Basic Research—Technology
Effect of Calcium Hydroxide and Double and Triple Antibiotic Pastes on the Bond Strength of Epoxy Resin–based Sealer to Root Canal Dentin Merve Akcay, DDS, PhD,* Hakan Arslan, DDS, PhD,† H€ useyin Sinan Topcuoglu, DDS, PhD,‡ and Oznur Tuncay, DDS, PhD‡ Abstract Introduction: The aim of this study was to evaluate the effects of calcium hydroxide (CH) and triple (TAP) and double (DAP) antibiotic pastes on the bond strength of an epoxy resin–based sealer (AH Plus Jet; Dentsply DeTrey, Konstanz, Germany) to the root canal dentin. Methods: Sixty-four single-rooted human mandibular premolars were decoronated and prepared using the rotary system to size 40. The specimens were randomly divided into a control group (without intracanal dressing) and 3 experimental groups that received an intracanal dressing with either CH, DAP, or TAP (n = 16). The intracanal dressing was removed by rinsing with 10 mL 17% EDTA followed by 10 mL 2.5% sodium hypochlorite. The root canals were then obturated with guttapercha and AH Plus Jet sealer. A push-out test was used to measure the bond strength between the root canal dentin and the sealer. The data were analyzed using 2-way analysis of variance and Tukey post hoc tests to detect the effect of the independent variables (intracanal medicaments and root canal thirds) and their interactions on the push-out bond strength of the root canal filling material to the root dentin (P = .05). Results: The push-out bond strength values were significantly affected by the intracanal medicaments (P < .001) but not by the root canal thirds (P > .05). In the middle and apical third, the bond strength of the TAP group was higher than those of the CH and DAP groups (P < .05). Conclusions: The DAP and CH did not affect the bond strength of the epoxy resin– based sealer. Additionally, the TAP improved the bond strength of the epoxy resin–based sealer in the middle and apical thirds. (J Endod 2014;40:1663–1667)
Key Words Bond strength, calcium hydroxide, double antibiotic paste, minocycline, resin-based sealer, triple antibiotic paste
T
he elimination of bacteria and their byproducts from the root canal system is 1 of the goals of root canal treatment. Thus, the combination of the instrumentation associated with various irrigation solutions and medicaments has been suggested (1–3). Calcium hydroxide (CH) has been verified as the most frequently used medicament because of its antimicrobial efficacy against most bacterial species identified in endodontic infections (4). Because infections of the root canal system are regarded as polymicrobial (ie, consisting of different species of bacteria and other microorganisms), antibiotic combinations have also been suggested (5–7). Antibiotic pastes have been used for specific root canal treatments and pulpal revascularization treatment (6, 8). Triple antibiotic paste (TAP) has been found to have antimicrobial properties and to be biocompatible (9–12). It consists of ciprofloxacin, metronidazole, and minocycline and was developed by Hoshino et al (10). In a previous report by Er et al (6), the root canal of a mandibular premolar with a large periapical lesion was initially filled with CH paste. However, because of the enlargement of the periradicular lesion despite the medicament placement, they changed the treatment protocol, and the root canals were filled with TAP. The TAP was removed after 3 months, and the periapical lesion showed complete healing after 12 months. Taneja and Kumari (7) attempted to treat a tooth with an extensive periapical lesion; however, the treatment protocol was changed to the use of TAP as an intracanal medicament because the symptoms did not subside. They concluded that TAP can be used clinically in the treatment of teeth with extensive periradicular lesions. In the retreatment of a traumatized tooth that had already undergone unsuccessful apical resection associated with a large periradicular lesion by Kusgoz et al (5), it was shown that TAP can be used as an intracanal medicament in the treatment of an unsuccessfully resected tooth associated with a large periapical lesion. In another case report and case series, it was also confirmed that using TAP as an antibacterial dressing during traditional root canal treatment was successful in healing large cystlike periradicular lesions without using a surgical approach (13, 14). Moreover, 1 previous study with a large sample size (87 teeth) showed that TAP dissolved clinical symptoms such as swelling, sinus tracts, induced or spontaneous dull pain, and pain on biting after treatment in primary teeth with periradicular lesions (15). Because case reports and studies have shown that minocycline causes visible crown discoloration (16–18), minocycline was eliminated in a double antibiotic paste (DAP) that consists of only ciprofloxacin and metronidazole (19, 20). In addition to the undesired discoloration, another problem in the use of antibiotic pastes is that it is not possible to remove the pastes from the root canals completely, which could have an effect on the adhesion of endodontic sealers to the root canal dentinal walls (21).
From the *Department of Pediatric Dentistry, Faculty of Dentistry, _Izmir Katip C¸elebi University, _Izmir, Turkey; †Department of Endodontics, Faculty of Dentistry, Ataturk University, Erzurum, Turkey; and ‡Department of Endodontics, Faculty of Dentistry, Erciyes University, _Izmir, Turkey. Address requests for reprints to Dr Merve Akcay, Department of Pedodontics, Faculty of Dentistry, Katip C¸elebi University, Izmir, 35620, Turkey. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2014 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2014.05.006
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Basic Research—Technology In a recent study by Yassen et al (22), it was shown that CH and antibiotic pastes caused degradation or demineralization of the radicular dentin. In addition, several studies showed that CH negatively affected various mechanical properties of the radicular dentin (23–25), and the alkaline pH of the CH could cause neutralization and denaturation of dentin organic proteins (24). Adhesion of the sealers to the root canal dentin by close contact is important to resist micromechanical forces during root canal treatment (26). Numerous investigators have evaluated the adhesion of resin-based sealer to root dentin after the placement of CH as an intracanal medicament (27, 28). However, there are limited data about the effect of the antibiotic pastes on the adhesion of resin-based sealer to root dentin. Therefore, the aim of this study was to evaluate the effects of TAP, DAP, and CH on the bond strength of an epoxy resin–based sealer (AH Plus Jet; Dentsply DeTrey, Konstanz, Germany) to root canal dentin. The null hypothesis was that there would be no difference between the medicaments in terms of the push-out bond strength of the epoxy resin–based sealer.
