risk of debris extrusion, has no influence on the incidence of dentinal crack formation, and improves the preservation of the original canal anatomy. The creation of a glide path may have no impact on Reciproc files (VDW, Munich, Germany) in reaching the full working length. Preflaring increases the accuracy of working length determination. Further randomized clinical trials are required to evaluate the effect of a glide path and preflaring on root canal treatment outcomes.

Comparison of Obturation Removal Efficiency from Straight Root Canals with ProTaper Gold or Reciproc Blue: A Micro-Computed Tomography Study

Background: The objective was to evaluate the efficiency of ProTaper Gold (PTG) and Reciproc Blue (RB) NiTi files in obturation material removal from straight root canals assessed by micro-computed tomography. Methods: Fifty-two anterior human teeth were shaped with a PTG rotary system until F2 (25/.08). Specimens were obturated with a continuous wave of condensation technique. For retreatment, specimens were randomly distributed in two experimental groups: PTG group (F4 file) and RB (R40 file). Micro-CT scans were performed before and after retreatment procedures. The percentage of the remaining obturation material compared to the original volume was calculated, as well as the retreatment time. The presence of separated files was recorded. A descriptive analysis was carried out, and nonparametric tests were employed. Results: The mean percentages of remaining obturation material in the PTG group and the RB group were 4.14 ± 4.30% and 4.18 ± 4.29%, respectively. The mean retreatment times for the PTG and RB groups were 144 ± 51 and 163 ± 88 s, respectively. There were no statistically significant differences, neither in removal efficiency (p > 0.05) nor in retreatment time (p > 0.05), between the two groups. The coronal and middle thirds presented significantly more remaining obturation material than the apical third (p < 0.05). No file separation occurred. Conclusions: ProTaper Gold and Reciproc Blue present with comparable efficiency in removing the obturation material, with a similar mean retreatment time.

Lubrication during root canal treatment

Lubrication is involved in all root canal treatment phases, from dental dam placement to canal obturation. Most often associated with instrumentation, lubrication is required to facilitate the mechanical action of hand/rotary files and to help emulsify and suspend the debris produced. Aqueous irrigation solutions such as sodium hypochlorite and ethylenediaminetetraacetic acid (EDTA) should be regarded as lubricants, but paste-type substances are marketed specifically for this purpose. As more patients demand the retention of challenging teeth with narrow and curved root canals, the importance of lubrication in all aspects of root canal treatment must be acknowledged.

Comparison of Shaping Ability of 10 Rotary and Reciprocating Systems: an In Vitro Study with AutoCad

Objective

The aim of this study was to compare the cutting are, root canal anatomy preservation and non-instrumented areas of F360®, F6-SkyTaper®, Hyflex-EDM®, iRACE®, Neoniti®, O.Shape®, P.Next®, Reciproc®, Revo-S® and Wave-One-Gold® size 25 files.

Materials and Methods

300 teeth with a single straight root and a circular or elliptical root canal were divided into 10 groups (1-F360®, 2- F6-SkyTaper®, 3-Hyflex-EDM®, 4-iRACE®, 5-Neoniti®, 6-O.Shape®, 7-P.Next®, 8-Reciproc®, 9-Revo-S® and 10-Wave-One-Gold®) cut into 3 cross sections using an ultrafine cutting disc. They were photographed under a stereo microscope and preinstrumentation analyses were made before rebuilding the teeth with# 10 K- File and epoxy glue. A glide path was created with #10 and #15 K files and each group was instrumented using rotary or reciprocating systems. Cutting areas, root canal anatomy preservation and non-instrumented areas were analyzed using the AutoCAD 2015 Levene's test, the Welch´s test, and the Games-Howell´s test. The Pearson’s chi-squared test was used for statistical analysis.

Results

Levene's test showed no equality of variances (P<0.05), therefore Welch´s and Games-Howell's tests were applied to cutting areas, showing significant differences in all thirds and overall (P<0.05). No differences in root canal anatomy preservation were observed (P>0.05). In non-instrumented areas, significant differences were found (P<0.05) in middle third being better in Reciproc®, Neoniti® and WaveOneGold®, and in apical thirds being higher P.Next®, Reciproc®, HyflexEDM®, Neoniti® and WaveOneGold®.

Conclusions

In cutting area, P.Next® and Reciproc® were superior in coronal third, Neoniti® and Hyflex EDM® medially and apically and Neoniti® and Reciproc® overall. Regarding the root canal anatomy preservation, all systems were similar. For non-instrumented areas, all systems achieved similar results coronally, but Reciproc®, Neoniti® and Wave One Gold® were superior in middle third and P.Next®, Reciproc®, Hyflex EDM®, Neoniti® and Wave One Gold® were superior in apically.