MICROSCOPY RESEARCH AND TECHNIQUE 00:00–00 (2015)

Evaluation of the Effect of Different Root Canal Obturation Techniques Using Two Root Canal Sealers on the Fracture Resistance of Endodontically Treated Roots IBRAHIM ERSOY,1* AND MEHMET SINAN EVCIL2 1 2

Department of Endodontics, Faculty of Dentistry, Sifa University, Izmir, Turkey Izmir Education Dental Hospital, Izmir, Turkey

KEY WORDS

AH plus; cold lateral condensation technique; MTA fillapex; single cone technique; system B; thermafill

ABSTRACT Aim. The aim of this study was to compare the fracture resistance of teeth filled with AH Plus and MTA Fillapex root canal sealers by using different root canal obturation techniques. Materials and Methods. One hundred and twenty pieces of single-rooted-and-canalled mandibular premolar teeth were selected. After the crowns were removed from the cemento-enamel junction, they were divided into 10 groups (n 5 12). All the root canals except for the Group 1 were shaped until F4 file with ProTaper Nickel- Titanyum (Ni-Ti) rotary system. Group 1: was not instrumented. Group 2: the root canals were shaped but not filled. Group 3: roots were filled with cold lateral condensation technique (CLC) by using AH Plus. Group 4: roots were filled with CLC by using MTA Fillapex. Group 5: roots were filled with single cone technique by using AH Plus. Group 6: roots were filled with single cone technique by using MTA Fillapex. Group 7: roots were filled with AH Plus by using vertical compaction method with continuous heat. Group 8: roots were filled with MTA Fillapex by using vertical compaction method with continuous heat. Group 9: roots were filled with AH Plus by using thermoplastic core carrier method. Group 10: roots were filled with MTA Fillapex by using thermoplastic core carrier method. Before embedding the samples in acrylic resin after standing in an oven at 37 C for 2 weeks for the hardening of the root canal sealers the 5 mm apical portion of the roots were immersed in wax in order to imitate the surrounding tissues. Polyvinyl siloxane impression material was used for the samples which were embedded in acrylic resin in a way that the coronal 8 mm remained outside in order to imitate the periodontal ligament. Lateral force was applied to the samples with 1 mm/min speed in the Universal Tester. The maximum force values (F-max) which cause fractures in the examples were determined and the results were subjected to statistical evaluation by using one-way Anova and Tukey HSD tests with the significance set at (P < 0.05). Results. The control group showed the maximum fracture resistance (P < 0.05). Thermafil group showed higher fracture resistance than single cone technique, cold lateral condensation technique, and system B (P < 0.05). Conclusions. It was concluded that shaping and widening of the root canals reduced the fracture resistance of teeth while Thermafil increased the resistance of roots against fracture. Microsc. Res. Tech. 00:000–000, 2015. V 2015 Wiley Periodicals, Inc. C

INTRODUCTION The success in the endodontic treatment depends on the cleaning, shaping, and disinfection of the root canals, not to allow any leakage (Bayırlı., 1991; Cunningham et al., 1982; Tauber et al., 1983; Wennberg et al., 1990; Timpawat et al., 2001). One of the biggest reasons for the failure of endodontic treatment in clinical practice is root fractures that may cause serious problems which may even lead to the removal of the teeth (Lam et al., 2005). Endodontically treated teeth are significantly prone to root fractures (Karapinar et al., 2009). It has been shown in many studies that during root canal treatment vertical root fracture occurred due to the operative procedures (Cohen et al., 2003). It has been reported that as a result of the mechanical and chemical preparation of the roots and excessive loss of C V

2015 WILEY PERIODICALS, INC.

material and force applied during root canal filling, the resistance of the roots against fracture reduces (Lam et al., 2005). The purpose of this study was to compare the effect of four different obturation techniques (single cone, cold lateral condensation technique, System-B, Thermafill) combined with two root canal sealers (AH Plus, MTA Fillapex) on the fracture resistance of root canals.

*Correspondence to: Ibrahim Ersoy, Department of Endodontics, Faculty of Dentistry, S¸ifa University, Izmir, Turkey. E-mail: [email protected] or [email protected] Received 20 November 2014; accepted in revised form 10 February 2015 REVIEW EDITOR: Dr. Francesca Cella Zanacchi DOI 10.1002/jemt.22487 Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com).