Materials and Methods Mandibular premolars were selected from a collection of teeth that had been extracted for reasons unrelated to this study. The specimens were immersed in 0.5% Chloramine T solution (Merck, Darmstadt, Germany) for 48 hours for disinfection. They were then stored in distilled water until they were used. The soft tissue and calculus were removed mechanically from the root surfaces with a periodontal scaler. The teeth were verified radiographically as having a single root canal without calcification. The exclusion criteria consisted of a tooth having more than a single root canal and apical foramen, root canal treatment, internal/external resorption, immature root apices, caries/cracks/ fractures on the root surface, and/or root canal curvature of more than 10 . According to the aforementioned criteria, 64 mandibular premolar teeth with similar root lengths from the cementoenamel junction to the root apex were selected. The specimens were decoronated using a diamond disk to acquire a standardized root length of 15 mm. A size 10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) was placed in the canal until it was visible at the major apical foramen, and the working length was determined by subtracting 1 mm from this measurement. The root canals were prepared using ProTaper rotary instruments (Dentsply Maillefer) up to an F4 (size 40, .06 taper). The root canals were irrigated with 2 mL 2.5% sodium hypochlorite (NaOCl) (ImidentMed, Konya, Turkey) between the instrument changes. A final flush was applied using 5 mL 17% EDTA for 60 seconds and 5 mL 1% NaOCl for 60 seconds. The specimens were dried using paper points (Dentsply Maillefer) and were randomly divided into a control group (without intracanal dressing) and 3 experimental groups that received an intracanal dressing with either CH, DAP, or TAP (n = 16).
Preparation of Intracanal Medicaments In the CH group, the CH paste in this group was prepared by mixing CH powder (Kalsin; Spot Dis Deposu AS, Izmir, Turkey) and distilled water. In the DAP group, equal amounts of metronidazole (Eczacıbası, Istanbul, Turkey) and ciprofloxacin (Biofarma, Istanbul, Turkey) were mixed with distilled water. Equal amounts of metronidazole, ciprofloxacin, and minocycline (Ratiopharm, Ulm, Germany) were mixed with distilled water in the TAP group. The powder/liquid ratios of the pastes were 3:1 with similar concentrations as those used in the study by Hoshino et al (10). The prepared pastes were placed into the root canals using a size #40 Lentulo spiral. The coronal openings of the root canals were sealed with a small cotton pellet and temporary filling material 1664
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(META Biomed Co Ltd, Cheongju, Korea) to avoid leakage. The specimens were stored at 37 C in 100% humidity for 3 weeks to simulate clinical conditions (18, 21). After 3 weeks, the medicaments were rinsed with 10 mL 17% EDTA followed by 10 mL 2.5% NaOCl (21) and a final irrigation with 5 mL distilled water. Subsequent to the procedures, the root canal was dried using paper points (Dentsply Maillefer). A single guttapercha cone (F4, Dentsply Maillefer) was then slightly coated with an epoxy resin–based sealer (AH Plus Jet) and placed in the root canal to the working length. Because the root canals were prepared using rotary instruments up to F4 files, all specimens were obturated using the single technique with matching taper F4 gutta-percha cones to obtain standard specimens for the push-out test (27). Mesiodistal and buccolingual radiographs were taken to confirm complete filling. After root filling, the coronal opening was filled with a temporary filling material, and the specimens were stored at 100% humidity at 37 C for 1 week to completely set. Each specimen was sectioned perpendicular to its long axis using a precision saw (IsoMet 1000; Buehler, Lake Bluff, IL) at a slow speed under water cooling. Three slices were obtained from each tooth (n = 48 for each group) at depths of 4, 7, and 10 mm (apical, middle, and coronal) and approximately 1 0.1 mm thickness. The diameter of each hole from the apical and coronal aspects was measured under a stereomicroscope (Zeiss Stemi 2000C; Carl Zeiss, Jena, Germany) at 32 magnification. The push-out test was performed on each specimen with a universal test machine (AGS-X; Shimadzu Corp, Tokyo, Japan) at a crosshead speed of 1 mm/min using 0.6-, 0.7-, and 0.8-mm diameter cylindrical pluggers, matching the diameter of each canal third. The diameter of the pluggers was approximately (at least) 80% of the diameter of the canal. The maximum load applied to the filling material before failure was recorded in newtons and converted to megapascals (MPa) according to the following formula: push-out bond strength (MPa) = maximum load (N)/adhesion area of root filling (A) (mm2) The adhesion area of the root canal filling was calculated using the following equation: pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi A ¼ ðpr1 þ pr2ÞXL; 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 (29). After the test procedure, each specimen was visually examined under a stereomicroscope at 32 magnification to evaluate the failure type. Three types of failure were categorized: adhesive failure (between the sealer and root dentin), cohesive fracture (within the sealer or root dentin), and mixed (a combination of cohesive and adhesive) (30). The data were analyzed using 2-way analysis of variance and Tukey post hoc tests to detect the effect of the independent variables (intracanal medicaments and root canal thirds) and their interactions on the push-out bond strength of the root canal filling material to the root dentin (P = .05). The failure mode data were statistically analyzed using the chi-square test (P = .05). All statistical analyses were realized by using software (SigmaStat for Windows Version 3.5; Systat Software, Inc, Erkrath, Germany) at a significance level of .05 and a confidence interval of 95%.
Results Two-way analysis of variance indicated that the push-out bond strength values were significantly affected by the intracanal medicaments (P < .001) but not by the root canal thirds (P > .05). However, there were significant interactions between the intracanal medicaments and the root canal thirds (P = .003) (Table 1). JOE — Volume 40, Number 10, October 2014
Basic Research—Technology TABLE 1. Two-way Analysis of Variance for the Intracanal Medicaments, the Root Canal Thirds, and the Interaction According to the Push-out Bond Strength Data (P < .05) Source of variation
Sum of squares
df
Mean squares
F
P value*
Intracanal medicament Root canal third Intracanal medicament root canal third Total
116.562 14.113 113.916 1229.048
3 2 6 181
38.854 7.056 18.986 6.435
7.104 1.290 3.471
.05). In the middle third, the bond strengths after CH and DAP were similar to that of the control group, and the bond strength after TAP was also similar to that of the control group (P > .05). However, the bond strength of the TAP group was higher than those of the CH and DAP groups in the middle third (P < .05). In the apical third, the bond strength of the TAP group was higher than those of the control groups and the CH (P < .05) and DAP (P < .05) groups. The chi-square test showed no significant differences in the failure mode within the groups (P > .05), whereas adhesive failure between the resin sealer and dentin was the most frequent type of failure mode in all of the groups.
