Effectiveness of XP-endo Finisher, EndoActivator, and File agitation on debris and smear layer removal in curved root canals: a comparative study

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1 DOI /s ORIGINAL ARTICLE Effectiveness of XP-endo Finisher, EndoActivator, and File agitation on debris and smear layer removal in curved root canals: a comparative study Amr M. Elnaghy 1 Ayman Mandorah 2 Shaymaa E. Elsaka 3 Received: 15 January 2016 / Accepted: 27 April 2016 The Society of The Nippon Dental University 2016 Abstract The purpose of this study was to assess the efficacy of the XP-endo Finisher (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) file on debris and smear layer removal in curved root canals in comparison to different irrigation regimens. Seventy-five freshly extracted human mandibular molar teeth with mesial root curved more than 20 were used in this study. The mesial root canals were mechanically prepared using the BT-Race rotary system (FKG Dentaire) and divided into five groups (n = 15) according to the following irrigation techniques: positive control, non-agitated, File agitation, XP-endo Finisher, and EndoActivator (Dentsply Tulsa Dental Specialities, Tulsa, OK, USA). Root canals were split longitudinally and evaluated by scanning electron microscopy. Five-grade scoring system was used to assess the presence of debris and smear layer at the coronal, middle, and apical regions. The XP-endo Finisher and EndoActivator groups revealed significantly lower debris and smear layer scores than the other groups at the coronal, middle, and apical regions (P \ 0.05). There was no significant difference between XP-endo Finisher and EndoActivator groups (P [ 0.05). The apical region had higher debris and smear layer scores compared with the coronal regions in all groups (P \ 0.05), except for the positive control group; there was no significant difference between the three & Amr M. Elnaghy aelnaghy@mans.edu.eg Department of Endodontics, Faculty of Dentistry, Mansoura University, Mansoura 35516, Egypt Dental Department, King Faisal Hospital, Makkah, Saudi Arabia Department of Dental Biomaterials, Faculty of Dentistry, Mansoura University, Mansoura, Egypt regions of the root canal (P [ 0.05). Irrigation of curved root canals using XP-endo Finisher and EndoActivator methods appears to be more effective on debris and smear layer removal than the other tested groups. Keywords Curved root canals Debris EndoActivator Smear layer XP-endo Finisher Introduction The cleaning and shaping of root canals is a crucial step in root canal treatment procedures [1]. Shaping of root canals produces an irregular layer of debris, known as the smear layer, which is formed on the dentinal walls [2, 3]. It has been reported that the smear layer hindered the penetration of intracanal disinfectants [4] and sealers into the dentinal tubules, which may lead to compromising the seal of canal filling [5, 6]. A systematic review and meta-analysis [7] reported that the general agreement has proceeded toward preferring the removal of the smear layer. Several irrigating solutions have been used to decrease residual debris, bacteria, necrotic tissues and the smear layer which is formed by the mechanical instrumentation of the root canal system [4, 8]. Sodium hypochlorite (NaOCl) has become the most commonly used irrigating solutions in endodontics [9]. Alternative irrigant solutions including a deproteinizing agent, EDTA and a calcium chelating agent have been suggested for the effective removal of the smear layer [10, 11]. To enhance cleanliness, irrigants should be in contact with root canal [8]. The conventional syringe irrigation method delivers solutions no further than mm beyond the needle tip [12]. This method is inadequate for complete cleaning of the complex anatomy of root canal system including isthmus, fins, lateral and

2 accessory canals [13]. It has been introduced different irrigation devices to enhance the flow and distribution of irrigating solutions within the root canal system [13, 14], particularly at the apical third level. The EndoActivator System (Dentsply Tulsa Dental Specialities, Tulsa, OK, USA) is a sonically driven canal irrigation system that includes a portable handpiece and 3 types of disposable flexible polymer tips of different sizes that do not cut root dentin [15]. Recently, a new nickel titanium rotary finishing file has been developed called the XP-endo Finisher file (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland). The XP-endo Finisher file is supposed to be used after any root canal instrumentation to accomplish an enhanced cleaning of the root canal while conserving dentin. It has been reported that XP-endo Finisher curved bulb can expand its extent 6 mm in diameter when the file tip is squeezed or 100-times of a corresponding