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Effect of Different Cavity Disinfectants on Strength of Composite Resin to Dentin
pyrig No Co t fo rP ub Shear Bond lication te ss e n c e
Ertugrul Ercana/Ali Erdemirb/Yahya Orcun Zorbac/Ayce Unverdi Eldenizd/Mehmet Dallie/ Bayram Íncee/Baris Kalayciogluf
Purpose: The aim of this study was to evaluate the effect of different cavity disinfectants on dentin bond strengths ofcomposite resin applied with two different adhesive systems. Materials and Methods: One hundred mandibular third molars were sectioned parallel to the occlusal surface to expose midcoronal dentin. The dentin surfaces were polished with waterproof-polishing papers. The specimens were randomly divided into 5 groups of 20 each. In group 1, the specimens were not treated with any cavity disinfectants and served as control. From groups 2 to 5, dentin surfaces were treated with the following cavity disinfectants, respectively; 2% chlorhexidine solution, 2.5% NaOCl, 1% chlorhexidine gel, 3% H2O2. The specimens were then randomly divided into 2 subgroups including ten teeth each to evaluate the effect of different bonding systems. Dentin bonding systems were applied to the dentin surfaces and the composite buildups were created. After the specimens were stored in an incubator for 24 h, the shear bond strength was measured at a crosshead speed of 1 mm/min. The bond strength data were analyzed with one way analysis of variance and Tukey-HSD tests. Results: There was no significant difference between chlorhexidine gel and control groups regardless of the type of the bonding agent (p > 0.05). On the other hand, pretreatment with NaOCl, H2O2 or chlorhexidine solutions had a negative effect on the shear bond strength of self-etching bonding systems. Conclusion: The findings of this study suggest that when NaOCl, H2O2 or chlorhexidine solution are used as a cavity disinfectant, an etch-and-rinse bonding system should be preferred. Keywords: bond strength, adhesive, composite resin, cavity disinfection, CHX gel.
J Adhes Dent 2009; 11: 343-346.
Submitted for publication: 20.06.08; accepted for publication: 05.02.09.
A
lthough cavity preparation is an operative procedure that attempts to remove all infected dentin prior to placing a restorative material, bacterial remnants during
a
Assistant Professor, Department of Operative Dentistry, Faculty of Dentistry, Kirikkale University, K›r›kkale, Turkey.
b
Associate Professor, Department of Endodontics, Faculty of Dentistry, Kirikkale University, K›r›kkale, Turkey.
c
Assistant Professor, Department of Endodontics, Faculty of Dentistry, Kirikkale University, K›r›kkale, Turkey.
d
Associate Professor, Department of Endodontics, Faculty of Dentistry, Selcuk University, Konya, Turkey.
e
Research Assistant, Department of Operative Dentistry, Faculty of Dentistry, Dicle University, Diyarbak›r, Turkey.
f
Research Assistant, Department of Mechanical Engineering, Faculty of Engineering, Kirikkale University, Kirikkale, Turkey.
Correspondence: Ertugrul Ercan, Department of Operative Dentistry, Faculty of Dentistry, Kirikkale University, 71100, Kirikkale, Turkey. Tel: +90-318-224-4927, Fax: +90-318-225-0685. e-mail:
[email protected]
Vol 11, No 5, 2009
and after the cavity preparation pose one of the major problem in restorative dentistry.2 This can lead not only to increased pulp sensitivity and pulpal inflammation, but also to secondary caries, necessitating replacement of the restoration.3,9 For these reasons, elimination of the bacteria from the cavity surfaces is of major importance, and a disinfectant solution that eliminates these residual bacteria could be useful after cavity preparation.12 The efficacy of these disinfectant solutions has been reported in a number of studies,4,6,13,18 and for two decades, many chemicals have been tested as cavity disinfectants, including chlorhexidine digluconate (CHX), disodium ethylene diamine tetraacetic acid (EDTA) dihydrate, sodium hypochlorite (NaOCl), hydrogen peroxide (H2O2) and iodine.4,6 Generally, a potential problem in the use of a disinfectant before dentin bonding agents is the possibility of an adverse effect on the bond strength of the composite resins. The objective of this study was to compare the effect of the most commonly used cavity disinfection materials on shear bond strength of composite with either a two-step self-etching or an etch-and-rinse bonding system. 343
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Fig 1 Preparation of specimens.
