MICROSCOPY RESEARCH AND TECHNIQUE 00:00–00 (2014)
Adhesive Interface and Bond Strength of Endodontic Sealers to Root Canal Dentine After Immersion in Phosphate-Buffered Saline MAYBELL TEDESCO, MARA CRISTINA SANTOS FELIPPE, WILSON TADEU FELIPPE, ANA MARIA HECKE ALVES, EDUARDO ANTUNES BORTOLUZZI, AND CLEONICE SILVEIRA TEIXEIRA* Department of Dentistry, Federal University of Santa Catarina, Florian opolis, Santa Catarina, CEP 88040-900, Brazil
KEY WORDS
adhesive interface; bond strength; endodontic sealers; scanning electron microscopy
ABSTRACT This study evaluated the bond strength (BS) and the adhesive interface of four endodontic sealers to root canal dentine, before, and after immersion in phosphate buffered saline (PBS) to simulate an in vivo environment. Eighty roots were instrumented using ProTaper rotatory files, under irrigation with 17% EDTA and 1% NaOCl. Posteriorly were divided into four groups (n 5 20) according to the sealer used: Endofill, AH Plus, Sealapex, and MTA Fillapex. Each group was divided into two subgroups (n 5 10) and stored at 37 C immersed in water for 7 days and in PBS for 60 days. From each subgroup, 1 mm thick sections were obtained. One section of each region (coronal, middle, and apical) was submitted to the push-out test and failures were observed. Twelve sections of each subgroup (four from each region) were evaluated under SEM. Three-way ANOVA evaluation for BS showed significant differences between groups and regions (P < 0.0001), but not between subgroups (P > 0.05). AH Plus had significantly higher BS than the others sealers, regardless of the analyzed subgroup (Tukey’s test, P < 0.5). The most common failures were adhesive to dentine and cohesive of the sealer. The SEM evaluation (Kruskal–Wallis, Mann–Whitney) showed homogeneous adhesive interface formed and sealer tags in all groups with significant statistical differences with AH Plus, regardless of PBS immersion. AH Plus was superior to the other sealers for both BS and quality of interface formation. Immersion in PBS did not interfere on BS or adhesive interface of the sealers tested. Microsc. Res. Tech. 00:000–000, 2014. V 2014 Wiley Periodicals, Inc. C
INTRODUCTION The success of endodontic treatment requires a tridimensional filling of the root canal systems with a nonirritating material (Gillen et al., 2011). Gutta percha has been the most commonly used material in combination with a sealer, and it can be used with different fillings techniques (Huffman et al., 2009; Lee et al., 2002; Sly et al., 2007). However, because it is difficult to seal the root canal completely, the association of gutta percha with different types of endodontic sealers has been widely studied (Gandolfi et al., 2013; Gesi et al., 2005). According to their composition, endodontic sealers can be classified as: zinc oxide-based, calcium hydroxide-based, glass ionomer-based, and resinbased (Assmann et al., 2011; Sagsen et al., 2011). More recently, mineral trioxide aggregate-based sealers (MTA) and bio aggregates, composed by bioceramics, have been used for root canal fillings (Gandolfi and Prati, 2010; Grech et al., 2013). One of the desirable properties of an endodontic sealer is the adhesion (Schwartz, 2006). The adhesion is defined as the sealer capacity to adhere to the root canal walls and the ability to promote the union of the core filling materials to each other and to the dentin C V
2014 WILEY PERIODICALS, INC.
lu et al., 2014). Sealer (Sousa-Neto et al., 2005; Topc¸uog penetration into dentinal tubules is considered potentially beneficial, and the adhesion to dentin is important to maintain the integrity of the sealer-dentin interface, especially in dynamic situations, during tooth flexure, operative procedures, or the preparation of post space (Shokouhinejad et al., 2011; Villanova et al., 2012). Push-out or micro-push out tests have been used to analyze the bond strength (BS) between dentin/sealer/ gutta percha, ultimately allowing the analysis of different regions of the root canal (Haragushiku et al., 2012; Huffman et al., 2009; Saghiri et al., 2010; Sagsen et al., 2011; Sly et al., 2007; Ungor et al., 2006; Vilanova et al., 2012). *Correspondence to: Cleonice Silveira Teixeira, Rua Haroldo Soares Glavan, 929, Condomınio Casa Blanca, casa 16, CEP: 88050-005, Cacupe, Florianopolis, SC, Brazil. E-mail: [email protected], [email protected] REVIEW EDITOR: Prof. Alberto Diaspro Received 12 May 2014; accepted in revised form 17 August 2014 Contract grant sponsor: Research Funding Agency of Santa Catarina State ‘FAPESC’; Contract grant number: TO 10027/2012-7. DOI 10.1002/jemt.22430 Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com).
2
M. TEDESCO ET AL.
TABLE 1. Endodontic sealers used in the experimental procedures, with their respective manufacturer, composition and batch number Sealer (Manufacturer) Composition Batch number Endofill (Denstply Ind. E Com., Petropolis, Brazil) AH plus (Denstply DeTrey, Konstanz, Germany) Sealapex (Sybron Endo/Kerr, Romulus, USA) MTA Fillapex (Angelus, Soluc¸~ oes, Odontologicas, Londrina, Brazil)
Zinc oxide; hydrogenated resin, bismuth subcarbonate, barium sulfate, sodium borate and eugenol and sweet almond oil. Paste A (epoxy)-Bisphenol-F epoxy, resin, bisphenol-F epoxy resin, calcium tungstate, zirconium oxide, silica, iron oxide pigments. Paste B: Dibenzyldiamine, Aminoadamantane, Tricyclodecanediamine, calcium tungstate, zirconium oxide, silica, and silicone oil. Isobultil salicylate, calcium hydroxide, barium sulphate, zinc oxide, titanium dioxide, zinc stearate Salicylate resin, resin diluent, Natural resin, bismuth oxide, silica nanoparticles, MTA, pigments
The analysis of the interaction between filling material and root dentin has been made by SEM and evaluated qualitatively as regards the adhesive interface formed and the penetration of endodontic sealers in the dentinal tubules (Haragushiku et al., 2012; Kokkas et al., 2004; Mamootil and Messer, 2007; Moradi et al., 2009). It has been argued that the depth penetration might be responsible to mechanical locking of the material due to sealer retention into tubules forming plugs. Researchers found that the immersion of specimens in the phosphate–buffered saline (PBS) may improve the BS of filling material to dentin, especially those specimens filled with MTA based sealers (Huffman et al., 2009; Reyes-Carmona et al., 2010). Besides, a SEM study showed greater depth of penetration of the AH26 sealer into dentinal tubules after 90 days immersion in PBS (Moradi et al., 2009).Therefore, the aim of this study was to evaluate ex vivo BS and adhesive interface of endodontic sealers to root canal dentin, through the push-out test and SEM, before and after immersion in PBS. The null hypothesis of this experiment is that the immersion in PBS does not affect the BS to dentin and the adhesive interface formation of several root canal sealers. MATERIAL AND METHODS Tooth Selection and Preparation The research project was previously approved by the “Research Ethics Committee” at the Federal University of Santa Catarina. Eighty extracted non-carious human maxillary central incisors were stored in 0.1% thymol solution at 4 C, pH 7, and used within 3 months after extraction. The teeth were radiographed in the mesiodistal direction and examined with stereoscopic lens with 43 magnification (Illuminated Magnifying Glass, Tokyo, Japan) with the objective of verifying the existence of a single, straight canal, apical foramen fully formed and free of cracks and imperfections. The crown of each tooth was removed 2 mm from the cementoenamel junction in coronal direction with a 0.15 diamond saw at slow speed (Isomet 1000; Buehler, Lake Bluff, IL). Working length was established at 1 mm from the apical foramen. Canals were prepared by a single operator in a crown-down manner using #4 to #2 Gates Glidden drills (Union Broach, York, PA), and rotary files (ProTaper Universal; Dentsply Maillefer, Ballaigues, Switzerland) were used incrementally up to a F5 rotary file. Patency of the apical foramen was maintained throughout the preparation, with a #15 FlexoFile (Dentsply Maillefer). Between the use of each instrument, canals were irrigated with 2 mL of 1% NaOCl. After final irrigation
