Single file reciprocating systems: A systematic review and meta-analysis of the literature: Comparison of reciproc and WaveOne.

The introduction of single-file nickel-titanium (NiTi) reciprocating systems has been a major breakthrough in the field of endodontics. Thus, the aim of this study was to compare the available reciprocating systems, Reciproc and WaveOne, using a meta-analysis with different parameters. A comprehensive electronic literature search for Reciproc and WaveOne using PubMed and Google scholar was initially conducted in September 2014 and updated in September 2016. Inclusion and exclusion criteria were then established. Twenty-six studies were qualified for the systematic review, and only three studies were considered for the meta-analysis using cyclic fatigue resistance as the main parameter. The time to fracture for the Reciproc and WaveOne systems ranged from 119.7 sec to 156.4 sec and 74.8 sec to 99.6 sec, respectively. The pooled difference in mean time to fracture was longer for the Reciproc system by 45.6 sec. This difference was statistically significantly at P value < 0.001. In conclusion, our study supports the finding that Reciproc is more resistant to cyclic fatigue than WaveOne. However, with regard to other parameters, mixed results were obtained. Well-designed randomized clinical trials comparing both systems under the same experimental conditions should be done in future studies.

INTRODUCTION

Canal shaping is an integral part of endodontic treatment because it removes bacteria and facilitates further successful irrigation and obturation.[12] Evolution of endodontic shaping instruments has occurred over time, which has proven to be beneficial for maximizing debridement and decreasing procedural errors.[23] The use of stainless steel hand files and H and K-files were the conventional shaping method.[3] These hand files were replaced by rotary systems. This was because of their troublesome use when shaping curved canals and owing to several disadvantages, including both rigidity that may cause many iatrogenic errors (transportations, ledges, and zipping) and the tendency to result in lengthy root canal treatment procedures.[23]

To overcome these difficulties, in 1988, Walia et al. introduced nickel–titanium (NiTi) files in endodontics.[4] He reported that NiTi had greater elastic flexibility than stainless steel.[4] This finding was later supported by others, and it was proven that NiTi superelasticity was an advantage in curved canals because it reduced forces on the walls, enhanced centering ability, and led to less iatrogenic errors.[56] This flexibility is due to the property of the NiTi alloy, which can undergo transformation between the austenitic and martensitic phases. The NiTi alloy can regain its original shape (austenite) after the application of stress or heat (martensite) in a characteristic called the “shape memory effect.”[5]

Most of the NiTi rotary systems move in a continuous rotation.[789101112] However, as in many other systems, the NiTi rotary system appears to have some drawbacks. When rotating in curved canals, it may lead to cyclic fatigue, which is file separation and fracture due to repeated tensile-compressive forces being applied to the file in maximum curved areas.[13] In some cases, using NiTi files can also be time consuming because they may require multiple exchanges of file sizes; some of these files need prior glide path preparation done with hand files.[3] This led to the revolution of single-file NiTi reciprocating systems, which has been adopted by Dr. Yared. He has also introduced the Reciproc system. The single-file NITi system consists of three files, including the R25 (ISO 25; 8%), R40 (ISO 40; 6%), and R50 (ISO 50; 5%); it has respective paper points and gutta-percha and a specific motor (VDW. SILVER) which was made in Munich, Germany.[3] This concept has many advantages over the conventional rotary NiTi systems: (1) greater time efficiency because it requires only a single file to prepare all the canals with no requirement for prior glide path preparation; (2) single files are made from M-wire (heated NiTi alloy) that give them the greatest flexibility and cyclic fatigue resistance; and (3) reciprocating systems, which move in rotating reciprocation movements (balanced force) with large rotating angles. One movement is counter-clock wise, which engages and cuts dentin, and the other is clock-wise, which disengages the file from the dentin to avoid taper lock and relieves stress on the file. This type of movement prevents file breakage and increases its resistance to both cyclic and torsional fatigue.[31415]

Another competitive single file NiTi reciprocation system, WaveOne, has also been launched. This system was introduced in 2011 by the Dentsply/Maillefer Company (Ballaigues, Switzerland), and consists of three single-use files, including small (ISO 21; 6%), primary (ISO 25; 8%), and large (ISO 40; 8%).[161718] This system also has the same M-wire and reciprocal movement features as Reciproc. Therefore, the aims of this systematic review and meta-analysis were to review the literature and compare the two reciprocating systems, Reciproc and WaveOne, with cyclic fatigue resistance, bending resistance, centering ability, cutting efficiency, canal debridement, clinical efficiency, and reusability cyclic fatigue resistance as the main parameters. This will help to provide the best available information to dentists in general, and endodontists in specific, to understand the differences between both the systems, and help them to decide whether to use Reciproc or WaveOne in cleaning and shaping the root canal system.

MATERIALS AND METHODS

Prior to the literature search, a research question was defined following the population, intervention, comparison, and outcome (PICO) format: “Does WaveOne single file NiTi system (intervention) compared to Reciproc single file NiTi system (comparison) have longer time to fracture (outcome) when shaping root canals?” A comprehensive electronic literature search for Reciproc and WaveOne using PubMed and Google scholar was initially conducted in September 2014 and updated in September 2016. All the resulting titles and abstracts were screened for topic relevance. Inclusion and exclusion criteria were then established. The articles were selected on the basis of following keywords: (1) Reciproc versus WaveOne; (2) Reciproc and WaveOne; and (3) WaveOne; or (4) Reciproc.

Inclusion criteria

Original peer reviewed studies

In-vitro and in-vivo studies

Studies comparing Reciproc versus WaveOne or a comparison of WaveOne versus Reciproc or other NiTi systems

Articles published in English

Success reported as reduced cyclic fatigue.

