Comparison of apically extruded debris associated with several nickel-titanium systems after determining working length by apex locator.

BACKGROUND/AIM: To compare apically extruded debris using ProTaper Universal (PTU), ProTaper Next (PTN), WaveOne (WO), Twisted File (TF), M-Two (MT), and Revo-S (RS) after determining the working length (WL) with root ZX.
MATERIALS AND METHODS: Seventy-two teeth were selected. The WL determination was performed with root ZX. The teeth were divided into six experimental groups, randomly. In groups, root canals were prepared with PTU to size F4/0.06, with PTN to size X4/0.06, with WO to size 40/0.08, with TF to size 40/0.04, with MT to size 40/0.06, and with RS to size AS40/0.06. After preparations were completed, final irrigation was performed with 2 mL distilled water, and a total of 10 mL of distilled water was used in each tooth. Tubes were stored in an incubator at 68°C for 5 days to evaporate the distilled water before weighing the dry debris. Data were analyzed by the Mann-Whitney U-test.
RESULTS: The RS group led to the highest amount of extruded debris, however, WO led to the least amount of extruded debris. There was no statistically difference among the groups (P > 0.05).
CONCLUSIONS: The authors conclude that the results obtained might depend on the apex locator used to determine the WL.

INTRODUCTION

One of the main steps of the root canal treatment is to provide the suitable conditions for periapical tissues to heal up by biomechanical instrumentation of the root canal system.[1] During the instrumentation, necrotic debris, residual pulp tissue, microorganisms, dentin chips, or irrigation solutions could be forced through the apical terminus to the periapical area. This situation may cause an inflammatory reaction and postoperative pain which is known as “flare-up.”[2] Flare-up is a complication which occurs as a result of swelling/pain of oral mucosa or soft tissues on face around the area of the tooth within a few hours or days after treatment. This may result in an early visit to a healthcare institute from the patient since clinical symptoms are so intense.[34] It has been regarded that it is not possible to prevent some of debris to be pushed out to the apical tissues, and no method has been found yet that does so.[5] According to the results of detailed researches, it is not possible for practitioners to decrease the qualitative extrusion of debris, but it seems likely to keep a quantitative amount under control using techniques such as crown-down to reach apical terminus.[6] Al-Omari and Dummer[7] reported that techniques including a linear filing motion, such as step-back techniques, create more debris than those with some sort of rotational motion. Reddy and Hicks[8] were the first to compare apical debris extrusion between manual instrumentation and engine driving systems. They suggested that rotation during instrumentation tended to pack dentinal debris into the flutes of the instruments and directed them forward to the surface in both the engine-driven techniques and the balanced force technique. Meanwhile, in most studies, it was shown that the instrumentation with an in-and-out motion extruded more debris through the apical terminus in comparison to filing with a rotational motion.[9] Mechanized instrumentation minimizes extrusion when compared to manual instrumentation.[10]

Previous studies showed that recently developed apex locators helped make the determination of the apical constriction more accurate and predictable.[1112] Kara Tuncer and Gerek[12] reported that postoperative pain occurred less often after determining the working length (WL) with an apex locator than with digital radiography.

The null hypothesis was that no significant difference would be observed among the groups in terms of the mean weight of apically extruded debris when an apex locator (root ZX) was used to determine the WL.

Several studies have compared multiple nickel-titanium (NiTi) systems in terms of apically extruded debris, but in this study, we intended to compare apically extruded debris using ProTaper Universal (PTU, Dentsply/Maillefer, Ballaigues, Switzerland), ProTaper Next (PTN, Dentsply Maillefer, Ballaigues, Switzerland), WaveOne (WO, Dentsply Maillefer, Ballaigues, Switzerland), Twisted File (TF, SybronEndo, Orange, CA), M-Two (MT, VDW, Antaeus, Munich, Germany), and Revo-S (RS, Micro Méga, Besançon, France) after determining the WL with root ZX (J. Morita USA, Irvine, CA, USA).