365439C 0705000020
8-1319 16832
with 3 mL of 17% EDTA and 3 mL of 1% NaOCl, canals were dried with paper points. Next, the root canals were randomly divided into four groups (n 5 20), according to the sealer used for obturation: Group 1, Endofill (Dentsply Ind, Petropolis, RJ, Brazil); Group 2, AH Plus (Dentsply DeTrey, Konstanz, Germany); Group 3, Sealapex (Sybron Endo/Kerr, Romulus, USA) and Group 4, MTA Fillapex (Angelus Industry of Dentistry Products S/A, Londrina, Brazil). The composition, manufactures, and batch number of the endodontic sealers used in this experiment are shown in Table 1. The endodontic sealer was introduced in the root canal with a lentulo spiral (Dentsply Maillefer), and the filling was complemented using master and accessory gutta percha points by the cold lateral condensation technique (Dentsply Maillefer). After vertical compaction and placement of temporary sealing (Citodur; Dorident, Vienna, Austria), 10 roots in each group were stored in distillated water for 1 week (n 5 10, subgroups A) or in PBS solution (Dermus, Florianopolis, SC, Brazil) for 60 days (n 5 10, subgroups B) at 37 C, with renewal of the solution every 07 days. Push-Out Test and Failures Evaluation The specimens were individually taken to a precision cutting machine (Isomet 1000) and serially sectioned perpendicular to the long axis by using a watercooled diamond saw (South Bay Technology, San Clement, CA). Approximately two 1.0-mm thick slices were
Fig. 1. Areas of the filling material-dentine interface analyzed. Four distinct areas (point 1–4 of the sample) where examined by SEM.
Microscopy Research and Technique
INTERFACE AND BOND STRENGTH OF SEALERS AFTER PBS
3
TABLE 2. Analysis of variance of the factors sealers (Endofill, AH Plus, Sealapex, and MTA Fillapex), root regions (coronal, middle, and apical), and subgroups (7 days in water and 60 days in PBS) a 5 0.05 Variation source
Sum of squares
Degrees of freedom
Mean squares
F-value
P-valuea
220.664 4.290 60.826 11.531 31.211 8.169 31.487 526,856
3 1 2 3 6 2 6 216
73.555 4.290 30.413 3.844 5.202 4.084 5.248 2,439
30.156 1.759 12.469 1.576 2.133 1.675 2.151
0.05). The results about presence, quantity and depth penetration of the endodontic sealers are shown in Figure 3B, 4, and 5. AH Plus showed presence of dense and long sealer tags (100 lm), with significant statisti-
cal differences as compared with the other groups, in both subgroups, A (07 days in water, P < 0.0001) and B (60 days in PBS, P 5 0.003). The samples of groups Endofill (G1), Sealapex (G3), and MTA Fillapex (G4) showed statistically similar results (P > 0.05) in both subgroups. DISCUSSION The results of the push-out test showed that the null hypothesis cannot be totally accepted. The endodontic sealers had different BS means among themselves, regardless of the analyzed subgroup, with the best results being achieved by AH Plus. In addition to the sealer, the root canal region and the interaction between the sealer, region, and subgroup, were also significant. These results can be explained by the following events: treatment applied at the dentin surface; different composition of sealers; and anatomic diversity of root canals. In this experiment, the smear layer was removed previously to the root canal obturation. Smear layer removal is one of the factors that influence depth penetration of endodontic sealers (Lee et al., 2002). Studies demonstrate that the removal of this layer favors the intratubular penetration of the sealers, thus improving mechanical locking, a factor that increases dislodgement resistance when TABLE 4. Types of failures observed when comparing the groups, regardless of region of the canal after the push-out test and according to different subgroups (%) Immersion Adhesive Cohesive Mixed subgroup Groups (%) (%) (%) A (07 days)
B (60 days)
G1A G2A G3A G4A G1B G2B G3B G4B
56.67 30.00 53.33 36.67 63.33 40.00 33.33 56.67
40.00 70.00 40.00 63.33 33.34 53.33 60.00 40.00
3.33 – 6.67 – 3.33 6.67 6.67 3.33
Fig. 2. Bond strength means (MPa) and confidence interval of the sealers Endofill (G1); AH Plus (G2); Sealapex (G3); and MTA Fillapex (G4) in each experimental subgroup: A (07 days in water) and B (60 days in PBS), considering coronal, middle, and apical root thirds. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Microscopy Research and Technique
INTERFACE AND BOND STRENGTH OF SEALERS AFTER PBS
5
Fig. 3. Results of adhesive interface evaluation (A) and the sealer penetration evaluation, (B) observed in subgroups, (A) 7 days in water, and (B) 60 days in PBS. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
submitted to external forces and leakage of fluids (Eldeniz et al., 2005; Gesi et al., 2005; Haragushiku et al., 2012; Lee et al., 2002; Onay et al., 2009; Saghiri et al., 2010; Sagsen et al., 2011; Sevimay and Dalat., 2003; Sevimay and Kalayci, 2005; Sly et al., 2007; Ungor et al., 2006; Vilanova et al., 2012). However, the tenaciousness of the sealer to the dentin walls cannot be attributed only to depth penetration of the sealers into dentinal tubules, but also to frictional resistance of the filling material on the surrounding walls of the root canal (Goracci et al., 2005). Frictional resistance may explain, in part, the higher BS to dentin obtained after the push-out test in the apical third when AH Plus was used. The results of this research corroborate those of others studies, which also obtained high values of BS at the apical third of the root canal (Huffman et al., 2009; Sly et al., 2007). Such results are associated with high frictional resistance in this region, both due to anatomy and high pressure applied on the surface during root canal filling by the lateral compaction technique. It is known also that radicular dentin adhesion depends on factors which interact with gutta percha surface or dentin, such as surface tension of the sealer and its ability to penetrate the dentin (Eldeniz et al., 2005). Another relevant factor is the anatomic diversity of root canals. In some cases, even after endodontic preparation, the surface of dentin walls can differ widely, also at the same region of the root. This dentin substrate variability may also be the cause of the Microscopy Research and Technique
divergences of the BS results in the same sealer, which can promote high standard deviation, even after careful standardization of the tooth selected for the experiment. The AH Plus sealer revealed means of BS significantly higher than the other sealers, regardless of the analyzed subgroup. These results corroborate those of other studies which observed high BS values of AH Plus when as compared to other sealers based on: zinc oxide; resins; calcium hydroxide and MTA (Eldeniz et al., 2005; Fisher et al., 2007; Huffman et al., 2009; Nunes et al., 2008; Ungor et al., 2006). AH Plus is a sealer based on epoxic resin and amines. The epoxic resin present in AH Plus can react with the amine group of the collagen network and create a covalent bond between sealer and dentin (Fisher et al., 2008; Manicardi et al., 2011). Sealers based on zinc oxide and eugenol are still widely spread and used, although they have lower resistance to compression, high solubility, and low BS to dentin due to low cohesion of the molecules (Lee et al., 2002). Nevertheless, the results obtained by Endofill were similar to those showed by Sealapex and MTA Fillapex. This result might be explained, partly, by the removal of smear layer that allowed similar sealer penetration in dentinal tubules between these groups. Furthermore, low values of adhesion with Sealapex sealer can be explained by the low cohesive resistance to traction. The chemical reaction that occurs between the components of Sealapex, calcium hydroxide and glycol