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MATERIALS AND METHODS One hundred and twenty noncarious, healthy, similar sized, single rooted, and single canal human mandibular premolars were used with complete root formation, extracted due to periodontal or prosthetic reasons. The soft tissues and residues on the teeth were cleaned. Teeth with more than one root canal and intracanal calcification justified with bucco-lingual and mesio-distal radiographs were excluded from the study. Then, they were examined with stereomicroscope (Novex, Arnhem, Netherlands) under 203 magnification in order to understand whether the root surface was cracked or fractured. Teeth with any fractures or cracks were eliminated and replaced by new teeth. Measurements were made in the area of cemento-enamel junction and 8 mm from the apex in both mesio-distal and bucco–lingual direction with an electronic caliper (Guangli, China) in order to standardize the samples. Teeth with 6.5 6 0.3 mm buccolingual diameter, 4.7 6 0.2 mm mesio-distal diameter of the enamel–cementum junction, and teeth ranging 4.8 6 0.3 mm in bucco-lingual diameter, 3.1 6 0.3 in mesio–diastal diameter in 8 mm from the apex of the enamel-cementum junction were included in the study. Teeth were stored in distilled water at room temperature until use. The length of the teeth were standardized by trimming the root length to 13 mm with a diamond bur (Zenith, Agerskov, Denmark) before starting the shaping of the root canals. After removing the pulp tissue with a barbed broach (Maillefer, Bellaigues, Switzerland) with a number 15 K-type canal device was pushed forward until the rasp tip appeared in the foramen apically by placing it into the root canal. The working length was adjusted 0.5 mm shorter than the obtained length. Then the teeth were randomly divided into 10 groups (n 5 12). Twelve randomly selected teeth were separated as control group (Group 1) in which no root canal preparation was performed. The teeth in experimental groups were washed with 3 mL 5% sodium hypochlorite (NaOCl) after a straight entry was made with a number 15 K-file on the root canals. A Gold Master (VDW GmbH, Munich, Germany) endodontic motor was used in order to widen the root canal and torque and rotational speed was adjusted for ProTaper according to recommendations of the manufacturer. The samples were extended until the f4 file of the ProTaper Universal system. After changing of each file the canals were washed with 3 mL 5% NaOCl solution (Wizard, Rehber Kimya san. Ve Tic. Istanbul, Turkey). Following the root canal preparations the root canals were washed first with 3 mL 5% NaOCl then with 3 mL 15% EDTA (Wizard, Rehber Kimya san Ve Tic Istanbul, Turkey) for 1 min then again with 3 mL 5% NaOCl solution in order to remove the smear layer. Finally, in order to terminate the activity of the solution the root canals were washed with 10 mL distilled water and dried with sterile paper points (Aceonedent, Geongg-do, Korea). At this stage 12 randomly selected teeth which were shaped but unfilled were isolated (Group 2). The remaining 96 teeth were randomly divided into eight groups (n 5 12). Later, Group 3 was filled with CLC using AH Plus. Group 4 was filled with CLC using MTA Fillapex. Group 5 was filled with

single cone technique using AH Plus. Group 6 was filled with single cone technique using MTA Fillapex. Group 7 was filled by using vertical compaction method with continuous heat and AH Plus. Group 8 was filled by using vertical compaction method with continuous heat and MTA Fillapex. Group 9 was filled with Thermoplastic core carrier method using AH Plus. Group 10 was filled with Thermoplastic core carrier method using MTA Fillapex. The coronal portions of all teeth were sealed with Cavit G (3M ESPE, Germany). Radiography was taken from the samples both in the mesio-distal and in bucco-lingual direction in order to ensure that the canals were fully filled. After being sure that the canals were filled fully the samples were kept in the oven at 37 C for 2 weeks. The samples were embedded in acrylic resin (IMICRYL, Konya, Turkey) in plastic cylinder molds prepared in 20 mm diameter and in 20 mm height for the fracture resistance test. Before embedding in acrylic resin 5 mm apical portions of the roots were immersed into molten wax in order to simulate the surrounding tissues and 0.2 to 0.3 mm periodontal ligament space was obtained. Later the samples were embedded in acrylic resin in a way so that a 8-mm portion of the coronal part remained outside. Before starting the polymerization by removing the samples, the wax on the root surface was cleaned with the help of a curette and these surfaces were covered with polyvinyl siloxane impression material (Elite HD, Zhermack, Italy) as a thin layer and were kept for polymerization by embedding them into acrylic resin again. The samples were placed into the sub fixing element of the Universal Tester device (InstronCorp, USA) for the fracture test. The steel end of the Instron test device was adjusted parallel to the long axis of the tooth and the tester was directed with a speed of 1 mm/min. At the fracture the displayed value was recorded in newton by stopping the test machine. According to these values the differences between the groups were analysed statistically by one-way analysis of variance and Tukey’s multiple comparison test (P < 0.05). RESULTS The fracture resistance of the samples in the Group 1 showed the highest value in all experimental groups with statistical significance (P < 0.05). The fracture resistance of the samples of the Group 9 (Thermafill1 AH Plus) and Group 10 (Thermafill1MTA Fillapex) had a statistically significantly higher fracture value (P < 0.05) than the other groups except the control group. The difference between the fracture resistance of the samples filled with CLC, single cone technique and System B filling technique were not statistically significant compared with each other and with Group 2 (P > 0.05). The highest fracture resistance values were observed in the control group. When comparing the root canal filling techniques the fracture resistance of the samples filled by the Thermafill filling technique with the other experimental groups (CLC, single cone technique, System B) was found to be highly significant statistically. Thermafill group gave the highest fracture resistance among all groups with statistical significance (P < 0.05) (Table 1). AH Plus and MTA Fillapex did not change the fracture resistance. The Microscopy Research and Technique