Discussion TAP has been used most often during revascularization procedures to disinfect the root canal system in necrotic immature teeth (8, 12, 19). Additionally, the paste can also be used traditionally in root canal treatment in infected root canals before root canal obturation with sealer because of its good antimicrobial properties (10). Many studies have reported that the conventional endodontic treatment of large cystlike periradicular lesions can be healed using TAP as an intracanal dressing without surgical endodontic treatment when using conventional endodontic treatment (6, 13, 14). Antibiotic pastes can influence the bond strength of the root filling negatively or positively. To the best of our knowledge, in the literature, there are no data about the effects of the antibiotic pastes on the adhesion of resin-based sealer to root dentin. Therefore, the aim of this study was to assess the effects of TAP, DAP, and CH on the bond strength of an epoxy resin–based sealer (AH Plus Jet) to root canal dentin. The null hypothesis was that there would be no difference between the medicaments in terms of the push-out bond strength of the epoxy resin–based sealer. However, our findings indicated that the bond strength of the TAP group was higher than those of the CH and DAP groups in the middle and apical thirds. Thus, the null hypothesis was rejected. The number and density of dentinal tubules varies along the root canal thirds (31). However, it has been reported that the alterations in
tubular density along the canal walls are unlikely to change the adhesion of root canal sealers (32). In the present study, an epoxy resin–based sealer was used, and the highest bond strength values in middle and apical thirds were observed in the TAP group. This could be caused by the fact that the epoxy resin–based sealers can react with exposed amino groups in collagen to create covalent bonds between the resin and collagen when the epoxide ring opens (33). Another factor of the increased bond strength in the apical region for TAP may be that the apical level has marked variations in structure, including irregular secondary dentin (even cementumlike tissue), accessory root canals, and areas of resorption or repaired resorption (34). Arslan et al (21) compared the efficacy of different irrigation protocols on the removal of TAP from artificial grooves in root canals in a recent study, and they showed that it was difficult to remove TAP from the root canals using irrigating solutions. In another current study, Berkhoff et al (35) showed that TAP was not effectively removed from the root canal systems, and more than 80% of the TAP is retained in the root canal system regardless of the irrigation technique used. Meanwhile, CH was effectively removed with significantly less residual presence; circumferentially, up to 350 mm of diffusion to the dentin of the TAP was also indicated in the same study. Investigators attributed these results to the penetration and binding into dentin of the TAP. Tanase et al (36) also indicated that minocycline in the TAP binds to calcium ions via chelation to form an insoluble complex in the tooth matrix. The highest bond strength values after TAP application could depend on a number of reasons, the most likely being the binding of residual minocycline to the calcium ions via chelation, which could increase bond strength after the application of TAP with minocycline. Moreover, the increasing bond strength of TAP may be related to less irrigant reaching the apex by the extension of a greater residual minocycline presence. In the present study, the residual antibiotic paste on the root canal walls was not evaluated. Future studies should be conducted to understand the mechanisms between the materials and residual minocycline. Limited data are available in the literature about the effects of antibiotic pastes on the bond strength of epoxy resin–based sealer to root dentin. Thus, the findings of this study can only be compared with the research in which the effects of various medicaments on the bond strength of root canal sealers were evaluated. Ustun et al (37) investigated the effects of CH and propolis intracanal medicament, which is
TABLE 2. Mean (standard deviation) of the Push-out Bond Strength Values (MPa) of the Root Canal Filling Material to the Root Dentin after Being Treated with Different Intracanal Medicaments According to the Root Canal Thirds Intracanal medicament Root canal third Coronal Middle Apical
Control A,a
5.11 (3.03) 3.49 (1.91)A,ab 3.37 (2.00)A,b
Calcium hydroxide A,a
3.44 (2.05) 2.98 (1.93)A,b 3.97 (1.88)A,b
DAP
TAP A,a
3.51 (1.22) 2.98 (2.13)A,b 3.29 (2.33)A,b
3.54 (1.66)A,a 5.43 (3.72)AB,a 6.83 (3.00)B,a
Mean values represented with the same lowercase letters (row) are not significantly different according to the Tukey test (P > .05). Mean values represented with the same uppercase letters (column) are not significantly different according to the Tukey test (P > .05).
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Basic Research—Technology Acknowledgments The authors deny any conflicts of interest related to this study.
References
Figure 1. Mean push-out bond strength values (MPa) of sealer to root canal dentin according to the different medicaments and the root canal thirds.
a complex mixture of resinous and balsamic substances collected from plants by honey bees, on the bond strength of epoxy resin–based sealer (AH Plus) to root dentin. They reported that no significant differences in bond strength were observed at the coronal and middle thirds, whereas the propolis group showed significantly superior push-out bond strength than the CH and control groups at the apical third. In the present study, the TAP group showed significantly superior push-out bond strength compared with the CH and DAP groups at the middle third as well as being superior to all of the groups in the apical third. This could be caused by a number of reasons, the most likely being the binding of minocycline to calcium ions via chelation, which may have provided the excellent adhesion and higher mean bond strength values that were observed in the TAP group (36). Amin et al (27) showed that prior CH placement did not affect the bond strength of an epoxy resin–based sealer (AH Plus). The finding in the present study that CH and DAP did not affect the bond strength of the epoxy resin–based sealer, and this finding was in agreement with that of the aforementioned study. A recent study showed that it was difficult to remove TAP from the root canals using irrigating solutions. Nevertheless, the researchers found that the use of 2.5% NaOCl improved the removal of TAP (21). In a different study by Rodig et al (38), the efficacy of different irrigating solutions in the removal of CH from the root canals was evaluated. According to those findings, chelating agents like citric acid and EDTA displayed the best results. Based on the findings of the aforementioned studies, in the present study, 10 mL 17% EDTA followed by 10 mL 2.5% NaOCl was used to remove intracanal medicaments. Antibiotic combinations, especially minocycline, could remain within the dentin. However, the possible undesirable effects are not yet known of the remaining medicaments. These remaining medicaments may induce drug-resistant bacteria or may lead to cytotoxic effects. Therefore, future studies should be conducted to optimize the most effective concentration and application time of the antibiotic combinations with the maximum antimicrobial effect and to investigate cytotoxicity.