6
M. TEDESCO ET AL.
Fig. 4. Images obtained by SEM (SE) and representative of AH Plus (G2A, 07 days in water). (A) Image of the middle third (325). The vestibular and palatal/lingual area represented by arrows in the specimens. (B) Higher magnification of the middle third (365). A large amount of tags could be seen. (C) Note the great amount of broken tags and the presence of bubbles in the sealer. (D) Higher magni-
fication of the demarcated area in (C) (31000). (E) Presence of long and dense tags. (F) Higher magnification of the demarcated area in (E) (31000). Note the presence of sealer lateral branches (arrow). The results on subgroup B (G2B, 60 days in PBS) were similar. GP: gutta percha S: sealer.
salicylate results in a molecule of disalicylate that does not bind to the dentin (Lee et al., 2002). According to the environment which the samples were kept immersed (water or PBS), there were no statistically differences among the subgroups, even when the MTA Fillapex was used. Materials based on MTA, when in contact with PBS, may originate carbonated apatite in a process called biomineralization, and may provide higher BS in the material dislodgement of the root canal (Bozeman et al., 2006). The BS of MTA Fillapex to dentin was statistically lower than AH Plus, even after immersion for 60 days in PBS.
In the present study, the sealers used in the root canal filling were tested by trying to simulate an in vivo environment. So, the entire roots were immersed in PBS with the filling sealed on this coronal portion with a temporary material. Only the apical foramen, with apical patency maintained, allowed contact of the filling material with PBS, providing limited access of solution. Studies show that the ability of MTA-based materials to generate carbonate apatite seems to be proportional to the available quantity of synthetic tissue fluid, such as PBS, ex vivo (Assmann et al., 2011) or in vivo (Dreger et al., 2012). In the Microscopy Research and Technique
INTERFACE AND BOND STRENGTH OF SEALERS AFTER PBS
7
Fig. 5. Images obtained by SEM (SE) and representative of Endofill (A, B), Sealapex (C, D), and MTA Fillapex (E, F). Subgroups A (7 days in water) and B (60 days in PBS) had similar results. (A) Specimen in which it was possible to detect the presence of gaps to dentine (3250), and (B) presence of few and short tags (31500). (C) The use of Sealapex provided many areas of interfacial gaps. (D) It was possible to notice the presence of many fractured tags (arrow) and cohesive
failure (star) of the sealer (31000). (E) With the use of MTA Fillapex many areas of gaps were noted, despite the amount of tags formed (3250). (F) Higher magnification of the demarcated area in (E). Note the dentine covered by sealer (cohesive failure of the material) and the presence of many tags with porous aspect (31000). S: sealer, De: dentine, GP: gutta percha.
study by Reyes-Carmona et al., 2010, the use of PBS improved the MTA BS to dentin. However, the samples were immersed in PBS after the cut, providing greater availability of the solution. The analysis of the failures modes, regardless of the sealer or the subgroup analyzed showed that most failures were adhesive or cohesive. The AH Plus sealer had a greater number of cohesive failures to the material in water or PBS, a fact that has been observed in other experiments (Lee et al., 2002; Ungor et al., 2006). The analysis of the samples by SEM showed clear images of the adhesive interface and the quantity of tags present in the samples. When evaluating the
quality of adhesive interface, gaps were observed in all sealers tested, although the use of AH Plus showed fewer gaps than the other sealers after 7 days in water. The failures observed at the interface by SEM might be generated during the chemical preparation of the samples (Teixeira et al., 2008). The solutions used to demineralize, fix or dissolve the organic tissue of the samples may affect the quality of the interface observed. Besides, in this study, the analyses were performed by direct visualization, and as the samples were placed on the microscope vacuum chamber, we cannot be sure that the gaps were not artifacts produced by the technique. The results of the evaluation
