Apical extrusion of debris and irrigants using ProTaper hand, M-two rotary and WaveOne single file reciprocating system: An ex vivo study

Abstract

Aims:

The purpose of this ex vivo study was to evaluate and compare the weight of debris and volume of irrigant extruded apically from teeth using different preparation techniques.

Subjects and Methods:

Thirty extracted human mandibular premolars with single canals and similar lengths were instrumented using hand ProTaper F2 (25, 0.08; Dentsply Maillefer, Ballaigues, Switzerland), M-two (25, 0.06; VDW, Munich, Germany) and WaveOne Primary (25, 0.08; Dentsply Maillefer, Ballaigues, Switzerland). Debris and irrigant extruded during instrumentation were collected into preweighed Eppendorf tubes. The volume of the irrigant was measured, and then the tubes were stored in an incubator at 70°C for 2 days. The Eppendorf tubes were weighed to obtain the final weight when the extruded debris was included. Three consecutive weights were obtained for each tube.

Statistical Analysis Used:

Data were statistically analyzed by one-way analysis of variance and Student's t-test.

Results:

There were no statistically significant differences among the groups. The WaveOne reciprocating system showed the maximum amount of apical extrusion of debris and irrigant among all the groups. The least amount of debris and irrigant was observed in ProTaper hand instrument (P > 0.05).

Conclusion:

All instrumentation techniques were associated with debris and irrigant extrusion.

INTRODUCTION

The goals of endodontic instrumentation include thorough debridement and disinfection of the root canal system, in addition, to create a suitable shape to achieve a complete three-dimensional obturation.[1] The concept of thorough instrumentation of the apical region has long been considered to be an essential component in the cleaning and shaping process by Grove.[2]

In an effort to obtain these goals, debris such as dentinal shavings, necrotic pulp tissue, bacteria and their byproducts or irrigants may be extruded into the periradicular tissues which can lead to an inflammatory response, postoperative pain and possible delayed healing.[3,4] Vande Visse and Brilliant have shown that in the absence of irrigant, no significant extrusion of debris was observed while a thick worm of debris extruded when an irrigant was used.[5]

Shaping and cleaning of the root canal system can be accomplished mainly by step-back and crown-down techniques. Both hand and rotary files are used with either of the two methods. More recently advanced instrument designs such as radial lands, noncutting tips, different flute depth, variable tapers and cross-sections and the use of different operational principles have been developed to improve working safety, to shorten the working time and to create a greater flare within the preparations. The newer systems also provide a cleaner and smoother preparation to receive the final obturation.[6,7,8]

A common finding of the studies examining the amount of apically extruded debris and irrigant was that the instrumentation techniques using a push-pull motion tend to produce a more apical extrusion of debris than instrumentation techniques using a rotational motion.[9] Various instrumentation techniques have been used in the past for evaluating the apical extrusion of debris, but very few studies are reported in the literature comparing both debris and irrigant utilizing the reciprocating WaveOne instrumentation design.

The purpose of this ex vivo study was to compare and evaluate the amount of apically extruded debris and irrigant in freshly extracted human mandibular premolars with single canal by three different instrumentation techniques using ProTaper hand, M-two and WaveOne primary.

SUBJECTS AND METHODS

Thirty freshly extracted mandibular premolars with a patent single root canal, and fully formed apices were selected for the study. Teeth were immersed in 2.5% sodium hypochlorite for 2 h and then stored in 10% formalin for complete disinfection.

The calculi and soft tissue remnants on the external surface were removed with a periodontal curette. The teeth were observed under an operating microscope to confirm that they had a single apical foramen. The teeth were digitally radiographed from buccal, lingual and proximal views to ensure that they had single canals and orifices. Pulpal tissues were removed prior, making sure that the debris extruded was dentinal shavings and not pulpal remnants during the process of chemomechanical preparation. The buccal cusp edge of each tooth was flattened as a reference point, and coronal access was prepared conventionally using a high-speed bur.

To achieve uniformity, the canal patency was controlled with a size 15 K-file (Dentsply Maillefer, Ballaigues, Switzerland). The working length (WL) of each canal was determined as 1 mm short of the length of a size 15 K-file that was visible at the major diameter of the apical foramen. The teeth were randomly divided into three groups according to the file used for the preparation of root canals.

