Performance of the Protaper Universal and Protaper Next files in relation to the apical extrusion of debris

Objective: the purpose of this literature review was to evaluate apical debris extrusion after root canal preparation with Protaper Universal and Protaper Next Rotary systems. Material and Methods: the question that supported the collection of scientific evidence for the present study was: Which rotary system presents the best performance regarding the apical extrusion of debris: Protaper Universal or Protaper Next? From the online search databases, a bibliographic research was carried out covering original research studies, using as descriptors: Apical extrusion debris, Protaper Universal and Protaper Next. Articles had to meet the following inclusion criteria: should have been published in the English language from 2014 to 2017 and should compare both mentioned rotary files systems regarding apical extrusion of debris in the same study. Ninety-six articles were found after research and six were included for this integrative review. Results: six studies remained included after the inclusion criteria analysis. Of these, 50% were published in 2016, 16.6% in 2015 and and 33% in 2014. Weight establishment of the extruded material was the methodology used in all studies to evaluate the performance of the files By analyzing the amount of apically extruded material, it was found that the Protaper Universal system extruded more quantity than the Protaper Next system. Conclusion: it was concluded that, although there is no system capable of performing the instrumentation without promoting apical extrusion, the Protaper Next rotary files system presented better performance when compared to the Protaper Universal files system, regarding the apical debris extrusion.


Introduction
T he objectives of the chemomechanical preparation (CMP) are debridement, disinfection and correct shaping of the root canal system.An adequate CMP favors three-dimensional filling 1 and creates optimum conditions to repair periapical tissues, 2 thus achieving the success of endodontic treatment.
During the CMP, the cutting action of files, whether manual or engine-driven, produces both organic and inorganic residual debris known as Smear Layer. 3 This smear, present on the instrumented root canal walls surface, contains traces of dentin scrapings, pulp tissue, odontoblastic processes and also bacteria in infected canals cases.It is composed of two layers; a superficial layer, weakly adhered to the root canal walls with a mean thickness of 1 to 2 mm, and a deeper layer, closely connected to the dentinal tubules, obliterating them, being able to reach 40 µm thickness. 4his debris, whether organic or inorganic, frequently is extruded into the periapical tissues during the CMP, probably causing undesirable complications such as the induction of inflammatory response with a possible appearance or perpetuation of periapical lesions or Flare-ups. 5,6lare-ups are characterized by the occurrence of pain and/or swelling subsequent to instrumentation, requiring an unscheduled appointment for treatment. 7This occurs because in symptomatic condition, the chemical mediators of inflammation, wich are already installed, are exarcerbated, further increasing the pain symptomatology.Products such as dentine with root canal irrigantshabe been related with inflammatory response in the periapical tissue.Besides that, in asymptomatic chronic periradicular lesions exist a balance between the microbial toxic effect of the infected canal and the host defenses.If bacteria-contaminated debris is apically extruded during CMP, there will be an acute inflammatory response due to the increase in the number of bacterial irritants. 8tudies evaluating the performance of different instrumentation systems have demonstrated that no instrumentation technique is able to prevent some debris from being extruded into the periapical tissues. 2,3,5,6[10] An example of this is the Protaper Universal System (Dentsply Maillefer, Ballaigues, Switzerland), made from conventional Nickel-Titanium alloy, proposes to instrument the entire canal through the sequence S1, S2, F1, F2, F3, F4 e F5.In addition, it has a convex triangular cross-sectional design, with progressive tapering along the length. 11 new generation of instruments know as Protaper Next (Dentsply Maillefer, Ballaigues, Switzerland) was introduced in endodontics.Produced from M-wire technology, they feature an asymmetric rectangular crosspsection design, 12 wich ensures tha only two of the rectangular angles are contacted against the walls of the canals, 8 thus reducing the number of files required for instrumentation. 13ue to the reduction of the number of intruments used during the PQM, as well as the differential design of the cross section of the Protaper Next instrument, it is assumed that during root canal instrumentation this system will present a lower amount of apical extrusion of debris and consequently, it promotes the lower intensity of post-operative pain.
Since the incidence of flare-ups has been reported ranging from 1.4% to 16% of cases, 14 it is essential the prevention of apical extrusion of debris to decrease the frequency of complications. 15Therefore, the objective of this article was to evaluate, the performance of the Protaper Universal and Protaper Next files systems regarding the apical extrusion of debris.