Microscopy Research and Technique
8
M. TEDESCO ET AL.
of the adhesive interface and presence of tags in subgroup B were similar to those obtained in subgroup A, in all groups analyzed. In relation to the penetration of the sealers into dentinal tubules, tags were observed in all groups. The absence of the smear layer probably improves deeper penetration of the sealers and greater density of tags (Bozeman et al., 2006; Haragushiku et al., 2012; Kokkas et al., 2004; Saghiri et al., 2010). The analysis showed that AH Plus had tags in greater quantity and depth than the others sealers. Also, it was observed greater quantity and depth of tags into dentinal tubules in buccal and lingual/palatal dentin orientations, with little quantity in the proximals. This characteristic was observed in other studies and explained by anatomical features and dentin tubule orientation (Mamootil and Messer, 2007; Moradi et al., 2009; Weis et al., 2004). CONCLUSIONS Within the limits of this study, it may be concluded that the immersion in PBS for 60 days did not affect the BS or the adhesive interface of the sealers analyzed. The use of AH Plus sealer promoted better results than Endofill, Sealapex, and MTA Fillapex. ACKNOWLEDGMENTS The authors deny any conflicts of interest related to this study. REFERENCES Assmann E, Scarparo RK, Bottcher DE, Grecca FS. 2011. Dentin bond strength of two mineral trioxide aggregate-based and one epoxy resin-based sealer. J Endod 38:219–221. Bozeman BT, Lemon RR, Eleazer PD. 2006. Elemental analysis of crystal precipitate from gray and white MTA. J Endod 32:425–428. Costa JA, Rached-J unior FA, Souza-Gabriel AE, Silva-Sousa YT, Sousa-Neto MD. 2010. Push-out strength of methacrylate resinbased sealers to root canal walls. Int Endod J 43:698–706. Dreger LAS, Felippe WT, Reyes-Carmona JF, Felippe GS, Bortoluzzi EA, Felippe MCS. 2012. Mineral trioxide aggregate and Portland Cement promote biomineralization in vivo. J Endod 38:324–329. Eldeniz UA, Erdemir A, Belli S. 2005. Shear bond strength of three resin based sealers to dentine with or without smear layer. J Endod 31:293–296. Fisher MA, Berzins DW, Bahcall JK. 2007. An in vitro comparison of bond strength of various obturation materials to root canal dentine using a push-out test design. J Endod 33:856–888. Gandolfi MG, Parrilli AP, Fini M, Prati C, Dummer PM. 2013. 3D micro-CT analysis of the interface voids associated with Thermafil root fillings used with AH Plus or a flowable MTA sealer. Int Endod J 46:253–263. Gandolfi MG, Prati C. 2010. MTA and F-doped MTA cements used as sealers with warm gutta percha Long-term study of sealing ability. Int Endod J 43:889–901. Gesi A, Raffaeli O, Goracci C, Pashley DH, Tay FR, Ferrari M. 2005. Interfacial strength of resilon and gutta percha to intraradicular dentine. J Endod 31:809–813. Gillen BM, Looney SW, Gu LS, Loushine BA, Weller RN, Loushine RJ, Pashley DH, Tay FR. 2011. Impact of the quality of coronal restoration versus the quality of root canal fillings on success of root canal treatment: a systematic review and meta-analysis. J Endod 37:895–902. Goracci C, Fabianelli A, Fadek ST, Papacchini F, Tay FR, Ferrari M. 2005. The contribution of friction to the dislocation resistance of bonded fiber posts. J Endod 31:608–612. Grech L, Mallia B, Camilleri J. 2013. Characterization of set intermediate restorative material, biodentine, bioaggregate and a prototype calcium silicate cement for use as root end filling materials. Int Endod J 46:1–10.
Haragushiku GA, Teixeira CS, Furuse AY, Sousa YTS, Sousa-Neto MD, Silva RG. 2012. Analysis of the interface and bond strength of resin based endodontic cement to root dentine. Micro Res Tech 75: 655–661. Huffman BD, Mai S, Pinnal Weller RN, Primus CM, Gutmann JL, Pashley DH, Tay FR. 2009. Dislocation resistance of ProRoot Endo Sealer, from radicular dentine. Int Endod J 42:34–46. Kokkas AB, Boutsioukis ACH, Vassiliadis LP, Stavrianos CK. 2004. The influence of the smear layer on dentinal tubules penetration depth of three different root canal sealers: an in vitro study. J Endod 30:100–102. Lee KW, Williams MC, Camps JJ, Pashley DH. 2002. Adhesion of endodontic sealers to dentine and gutta-percha. J Endod 28:684– 688. Mamootil K, Messer HH. 2007. Penetration of dentinal tubules by endodontic sealer cements in extracted teeth and in vivo. Int Endod J 40:873–881. Manicardi CA, Versiani MA, Saguy PC, Pecora JD, Sousa-Neto MD. 2011. Influence of filling materials on bonding interface of thinwalled root reinforced with resin and quartz-fiber posts. J Endod 37:531–537. Moradi S, Ghoddusi J, Forghani N. 2009. Evaluation of dentinal tubule penetration after the use of dentine bonding agents as a root canal sealer. J Endod 35:1563–1566. Nunes VH, Silva RG, Alfredo E, Sousa-Neto MD, Silva-Sousa YT. 2008. Adhesion of epiphany and AH Plus sealers to human dentine treated with different solutions. Brazil Dentistry J 19:46–50. Onay EO, Ungor M, Ari H, Belli S, Orgus E. 2009. Push-out bond strength and SEM evaluation of new polymeric root canal fillings. Oral Surg Oral Med Oral Pathol Oral Radiol Endodont 107:879– 885. Reyes-Carmona JE, Felippe M, Felippe WT. 2010. The biomineralization ability of mineral trioxide aggregate and portland cement on dentine enhances the push-out strength. J Endod 36:286–291. Saghiri MA, Shokouhinejad N, Lofti M, Aminsobhani M, Saghiri AM. 2010. Push-out bond strength of mineral trioxide aggregate in the presence of alkaline pH. J Endod 36:1856–1859. Sagsen B, Ustun Y, Demirbuga S, Pala K. 2011. Push-out bond strength of two new calcium silicate-based endodontic sealers to root canal dentine. Int Endod J 44:1088–1091. Schwartz RS. Adhesive dentistry and endodontics. 2006. Part 2: Bonding in the root canal system the promise and the problems: A review. J Endod 32:1125–1135. Sevimay S, Dalat D. 2003. Evaluation of penetration and adaptation of three different sealer a SEM study. J Oral Rehab 30:951–955. Sevimay S, Kalayci A. 2005. Evaluation of apical sealing ability and adaptation to dentine of two resin-based sealers. J Oral Rehab 32: 105–110. Shokouhinejad N, Sabeti M, GorjestanI H, Saghiri MA, Lofti M, Hoseini A. 2011. Penetration of epiphany, epiphany self-etch, and AH plus into dentinal tubules: A scanning electron microscopy study. J Endod 37:1316–1319. Sly MM, Moore K, Platt JA, Brown CE. 2007. Push-out bond strength of a new endodontic obturation system (Resilon/Epiphany). J Endod 33:160–162. Sousa-Neto MD, Silva Coelho FI, Marchesan MA, Alfredo E, SilvaSousa YT. 2005. Ex vivo study of the adhesion of an epoxy-based sealer to human dentine submitted to irradiation with Er: YAG and Nd: YAG lasers. Int Endod J 38:866–870. Teixeira CS, Felippe MC, Silva-Sousa YT, de Sousa-Neto MD. 2008. Interfacial evaluation of experimentally weakened roots restored with adhesive materials and fiber posts: An SEM analysis. J Dent 36:672–682. Topc¸uo glu HS, Demirbuga S, Tuncay O, Arslan H, Kesim B, Yasa B. 2014. The bond strength of endodontic sealers to root dentine exposed to different gutta-percha solvents. Int Endod J [Epub ahead of print]. Ungor M, Onay EO, Orucuglu U. 2006. Push-out bond strengths: the epiphany-resilon endodontic obturation system compared with different pairings of epiphany, resilon, AH plus and gutta-percha. Int Endod J 39:643–647. Vilanova WV, Carvalho-Junior JR, Alfredo E, Sousa-Neto MD, SilvaSousa YTC. 2012. Effect of intracanal irrigants on the bond strength of epoxy resin based and methacrylate resin based sealers to root canal walls. Int Endod J 45:42–48. Weis MV, Parashos P, Messer HH. 2004. Effect of obturation technique on sealer cement thickness and dentinal tubule penetration. Int Endod J 10:653–663.