sized file [16, 17]. The XP-endo Finisher has a small core size (ISO 25 in diameter and zero taper) with improved flexibility. The XPendo Finisher file is formed using a proprietary NiTi alloy (Martensite-Austenite Electropolish-FleX). The XP-endo Finisher file performs at different temperature and is claimed to have a high flexibility [16, 17]. The aim of this study was to evaluate the effectiveness of the XP-endo Finisher file on debris and smear layer removal in curved root canals after biomechanical instrumentation in comparison to different irrigation regimens. The null hypothesis was that there is no statistically significant difference between the examined agitation methods. Materials and methods Selection and specimen preparation Seventy-five freshly extracted human mandibular molar teeth with mesial root curved more than 20 according to method of Schneider [18] were used in this study. Teeth were stored in 0.5 % chloramine-t at 4 C until use. Teeth were checked by radiographs to insure complete apex formation. The access cavity was prepared, and the mesial root was separated from the distal root using a low speed diamond saw (Isomet 1000, Buehler Ltd., Lake Bluff, IL, USA). The specimens were decoronated using a low speed diamond saw under water to achieve a standardized root length of 15 mm. The working length was established at 109 magnification using a surgical microscope (Global Surgical, St. Louis, MO, USA) by inserting size 10 K-file to root canal terminus and subtracting 1 mm from this measurement. The apex was sealed with sticky wax to prevent the irrigant solutions from escaping through the apex to simulate in vivo situations [19, 20]. The mesial root canals were mechanically prepared using the BT-Race rotary system (FKG Dentaire) and the Rooter-Endo-motor (FKG Dentaire) with 800 rpm and 1.5 N cm, under constant irrigation with 2.5 % NaOCl using 30-gauge needle (NaviTip; Ultradent, South Jordan, UT, USA). Biomechanical preparation of the root canals was instrumented as follows: 1. Glide path was established using ScoutRace #15/ BT1 #10/0.06, BT2 #35/0.00, and BT3 #35/0.04 files were used to the full WL. Then, the root canals were irrigated with 10 ml distilled water to prevent the extended effects of the NaOCl solution [21]. Final irrigation procedures After biomechanical preparation of the root canals, the specimens were divided randomly into 5 groups of 15 teeth each. The groups were as follows: Group 1 (n = 15): positive control; no final rinse and no additional agitation of the irrigant were performed. Group 2 (n = 15): non-agitated; final rinse with 5 ml 17 % EDTA (CanalPro, Coltene/Whaledent, Langenau, Germany) and no additional agitation of the irrigant was performed. Group 3 (n = 15): File agitation; 17 % EDTA was agitated with the BT2 file placed at the WL, with slight inand-out movements for 60 s. Group 4 (n = 15): XP-endo Finisher file; 17 % EDTA was agitated with XP-endo Finisher file which set at 800 rpm and advanced to the WL. Slow and gentle 7 8 mm lengthwise movements were made for 60 s. Group 5 (n = 15): EndoActivator (Dentsply Tulsa); 17 % EDTA was agitated with the EndoActivator red tip (25/0.04) at 10,000 cycles/min for 60 s. After EDTA agitation, the specimens in groups 2 5 were irrigated for 60 s with 1 ml 2.5 % NaOCl followed by a final rinse with 5 ml sterile saline solution. The root canals were then dried with size 35 paper points (FKG Dentaire), and the specimens were stored in 1.5 ml Eppendorf tubes [19]. Scanning electron microscopy analysis A diamond disc at low speed was used to groove the roots through the buccal and lingual surfaces. Then, the roots were split longitudinally with a chisel and mallet into 2 halves. For each specimen, the half enclosing the most visible part of the apex was selected and the other half was discarded. Then, each specimen was grooved to 3 levels from the root apices using a diamond bur to define the coronal, middle, and apical thirds [15]. The specimen was

3 dehydrated with ascending concentrations of ethyl alcohol ( %), and placed in a desiccator for 24 h. Each specimen was coated with gold and evaluated under a scanning electron microscope (SEM) (JEOL, JSM- 6510LV, JEOL Ltd., Tokyo, Japan). The photomicrographs from the apical to coronal thirds of the root of each specimen were taken at 4009 for debris and for smear layer evaluation [19]. The photomicrographs were analyzed by 2 examiners who were specialists in endodontics and were blind to group status. The presence of debris was evaluated by using the following scores: score 1; clean root canal wall and only few small debris particles, score 2; few small agglomerations of debris, score 3; many agglomerations of debris covering less than 50 % of the root canal wall, score 4; more than 50 % of the root canal wall covered by