Conclusions Within the limitations of the present study, it can be concluded that DAP and CH did not affect the bond strength of the epoxy resin–based sealer. However, TAP improved the bond strength of the epoxy resin– based sealer in the middle and apical thirds. 1666
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1. Estrela C, Holland R, Bernabe PF, et al. Antimicrobial potential of medicaments used in healing process in dogs’ teeth with apical periodontitis. Braz Dent J 2004;15: 181–5. 2. Nair PN. On the causes of persistent apical periodontitis: a review. Int Endod J 2006; 39:249–81. 3. Athanassiadis B, Abbott PV, Walsh LJ. The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics. Austr Dent J 2007;52: S64–82. 4. Bystrom A, Claesson R, Sundqvist G. The antibacterial effect of camphorated paramonochlorophenol, camphorated phenol and calcium hydroxide in the treatment of infected root canals. Endod Dent Traumatol 1985;1:170–5. 5. Kusgoz A, Yildirim T, Er K, Arslan I. Retreatment of a resected tooth associated with a large periradicular lesion by using a triple antibiotic paste and mineral trioxide aggregate: a case report with a thirty-month follow-up. J Endod 2009;35: 1603–6. 6. Er K, Kustarci A, Ozan U, Tasdemir T. Nonsurgical endodontic treatment of dens invaginatus in a mandibular premolar with large periradicular lesion: a case report. J Endod 2007;33:322–4. 7. Taneja S, Kumari M. Use of triple antibiotic paste in the treatment of large periradicular lesions. J Investig Clin Dent 2012;3:72–6. 8. Bezgin T, Yilmaz AD, Celik BN, Sonmez H. Concentrated platelet-rich plasma used in root canal revascularization: 2 case reports. Int Endod J 2014;47:41–9. 9. Sato I, Ando-Kurihara N, Kota K, et al. Sterilization of infected root-canal dentine by topical application of a mixture of ciprofloxacin, metronidazole and minocycline in situ. Int Endod J 1996;29:118–24. 10. Hoshino E, Kurihara-Ando N, Sato I, et al. In-vitro antibacterial susceptibility of bacteria taken from infected root dentine to a mixture of ciprofloxacin, metronidazole and minocycline. Int Endod J 1996;29:125–30. 11. Thibodeau B, Teixeira F, Yamauchi M, et al. Pulp revascularization of immature dog teeth with apical periodontitis. J Endod 2007;33:680–9. 12. Gomes-Filho JE, Duarte PC, de Oliveira CB, et al. Tissue reaction to a triantibiotic paste used for endodontic tissue self-regeneration of nonvital immature permanent teeth. J Endod 2012;38:91–4. 13. Ozan U, Er K. Endodontic treatment of a large cyst-like periradicular lesion using a combination of antibiotic drugs: a case report. J Endod 2005;31:898–900. 14. Taneja S, Kumari M, Parkash H. Nonsurgical healing of large periradicular lesions using a triple antibiotic paste: a case series. Contemp Clin Dent 2010;1:31–5. 15. Takushige T, Cruz EV, Asgor Moral A, Hoshino E. Endodontic treatment of primary teeth using a combination of antibacterial drugs. Int Endod J 2004;37:132–8. 16. Kim JH, Kim Y, Shin SJ, et al. Tooth discoloration of immature permanent incisor associated with triple antibiotic therapy: a case report. J Endod 2010;36: 1086–91. 17. Miller EK, Lee JY, Tawil PZ, et al. Emerging therapies for the management of traumatized immature permanent incisors. Pediatr Dent 2012;34:66–9. 18. Akcay M, Arslan H, Yasa B, et al. Spectrophotometric analysis of crown discoloration induced by various antibiotic pastes used in revascularization. J Endod 2014;40: 845–8. 19. Iwaya SI, Ikawa M, Kubota M. Revascularization of an immature permanent tooth with apical periodontitis and sinus tract. Dent Traumatol 2001;17:185–7. 20. Hargreaves KM, Diogenes A, Teixeira FB. Treatment options: biological basis of regenerative endodontic procedures. J Endod 2013;39:S30–43. 21. Arslan H, Capar ID, Saygili G, et al. Efficacy of various irrigation protocols on the removal of triple antibiotic paste. Int Endod J 2014;47:594–9. 22. Yassen GH, Chu TM, Eckert G, Platt JA. Effect of medicaments used in endodontic regeneration technique on the chemical structure of human immature radicular dentin: an in vitro study. J Endod 2013;39:269–73. 23. Sahebi S, Moazami F, Abbott P. The effects of short-term calcium hydroxide application on the strength of dentine. Dent Traumatol 2010;26:43–6. 24. Andreasen JO, Farik B, Munksgaard EC. Long-term calcium hydroxide as a root canal dressing may increase risk of root fracture. Dent Traumatol 2002;18:134–7. 25. Marending M, Stark WJ, Brunner TJ, et al. Comparative assessment of time-related bioactive glass and calcium hydroxide effects on mechanical properties of human root dentin. Dent Traumatol 2009;25:126–9. 26. Erickson RL. Surface interactions of dentin adhesive materials. Oper Dent 1992;(Suppl 5):81–94. 27. Amin SA, Seyam RS, El-Samman MA. The effect of prior calcium hydroxide intracanal placement on the bond strength of two calcium silicate-based and an epoxy resinbased endodontic sealer. J Endod 2012;38:696–9.
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Basic Research—Technology 28. Carvalho CN, Bauer J, Ferrari PH, et al. Influence of calcium hydroxide intracanal medication on bond strength of two endodontic resin-based sealers assessed by micropush-out test. Dent Traumatol 2013;29:73–6. 29. Prado M, Simao RA, Gomes BP. Effect of different irrigation protocols on resin sealer bond strength to dentin. J Endod 2013;39:689–92. 30. Nagas E, Uyanik MO, Eymirli A, et al. Dentin moisture conditions affect the adhesion of root canal sealers. J Endod 2012;38:240–4. 31. Tao L, Pashley DH. Shear bond strengths to dentin: effects of surface treatments, depth and position. Dent Mater 1988;4:371–8. 32. Babb BR, Loushine RJ, Bryan TE, et al. Bonding of self-adhesive (self-etching) root canal sealers to radicular dentin. J Endod 2009;35:578–82. 33. Lee KW, Williams MC, Camps JJ, Pashley DH. Adhesion of endodontic sealers to dentin and gutta-percha. J Endod 2002;28:684–8.
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34. Mjor IA, Smith MR, Ferrari M, Mannocci F. The structure of dentine in the apical region of human teeth. Int Endod J 2001;34:346–53. 35. Berkhoff JA, Chen PB, Teixeira FB, Diogenes A. Evaluation of triple antibiotic paste removal by different irrigation procedures. J Endod 2014;40:1172–7. 36. Tanase S, Tsuchiya H, Yao J, et al. Reversed-phase ion-pair chromatographic analysis of tetracycline antibiotics. Application to discolored teeth. J Chromatogr B Biomed Sci Appl 1998;706:279–85. 37. Ustun Y, Arslan S, Aslan T. Effects of calcium hydroxide and propolis intracanal medicaments on bond strength of resin-based endodontic sealer as assessed by pushout test. Dent Mater J 2013;32:913–9. 38. Rodig T, Vogel S, Zapf A, Hulsmann M. Efficacy of different irrigants in the removal of calcium hydroxide from root canals. Int Endod J 2010;43: 519–27.