Microscopy Research and Technique
Adhesive Interface and Bond Strength of Endodontic Sealers to Root Canal Dentine After Immersion in Phosphate-Buffered Saline MAYBELL TEDESCO, MARA CRISTINA SANTOS FELIPPE, WILSON TADEU FELIPPE, ANA MARIA HECKE ALVES, EDUARDO ANTUNES BORTOLUZZI, AND CLEONICE SILVEIRA TEIXEIRA* Department of Dentistry, Federal University of Santa Catarina, Florian opolis, Santa Catarina, CEP 88040-900, Brazil
KEY WORDS
adhesive interface; bond strength; endodontic sealers; scanning electron microscopy
ABSTRACT This study evaluated the bond strength (BS) and the adhesive interface of four endodontic sealers to root canal dentine, before, and after immersion in phosphate buffered saline (PBS) to simulate an in vivo environment. Eighty roots were instrumented using ProTaper rotatory files, under irrigation with 17% EDTA and 1% NaOCl. Posteriorly were divided into four groups (n 5 20) according to the sealer used: Endofill, AH Plus, Sealapex, and MTA Fillapex. Each group was divided into two subgroups (n 5 10) and stored at 37 C immersed in water for 7 days and in PBS for 60 days. From each subgroup, 1 mm thick sections were obtained. One section of each region (coronal, middle, and apical) was submitted to the push-out test and failures were observed. Twelve sections of each subgroup (four from each region) were evaluated under SEM. Three-way ANOVA evaluation for BS showed significant differences between groups and regions (P < 0.0001), but not between subgroups (P > 0.05). AH Plus had significantly higher BS than the others sealers, regardless of the analyzed subgroup (Tukey’s test, P < 0.5). The most common failures were adhesive to dentine and cohesive of the sealer. The SEM evaluation (Kruskal–Wallis, Mann–Whitney) showed homogeneous adhesive interface formed and sealer tags in all groups with significant statistical differences with AH Plus, regardless of PBS immersion. AH Plus was superior to the other sealers for both BS and quality of interface formation. Immersion in PBS did not interfere on BS or adhesive interface of the sealers tested. Microsc. Res. Tech. 00:000–000, 2014. V 2014 Wiley Periodicals, Inc. C
INTRODUCTION The success of endodontic treatment requires a tridimensional filling of the root canal systems with a nonirritating material (Gillen et al., 2011). Gutta percha has been the most commonly used material in combination with a sealer, and it can be used with different fillings techniques (Huffman et al., 2009; Lee et al., 2002; Sly et al., 2007). However, because it is difficult to seal the root canal completely, the association of gutta percha with different types of endodontic sealers has been widely studied (Gandolfi et al., 2013; Gesi et al., 2005). According to their composition, endodontic sealers can be classified as: zinc oxide-based, calcium hydroxide-based, glass ionomer-based, and resinbased (Assmann et al., 2011; Sagsen et al., 2011). More recently, mineral trioxide aggregate-based sealers (MTA) and bio aggregates, composed by bioceramics, have been used for root canal fillings (Gandolfi and Prati, 2010; Grech et al., 2013). One of the desirable properties of an endodontic sealer is the adhesion (Schwartz, 2006). The adhesion is defined as the sealer capacity to adhere to the root canal walls and the ability to promote the union of the core filling materials to each other and to the dentin C V
2014 WILEY PERIODICALS, INC.
lu et al., 2014). Sealer (Sousa-Neto et al., 2005; Topc¸uog penetration into dentinal tubules is considered potentially beneficial, and the adhesion to dentin is important to maintain the integrity of the sealer-dentin interface, especially in dynamic situations, during tooth flexure, operative procedures, or the preparation of post space (Shokouhinejad et al., 2011; Villanova et al., 2012). Push-out or micro-push out tests have been used to analyze the bond strength (BS) between dentin/sealer/ gutta percha, ultimately allowing the analysis of different regions of the root canal (Haragushiku et al., 2012; Huffman et al., 2009; Saghiri et al., 2010; Sagsen et al., 2011; Sly et al., 2007; Ungor et al., 2006; Vilanova et al., 2012). *Correspondence to: Cleonice Silveira Teixeira, Rua Haroldo Soares Glavan, 929, Condomınio Casa Blanca, casa 16, CEP: 88050-005, Cacupe, Florianopolis, SC, Brazil. E-mail: [email protected], [email protected] REVIEW EDITOR: Prof. Alberto Diaspro Received 12 May 2014; accepted in revised form 17 August 2014 Contract grant sponsor: Research Funding Agency of Santa Catarina State ‘FAPESC’; Contract grant number: TO 10027/2012-7. DOI 10.1002/jemt.22430 Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com).
2
M. TEDESCO ET AL.
TABLE 1. Endodontic sealers used in the experimental procedures, with their respective manufacturer, composition and batch number Sealer (Manufacturer) Composition Batch number Endofill (Denstply Ind. E Com., Petropolis, Brazil) AH plus (Denstply DeTrey, Konstanz, Germany) Sealapex (Sybron Endo/Kerr, Romulus, USA) MTA Fillapex (Angelus, Soluc¸~ oes, Odontologicas, Londrina, Brazil)
Zinc oxide; hydrogenated resin, bismuth subcarbonate, barium sulfate, sodium borate and eugenol and sweet almond oil. Paste A (epoxy)-Bisphenol-F epoxy, resin, bisphenol-F epoxy resin, calcium tungstate, zirconium oxide, silica, iron oxide pigments. Paste B: Dibenzyldiamine, Aminoadamantane, Tricyclodecanediamine, calcium tungstate, zirconium oxide, silica, and silicone oil. Isobultil salicylate, calcium hydroxide, barium sulphate, zinc oxide, titanium dioxide, zinc stearate Salicylate resin, resin diluent, Natural resin, bismuth oxide, silica nanoparticles, MTA, pigments
The analysis of the interaction between filling material and root dentin has been made by SEM and evaluated qualitatively as regards the adhesive interface formed and the penetration of endodontic sealers in the dentinal tubules (Haragushiku et al., 2012; Kokkas et al., 2004; Mamootil and Messer, 2007; Moradi et al., 2009). It has been argued that the depth penetration might be responsible to mechanical locking of the material due to sealer retention into tubules forming plugs. Researchers found that the immersion of specimens in the phosphate–buffered saline (PBS) may improve the BS of filling material to dentin, especially those specimens filled with MTA based sealers (Huffman et al., 2009; Reyes-Carmona et al., 2010). Besides, a SEM study showed greater depth of penetration of the AH26 sealer into dentinal tubules after 90 days immersion in PBS (Moradi et al., 2009).Therefore, the aim of this study was to evaluate ex vivo BS and adhesive interface of endodontic sealers to root canal dentin, through the push-out test and SEM, before and after immersion in PBS. The null hypothesis of this experiment is that the immersion in PBS does not affect the BS to dentin and the adhesive interface formation of several root canal sealers. MATERIAL AND METHODS Tooth Selection and Preparation The research project was previously approved by the “Research Ethics Committee” at the Federal University of Santa Catarina. Eighty extracted non-carious human maxillary central incisors were stored in 0.1% thymol solution at 4 C, pH 7, and used within 3 months after extraction. The teeth were radiographed in the mesiodistal direction and examined with stereoscopic lens with 43 magnification (Illuminated Magnifying Glass, Tokyo, Japan) with the objective of verifying the existence of a single, straight canal, apical foramen fully formed and free of cracks and imperfections. The crown of each tooth was removed 2 mm from the cementoenamel junction in coronal direction with a 0.15 diamond saw at slow speed (Isomet 1000; Buehler, Lake Bluff, IL). Working length was established at 1 mm from the apical foramen. Canals were prepared by a single operator in a crown-down manner using #4 to #2 Gates Glidden drills (Union Broach, York, PA), and rotary files (ProTaper Universal; Dentsply Maillefer, Ballaigues, Switzerland) were used incrementally up to a F5 rotary file. Patency of the apical foramen was maintained throughout the preparation, with a #15 FlexoFile (Dentsply Maillefer). Between the use of each instrument, canals were irrigated with 2 mL of 1% NaOCl. After final irrigation