MATERIALS AND METHODS

Seventy-two extracted, intact, human maxillary incisor teeth with straight root and canal were selected. All teeth were analyzed by digital radiography in buccal and proximal directions to confirm noncomplicated root canal anatomy, single root canals, and mature root formation. Soft tissue remnants, debris, and dental calculi were cleaned and stored in distilled water. After the access cavity was prepared, and the incisal surface of the teeth was straightened for obtaining a flat surface with a high-speed bur. Pulp remnants were extracted with a #25 barbed broach regardless of any instrumentation, and teeth were placed in a block full of alginate afterward. The WL determination was performed with an apex locator (root ZX) using #15 K-File. After the tooth was plugged-out from alginate, the root surface was cleaned of alginate remnants and divided into six experimental groups randomly.

Myers and Montgomery experimental model were used.[13] Stoppers were separated from Eppendorf tubes. An analytical balance with an accuracy of 10−5 was used to measure the preexperimental weights of the tubes 3 times each, and the mean values were calculated. A hole was prepared on each stopper, and teeth were placed up to the cemento-enamel junction along with a 27-gauge needle to balance air pressure inside and outside the tubes. The teeth were also fixed to the stoppers with cyanoacrylate. Stoppers were then attached to their Eppendorfs and tubes were fitted into the vials. Preparation and irrigation were performed by one operator to avoid variation and eliminate biases.

Group 1

Root canals were prepared with PTU instruments which were used at 300 rpm with 2 Ncm torque with a torque controlled endodontic motor (X-Smart, Dentsply Maillefer, Konstanz, Switzerland). An SX file was used at one-half of the WL, S1 and S2 files were used at two-thirds of the WL, and F1 (20/0.07), F2 (25/0.08), F3 (30/0.06), and F4 (40/0.06) files were used at full WL. SX, S1, and S2 were used with brushing motion meanwhile other files were used with a gentle in-and-out motion. Irrigation was performed after every file with distilled water with open ended needle.

Group 2

Root canals were prepared using PTN system with a gentle in-and-out motion at 300 rpm and 2 Ncm torque with a torque controlled endodontic motor. The first SX was used at one-half of the WL, and X1 (17/0.04), X2 (25/0.06), X3 (30/0.06), and X4 (40/0.06) were used at full WL.

Group 3

Root canals were prepared using a WO reciprocating file (40/0.08) with a gentle in-and-out pecking motion and a WO reciprocating motor (WO Endo Motor, Dentsply Maillefer). The WO motor was used with the manufacturer's configuration setup (The WO mode has 350 rpm). Irrigation was performed after every three pecks to prevent plugging of the canal with debris.

Group 4

Root canals were prepared using the TF instruments with a torque controlled endodontic motor. All the TF instruments were used to the WL according to the manufacturer's instructions using a gentle in-and-out motion (500 rpm). The instrumentation sequence was size 24, 0.04 taper, size 25, 0.06 taper, size 25, 0.08 taper, and enlargement was completed using size 30, 0.06 taper, size 35, 0.06 taper, and size 40, 0.04 taper.

Group 5

Root canals were prepared using an MT system with a torque controlled endodontic motor (300 rpm speed and 1.2 Ncm torque). (10/0.04), (15.05), (20/0.06), (25/06), (30/0.06), (35/0.06), and (40/0.06) files were used, and irrigation was performed between every file.

Group 6

Root canals were prepared with a torque controlled endodontic motor using RS NiTi instrument system, which includes three shaping instruments (300 rpm). The coronal two-third of the root canal were shaped and cleaned with an instrument (SC) number 1 (SC1). The SC2 and the universal shaper (SU) were used at the WL. AS30 (size 30, 0.06 taper), AS35 (size 35, 0.06 taper), and AS40 (size 40, 0.06 taper) were also used at the WL to provide apical enlargement to a size 40.

After preparations were completed, final irrigation was performed with 2 mL distilled water, and a total of 10 mL of distilled water was used in each tooth. The distilled water as an irrigation solution was used instead of sodium hypochlorite (NaOCl), since NaOCl could crystallize during the evaporation process. The teeth were removed from Eppendorf tubes. The apical part of the teeth was washed with distilled water to collect adhered debris at the root surface. Then tubes were stored in an incubator at 68°C for 5 days to evaporate the distilled water before weighing the dry debris. Tubes were weighed using the same analytical balance to obtain the final weight of the tubes including the extruded debris. Each tube was weighed 3 times, and the mean value was calculated. The dry weight of debris was calculated by subtracting the weight of empty tube from the weight of tube with extruded debris.