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Effect of Calcium Hydroxide and Double and Triple Antibiotic Pastes on the Bond Strength of Epoxy Resin–based Sealer to Root Canal Dentin Merve Akcay, DDS, PhD,* Hakan Arslan, DDS, PhD,† H€ useyin Sinan Topcuoglu, DDS, PhD,‡ and Oznur Tuncay, DDS, PhD‡ Abstract Introduction: The aim of this study was to evaluate the effects of calcium hydroxide (CH) and triple (TAP) and double (DAP) antibiotic pastes on the bond strength of an epoxy resin–based sealer (AH Plus Jet; Dentsply DeTrey, Konstanz, Germany) to the root canal dentin. Methods: Sixty-four single-rooted human mandibular premolars were decoronated and prepared using the rotary system to size 40. The specimens were randomly divided into a control group (without intracanal dressing) and 3 experimental groups that received an intracanal dressing with either CH, DAP, or TAP (n = 16). The intracanal dressing was removed by rinsing with 10 mL 17% EDTA followed by 10 mL 2.5% sodium hypochlorite. The root canals were then obturated with guttapercha and AH Plus Jet sealer. A push-out test was used to measure the bond strength between the root canal dentin and the sealer. The data were analyzed using 2-way analysis of variance and Tukey post hoc tests to detect the effect of the independent variables (intracanal medicaments and root canal thirds) and their interactions on the push-out bond strength of the root canal filling material to the root dentin (P = .05). Results: The push-out bond strength values were significantly affected by the intracanal medicaments (P < .001) but not by the root canal thirds (P > .05). In the middle and apical third, the bond strength of the TAP group was higher than those of the CH and DAP groups (P < .05). Conclusions: The DAP and CH did not affect the bond strength of the epoxy resin– based sealer. Additionally, the TAP improved the bond strength of the epoxy resin–based sealer in the middle and apical thirds. (J Endod 2014;40:1663–1667)
Key Words Bond strength, calcium hydroxide, double antibiotic paste, minocycline, resin-based sealer, triple antibiotic paste
T
he elimination of bacteria and their byproducts from the root canal system is 1 of the goals of root canal treatment. Thus, the combination of the instrumentation associated with various irrigation solutions and medicaments has been suggested (1–3). Calcium hydroxide (CH) has been verified as the most frequently used medicament because of its antimicrobial efficacy against most bacterial species identified in endodontic infections (4). Because infections of the root canal system are regarded as polymicrobial (ie, consisting of different species of bacteria and other microorganisms), antibiotic combinations have also been suggested (5–7). Antibiotic pastes have been used for specific root canal treatments and pulpal revascularization treatment (6, 8). Triple antibiotic paste (TAP) has been found to have antimicrobial properties and to be biocompatible (9–12). It consists of ciprofloxacin, metronidazole, and minocycline and was developed by Hoshino et al (10). In a previous report by Er et al (6), the root canal of a mandibular premolar with a large periapical lesion was initially filled with CH paste. However, because of the enlargement of the periradicular lesion despite the medicament placement, they changed the treatment protocol, and the root canals were filled with TAP. The TAP was removed after 3 months, and the periapical lesion showed complete healing after 12 months. Taneja and Kumari (7) attempted to treat a tooth with an extensive periapical lesion; however, the treatment protocol was changed to the use of TAP as an intracanal medicament because the symptoms did not subside. They concluded that TAP can be used clinically in the treatment of teeth with extensive periradicular lesions. In the retreatment of a traumatized tooth that had already undergone unsuccessful apical resection associated with a large periradicular lesion by Kusgoz et al (5), it was shown that TAP can be used as an intracanal medicament in the treatment of an unsuccessfully resected tooth associated with a large periapical lesion. In another case report and case series, it was also confirmed that using TAP as an antibacterial dressing during traditional root canal treatment was successful in healing large cystlike periradicular lesions without using a surgical approach (13, 14). Moreover, 1 previous study with a large sample size (87 teeth) showed that TAP dissolved clinical symptoms such as swelling, sinus tracts, induced or spontaneous dull pain, and pain on biting after treatment in primary teeth with periradicular lesions (15). Because case reports and studies have shown that minocycline causes visible crown discoloration (16–18), minocycline was eliminated in a double antibiotic paste (DAP) that consists of only ciprofloxacin and metronidazole (19, 20). In addition to the undesired discoloration, another problem in the use of antibiotic pastes is that it is not possible to remove the pastes from the root canals completely, which could have an effect on the adhesion of endodontic sealers to the root canal dentinal walls (21).
From the *Department of Pediatric Dentistry, Faculty of Dentistry, _Izmir Katip C¸elebi University, _Izmir, Turkey; †Department of Endodontics, Faculty of Dentistry, Ataturk University, Erzurum, Turkey; and ‡Department of Endodontics, Faculty of Dentistry, Erciyes University, _Izmir, Turkey. Address requests for reprints to Dr Merve Akcay, Department of Pedodontics, Faculty of Dentistry, Katip C¸elebi University, Izmir, 35620, Turkey. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2014 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2014.05.006
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Basic Research—Technology In a recent study by Yassen et al (22), it was shown that CH and antibiotic pastes caused degradation or demineralization of the radicular dentin. In addition, several studies showed that CH negatively affected various mechanical properties of the radicular dentin (23–25), and the alkaline pH of the CH could cause neutralization and denaturation of dentin organic proteins (24). Adhesion of the sealers to the root canal dentin by close contact is important to resist micromechanical forces during root canal treatment (26). Numerous investigators have evaluated the adhesion of resin-based sealer to root dentin after the placement of CH as an intracanal medicament (27, 28). However, there are limited data about the effect of the antibiotic pastes on the adhesion of resin-based sealer to root dentin. Therefore, the aim of this study was to evaluate the effects of TAP, DAP, and CH on the bond strength of an epoxy resin–based sealer (AH Plus Jet; Dentsply DeTrey, Konstanz, Germany) to root canal dentin. The null hypothesis was that there would be no difference between the medicaments in terms of the push-out bond strength of the epoxy resin–based sealer.