365439C 0705000020
8-1319 16832
with 3 mL of 17% EDTA and 3 mL of 1% NaOCl, canals were dried with paper points. Next, the root canals were randomly divided into four groups (n 5 20), according to the sealer used for obturation: Group 1, Endofill (Dentsply Ind, Petropolis, RJ, Brazil); Group 2, AH Plus (Dentsply DeTrey, Konstanz, Germany); Group 3, Sealapex (Sybron Endo/Kerr, Romulus, USA) and Group 4, MTA Fillapex (Angelus Industry of Dentistry Products S/A, Londrina, Brazil). The composition, manufactures, and batch number of the endodontic sealers used in this experiment are shown in Table 1. The endodontic sealer was introduced in the root canal with a lentulo spiral (Dentsply Maillefer), and the filling was complemented using master and accessory gutta percha points by the cold lateral condensation technique (Dentsply Maillefer). After vertical compaction and placement of temporary sealing (Citodur; Dorident, Vienna, Austria), 10 roots in each group were stored in distillated water for 1 week (n 5 10, subgroups A) or in PBS solution (Dermus, Florianopolis, SC, Brazil) for 60 days (n 5 10, subgroups B) at 37 C, with renewal of the solution every 07 days. Push-Out Test and Failures Evaluation The specimens were individually taken to a precision cutting machine (Isomet 1000) and serially sectioned perpendicular to the long axis by using a watercooled diamond saw (South Bay Technology, San Clement, CA). Approximately two 1.0-mm thick slices were
Fig. 1. Areas of the filling material-dentine interface analyzed. Four distinct areas (point 1–4 of the sample) where examined by SEM.
Microscopy Research and Technique
INTERFACE AND BOND STRENGTH OF SEALERS AFTER PBS
3
TABLE 2. Analysis of variance of the factors sealers (Endofill, AH Plus, Sealapex, and MTA Fillapex), root regions (coronal, middle, and apical), and subgroups (7 days in water and 60 days in PBS) a 5 0.05 Variation source
Sum of squares
Degrees of freedom
Mean squares
F-value
P-valuea
220.664 4.290 60.826 11.531 31.211 8.169 31.487 526,856
3 1 2 3 6 2 6 216
73.555 4.290 30.413 3.844 5.202 4.084 5.248 2,439
30.156 1.759 12.469 1.576 2.133 1.675 2.151
0.05). The results about presence, quantity and depth penetration of the endodontic sealers are shown in Figure 3B, 4, and 5. AH Plus showed presence of dense and long sealer tags (100 lm), with significant statisti-
cal differences as compared with the other groups, in both subgroups, A (07 days in water, P < 0.0001) and B (60 days in PBS, P 5 0.003). The samples of groups Endofill (G1), Sealapex (G3), and MTA Fillapex (G4) showed statistically similar results (P > 0.05) in both subgroups. DISCUSSION The results of the push-out test showed that the null hypothesis cannot be totally accepted. The endodontic sealers had different BS means among themselves, regardless of the analyzed subgroup, with the best results being achieved by AH Plus. In addition to the sealer, the root canal region and the interaction between the sealer, region, and subgroup, were also significant. These results can be explained by the following events: treatment applied at the dentin surface; different composition of sealers; and anatomic diversity of root canals. In this experiment, the smear layer was removed previously to the root canal obturation. Smear layer removal is one of the factors that influence depth penetration of endodontic sealers (Lee et al., 2002). Studies demonstrate that the removal of this layer favors the intratubular penetration of the sealers, thus improving mechanical locking, a factor that increases dislodgement resistance when TABLE 4. Types of failures observed when comparing the groups, regardless of region of the canal after the push-out test and according to different subgroups (%) Immersion Adhesive Cohesive Mixed subgroup Groups (%) (%) (%) A (07 days)
B (60 days)
G1A G2A G3A G4A G1B G2B G3B G4B
56.67 30.00 53.33 36.67 63.33 40.00 33.33 56.67
40.00 70.00 40.00 63.33 33.34 53.33 60.00 40.00
3.33 – 6.67 – 3.33 6.67 6.67 3.33
Fig. 2. Bond strength means (MPa) and confidence interval of the sealers Endofill (G1); AH Plus (G2); Sealapex (G3); and MTA Fillapex (G4) in each experimental subgroup: A (07 days in water) and B (60 days in PBS), considering coronal, middle, and apical root thirds. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Microscopy Research and Technique
INTERFACE AND BOND STRENGTH OF SEALERS AFTER PBS
5
Fig. 3. Results of adhesive interface evaluation (A) and the sealer penetration evaluation, (B) observed in subgroups, (A) 7 days in water, and (B) 60 days in PBS. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
submitted to external forces and leakage of fluids (Eldeniz et al., 2005; Gesi et al., 2005; Haragushiku et al., 2012; Lee et al., 2002; Onay et al., 2009; Saghiri et al., 2010; Sagsen et al., 2011; Sevimay and Dalat., 2003; Sevimay and Kalayci, 2005; Sly et al., 2007; Ungor et al., 2006; Vilanova et al., 2012). However, the tenaciousness of the sealer to the dentin walls cannot be attributed only to depth penetration of the sealers into dentinal tubules, but also to frictional resistance of the filling material on the surrounding walls of the root canal (Goracci et al., 2005). Frictional resistance may explain, in part, the higher BS to dentin obtained after the push-out test in the apical third when AH Plus was used. The results of this research corroborate those of others studies, which also obtained high values of BS at the apical third of the root canal (Huffman et al., 2009; Sly et al., 2007). Such results are associated with high frictional resistance in this region, both due to anatomy and high pressure applied on the surface during root canal filling by the lateral compaction technique. It is known also that radicular dentin adhesion depends on factors which interact with gutta percha surface or dentin, such as surface tension of the sealer and its ability to penetrate the dentin (Eldeniz et al., 2005). Another relevant factor is the anatomic diversity of root canals. In some cases, even after endodontic preparation, the surface of dentin walls can differ widely, also at the same region of the root. This dentin substrate variability may also be the cause of the Microscopy Research and Technique
divergences of the BS results in the same sealer, which can promote high standard deviation, even after careful standardization of the tooth selected for the experiment. The AH Plus sealer revealed means of BS significantly higher than the other sealers, regardless of the analyzed subgroup. These results corroborate those of other studies which observed high BS values of AH Plus when as compared to other sealers based on: zinc oxide; resins; calcium hydroxide and MTA (Eldeniz et al., 2005; Fisher et al., 2007; Huffman et al., 2009; Nunes et al., 2008; Ungor et al., 2006). AH Plus is a sealer based on epoxic resin and amines. The epoxic resin present in AH Plus can react with the amine group of the collagen network and create a covalent bond between sealer and dentin (Fisher et al., 2008; Manicardi et al., 2011). Sealers based on zinc oxide and eugenol are still widely spread and used, although they have lower resistance to compression, high solubility, and low BS to dentin due to low cohesion of the molecules (Lee et al., 2002). Nevertheless, the results obtained by Endofill were similar to those showed by Sealapex and MTA Fillapex. This result might be explained, partly, by the removal of smear layer that allowed similar sealer penetration in dentinal tubules between these groups. Furthermore, low values of adhesion with Sealapex sealer can be explained by the low cohesive resistance to traction. The chemical reaction that occurs between the components of Sealapex, calcium hydroxide and glycol