debris, and score 5; complete or nearly complete root canal wall covered by debris [19]. The presence or absence of a smear layer was evaluated using the following scores [20]: score 1; no smear layer and dentinal tubules open, score 2; small amounts of scattered smear layers and dentinal tubules open, score 3; thin smear layer and dentinal tubules partially open (characteristic image of crescent), score 4; partial covering with a thick smear layer, and score 5; total covering with a thick smear layer. This scoring system was applied to the coronal, middle, and apical thirds of the canal. Before scoring, the 2 examiners evaluated the first 30 specimens together for calibration purposes. The results were tabulated and submitted to statistical analysis [19]. Statistical analysis The data were analyzed using the Statistical Package for the Social Sciences, version 15 (SPSS, Chicago, IL, USA). The agreements between the 2 examiners regarding the debris and smear layer scores were evaluated with Cohen kappa. Comparisons between groups were analyzed statistically using the Kruskal Wallis nonparametric analysis of variance and Mann Whitney U tests. Statistical significance level was set at P \ Results Excellent agreement was revealed between the two examiners (K = 0.864). This suggests that there was reliability and reproducibility between the examiners. Table 1 shows the mean and standard deviation results of SEM analysis of the root canal walls regarding debris and smear layer scores. Debris and smear layer scores The results of debris and smear layer scores of tested groups are presented in Table 1. The XP-endo Finisher (group 4) and EndoActivator (group 5) revealed significantly lower debris and smear layer scores than the other groups at the coronal, middle, and apical regions (P \ 0.05). There was no significant difference between XP-endo Finisher and EndoActivator groups (P [ 0.05). Similarly, there was no significant difference between nonagitated and File agitation groups in debris and smear layer scores at the coronal, middle, and apical regions (P [ 0.05). A comparison between root canal regions, the apical region had higher debris and smear layer scores compared with the coronal regions in all groups (P \ 0.05), except for the positive control group; there was no significant difference between the three regions of the root canal (P [ 0.05). Figure 1 shows representative photomicrographs of smear layer of each group at the coronal, middle, and apical regions. A post hoc power analysis was performed using GPower v3.1.3 software (University of Düsseldorf; Düsseldorf, Germany), indicated that a total sample size of 75 specimens would have been needed to obtain power of Table 1 Debris and smear layer median scores for the tested groups Parameter Groups Positive control Non-agitated File agitation XP-endo Finisher EndoActivator Debris scores Coronal 5 Aa 3 Ba 3 Ba 2 Ca 2 Ca Middle 5 Aa 4 Bb 3 Ba 2 Ca 2 Ca Apical 5 Aa 4 Bb 4 Bb 3 Cb 2 Ca Smear layer scores Coronal 5 Aa 3 Ba 3 Ba 2 Ca 2 Ca Middle 5 Aa 4 Bb 4 Bb 3 Cb 2 Ca Apical 5 Aa 4 Bb 4 Bb 3 Cb 3 Cb Median values represented with common or same superscript uppercase letters (row) or lowercase letters (column) are not significantly different (P [ 0.05)

4 Fig. 1 Representative scanning electron microscope photomicrographs (10009) of smear layer of different tested groups at the coronal (C), middle (M) and apical (A) thirds Discussion The goal of the endodontic treatment is the elimination of microorganisms and the avoidance of reinfection. To accomplish this, root canals are cleaned before root canal obturation through mechanical instrumentation accompanied with irrigants and intracanal medications [22]. In cases of infected root canals, remaining debris and smear layer harbor microorganisms and their by-products [23]. The smear layer which is an amorphous and irregular layer is formed on root canal walls after instrumentation. Potential detrimental effects may happen if the smear layer is not removed throughout root canal treatment [19]. Microorganisms remaining in the smear layer after mechanical preparation of an infected root canal can survive and reinfect the canal [19]. It has been reported that the smear layer hindered the intracanal disinfectants and sealers from diffusion into dentinal tubules and has the possibility of diminishing the seal of the root canal filling [24, 25]. Syringe irrigation is a typical method for root canal irrigation; however, this method is not effective in the apical third of the root canal [26]. It is difficult to entirely eliminate the remaining debris and smear layer, especially in the apical third of the curved root canal due to the smaller size of the apical third compared with the other regions hinders the circulation and action of the irrigating solutions [27]. Consequently, the