Statistical analyses

Descriptive and comparative statistics were performed using IBM SPSS v21 (SPSS Inc., Chicago, IL, USA). Differences among the groups were analyzed by the Mann-Whitney U-test. The value P < 0.05 was considered statistically significant for all tests. The distribution of the data was examined using the Shapiro-Wilk test. Variables are expressed as means ± standard deviation (SD).

RESULTS

The mean values and SDs for all groups are listed in Table 1. The apical debris extrusion were shown in all specimens, but there was no statistically difference among the groups in terms of weight of extruded debris (P > 0.05). The RS group led to the highest amount of extruded debris (P > 0.05). The PTU and TF groups caused a similar amount of extruded debris (P > 0.05), and the PTN and MT groups caused a similar amount of extruded debris (P > 0.05). On the other hand, the WO led to the least amount of extruded debris.

Table 1

Mean weights and standard deviations (SD) of apically extruded debris instrument by instruments

DISCUSSION

In the literature, there were several investigations associated with apical extrusion using NiTi instruments. In these studies, a commonly used method[131415] was preferred to collect apically extruded debris in this study. This methodology could be disadvantageous, since there is not any barrier to mimic the periodontal ligament against the apical extrusion. However, this situation may be overlooked, since this study aimed only to compare the file systems using this method.

To authors’ knowledge, no data were found about the comparison of the amount of apical extrusion caused by several NiTi systems on after determining an apex locator. The main objective of the current study was to compare the several rotary NiTi systems in terms of the amount of apically extruded debris after the WL were determined with the apex locator.

In the most of the studies,[16171819] the WL was determined with inspection using a hand file which is protruded until the apical major foramen. The WL was accepted as 1 mm from this length in studies. However, the WL should terminated at the apical minor foramen which is ranged from 0.3 to 3.80 mm out of the radiologic apex.[2021] In this study, thus, root ZX was used for determining the WL because of its high capable of determining of the apical minor foramen.

Previous studies have reported that apically extruded debris could be affected by the instrumentation technique, design, and taper differences of the instrument.[1617] Therefore, this study compared several NiTi systems which have different features such as design, taper, and instrumentation motion.

Gambarini et al.[22] reported that the TF causes less postoperative pain when compared with WO. On the other hand, Üstün et al.[18] demonstrated that WO extruded less debris than PTN and TF, and there was no difference found between the PTN–TF and WO–TF groups. In the same study, the researchers found the difference between the WO and PTN. Similarly, this study showed that WO caused less debris extrusion than the others, but the difference was not significant. These findings did not contradict the results of the study made by Bürklein et al.[17] They reported that Reciproc extruded significantly more debris than MT. This may be explained with WO and Reciproc having a different design. Capar et al.[19] have reported that the TF adaptive system extruded significantly less debris than the PTU. These results contradict our findings, in which TF and PTU extruded similar amount of debris. However, in the same study, they found the difference between the PTN and TF systems without any significance; this finding coincides with our results. In the two studies, there was a difference among the motions used for the TF systems, though Gambarini et al.[22] reported that there was no significant difference between TF and TF Adaptive.

Moreover, Tasdemir et al.[23] revealed that PTU extruded more debris than MT, and they found the difference between PTU and MT. Similarly, in this study, PTU extruded more debris than MT; however, there was no significant difference among them. In a previous study, it was found that the PTN system extruded significantly less debris than the PTU system.[24] However, in this study, the researchers found no significant difference between the PTU and PTN. Koçak et al.[14] demonstrated that RS and PTU caused similar amounts of apically extruded debris, and this finding confirmed our results. Moreover, the differences in the findings between the previous mentioned studies and this study could be explained with being used an apex locator in this study. This study demonstrated that there was statistically no significant difference among the tested NiTi systems; therefore, the hypothesis was accepted for this study. Nevertheless, these systems should be evaluated with further clinical studies to compare their clinical performance.

CONCLUSIONS

Within the limitations, this study showed that all the tested NiTi systems extruded debris. Although WO caused less debris than the other NiTi systems, there was no significant difference. The authors concluded that this situation might be dependent on the apex locator used to determine the WL.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.