SCANNING VOL. 37, 406–408 (2015) © Wiley Periodicals, Inc.
Micro Push-Out Bond Strength of Resin Cement in Roots Exhibiting the Butterfly Effect € ,1 ERTUGRUL KARATASS ,1 FATIH CAKICI,2 HAKAN ARSLAN,1 AHMET DEMIRHAN UYGUN,1 HICRAN ATESS GU¨NDUZ 1 AND MELTEM ALSANCAK 1 2
Department of Endodontics, Faculty of Dentistry, Atat€urk University, Erzurum, Turkey Department of Endodontics, Faculty of Dentistry, Ordu University, Ordu, Turkey
Summary: The aim of this study was to determine the bond strength of resin cement in root sections with or without butterfly effect. Fifteen single-rooted human maxillary central incisors were decoronated and prepared up to size 40. After post space preparation, the resin cement was placed into the post space and the fiber posts were luted. 1 mm thickness slices were obtained and the presence of the butterfly effect was recorded. A push-out test was then used to measure the bond strength between the resin cement and root dentin. Data were analyzed using independent samples of t and x2 tests (p ¼ 0.05). The sections exhibiting butterfly effect showed higher push-out bond strength values than those of without butterfly effect (p < 0.05). Butterfly effect can influence the push-out bond strength. Thus, this phenomena should be taken into account, when push-out bond strength test is performed. Root sections exhibiting butterfly effect resulted in higher push-out bond strength values to root sections without butterfly effect. SCANNING 37:406–408, 2015. © 2015 Wiley Periodicals, Inc. Key words: bond strength, butterfly effect, fiber post, resin cement
Introduction Butterfly effect is an optical phenomenon, which can be seen in some cross-sections of roots (Russell et al., 2013). According to Vasiliadis et al. (’83), dentinal
tubular sclerosis differs in the mesiodistal and buccolingual directions and this difference results in a butterfly shape in transverse sections of the roots. The dentinal tubules causes refract and scatter of the light (Vasiliadis et al., 2011). When the dentinal tubules decreased, the light transmission would increase resulting in translucent appearance (Russell et al., 2013). The available literature is limited about the butterfly effect. Russell et al. (2014) reported that root sections with the butterfly effect are harder mesiodistally. In a recent study by Kuci et al. (2014) butterfly effect was considered as a reason for increased sealer penetration in the buccolingual direction compared to the mesiodistal direction. Fiber-reinforced composites posts are popular for restoring insufficient tooth structure because of their elastic properties similar to those of dentin (Chieruzzi et al., 2012; Chuang et al., 2010). Several factors affect the retention of fiber-reinforced composite post within root canals, such as time of post space preparation and cementation, type of post and its adaptation to the post space, type of endodontic cement, adhesive and cementation system, and operative procedures (Alfredo et al., 2006; Jongsma et al., 2010). However, there is no available data whether the butterfly effect has an effect on the push-out bond strength of resin cement to root dentin or not. Thus, the purpose of our study was to investigate micro push-out bond strength of resin cement in roots with or without butterfly effect. The null hypothesis was that there would be no difference between the groups.
Materials and Methods Conflicts of interest: None. Address for reprints: Hakan Arslan, Department of Endodontics, Faculty of Dentistry, Atat€ urk University, Erzurum 25640, Turkey. E-mail address: [email protected]
Received 7 April 2015; revised 4 May 2015; Accepted with revision 11 May 2015 DOI: 10.1002/sca.21228 Published online 29 May 2015 in Wiley Online Library (wileyonlinelibrary.com).
Fifteen single-rooted human teeth with similar dimension were selected from a collection of teeth that had been extracted for reasons unrelated to this study. Thus, the ethical approval was not required. All of the teeth were stored in distilled water until they were used. Teeth were decoronated with diamond bur under water cooling to obtain a standardized root length of 14 mm. A #10 K-file (Dentsply Maillefer, Ballaigues,
Arslan et al.: Butterfly effect and bond strength
Representative images for sections (A) with butterfly effect, and (B) without butterfly effect.
Switzerland) was moved down into the root canal until the file was just visible. The length of the file was recorded, and the working length was determined as 1 mm less than this length. The roots were prepared by using ProTaper universal rotary instruments (Dentsply Maillefer) up to F4 (size 40) instrument. 2 mL of 2.5% NaOCl was used between instrument changes. The final irrigation protocol was performed using 5 mL of 17% EDTA for 1 min, 5 mL of 2.5% NaOCl, followed by 5 mL distilled water. The root canals were dried, and filled with AH Plus sealer (Dentsply DeTrey, Kontanz, Germany) and gutta-percha (Dentsply Maillefer) using cold lateral compaction technique. The roots were then stored at 37˚C and 100% humidity for 7 days. In experimental groups, the root canal filling material was removed using a heated plugger (size 2; VDW GmbH, Munich, Germany) prior to post space preparation. A 9-mm-deep post space preparation was performed, and the posts (Rebilda post, size 1.5, VOCO, Cuxhaven, Germany) were cemented into post space by using self-adhesive resin luting agent (Bifix SE; Voco). The roots were embedded in acrylic and sectioned perpendicular to the longitudinal axis of the root using a slow-speed diamond saw (Isomet; Buehler, Lake Bluff, IL) under water-cooling to obtain a thickness of 1 0.1 mm. Sixty sections were obtained from 15 bonded post. All sections were evaluated under stereomicroscope and 10 sections had the butterfly effect (Fig. 1). Ten sections were selected from samples without the butterfly effect by randomly. The micro push-out bond strength was performed using a universal TABLE I
testing machine (Instron Corp., Canton, MA) at a crosshead speed of 0.5 mm per minute. The maximum load at failure was recorded in Newtons and converted to MPa by dividing the load by the bonded area (A). The bonded area was calculated using the formulaﬃ pﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ A ¼ (pr1þ pr2) X L, where L ¼ ðr1 r2Þ2 þ h2, r1 is the smaller radius, r2 is the larger radius of the canal diameter (mm), h represents the thickness of the root section (mm) and p is the constant 3.14. After the test procedure, each specimen was visually examined under a stereomicroscope to evaluate failure mode. Three types of failure were classified: adhesive failure (between the cement and root dentin); cohesive fracture (within the dentin; cement layer; or post); and mixed (a combination of the two; cohesive and adhesive). Data were analyzed using independent sample t test (p ¼ 0.05). The failure mode data were analyzed using the x2 test (p ¼ 0.05). All statistical analyses were performed using IBM1 SPSS1 Statistics 20 software (IBM SPSS, Inc. Chicago, IL).