The groups were as follows:

• Group 1: ProTaper hand files (Dentsply Maillefer, Ballaigues, Switzerland) were used according to manufacturer's instructions using a gentle in and out motion. The instrumentation sequence was SX at two-third of the WL, S1 and S2 at 1 mm short of WL, and F1 and F2 at the WL already determined.

• Group 2: M-two Ni-Ti rotary instruments (VDW, Munich, Germany) were used in an Endodontic motor (X-mart plus, Dentsply Maillefer, Ballaigues, Switzerland) at 300 rpm. The standard set for this system includes number 10 to number 25, and tapers ranging from 0.04 to 0.06 (size 10/0.04 taper, size 15/0.05 taper, size 20/0.06 taper, size 25/0.06 taper). A glide path was established with a number 10 stainless steel K-type file, instruments taken at the WL already determined with light apical pressure. M-two instruments were used in a simultaneous technique without any early coronal enlargement.

• Group 3: The WaveOne Primary file, tip size ISO 25 (Dentsply Maillefer, Ballaigues, Switzerland) was used to prepare the canals. The WaveOne is a single file reciprocating system which works on balanced force technique and requires no change of file. The instrumentation was done in pecking motion and was completed up to the WL already determined.

In this study, the experimental model described by Myers and Montgomery was used.[9] Eppendorf tubes were used in the experiment and stoppers were separated from them. An analytical balance with an accuracy of 10⁻⁴ g was used to measure the initial weights of the tubes. Three consecutive weights were obtained for each tube, and the mean value was calculated. A hole was created on each stopper. Each tooth was cemented up to the cementoenamel junction, and a 27-G needle was placed alongside the stopper which helped as a drainage canula and maintained the air pressure inside and outside the tube.

Then, each stopper with the tooth and the needle was attached to its Eppendorf tube, and the tubes were fitted into vials. The Eppendorf tube was shielded by a rubber dam sheet to eliminate bias during chemomechanical preparation. In each sample, a total of 4 mL distilled water was used as an irrigant between the files (groups 1 and 2), between pecking sequences in (group 3).

Immediately after canal instrumentation, the Eppendorf tube was removed from the vial and volume of irrigant was measured. Calibrated Eppendorf tube was filled with saline and compared with experimental tube following the same method given by Myers and Montgomery. After the chemomechanical preparation was completed, the stopper, needle, and tooth were separated from the tube and debris adhering to the root surface was collected by washing the root with 0.5 mL of distilled water in the tube. The tubes were then stored in an incubator at 70°C for 2 days to evaporate the distilled water before weighing the dried debris. The tubes were weighed using the same analytical balance to obtain the final weight of tubes including the extruded debris. Three consecutive weights were obtained for each tube, and the mean was calculated. The dry weight of the extruded debris was calculated by subtracting the weight of the empty tube from that of the tube containing debris.

The mean dry weights of extruded debris were analyzed statistically using SPSS version 20.0 software (SPSS Inc., Chicago, IL, USA). The mean extrusion values and standard deviation for each group, median values and the range of extrusion (minimum and maximum) were evaluated.

Multiple group comparisons were analyzed by one-way analysis of variance followed by Student's t-test (unpaired) for pairwise comparisons. A P < 0.05 was considered for statistical significance.

RESULTS

The amount of apically extruded debris and irrigant was recorded for all the groups. The WaveOne reciprocating system showed the maximum amount of apical extrusion of debris and irrigant among all the groups. The least amount of debris and irrigant was observed in ProTaper hand instrument. The P value for each group was >0.05 showing that no significant difference existed among the groups. The mean values and standard deviations for all groups are listed in Table 1 along with the volume of irrigants in Table 2.

Table 1.

Mean weights and standard deviations of groups

Table 2.

Volume of irrigant solution using Myers and Montgomery's method (10^-2 ml precision)

DISCUSSION

Proper cleansing of the root canal space is considered essential for success in endodontics.[10] An acute inflammatory response may develop in the periradicular tissues as a result of insults from the root canal system, which can be mechanical, chemical, or microbial in origin.