ROOT CANAL OBTURATION TECHNIQUES

Groups

TABLE 1. Fracture values and standard deviations N Mean 6 SS Min- Max

Control Group Shaped but not filled Cold Lateral Condensation1 AH Plus Cold Lateral Condensation 1 MTA Fillapex Single Cone1 AH Plus Single Cone 1 MTA Fillapex System B1 AH Plus System B1 MTA Fillapex Thermafil1 AH Plus 10-Thermafil1 MTA Fillapex

12 12 12

414 6 104 241 6 73 239 6 69

2782627 1312380 1452384

12

238 6 36

1842304

12 12 12 12 12 12

245 6 94 192 6 41 174 6 80 213 6 87 280 6 88 284 6 124

1472465 1272277 932362 772364 1572445 1242496

fracture line of One hundred and four out of 120 (%87) specimens was determined as bucco-lingual. The fracture line in 10 of the specimens (8%) was found both as bucco-lingual and proximal direction in 6 of the teeth (5%) the line was found to be proximal direction. DISCUSSION Strong occlusal forces or trauma can cause crown or root fractures, especially in root canal-treated teeth. Endodontic procedures causing more material losses and the dehydration of the dentin after endodontic treatment are the most common causes of this condition (Helfer et al., 1972; Teixeira et al., 2004). Various researches were conducted on the strengthening of the tooth structure after endodontic treatment and it was observed that none of the methods was completely adequate in preventing the tooth from fracture. When dental fracture arises, despite the treatment attempts on the fractured teeth the prognosis is usually not good (Johnson et al., 2000; Stewart et al., 1990; Trope et al., 1992; Yokoyama et al., 1998). In our work it was determined that after the fracture test approximately fracture line occurred buccolingually in 87% of the samples, both bucco-lingually and proximally in 8% of the samples and only proximally in 5% of the samples. The reason for this as Lertchirakarn (1999) mentioned also, is associated with the stress occurred likely in the samples due to the breaking test device. Schafer (2007) reported in their study in which root canals were not widened and root canals widened but not filled were compared that fracture resistance of nonwidened root canals were statistically significantly higher. In our study, statistically significant difference was found between the fracture resistance of widened and nonwidened groups. We associate this with the loss of tooth structure occurring during endodontic treatment. Zamin (2012) reported in their in vitro study in which they compared different root sealers that the root canal sealers did not increase the fracture resistance. In a study in which Sagsen (2012) examined the effect of root canal sealers on the fracture resistance of the teeth, the samples were filled by using Gutta Percha (GP)/AH Plus, GP/ I Root SP (Calsium silicate) and GP/MTA Fillapex (Calcium Silicate) root canal sealer with CLC and the fracture resistance of teeth were examined. There was not any statistically significant difference among the groups AH Plus, I Root SP, and MTA Fillapex in terms of fracture resistance. However, Microscopy Research and Technique