Exclusion criteria

Studies comparing only Reciproc with other systems

Studies comparing only WaveOne with other systems

Studies comparing single file reciprocating systems with another NiTi rotary system, and data do not clearly show the difference between Reciproc and WaveOne

Effects of Reciproc or WaveOne in retreatment cases.

Data extraction

The electronic database literature search resulted in a total of 197 citations. Two of the authors independently reviewed the articles against the checklist to assess evidence for efficacy of therapy or prevention [Table 1]. Disagreement was resolved by consensus. The process of article selection and review is detailed in Figure 1. This systematic review was prepared according to the PRISMA guidelines. Relevant data was then extracted from the final 26 articles selected for the systematic review. Meta-analysis was performed using a random effects model to calculate the pooled time to fracture. To measure publication bias, a funnel plot was graphed, and the Fail-Safe N and Begg and Mazumdar rank correlation tests were conducted. StatsdIrect software (StatsDirect Ltd, Cheshire, UK) 2.7.8 was used for the statistical analysis.

Table 1

Checklist to assess evidence of therapy or prevention measures

Figure 1

The stepwise process of selecting and reviewing the articles included in the meta-analysis

RESULTS

Twenty-six studies qualified for the systematic review [Table 2]. Because of the extreme heterogeneity of the final selected articles, only three studies were considered for the meta-analysis using cyclic fatigue resistance as the main parameter. The three studies selected for meta-analysis and their results are summarized in Table 3.

Table 2

Studies included for the systematic review and their conclusions

Table 3

Studies included in the meta-analysis

The time to fracture for the Reciproac and WaveOne systems ranged from 119.7 s to 156.4 s and 74.8 s to 99.6 s, respectively. The pooled difference in mean time to fracture was longer for the Reciproac system by 45.6 s. This difference was statistically significant at P < 0.001 [Figure 2; Table 3].

Figure 2

Results of the random effects model used for the meta-analysis demonstrating the detailed statistics for each study

The Fail-Safe N is 256 and the Begg and Mazumdar's Kendal tau with continuity correction showed a nonsignificant correlation with P value (one-tailed) = 0.50, which indicates that publication bias was nonexistent in this analysis.

DISCUSSION

It has been shown that endodontic NiTi reciprocating instruments are safe and effective for preparing even the most severe curved root canals in much less chair time.[19] Our systematic review resulted in 26 studies that fulfilled our inclusion and exclusion criteria. These studies investigated different parameters and compared the Reciproc and WaveOne systems. When considering the shaping ability, Saber et al. concluded that Reciproc and WaveOne instruments respected the original canal curvatures with no significant differences between them. However, Reciproc was significantly faster for preparing root canals[15] and demonstrated statistically higher cutting efficiency than WaveOne.[19] Lim et al. reported that a glide path larger than #15 should be established before using the WaveOne file.[20] In contrast, Coelho et al. reported no significant differences between both the files in regard to maintaining centric ability with or without glide path can be demonstrated, and that glide path seems to be unnecessary and would only result in increased working time.[21]

Carvalho et al. found that both the systems presented similar cleaning effectiveness, whereas Topcu et al. reported that WaveOne performed better canal debridement than Reciproc.[2223] De-Deus et al. evaluated the amount of apical extruded dentin and found that there were no significant differences between the two reciprocating instruments.[24] In contrast, others found that Reciproc was associated with less apical debris extrusion compared to several other systems including WaveOne.[25] In regards to postoperative pain and analgesic intake, there was no significant difference between Reciproc and WaveOne systems.[26] In addition, reciprocating systems also showed no significant difference when compared to continuous rotation systems.[26] Both the instruments appeared safe for reuse because they showed no microcracks during instrumentation unless they were reused for up to five canals.[18] However, Helvacioglu-Yigit et al. have shown that significant differences can be noticed only at the apical 3 mm of the prepared canals between the reciprocating systems and untreated controls,[27] whereas others support that Reciproc indeed can cause more dentinal cracks compared to WaveOne.[28] Whether these cracks can carry any clinical significance or not is a question that needs to be answered. Moreover, no statistically significant differences were found between files with regard to instrument fracture and spiral distortion.[14] De Meireles et al. reported that both systems showed similar results with regard to apical transport and both remain centered during canal preparation.[29]

It is clear that there is disagreement between reports in the literature. It also can be noted that studying different parameters may be advantageous for studying and comparing different systems. However, in the present meta-analysis, only three studies fulfilled the inclusion and exclusion criteria.[303132] All of them stated that Reciproc was more cyclic fatigue resistant than WaveOne. One study showed that Reciproc had lower torsional resistance than WaveOne.[32] Another study showed that cyclic fatigue resistance was not reduced after immersion in sodium hypochlorite with Reciproc being the most fatigue resistant.[31] These two single-file reciprocating systems appear to differ significantly in the way to achieve more cyclic fatigue resistance. Both systems are made from the same M-wire NiTi alloy, which gives them the greatest cycle fatigue resistant, however, they both have different cross sections consisting of S-shape and concave triangular for Reciproc and WaveOne, respectively. The cross section affected the cyclic fatigue as the smaller cross-sectional area the more fatigue resistant is the wire.[32] The resulting sample size after reviewing articles and applying the inclusion and extrusion criteria was too small for acceptable statistical power because of the heterogeneity of the experimental conditions. This is one limitation of the study. Most of the included studies involved in-vitro tests, which is also a limitation because they did not mimic the real patient's oral environment.

CONCLUSIONS

Our study appears to support the concept that Reciproc is more resistant to cyclic fatigue than WaveOne. However, with regard to other parameters, mixed results were found. Well-designed randomized clinical trials comparing the shaping ability, clinical efficiency, and reusability of Reciproc and WaveOne under the same experimental conditions should be conducted in future studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.