Materials and Methods Mandibular premolars were selected from a collection of teeth that had been extracted for reasons unrelated to this study. The specimens were immersed in 0.5% Chloramine T solution (Merck, Darmstadt, Germany) for 48 hours for disinfection. They were then stored in distilled water until they were used. The soft tissue and calculus were removed mechanically from the root surfaces with a periodontal scaler. The teeth were verified radiographically as having a single root canal without calcification. The exclusion criteria consisted of a tooth having more than a single root canal and apical foramen, root canal treatment, internal/external resorption, immature root apices, caries/cracks/ fractures on the root surface, and/or root canal curvature of more than 10 . According to the aforementioned criteria, 64 mandibular premolar teeth with similar root lengths from the cementoenamel junction to the root apex were selected. The specimens were decoronated using a diamond disk to acquire a standardized root length of 15 mm. A size 10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) was placed in the canal until it was visible at the major apical foramen, and the working length was determined by subtracting 1 mm from this measurement. The root canals were prepared using ProTaper rotary instruments (Dentsply Maillefer) up to an F4 (size 40, .06 taper). The root canals were irrigated with 2 mL 2.5% sodium hypochlorite (NaOCl) (ImidentMed, Konya, Turkey) between the instrument changes. A final flush was applied using 5 mL 17% EDTA for 60 seconds and 5 mL 1% NaOCl for 60 seconds. The specimens were dried using paper points (Dentsply Maillefer) and were randomly divided into a control group (without intracanal dressing) and 3 experimental groups that received an intracanal dressing with either CH, DAP, or TAP (n = 16).
Preparation of Intracanal Medicaments In the CH group, the CH paste in this group was prepared by mixing CH powder (Kalsin; Spot Dis Deposu AS, Izmir, Turkey) and distilled water. In the DAP group, equal amounts of metronidazole (Eczacıbası, Istanbul, Turkey) and ciprofloxacin (Biofarma, Istanbul, Turkey) were mixed with distilled water. Equal amounts of metronidazole, ciprofloxacin, and minocycline (Ratiopharm, Ulm, Germany) were mixed with distilled water in the TAP group. The powder/liquid ratios of the pastes were 3:1 with similar concentrations as those used in the study by Hoshino et al (10). The prepared pastes were placed into the root canals using a size #40 Lentulo spiral. The coronal openings of the root canals were sealed with a small cotton pellet and temporary filling material 1664
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(META Biomed Co Ltd, Cheongju, Korea) to avoid leakage. The specimens were stored at 37 C in 100% humidity for 3 weeks to simulate clinical conditions (18, 21). After 3 weeks, the medicaments were rinsed with 10 mL 17% EDTA followed by 10 mL 2.5% NaOCl (21) and a final irrigation with 5 mL distilled water. Subsequent to the procedures, the root canal was dried using paper points (Dentsply Maillefer). A single guttapercha cone (F4, Dentsply Maillefer) was then slightly coated with an epoxy resin–based sealer (AH Plus Jet) and placed in the root canal to the working length. Because the root canals were prepared using rotary instruments up to F4 files, all specimens were obturated using the single technique with matching taper F4 gutta-percha cones to obtain standard specimens for the push-out test (27). Mesiodistal and buccolingual radiographs were taken to confirm complete filling. After root filling, the coronal opening was filled with a temporary filling material, and the specimens were stored at 100% humidity at 37 C for 1 week to completely set. Each specimen was sectioned perpendicular to its long axis using a precision saw (IsoMet 1000; Buehler, Lake Bluff, IL) at a slow speed under water cooling. Three slices were obtained from each tooth (n = 48 for each group) at depths of 4, 7, and 10 mm (apical, middle, and coronal) and approximately 1 0.1 mm thickness. The diameter of each hole from the apical and coronal aspects was measured under a stereomicroscope (Zeiss Stemi 2000C; Carl Zeiss, Jena, Germany) at 32 magnification. The push-out test was performed on each specimen with a universal test machine (AGS-X; Shimadzu Corp, Tokyo, Japan) at a crosshead speed of 1 mm/min using 0.6-, 0.7-, and 0.8-mm diameter cylindrical pluggers, matching the diameter of each canal third. The diameter of the pluggers was approximately (at least) 80% of the diameter of the canal. The maximum load applied to the filling material before failure was recorded in newtons and converted to megapascals (MPa) according to the following formula: push-out bond strength (MPa) = maximum load (N)/adhesion area of root filling (A) (mm2) The adhesion area of the root canal filling was calculated using the following equation: pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi A ¼ ðpr1 þ pr2ÞXL; 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 (29). After the test procedure, each specimen was visually examined under a stereomicroscope at 32 magnification to evaluate the failure type. Three types of failure were categorized: adhesive failure (between the sealer and root dentin), cohesive fracture (within the sealer or root dentin), and mixed (a combination of cohesive and adhesive) (30). The data were analyzed using 2-way analysis of variance and Tukey post hoc tests to detect the effect of the independent variables (intracanal medicaments and root canal thirds) and their interactions on the push-out bond strength of the root canal filling material to the root dentin (P = .05). The failure mode data were statistically analyzed using the chi-square test (P = .05). All statistical analyses were realized by using software (SigmaStat for Windows Version 3.5; Systat Software, Inc, Erkrath, Germany) at a significance level of .05 and a confidence interval of 95%.
Results Two-way analysis of variance indicated that the push-out bond strength values were significantly affected by the intracanal medicaments (P < .001) but not by the root canal thirds (P > .05). However, there were significant interactions between the intracanal medicaments and the root canal thirds (P = .003) (Table 1). JOE — Volume 40, Number 10, October 2014
Basic Research—Technology TABLE 1. Two-way Analysis of Variance for the Intracanal Medicaments, the Root Canal Thirds, and the Interaction According to the Push-out Bond Strength Data (P < .05) Source of variation
Sum of squares
df
Mean squares
F
P value*
Intracanal medicament Root canal third Intracanal medicament root canal third Total
116.562 14.113 113.916 1229.048
3 2 6 181
38.854 7.056 18.986 6.435
7.104 1.290 3.471
.05). In the middle third, the bond strengths after CH and DAP were similar to that of the control group, and the bond strength after TAP was also similar to that of the control group (P > .05). However, the bond strength of the TAP group was higher than those of the CH and DAP groups in the middle third (P < .05). In the apical third, the bond strength of the TAP group was higher than those of the control groups and the CH (P < .05) and DAP (P < .05) groups. The chi-square test showed no significant differences in the failure mode within the groups (P > .05), whereas adhesive failure between the resin sealer and dentin was the most frequent type of failure mode in all of the groups.