objective of this study was to assess the effectiveness of the XP-endo Finisher file in removing the debris and smear layer in curved root canals after biomechanical instrumentation in comparison to different irrigation regimens by using SEM. SEM is a valuable tool to assess the cleanliness of canal walls as it allows assessment of the whole segment of the canal on the basis of a distinct numeric evaluation score for debris and smear layer [1, 28, 29]. The results lead to the rejection of the null hypothesis since differences on debris and smear layer removal were found between the groups. The most generally used irrigant in endodontics is NaOCl as it has bactericidal effect and results in tissue dissolution [30]. Among other irrigants used during root canal preparation is EDTA. The efficiency of different concentrations of EDTA for smear layer removal has been investigated, and this generally considered as an effective procedure in the removal of the smear layer in comparison with other substances in the final irrigation [19, 24, 29]. Similarly, in the present study, the groups treated with EDTA revealed substantial debris and smear layer removal, irrespective of the technique used. XP-endo Finisher and EndoActivator groups resulted in more effective debris and smear layer removal than other groups. It has been reported that the EndoActivator system increases the efficiency of irrigation better than traditional needle irrigation [31]. It has polymer-based tips that do not damage the canal wall [32]. The finding in this study regarding the results of XP-endo Finisher file in debris and smear layer removal can be attributed to its metallurgy. The development and manufacture of XP-endo Finisher files are dependent on the shape-memory principles of the NiTi alloy. The file is straight in its martensitic phase which is formed when it is cooled. When the file is subjected to the body temperature (the canal) it will convert its shape because of its shape-memory to the austenitic phase.

5 It has been claimed by the manufacturer that the austeniticphase shape in the rotation mode permits the file to contact and clean areas that are otherwise difficult to reach with regular instruments. After the file has been cooled down, it can be returned manually to its original straight shape (martensitic phase) again [17]. Except for the positive control group, the results revealed that regardless of irrigation regimens used, the coronal thirds were significantly cleaner when compared with the apical one-third. This finding is in agreement with previous studies [24, 28, 33, 34]. This finding could be attributed to the larger diameter in these areas, exposing dentin to a higher volume of irrigants and making smear layer and debris removal easier [28, 34, 35]. It has been reported that the total removal of the smear layer happened only in root canal prepared to an apical diameter of minimum 0.30 mm [36]. In the present study, the last file used for the preparation of root canals was BT3 #35/0.04; which seems to be suitable for hydrodynamic flow [37]. Although the scoring method used in the present study involved qualitative analysis; it is a simple and direct scoring system, performed by calibrated examiners with concordance between them [32]. In addition, the large number of observations made, evidently increase the reliability of the results obtained [32, 38]. Conclusion Within the limitations of this study, it can be concluded that irrigation of curved root canals using XP-endo Finisher and EndoActivator methods seems to be more effective in the removal of debris and smear layer compared with other tested groups. None of the irrigation methods assessed in this study totally removed the debris and smear layer. Root canal cleanliness was noticeably improved in the coronal than in the apical root canal region. Future studies are required to confirm these introductory data and to assess the biofilm removal and apical disinfection. Acknowledgments The authors would like to thank FKG Dentaire SA for providing the materials used in this study. The authors deny any conflicts of interest related to this study. Compliance with ethical standards Conflict of interest The authors declare that they have no conflicts of interest. References 1. Metzger Z, Teperovich E, Cohen R, Zary R, Paqué F, Hülsmann M. The self-adjusting file (SAF). Part 3: removal of debris and smear layer-a scanning electron microscope study. J Endod. 2010;36: McComb D, Smith DC. A preliminary scanning electron microscopic study of root canals after endodontic procedures. J Endod. 1975;1: Byström A, Sundqvist G. Bacteriologic evaluation of the efficacy of mechanical root canal instrumentation in endodontic therapy. Scand J Dent Res. 1981;89: Orstavik D, Haapasalo M. 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