« ∑—πμ ®ÿÓœ 2559;39:9-18 CU Dent J. 2016;39:9-18 ∫ ∑ «‘ ∑ ¬ “ ° “ √ Original Article Effect of chlorhexidine as a vehicle for sodium perborate in non-vital tooth bleaching on microleakage of resin composite Nuchjaree Bunphawatthanarak, D.D.S.1 Peraya Puapichartdumrong, D.D.S., Ph.D.1 Thosapol Piyapattamin, D.D.S., Ph.D.2 1Department of Restorative Dentistry, Faculty of Dentistry, Naresuan University 2Department of Preventive Dentistry, Faculty of Dentistry, Naresuan University Abstract Objective To study the effect of chlorhexidine (CHX) as a vehicle for sodium perborate (SP) on microleakage of resin composite by using glucose filtration. Materials and methods Thirty six single-rooted teeth were used. The specimens with cavity were prepared and divided into three groups: Group 1, SP mixed with 2% CHX; Group 2, SP mixed with distilled water; Group 3, SP mixed with 30% hydrogen peroxide. With a total conduction of three times, bleaching agent was applied in the cavities for 1 week and rinsed. The cavities were then filled with resin composite. The specimens were thermocycled for 500 cycles, followed by a microleakage determination (glucose filtration). The concentration of leaked glucose was analyzed by spectropho- tometer. Dentin surfaces of each group were prepared and observed under SEM. Results Mean concentrations and standard deviations of leaked glucose (mM) were 1.001 ± 0.147, 1.005 ± 0.093, and 1.304 ± 0.406, in Groups 1, 2, and 3, respectively. Inter-group significant differences were found by a one-way ANOVA (p < 0.05). Using the post-hoc Tukey HSDûs test analysis, some significant differences were found between Groups 1 and 3, together with Groups 2 and 3 (p < 0.05). The morphology of dentin surfaces under SEM of Group 1 showed mild erosion similar to that of Group 2. Group 3 showed more eroded dentin. Conclusion Using CHX as a vehicle for SP in this study did not affect the microleakage of resin composite and dentin. Clinically, CHX may be a good vehicle for non-vital tooth bleaching. (CU Dent J. 2016;39:9-18) Key words: chlorhexidine; glucose filtration; microleakage; non-vital tooth bleaching; sodium perborate Correspondence: Peraya Puapichartdumrong, [email protected] 10 Bunphawatthanarak N, et al CU Dent J. 2016;39:9-18 Introduction tubules for eliminating bacteria (Heling et al., 1992). The walking bleach method is non-vital tooth After bleaching process, it is a common practice bleaching which is easy to perform and preserves tooth to restore an access cavity with resin composite. Using structure for the anterior teeth. The bleaching agent is CHX as a bleaching agentûs vehicle may affect the put inside the pulp chamber proper. There are many quality of bonding between restorative material and dentin. types of bleaching agents, for example hydrogen A recent study on the bleaching process has shown that SP mixed with 2% CHX solution did not significantly peroxide (H2O2), sodium perborate (SP; NaBO3·4H2O), affect the bond strength between dentin and resin superoxol (30% H2O2), carbamide peroxide composite, when compared to that mixed with distilled (CO(NH2)2H2O) (Plotino et al., 2008). water (Buranakiattipuntr et al., 2011). SP mixed with distilled water is used as bleaching agent in walking bleach technique (Holmstrup et al., In order to prevent the microbial contamination 1988). Instead of water, 3% H2O2 can be used in case caused by microleakage of temporary filling during the of severe discolored tooth (Nutting and Poe, 1963). bleaching process, using 2% CHX as a vehicle of SP When the bleaching paste is put inside the pulp for non-vital tooth bleaching can be considered a chamber proper, the top is sealed with temporary beneficial alternative to distilled water. However, there filling. H2O2 is released from the chemical reaction of have been few studies on the effect of SP and CHX on bleaching paste. H2O2 can then generate different free the microleakage of resin composite and dentin. Some radicals, together with reactive but unstable oxygen leakage studies in endodontics include dye penetration molecules, which subsequently change to oxygen gas. (Starkey et al., 1993), radioisotope studies (Ha¨ıkel et al., The leakage of temporary filling caused by pressure 1999), bacterial penetration (Chailertvanitkul et al., from oxygen gas has been claimed during the walking 1996), fluid filtration (Pommel and Camps, 2001). Each bleach procedure (Hosoya et al., 2000). Consequently, technique has its own advantages and disadvantages. saliva and other microorganisms can penetrate into pulp The results from studies using different techniques cause chamber. some conflicts and arguments, due to different opinions (Wu and Wesselink, 1993). In case of the leakage of temporary filling, chlorhexidine (C22H30CI2N10, CHX) gel has been Because of its small molecular size (MW = 180 suggested as a