Discussion TAP has been used most often during revascularization procedures to disinfect the root canal system in necrotic immature teeth (8, 12, 19). Additionally, the paste can also be used traditionally in root canal treatment in infected root canals before root canal obturation with sealer because of its good antimicrobial properties (10). Many studies have reported that the conventional endodontic treatment of large cystlike periradicular lesions can be healed using TAP as an intracanal dressing without surgical endodontic treatment when using conventional endodontic treatment (6, 13, 14). Antibiotic pastes can influence the bond strength of the root filling negatively or positively. To the best of our knowledge, in the literature, there are no data about the effects of the antibiotic pastes on the adhesion of resin-based sealer to root dentin. Therefore, the aim of this study was to assess the effects of TAP, DAP, and CH on the bond strength of an epoxy resin–based sealer (AH Plus Jet) to root canal dentin. The null hypothesis was that there would be no difference between the medicaments in terms of the push-out bond strength of the epoxy resin–based sealer. However, our findings indicated that the bond strength of the TAP group was higher than those of the CH and DAP groups in the middle and apical thirds. Thus, the null hypothesis was rejected. The number and density of dentinal tubules varies along the root canal thirds (31). However, it has been reported that the alterations in
tubular density along the canal walls are unlikely to change the adhesion of root canal sealers (32). In the present study, an epoxy resin–based sealer was used, and the highest bond strength values in middle and apical thirds were observed in the TAP group. This could be caused by the fact that the epoxy resin–based sealers can react with exposed amino groups in collagen to create covalent bonds between the resin and collagen when the epoxide ring opens (33). Another factor of the increased bond strength in the apical region for TAP may be that the apical level has marked variations in structure, including irregular secondary dentin (even cementumlike tissue), accessory root canals, and areas of resorption or repaired resorption (34). Arslan et al (21) compared the efficacy of different irrigation protocols on the removal of TAP from artificial grooves in root canals in a recent study, and they showed that it was difficult to remove TAP from the root canals using irrigating solutions. In another current study, Berkhoff et al (35) showed that TAP was not effectively removed from the root canal systems, and more than 80% of the TAP is retained in the root canal system regardless of the irrigation technique used. Meanwhile, CH was effectively removed with significantly less residual presence; circumferentially, up to 350 mm of diffusion to the dentin of the TAP was also indicated in the same study. Investigators attributed these results to the penetration and binding into dentin of the TAP. Tanase et al (36) also indicated that minocycline in the TAP binds to calcium ions via chelation to form an insoluble complex in the tooth matrix. The highest bond strength values after TAP application could depend on a number of reasons, the most likely being the binding of residual minocycline to the calcium ions via chelation, which could increase bond strength after the application of TAP with minocycline. Moreover, the increasing bond strength of TAP may be related to less irrigant reaching the apex by the extension of a greater residual minocycline presence. In the present study, the residual antibiotic paste on the root canal walls was not evaluated. Future studies should be conducted to understand the mechanisms between the materials and residual minocycline. Limited data are available in the literature about the effects of antibiotic pastes on the bond strength of epoxy resin–based sealer to root dentin. Thus, the findings of this study can only be compared with the research in which the effects of various medicaments on the bond strength of root canal sealers were evaluated. Ustun et al (37) investigated the effects of CH and propolis intracanal medicament, which is
TABLE 2. Mean (standard deviation) of the Push-out Bond Strength Values (MPa) of the Root Canal Filling Material to the Root Dentin after Being Treated with Different Intracanal Medicaments According to the Root Canal Thirds Intracanal medicament Root canal third Coronal Middle Apical
Control A,a
5.11 (3.03) 3.49 (1.91)A,ab 3.37 (2.00)A,b
Calcium hydroxide A,a
3.44 (2.05) 2.98 (1.93)A,b 3.97 (1.88)A,b
DAP
TAP A,a
3.51 (1.22) 2.98 (2.13)A,b 3.29 (2.33)A,b
3.54 (1.66)A,a 5.43 (3.72)AB,a 6.83 (3.00)B,a
Mean values represented with the same lowercase letters (row) are not significantly different according to the Tukey test (P > .05). Mean values represented with the same uppercase letters (column) are not significantly different according to the Tukey test (P > .05).
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Basic Research—Technology Acknowledgments The authors deny any conflicts of interest related to this study.
References
Figure 1. Mean push-out bond strength values (MPa) of sealer to root canal dentin according to the different medicaments and the root canal thirds.
a complex mixture of resinous and balsamic substances collected from plants by honey bees, on the bond strength of epoxy resin–based sealer (AH Plus) to root dentin. They reported that no significant differences in bond strength were observed at the coronal and middle thirds, whereas the propolis group showed significantly superior push-out bond strength than the CH and control groups at the apical third. In the present study, the TAP group showed significantly superior push-out bond strength compared with the CH and DAP groups at the middle third as well as being superior to all of the groups in the apical third. This could be caused by a number of reasons, the most likely being the binding of minocycline to calcium ions via chelation, which may have provided the excellent adhesion and higher mean bond strength values that were observed in the TAP group (36). Amin et al (27) showed that prior CH placement did not affect the bond strength of an epoxy resin–based sealer (AH Plus). The finding in the present study that CH and DAP did not affect the bond strength of the epoxy resin–based sealer, and this finding was in agreement with that of the aforementioned study. A recent study showed that it was difficult to remove TAP from the root canals using irrigating solutions. Nevertheless, the researchers found that the use of 2.5% NaOCl improved the removal of TAP (21). In a different study by Rodig et al (38), the efficacy of different irrigating solutions in the removal of CH from the root canals was evaluated. According to those findings, chelating agents like citric acid and EDTA displayed the best results. Based on the findings of the aforementioned studies, in the present study, 10 mL 17% EDTA followed by 10 mL 2.5% NaOCl was used to remove intracanal medicaments. Antibiotic combinations, especially minocycline, could remain within the dentin. However, the possible undesirable effects are not yet known of the remaining medicaments. These remaining medicaments may induce drug-resistant bacteria or may lead to cytotoxic effects. Therefore, future studies should be conducted to optimize the most effective concentration and application time of the antibiotic combinations with the maximum antimicrobial effect and to investigate cytotoxicity.