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there was statistically significant difference between the fracture resistance of filled either with one of these three sealers and widened but nonfilled specimens. This may be due to adhesive feature and sealing ability of AH Plus and chemical bonding ability of calcium silicate cements to root dentine. In a study by Williams (2006) it was stated that root canal sealers increased the fracture resistance of teeth a little and that actually the fracture resistance increased with core materials but that both the root canal sealers and the core material had less effect on the fracture resistance of dentin. In our work, AH Plus and MTA Fillapex were used as root canal sealers and we conclude that these two sealers did not have any effect on the fracture resistance of the samples. In another study evaluating the effect of spreader use on the fracture resistance of roots filled with lateral condensation technique, number 25 had the highest fracture resistance followed by 35 and 40 with statistical significance (Piskin et al., 2008). It was expressed in many studies that the fracture resistance of the roots reduced due to excessive removal of dentin in order to facilitate the usage of pluggers in heat condensation technique with vertical compaction and spreaders in cold lateral condensation technique (Lertchirakarn et al., 1999; Lindauer et al., 1989; Murgel et al., 1990). In this study it was determined that the cold lateral condensation techniques and the Obtura technique with continuous heat did not increase the fracture resistance of the teeth and we might suggest that the reason for this is the force which was created in the root canals by the spreader and plugger. According to our findings System B technique is one of the groups that showed the least fracture resistance and we believe that this is due to the force which was created by the plugger used and the heat applied caused thermal expansion in the root dentin and this affected the fracture resistance adversely. It was reported that the force applied to the roots in lateral condensation and Obtura techniques was twice as more as the force applied in Thermafill technique (Harvey et al., 1981). Saw and Messer (1995) reported in their study comparing the forces applied to the roots during the lateral condensation, Obtura and Thermafill techniques that the maximum force occurred during lateral condensational. It was reported that while placing the softened gutta-percha on the carrier into the canal it is condensed with a lower force. Saw and Messer reported in the same study that more thermal intensity occurred in Thermafill and Obtura groups and dentin showed more thermal intensity particularly in the coronal region while during cold lateral condensation technique more tension occurred especially in the apical region (Saw et al., 1995). In the work conducted by Teixeira (2004) statistically significant difference was not reported in the comparison of the fracture resistance between the teeth filled with cold lateral condensation or vertical condensation regardless of whether the root canal filling material was gutta-percha or resilon (Teixeira et al., 2004). It was reported that there was not any significant difference in the comparison of fracture resistance between the cold lateral condensation, System B and Thermafill by using AH 26 and it was reported that these

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techniques did not increase the root fracture resistance of teeth significantly (Topcuoglu et al., 2012). In a review carried out by Tang the articles about the effects of the root canal filling techniques on the fracture resistance of the teeth were examined. As a result, it was reported that in order to increase the fracture resistance of the endodontically treated teeth, root canal filling materials should steadily bond to the root canal wall and show flexibility similar to the elasticity modulus (Tang et al., 2010). Grande et al. (2007) report that the wide range in standard deviation is statistically acceptable and normal due to anatomical and morphological differences of extracted teeth and efforts to minimize these differences is highly important. According to our study we came to the conclusion that the samples filled by applying four different filling techniques and using AH Plus and MTA Fillapex are close to the fracture resistance of the dentin but the samples filled by the Thermafill filling technique increased the fracture resistance of the roots according to the CLC, single cone technique, and the obturation technique with continuous heat and this was concluded to be statistically significant. We believe that the reason for it is the core carrier used in Thermafill technique that supported the root dentin sufficiently and therefore it increased the fracture resistance of the roots. CONCLUSIONS According to the result of the present study, it was shown that AH Plus and MTA Fillapex were not effective on the fracture resistance of the roots, but Thermafill increased the fracture resistance of the roots. The cold lateral condensation, single cone, and System B root canal filling techniques did not increase the fracture resistance of the roots. Based on these results we suggest to develop techniques and materials that increase the fracture resistance of the roots in terms of the prognosis of the teeth and to conduct further researches. ACKNOWLEDGMENTS The authors deny any conflicts of interest. I affirm that I/We have no financial affiliation (e.g., employment, direct payment, stock holdings, retainers, consultantships, patent licensing arrangements or honoraria), or involvement with any commercial organization with direct financial interest in the subject or materials discussed in this manuscript, nor have any such arrangements existed in the past three years. REFERENCES Bayırlı G. 1991. Endodontik Tedavi, 1st ed. Istanbul: Istanbul University Press. pp. 387–441. Cohen S, Blanco L, Berman L. 2003. Vertical root fractures: Clinical and radiographic diagnosis. JADA 134:434–441.