vehicle for the bleaching process, Da) and being a nutrient for bacteria, glucose has been because of its anti-microbial property which helps selected as the tracer. A new method has then been prevent the bacterial contamination. Additionally, SP proposed for the measurement of leakages, by using a mixed with 2% CHX gel did not affect the bleaching quantitative measurement of glucose solution (Xu et al., efficiency, when compared to those mixed with 30% 2005). A spectrophotometer was used to analyze H2O2 or distilled water (de Oliveira et al., 2006). CHX the quantity of the glucose solution flowing through has a unique property known as substantivity, the filling material. If glucose could enter the root canal application of 2% CHX solution for 5 min has continued from the oral cavity, bacteria that might survive root the anti-microbial substantivity in dentin for up to canal preparation and obturation could then multiply 4 weeks (Khademi et al., 2006) and remained for up to and potentially lead to periapical inflammation. This 12 weeks after application for 10 min (Rosenthal et al., method is believed to be the most clinically relevant 2004). Moreover, previous study found that 0.2% CHX practice for the leakage measurement, when compared solution can penetrate up to 500 μm within dentinal to the others. Hence, the objective of this study was to « ∑—πμ ®ÿÓœ 2559;39:9-18 Bunphawatthanarak N, et al 11 study the effect of CHX as a vehicle for SP on the junction (CEJ) and 2-mm above CEJ (Fig. 1A). By microleakage of resin composite, by using a glucose using a fissure diamond bur (Jota diamond #012, filtration method. JOTA AG, Rüthi SG, Switzerland) and a template, a cylindrical cavity with a diameter of 3 mm was prepared through the pulp chamber proper (Fig. 1B). Materials and methods The final diameter of 3 ± 0.05 mm was measured by a digital vernier caliper (500-171, Mitutoya, Kawasaki, This study was approved by the Ethics Committees Japan) with an accuracy of ± 0.01 mm. of Naresuan University. Thirty six single-rooted premolars, which had been extracted for some The cavities were rinsed with each 2-mL orthodontic purposes from 18-to 25-year-old patients, solution for 1 min, that is, 2.5% NaOCl, 17% EDTA were used. Clinically, all teeth had completed root and 2.5% NaOCl, respectively. They were then dried formation and showed no carious lesion, crack, or with cotton pellets and paper points. The apical side of 2 restorative materials on crown. The extracted teeth were specimen was placed on the center of 22 x 22 mm immediately stored in 0.1% thymol solution at 25°C glass cover slip (Fig. 2). until use. After the removal of the soft tissues, each The specimens were randomly divided into tooth was embedded in a cylindrical mold, 14 mm in three groups (n = 12 for each group). Freshly prepared diameter and 20 mm in height, with self-curing acrylic bleaching agent of SP (Faculty of Dentistry, resin. The crown specimens with a 2-mm-height were Chulalongkorn University, Bangkok, Thailand) mixed prepared by horizontally cutting at cemento-enamel with 2% CHX (Kemcolour International, GIDC Fig. 1 Specimen preparation: tooth fixed in acrylic resin with preparation lines (A), specimen after cutting with 2 mm thickness and cavity preparation with 3 mm diameter (B). Fig. 2 Specimen preparation for bleaching application. Bleaching agent was applied in the cylindrical cavity. The top surface of cavity was covered with a glass cover slip and sealed with the temporary material. 12 Bunphawatthanarak N, et al CU Dent J. 2016;39:9-18 Industrial Estate, Ankleshwar, India) for Group 1, specimens were thermocycled for 500 cycles in 5 ± 1°C with distilled water for Group 2, and with 30% H2O2 and 55 ± 1°C (Rossomando and Wendt Jr, 1995). (Sigma-Aldrich®, St. Louis, MO, USA) for Group 3 The dwell time was 60 s, with the 2-s-between-bath- (20 mg/10 μL for each specimen). Bleaching paste time. was applied in the prepared cavity of each specimen. This glucose filtration leakage model was The top surface of cavity was covered with a 12- modified from those previously reported mm-diameter glass cover slip (Electron microscopy (Puapichartdumrong et al., 2003; Xu et al., 2005). Sciences, Hatfield, PA, USA), and sealed with a Briefly, the self-curing acrylic resin model comprised 3-mm-thick temporary material (Cavit-W, ESPE, two chambers, in which the specimen could be put Seefeld, Germany) (Rotstein, 2001) (Fig. 2). All specimens between. Each chamber was fixed together with four were stored at 37°C and 100% humidity for one week. screws. The apical side of chamber was filled with 1.1 The cavities were rinsed with 20 mL of distilled water. mL of distilled water, whereas the coronal side was The mentioned procedures were conducted in this circulated with 1 M glucose solution (1.7 mL/min) by manner for a total of three times.