6
M. TEDESCO ET AL.
Fig. 4. Images obtained by SEM (SE) and representative of AH Plus (G2A, 07 days in water). (A) Image of the middle third (325). The vestibular and palatal/lingual area represented by arrows in the specimens. (B) Higher magnification of the middle third (365). A large amount of tags could be seen. (C) Note the great amount of broken tags and the presence of bubbles in the sealer. (D) Higher magni-
fication of the demarcated area in (C) (31000). (E) Presence of long and dense tags. (F) Higher magnification of the demarcated area in (E) (31000). Note the presence of sealer lateral branches (arrow). The results on subgroup B (G2B, 60 days in PBS) were similar. GP: gutta percha S: sealer.
salicylate results in a molecule of disalicylate that does not bind to the dentin (Lee et al., 2002). According to the environment which the samples were kept immersed (water or PBS), there were no statistically differences among the subgroups, even when the MTA Fillapex was used. Materials based on MTA, when in contact with PBS, may originate carbonated apatite in a process called biomineralization, and may provide higher BS in the material dislodgement of the root canal (Bozeman et al., 2006). The BS of MTA Fillapex to dentin was statistically lower than AH Plus, even after immersion for 60 days in PBS.
In the present study, the sealers used in the root canal filling were tested by trying to simulate an in vivo environment. So, the entire roots were immersed in PBS with the filling sealed on this coronal portion with a temporary material. Only the apical foramen, with apical patency maintained, allowed contact of the filling material with PBS, providing limited access of solution. Studies show that the ability of MTA-based materials to generate carbonate apatite seems to be proportional to the available quantity of synthetic tissue fluid, such as PBS, ex vivo (Assmann et al., 2011) or in vivo (Dreger et al., 2012). In the Microscopy Research and Technique
INTERFACE AND BOND STRENGTH OF SEALERS AFTER PBS
7
Fig. 5. Images obtained by SEM (SE) and representative of Endofill (A, B), Sealapex (C, D), and MTA Fillapex (E, F). Subgroups A (7 days in water) and B (60 days in PBS) had similar results. (A) Specimen in which it was possible to detect the presence of gaps to dentine (3250), and (B) presence of few and short tags (31500). (C) The use of Sealapex provided many areas of interfacial gaps. (D) It was possible to notice the presence of many fractured tags (arrow) and cohesive
failure (star) of the sealer (31000). (E) With the use of MTA Fillapex many areas of gaps were noted, despite the amount of tags formed (3250). (F) Higher magnification of the demarcated area in (E). Note the dentine covered by sealer (cohesive failure of the material) and the presence of many tags with porous aspect (31000). S: sealer, De: dentine, GP: gutta percha.
study by Reyes-Carmona et al., 2010, the use of PBS improved the MTA BS to dentin. However, the samples were immersed in PBS after the cut, providing greater availability of the solution. The analysis of the failures modes, regardless of the sealer or the subgroup analyzed showed that most failures were adhesive or cohesive. The AH Plus sealer had a greater number of cohesive failures to the material in water or PBS, a fact that has been observed in other experiments (Lee et al., 2002; Ungor et al., 2006). The analysis of the samples by SEM showed clear images of the adhesive interface and the quantity of tags present in the samples. When evaluating the
quality of adhesive interface, gaps were observed in all sealers tested, although the use of AH Plus showed fewer gaps than the other sealers after 7 days in water. The failures observed at the interface by SEM might be generated during the chemical preparation of the samples (Teixeira et al., 2008). The solutions used to demineralize, fix or dissolve the organic tissue of the samples may affect the quality of the interface observed. Besides, in this study, the analyses were performed by direct visualization, and as the samples were placed on the microscope vacuum chamber, we cannot be sure that the gaps were not artifacts produced by the technique. The results of the evaluation