Results The mean of the micro push-out bond strength values (MPa) and standard deviations are presented in Table I. Independent sample t test of the micro push-out bond strength testing data revealed that samples having butterfly effect had significantly higher bond strength values than those of without butterfly effect (p < 0.05) (Fig. 2). Adhesive failure was the most determined
Bond strength standard deviation, and failure modes in the groups Failure modes
Bond strength standard deviation
Sections exhibiting butterfly effect Sections without butterfly effect
4.05 2.52a 3.03 0.26b
9 (90%) 10 (100%)
0 (0%) 0 (0%)
1 (10%) 0 (0%)
Different letters shows the statistically significant differences.
SCANNING VOL. 37, 6 (2015)
Fig 2. Bond strength values according to the groups. The sections exhibiting butterfly effect showed higher bond strength values than those of without butterfly effect (p < 0.05).
failure type among the specimens. There was no statistically significant difference between the groups in terms of failure type (p > 0.05).
Discussion According to a recent study by Russell et al. (2014) root sections with the butterfly effect have higher hardness scores. The butterfly effect can influence the micro pushout bond strength values of resin cement to root dentin. However, there is no available data in the current literature. The results of the present study revealed that the mean micro push-out bond strengths values were higher in root sections exhibiting butterfly effect than those of without butterfly effect. Thus, the null hypothesis that there would be no difference between the groups was rejected. The butterfly effect on the root sections is due to the dentinal tubular sclerosis in mesiodistal and buccolingual directions (Russell et al., 2014). The retention between the resinous material and dentin is provided by micromechanical retention from the collagen matrix in the intertubular dentin (Schwartz, 2006). Higher micro pushout bond strength values can be explained by the sclerotic areas. However, this is the first study in which the butterfly effect was evaluated in terms of micro push-out bond strength of resin cement. Thus, further studies should be conducted to confirm the findings of the present study.
Conclusion There have not been so many researches about the butterfly effect in the literature and its effects on the bonding mechanisms has been still unknown. According to the
results of the present study it can be concluded that the mean micro push-out bond strengths values were higher in root sections exhibiting butterfly effect than those of without butterfly effect. Because butterfly effect can influence the push-out bond strength, this phenomena should be taken into account in push-out bond strength tests.
References Alfredo E, de Souza ES, Marchesan MA, et al. 2006. Effect of eugenol-based endodontic cement on the adhesion of intraradicular posts. Braz Dent J 17:130–133. Chieruzzi M, Pagano S, Pennacchi M, et al. 2012. Compressive and flexural behaviour of fibre reinforced endodontic posts. J Dent 40:968–978. Chuang SF, Yaman P, Herrero A, Dennison JB, Chang CH. 2010. Influence of post material and length on endodontically treated incisors: an in vitro and finite element study. J Prosthet Dent 104:379–388. Jongsma LA, Bolhuis PB, Pallav P, Feilzer AJ, Kleverlaan CJ. 2010. Benefits of a two-step cementation procedure for prefabricated fiber posts. J Adhes Dent 12:55–62. Kuci A, Alacam T, Yavas O, Ergul-Ulger Z, Kayaoglu G. 2014. Sealer penetration into “dentinal tubules in the presence or absence of smear layer: a confocal laser scanning microscopic study. J Endod 40:1627–1631. Russell AA, Chandler NP, Hauman C, Siddiqui AY, Tompkins GR. 2013. The butterfly effect: an investigation of sectioned roots. J Endod 39:208–210. Russell AA, Chris He LH, Chandler NP. 2014. Investigation of dentin hardness in roots exhibiting the butterfly effect. J Endod 40:842–844. Schwartz RS. 2006. Adhesive dentistry and endodontics. Part 2: bonding in the root canal system-the promise and the problems: a review. J Endod 32:1125–1134. Vasiliadis L, Darling AI, Levers BG. 1983. The amount and distribution of sclerotic human root dentine. Arch Oral Biol 28:645–649. Vasiliadis L, Stavrianos C, Dagkalis P, et al. 2011. Translucent root dentine in relationship to increasing age: review of the literature. Res J Biol Sci 6:92–95.