Mechanical and chemical injuries are usually associated with iatrogenic factors, such as over-instrumentation, apical extrusion of debris or irrigant, perforations, etc.[5] Apical extrusion of contaminated debris into the periradicular tissues is one of the principal cause of mid treatment flare-up and postoperative pain.[3]

Many studies have looked at various aspects of apically extruded debris and irrigants. The results have shown that preparation up to the apex, the diameter of apical patency, the amount of irrigant used, formation of a dentin plug, the use of step-back versus crown-down technique, and the use of conventional hand filing versus rotary motion, all have a correlation to the amount of extruded debris.[4,6,8,11] Irrigation or chemical debridement is accepted as being a necessary aid in the chemomechanical cleansing of the root canal as irrigation assists in debris removal. More debris are removed when greater quantities of irrigating solutions are used.[5] Furthermore, the proximity of the irrigating needle to the apex plays an important role in removing the canal debris.[12]

A common finding of nearly all the studies in endodontic literature led to a generalized view that the crown-down technique extrudes less debris and irrigants apically as compared to the step-back technique[9] and that a linear filing motion extrudes more debris when compared to instruments used in rotational motion.[4]

In this study, we are comparing the volume of irrigant and debris extrusion by using hand and rotary file system with single and multiple files (Hand ProTaper, Rotary WaveOne and M-two). It must be emphasized that the results of this study directly focuses on a comparison between the different generations of new file system leading emphasis on the periapical extrusion by same.

Beeson et al. reported that, when the instrumentation was performed to the apical foramen, significantly more debris was forced apically than when instrumentation was done 1 mm short.[8]

Tanalp et al. reported an accumulation of 0.00153 g of apical debris using ProTaper system (ProTaper F3) with decoronated mandibular incisors.[13] The higher amount of collected debris compared with our data may be caused by the difference in teeth used and final finishing file, that is, mandibular premolars and ProTaper F2.

M-two is used in single length method in which all the instruments were used till WL and very small hand files are used for initial glide path. In M-two files, the distance between the cutting blades increases from the instrument tip to the shaft, the progressive pitch and absence of radial lands produce less dentinal debris. Space for dentin removal is deeper at the back of the blade. This reduces the risk of apical extrusion.[14]

The WaveOne files are manufactured with M-wire NiTi alloy, composed of 508 nitinol, under specific tensions and heat treatments at various temperatures.[15] These instruments work on the reciprocating action and simulate the Balanced Force Technique, as theorized by Roane and Sabala[16] Reciprocating motion provides the advantage of preserving complex canal anatomies as stated by Berutti et al.[17]

Gianluca et al. evaluated the incidence of postoperative pain when TF15, WaveOne, and TF Adaptive systems were used for chemomechanical preparation for root canals. They measured that the incidence of postoperative pain was significantly higher with the WaveOne single file reciprocating system.[18]

The present study agrees with the above literature as during comparative evaluation; WaveOne single file system showed the maximum amount of apical debris and irrigant extrusion when compared to ProTaper hand and M-two rotary. The reciprocation movement in WaveOne system is formed by a wider cutting angle and smaller release angle. While rotating in the release angle the flutes will not remove debris but push them apically. Moreover, WaveOne file is quite big, rigid with an increased taper (in the study 0.08 taper primary file is used which corresponds to ISO size 25) which is directed to reach the apex.[19]

Based on the results of this study, independent of the systems used, all instrumentation techniques produced debris and irrigant extrusion. Further studies should evaluate the behavior of newly introduced NiTi systems in complicated root canals.

CONCLUSION

With the given data and observations obtained in the sample size and limitations of the study, there was no statistical significant difference between the apical extrusion of debris and irrigant by all the instrumentation techniques. There was moderately lesser amount of debris and irrigant extrusion by ProTaper hand as compared to M-two rotary. Although all instrumentation techniques produced debris and irrigant, WaveOne single file reciprocating system showed the maximum amount of apical debris and irrigant extruded when compared to ProTaper hand and M-two rotary.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.