Microscopy Research and Technique
8
M. TEDESCO ET AL.
of the adhesive interface and presence of tags in subgroup B were similar to those obtained in subgroup A, in all groups analyzed. In relation to the penetration of the sealers into dentinal tubules, tags were observed in all groups. The absence of the smear layer probably improves deeper penetration of the sealers and greater density of tags (Bozeman et al., 2006; Haragushiku et al., 2012; Kokkas et al., 2004; Saghiri et al., 2010). The analysis showed that AH Plus had tags in greater quantity and depth than the others sealers. Also, it was observed greater quantity and depth of tags into dentinal tubules in buccal and lingual/palatal dentin orientations, with little quantity in the proximals. This characteristic was observed in other studies and explained by anatomical features and dentin tubule orientation (Mamootil and Messer, 2007; Moradi et al., 2009; Weis et al., 2004). CONCLUSIONS Within the limits of this study, it may be concluded that the immersion in PBS for 60 days did not affect the BS or the adhesive interface of the sealers analyzed. The use of AH Plus sealer promoted better results than Endofill, Sealapex, and MTA Fillapex. ACKNOWLEDGMENTS The authors deny any conflicts of interest related to this study. REFERENCES Assmann E, Scarparo RK, Bottcher DE, Grecca FS. 2011. Dentin bond strength of two mineral trioxide aggregate-based and one epoxy resin-based sealer. J Endod 38:219–221. Bozeman BT, Lemon RR, Eleazer PD. 2006. Elemental analysis of crystal precipitate from gray and white MTA. J Endod 32:425–428. Costa JA, Rached-J unior FA, Souza-Gabriel AE, Silva-Sousa YT, Sousa-Neto MD. 2010. Push-out strength of methacrylate resinbased sealers to root canal walls. Int Endod J 43:698–706. Dreger LAS, Felippe WT, Reyes-Carmona JF, Felippe GS, Bortoluzzi EA, Felippe MCS. 2012. Mineral trioxide aggregate and Portland Cement promote biomineralization in vivo. J Endod 38:324–329. Eldeniz UA, Erdemir A, Belli S. 2005. Shear bond strength of three resin based sealers to dentine with or without smear layer. J Endod 31:293–296. Fisher MA, Berzins DW, Bahcall JK. 2007. An in vitro comparison of bond strength of various obturation materials to root canal dentine using a push-out test design. J Endod 33:856–888. Gandolfi MG, Parrilli AP, Fini M, Prati C, Dummer PM. 2013. 3D micro-CT analysis of the interface voids associated with Thermafil root fillings used with AH Plus or a flowable MTA sealer. Int Endod J 46:253–263. Gandolfi MG, Prati C. 2010. MTA and F-doped MTA cements used as sealers with warm gutta percha Long-term study of sealing ability. Int Endod J 43:889–901. Gesi A, Raffaeli O, Goracci C, Pashley DH, Tay FR, Ferrari M. 2005. Interfacial strength of resilon and gutta percha to intraradicular dentine. J Endod 31:809–813. Gillen BM, Looney SW, Gu LS, Loushine BA, Weller RN, Loushine RJ, Pashley DH, Tay FR. 2011. Impact of the quality of coronal restoration versus the quality of root canal fillings on success of root canal treatment: a systematic review and meta-analysis. J Endod 37:895–902. Goracci C, Fabianelli A, Fadek ST, Papacchini F, Tay FR, Ferrari M. 2005. The contribution of friction to the dislocation resistance of bonded fiber posts. J Endod 31:608–612. Grech L, Mallia B, Camilleri J. 2013. Characterization of set intermediate restorative material, biodentine, bioaggregate and a prototype calcium silicate cement for use as root end filling materials. Int Endod J 46:1–10.
Haragushiku GA, Teixeira CS, Furuse AY, Sousa YTS, Sousa-Neto MD, Silva RG. 2012. Analysis of the interface and bond strength of resin based endodontic cement to root dentine. Micro Res Tech 75: 655–661. Huffman BD, Mai S, Pinnal Weller RN, Primus CM, Gutmann JL, Pashley DH, Tay FR. 2009. Dislocation resistance of ProRoot Endo Sealer, from radicular dentine. Int Endod J 42:34–46. Kokkas AB, Boutsioukis ACH, Vassiliadis LP, Stavrianos CK. 2004. The influence of the smear layer on dentinal tubules penetration depth of three different root canal sealers: an in vitro study. J Endod 30:100–102. Lee KW, Williams MC, Camps JJ, Pashley DH. 2002. Adhesion of endodontic sealers to dentine and gutta-percha. J Endod 28:684– 688. Mamootil K, Messer HH. 2007. Penetration of dentinal tubules by endodontic sealer cements in extracted teeth and in vivo. Int Endod J 40:873–881. Manicardi CA, Versiani MA, Saguy PC, Pecora JD, Sousa-Neto MD. 2011. Influence of filling materials on bonding interface of thinwalled root reinforced with resin and quartz-fiber posts. J Endod 37:531–537. Moradi S, Ghoddusi J, Forghani N. 2009. Evaluation of dentinal tubule penetration after the use of dentine bonding agents as a root canal sealer. J Endod 35:1563–1566. Nunes VH, Silva RG, Alfredo E, Sousa-Neto MD, Silva-Sousa YT. 2008. Adhesion of epiphany and AH Plus sealers to human dentine treated with different solutions. Brazil Dentistry J 19:46–50. Onay EO, Ungor M, Ari H, Belli S, Orgus E. 2009. Push-out bond strength and SEM evaluation of new polymeric root canal fillings. Oral Surg Oral Med Oral Pathol Oral Radiol Endodont 107:879– 885. Reyes-Carmona JE, Felippe M, Felippe WT. 2010. The biomineralization ability of mineral trioxide aggregate and portland cement on dentine enhances the push-out strength. J Endod 36:286–291. Saghiri MA, Shokouhinejad N, Lofti M, Aminsobhani M, Saghiri AM. 2010. Push-out bond strength of mineral trioxide aggregate in the presence of alkaline pH. J Endod 36:1856–1859. Sagsen B, Ustun Y, Demirbuga S, Pala K. 2011. Push-out bond strength of two new calcium silicate-based endodontic sealers to root canal dentine. Int Endod J 44:1088–1091. Schwartz RS. Adhesive dentistry and endodontics. 2006. Part 2: Bonding in the root canal system the promise and the problems: A review. J Endod 32:1125–1135. Sevimay S, Dalat D. 2003. Evaluation of penetration and adaptation of three different sealer a SEM study. J Oral Rehab 30:951–955. Sevimay S, Kalayci A. 2005. Evaluation of apical sealing ability and adaptation to dentine of two resin-based sealers. J Oral Rehab 32: 105–110. Shokouhinejad N, Sabeti M, GorjestanI H, Saghiri MA, Lofti M, Hoseini A. 2011. Penetration of epiphany, epiphany self-etch, and AH plus into dentinal tubules: A scanning electron microscopy study. J Endod 37:1316–1319. Sly MM, Moore K, Platt JA, Brown CE. 2007. Push-out bond strength of a new endodontic obturation system (Resilon/Epiphany). J Endod 33:160–162. Sousa-Neto MD, Silva Coelho FI, Marchesan MA, Alfredo E, SilvaSousa YT. 2005. Ex vivo study of the adhesion of an epoxy-based sealer to human dentine submitted to irradiation with Er: YAG and Nd: YAG lasers. Int Endod J 38:866–870. Teixeira CS, Felippe MC, Silva-Sousa YT, de Sousa-Neto MD. 2008. Interfacial evaluation of experimentally weakened roots restored with adhesive materials and fiber posts: An SEM analysis. J Dent 36:672–682. Topc¸uo glu HS, Demirbuga S, Tuncay O, Arslan H, Kesim B, Yasa B. 2014. The bond strength of endodontic sealers to root dentine exposed to different gutta-percha solvents. Int Endod J [Epub ahead of print]. Ungor M, Onay EO, Orucuglu U. 2006. Push-out bond strengths: the epiphany-resilon endodontic obturation system compared with different pairings of epiphany, resilon, AH plus and gutta-percha. Int Endod J 39:643–647. Vilanova WV, Carvalho-Junior JR, Alfredo E, Sousa-Neto MD, SilvaSousa YTC. 2012. Effect of intracanal irrigants on the bond strength of epoxy resin based and methacrylate resin based sealers to root canal walls. Int Endod J 45:42–48. Weis MV, Parashos P, Messer HH. 2004. Effect of obturation technique on sealer cement thickness and dentinal tubule penetration. Int Endod J 10:653–663.
Microscopy Research and Technique