Cunningham WT, Martin HA. 1982. Scanning electron microscope evaluation of root canal debridement with the endosonic ultrasonic synergistic system. Oral Surg Oral Med Oral Pathol 53:527–531. Grande NM, Plotino G, Lavorgna L, et al. 2007. Influence of different root canal filling materials on the mechanical properties of root canal dentin. J Endod 33:859–863. Harvey TE, White JT, Leeb IJ. 1981. Lateral condensation stress in root canals. J Endod 7:151–155. Helfer AR, Melnick S, Schilder H. 1972. Determination of the moisture content of vital and pulpless teeth. Oral Surg Oral Med Oral Pathol 34:661–670. Johnson ME, Stewart GP, Nielsen CJ, Hatton JF. 2000. Evaluation of root reinforcement of endodontically treated teeth. Oral Surg Oral Med Oral Pathol 90:360–364. Karapınar M, Sunay H,Tanalp J, Bayirli G. 2009. Fracture resistance of root using different canal filling systems. Int Endod J 42:705– 710. Lam PP, Palamaara JE, Messer HH. 2005. Fracture strength of tooth roots following canal preparation by hand and rotary instrumentation. J Endod 31:529–532. Lertchirakarn V, Palamara JE, Messer HH. 1999. Load and strain during lateral condensation and vertical root fracture. J Endod 25: 99–104. Lindauer PA, Campbell AD, Hicks ML, Pelleu GB. 1989. Vertical root fractures in curved roots under simulated clinical conditions. J Endod 15:345–349. Murgel CA, Walton RE. 1990. Vertical root fracture and dentine deformation in curved roots: The influence of spreader desing. Endod Dent Traumatol 6:273–278. Piskin B, Aydın B, Sarıkanat M. 2008. The effect of spreader size on fracture resistance of maxillary incisor roots. Int Endod J 41:54– 59. Sagsen B, Ustun Y, Pala K, Demirbuga S. 2012. Resistance to fracture of roots filled with different sealers. Dent Mater 31:528–532. Saw LH, Messer HH. 1995. Root strains associated with different obturation techniques. J Endod 21:314–320. Schafer E, Zandbiglari T, Schafer J. 2007. Influence of resin based adhesive root canal filling on the resistance to fracture of endodontically treated roots: An in vitro preliminary study. Oral Surg Oral Med Oral Pathol 103:274–279. Stewart GG. 1990. Clinical application of glass ionomer cements in endodontics: Case reports. Int Endod J 23:172–178. Tang W, Wu Y, Smales JR. 2010. Identifying and reducing risk for potential fractures in endodontically treated teeth. J Endod 36: 609–617. Tauber R, Morse DR, Sinai IA, Furst ML. 1983. A magnifying lens comparative evaluation of conventional and ultrasonically energized filling. J Endod 9:269–271. Teixeira FB, Teixeira EC, Thompson JY, Trope M. 2004. Fracture resistance of roots endodontically treated with a new resin filling material. JADA 135:646–652. Timpawat S, Amornchat C, Trisuwan W. 2001. Bacterial coronal leakage after obturation with three root canal sealers. J Endod 27:36– 39. Topcuoglu HS, Arslan H, Keles A, Koseoglu M. 2012. Fracture resistance of roots filled with different obturation techniques. Med Oral Patol Oral Cir Bucal 17:528–532. Trope M, Rosenberg ES. 1992. Multidisciplinary approach to the repair of vertically fractured teeth. J Endod 18:460–463. Wennberg A, Orstavik D. 1990. Adhesion of root canal sealers to bovine dentine and gutta-percha. Int Endod J 23:13–19. Williams C, Loushine RJ, Weller RN, Pashley DH, Tay FR. 2006. A comparision of cohesive strength and stiffness of resilon and guttapercha. J Endod 32:553–555. Yokoyama K, Matsumoto K, Kinoshita J, Sasaki H, Komori T. 1998. Treatment of maxillary molars with vertical fractures. Endod Dent Traumatol 14:287–289. Zamin C, Terezinha YC Silva-Souza, Evangelista A Souza- Gabriel, Messias DF, Souza-Neto DM. 2012. Fracture susceptibility of endodontically treated teeth. Dent Traumatol 28:282–286.

Microscopy Research and Technique

Evaluation of the effect of different root canal obturation techniques using two root canal sealers on the fracture resistance of endodontically treated roots.

The aim of this study was to compare the fracture resistance of teeth filled with AH Plus and MTA Fillapex root canal sealers by using different root ...
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