Conclusions Within the limitations of the present study, it can be concluded that DAP and CH did not affect the bond strength of the epoxy resin–based sealer. However, TAP improved the bond strength of the epoxy resin– based sealer in the middle and apical thirds. 1666
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1. Estrela C, Holland R, Bernabe PF, et al. Antimicrobial potential of medicaments used in healing process in dogs’ teeth with apical periodontitis. Braz Dent J 2004;15: 181–5. 2. Nair PN. On the causes of persistent apical periodontitis: a review. Int Endod J 2006; 39:249–81. 3. Athanassiadis B, Abbott PV, Walsh LJ. The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics. Austr Dent J 2007;52: S64–82. 4. Bystrom A, Claesson R, Sundqvist G. The antibacterial effect of camphorated paramonochlorophenol, camphorated phenol and calcium hydroxide in the treatment of infected root canals. Endod Dent Traumatol 1985;1:170–5. 5. Kusgoz A, Yildirim T, Er K, Arslan I. Retreatment of a resected tooth associated with a large periradicular lesion by using a triple antibiotic paste and mineral trioxide aggregate: a case report with a thirty-month follow-up. J Endod 2009;35: 1603–6. 6. Er K, Kustarci A, Ozan U, Tasdemir T. Nonsurgical endodontic treatment of dens invaginatus in a mandibular premolar with large periradicular lesion: a case report. J Endod 2007;33:322–4. 7. Taneja S, Kumari M. Use of triple antibiotic paste in the treatment of large periradicular lesions. J Investig Clin Dent 2012;3:72–6. 8. Bezgin T, Yilmaz AD, Celik BN, Sonmez H. Concentrated platelet-rich plasma used in root canal revascularization: 2 case reports. Int Endod J 2014;47:41–9. 9. Sato I, Ando-Kurihara N, Kota K, et al. Sterilization of infected root-canal dentine by topical application of a mixture of ciprofloxacin, metronidazole and minocycline in situ. Int Endod J 1996;29:118–24. 10. Hoshino E, Kurihara-Ando N, Sato I, et al. In-vitro antibacterial susceptibility of bacteria taken from infected root dentine to a mixture of ciprofloxacin, metronidazole and minocycline. Int Endod J 1996;29:125–30. 11. Thibodeau B, Teixeira F, Yamauchi M, et al. Pulp revascularization of immature dog teeth with apical periodontitis. J Endod 2007;33:680–9. 12. Gomes-Filho JE, Duarte PC, de Oliveira CB, et al. Tissue reaction to a triantibiotic paste used for endodontic tissue self-regeneration of nonvital immature permanent teeth. J Endod 2012;38:91–4. 13. Ozan U, Er K. Endodontic treatment of a large cyst-like periradicular lesion using a combination of antibiotic drugs: a case report. J Endod 2005;31:898–900. 14. Taneja S, Kumari M, Parkash H. Nonsurgical healing of large periradicular lesions using a triple antibiotic paste: a case series. Contemp Clin Dent 2010;1:31–5. 15. Takushige T, Cruz EV, Asgor Moral A, Hoshino E. Endodontic treatment of primary teeth using a combination of antibacterial drugs. Int Endod J 2004;37:132–8. 16. Kim JH, Kim Y, Shin SJ, et al. Tooth discoloration of immature permanent incisor associated with triple antibiotic therapy: a case report. J Endod 2010;36: 1086–91. 17. Miller EK, Lee JY, Tawil PZ, et al. Emerging therapies for the management of traumatized immature permanent incisors. Pediatr Dent 2012;34:66–9. 18. Akcay M, Arslan H, Yasa B, et al. Spectrophotometric analysis of crown discoloration induced by various antibiotic pastes used in revascularization. J Endod 2014;40: 845–8. 19. Iwaya SI, Ikawa M, Kubota M. Revascularization of an immature permanent tooth with apical periodontitis and sinus tract. Dent Traumatol 2001;17:185–7. 20. Hargreaves KM, Diogenes A, Teixeira FB. Treatment options: biological basis of regenerative endodontic procedures. J Endod 2013;39:S30–43. 21. Arslan H, Capar ID, Saygili G, et al. Efficacy of various irrigation protocols on the removal of triple antibiotic paste. Int Endod J 2014;47:594–9. 22. Yassen GH, Chu TM, Eckert G, Platt JA. Effect of medicaments used in endodontic regeneration technique on the chemical structure of human immature radicular dentin: an in vitro study. J Endod 2013;39:269–73. 23. Sahebi S, Moazami F, Abbott P. The effects of short-term calcium hydroxide application on the strength of dentine. Dent Traumatol 2010;26:43–6. 24. Andreasen JO, Farik B, Munksgaard EC. Long-term calcium hydroxide as a root canal dressing may increase risk of root fracture. Dent Traumatol 2002;18:134–7. 25. Marending M, Stark WJ, Brunner TJ, et al. Comparative assessment of time-related bioactive glass and calcium hydroxide effects on mechanical properties of human root dentin. Dent Traumatol 2009;25:126–9. 26. Erickson RL. Surface interactions of dentin adhesive materials. Oper Dent 1992;(Suppl 5):81–94. 27. Amin SA, Seyam RS, El-Samman MA. The effect of prior calcium hydroxide intracanal placement on the bond strength of two calcium silicate-based and an epoxy resinbased endodontic sealer. J Endod 2012;38:696–9.
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Basic Research—Technology 28. Carvalho CN, Bauer J, Ferrari PH, et al. Influence of calcium hydroxide intracanal medication on bond strength of two endodontic resin-based sealers assessed by micropush-out test. Dent Traumatol 2013;29:73–6. 29. Prado M, Simao RA, Gomes BP. Effect of different irrigation protocols on resin sealer bond strength to dentin. J Endod 2013;39:689–92. 30. Nagas E, Uyanik MO, Eymirli A, et al. Dentin moisture conditions affect the adhesion of root canal sealers. J Endod 2012;38:240–4. 31. Tao L, Pashley DH. Shear bond strengths to dentin: effects of surface treatments, depth and position. Dent Mater 1988;4:371–8. 32. Babb BR, Loushine RJ, Bryan TE, et al. Bonding of self-adhesive (self-etching) root canal sealers to radicular dentin. J Endod 2009;35:578–82. 33. Lee KW, Williams MC, Camps JJ, Pashley DH. Adhesion of endodontic sealers to dentin and gutta-percha. J Endod 2002;28:684–8.
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34. Mjor IA, Smith MR, Ferrari M, Mannocci F. The structure of dentine in the apical region of human teeth. Int Endod J 2001;34:346–53. 35. Berkhoff JA, Chen PB, Teixeira FB, Diogenes A. Evaluation of triple antibiotic paste removal by different irrigation procedures. J Endod 2014;40:1172–7. 36. Tanase S, Tsuchiya H, Yao J, et al. Reversed-phase ion-pair chromatographic analysis of tetracycline antibiotics. Application to discolored teeth. J Chromatogr B Biomed Sci Appl 1998;706:279–85. 37. Ustun Y, Arslan S, Aslan T. Effects of calcium hydroxide and propolis intracanal medicaments on bond strength of resin-based endodontic sealer as assessed by pushout test. Dent Mater J 2013;32:913–9. 38. Rodig T, Vogel S, Zapf A, Hulsmann M. Efficacy of different irrigants in the removal of calcium hydroxide from root canals. Int Endod J 2010;43: 519–27.
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