Material and Methods
To guide the achievement of the present study, the following question was asked: which rotary instrumentation technique leads to the largest amount of apical debris extrusion: Protaper Universal or Protaper Next?
Thus, an online search was carried out in the following databases: Medical Literature Analysis and Retrieval System Online (PubMed), Latin American and Caribbean Literature in Health Sciences (Lilacs) and Scientific Electronic Library Online (Scielo), using as descriptors: Apical Extrusion Debris, Protaper Universal and Protaper Next.Four reviewers performed a manual search, after reading the title, abstract and keywords.When the information contained in these topics was insufficient, articles were read in their entirety.References of possible studies to be used, as well as the cross search of author´s databases, served as a guide for the selection of new relevant articles.
As inclusion criteria for both electronic and manual research, articles of literature review or systematic review and in vitro research, published in the English language between 2014 and 2016 were considered.Such articles should address only the comparison of the amount of apically extruded material (debris) using the Protaper Universal and Protaper Next files systems.Were excluded laboratory studies in artificial teeth simulators or developed in deciduous teeth, non-English language, absence of abstract or only the presence of abstract.Studies involving extrusion of debris using different types of files or that approached the extrusion during root canal retreatment, were also discarded.The final synthesis was developed in a descriptive way, regarding the results and conclusions obtained from each of the studies.

Results
Two hundred fifty three publications were obtained after research and six studies remained included after the inclusion criteria analysis (Table 1 A total of 44 bibliographical references were identified in Scielo, noe articles were selected.No longer Lilacs were identified 113 references and noe articles were used.In PUbMED, 96 references were identified, six articles remaining.As to the design of the study, 100% of the articles were cross-sectional and 100% structured in the English language.Of th articles selected, two were published in Oxford and the others in Copenhagen, Baltimore, Milan and India.
Weight establishment of the extruded material was the methodology used in all studies to evaluate the performance of the files.
By analyzing the amount of apically extruded material (mean and standard deviation), it was found that the Protaper Universal system extruded more quantity than the Protaper Next system.

Discussion
During root canal preparation procedures, dentin scrapings, pulp tissue, microorganisms and/or irrigants may be extruded into the periapical tissues.These extruded irritants are responsible for post-operative inflammation and poor healing of the perirradicular tissues, which can cause post-treatment complications, like as flare-up. 5 Therefore, the present study aimed to evaluate which rotary instrumentation technique leads to the greatest amount of extruded apical debris, using two different systems instrumentation (Protaper Universal and Protaper Next).
The teeth instrumented with the Protaper next system presented a lower percentage of extruded irritants when compared to the Protaper Universal system, as reported by 83% of the articles under study, 10,17-20 as well as when another system was evaluated together. 17uch findings can be justified by the fact that the Protaper Next instruments are made with memory wire technology (M-wire) and have a rectangular design, which minimizes the contact between the file and the dentin walls. 21The Protaper Universal files, these are made of conventional Nickel Titanium wire and have triangular convex cut design with progressive tapering along its length, which entails greater contact between the instrument and the root canal walls and consequently, greater accumulation of extruded material. 22n addition, a reduction in the number of instruments decreases the number of walls played during instrumentation, one of the reasons why systems with smaller numbers of files result in less extrusion of debris. 23In contrast, although in another study was concluded that Protaper Next, Protaper Universal and TF extruded similar amounts of debris, 2 differences in results may be due to different employed methodologies, since apical locator was used to determine the working length, wich may influence the results directly, once keeping the length one millimeter short of the foramen contributes to less extrusion. 24nother factor that interferes with the amount of material extruded apically is the pulp condition.In vital teeth, the present pulp tissue serves as a physical barrier preventing the extrusion of debris, whereas, in necrotic teeth, such resistance is not found. 25In addition, it can be said that normal periapical tissues or with some degree of bone resorption determine the extent to which the debris can reach. 26ccording to the results, it was noticed that Protaper Next files produced less amount of apically extruded material when compared to Protaper Universal files.It was also verified that other parameters should be evaluated to quantify the extruded material, as the state of the pulp (if vital or necrotic), the apical limit of instrumentation, the technique and the type of instrument.

Conclusion
Articles selected in this study mostly reported that the Protaper Next rotary files system presented better performance than the Protaper Universal rotary files system regarding the apical extrusion of debris.

Table 1 .
).Of these, 50% were published in 2016, 16.6% in 2015 and 33.4% in 2014.Identification of the selected studies for the integrative review microscopic evaluation of dentinal cracks at different instrumentation lengths by using different rotary files Protaper Universal, Protaper Next, and Hyflex CM: an ex vivo study.Scientifica.2016;2016:1-7.12. Cabanillas C, Monterde M, Pallarés A, Aranda S, Montes R. Assessment Using Auto CAD Software of the Preparation of Dentin Walls in Root Canals Produced by 4 Different Endodontic Instrument Systems.Int J Dent. 2015;2015:1-5.13.Khalap ND, Hegde V, Kokate S. Fracture resistance exhibited by endodontically treated and retreated teeth shaped by Protaper Next versus WaveOne: An in