MATERIALS AND METHODS One hundred caries-free human third permanent mandibular molars were used in this study. The teeth were cleaned of calculus and soft tissue debris with a periodontal probe. The teeth were sectioned with a low-speed diamond disk saw (Buehler; Lake Bluff, IL, USA) under water coolant to expose mid-coronal dentin. The sections of the teeth including the roots were embedded in autopolymerizing acrylic resin to form cylinders 2.5 cm in diameter and 5 cm high (Fig 1). Dentin surfaces were flattened using 600-, 800- and 1200-grit waterproof polishing papers. The teeth were randomly divided into 5 main groups of 20 teeth each. In group 1, the specimens were not treated with any cavity disinfectant and served as control. The teeth in experimental groups were treated with one of the following cavity disinfectants: CHX solution (2%), NaOCl (2.5%), CHX gel (1%) or H2O2 (3%) for 20 s. The dentin surfaces of the teeth were then dried with air for 10 s. Each group was then randomly divided into two subgroups of ten teeth each according to the bonding agent used, either Clearfil SE Bond (Clearfil SE bond, Kuraray, Osaka, Japan) or Prime & Bond NT (Dentsply Caulk, Milford, DE, USA). For the Clearfil SE Bond system (Clearfil SE Bond, Kuraray), primer was applied to the dentin surface using a sponge supplied by the manufacturer and rubbed for 20 s. The dentin surface was then dried with oil-free compressed air. After this etching and priming step, the SE bonding agent was applied to dentin surfaces and light cured for 20 s with a 1000 mW/cm2 LED device (Elipar Freelight, 3M ESPE, Seefeld, Germany). For Prime & Bond NT (PBNT) (Dentsply Caulk), the dentin surface was etched with 34% phosphoric acid gel (Dentsply Caulk) for 20 s, rinsed for 20 s with an air-water syringe and dried with compressed air. Then, Prime & Bond NT was applied, left undisturbed for 30 s, lightly air dried for 2 s, and light cured for 20 s. After adhesive application, the specimens were clamped in the Ultradent Bonding Jig (Ultradent Products; South Jordan, UT, USA). A hybrid restorative composite (Clearfil APX Shade A3, Kuraray) was carefully inserted into the surface by packing the material into cylindrical-shaped plastic matrices with an internal diameter of 2.34 mm and a height of 3 mm. Excess composite was carefully removed from the pe344
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pyrig No Co t fo riphery of the matrix with an explorer. The composite r P was cured with an LED curing light (Elipar Freelight) for u 20 blsi (Fig cat 1). i After storing in an incubator at 37ºC in 100% te humidity for on e s e n cma24 h, the specimens were placed in a universalstesting
Ercan et al
chine and the shear bond strength was measured at a crosshead speed of 1 mm/min. The shear bond strength of composite resin to dentin was recorded in Newtons (N) and calculated in MPa taking into account the cross-sectional area of the composite buildup. The mean and standard deviation were calculated for the different groups. One way analysis of variance and Tukey HSD tests were performed to determine significant differences in bond strengths between the groups. After the testing procedure, the fractured surfaces were observed with a dissecting microscope (SZ-TP Olympus; Tokyo, Japan) at a magnification of 20X to determine failure modes and classified as adhesive failures, cohesive failures within the composite, or cohesive failures within the tooth. One specimen from each group was sputter coated with gold after fracture and prepared for SEM examination. Coated specimens were then observed under the SEM (JSM5600, JEOL; Tokyo, Japan) with different magnifications.
RESULTS The mean and standard deviations of shear bond strengths for each group are presented in Table 1. When the results were analyzed, the mean shear bond strength values in the Clearfil SE Bond group which had been treated with CHX solution, NaOCl or H2O2 were significantly lower than the other groups (p < 0.05). Shear bond strength was not adversely affected by any cavity disinfectants in groups in which Prime & Bond NT was applied after acid etching. Regardless of the bonding agent, used CHX gel demonstrated no adverse effect on shear bond strength of composite resin. The distribution of fracture modes observed with a dissecting microscope at a magnification 20X is shown for all groups in Table 2. The predominant mode of failure in groups 2, 3 and 5 was adhesive. The other groups showed an equal distribution of the different failure modes. Figures 2a and 2b show the SEM micrographs of dentin surfaces after fracture in groups 2 and 3, respectively. Resin tags on dentin surfaces treated with the self-etching system were not clearly visible. However, in Figs 2c and 2d, dentin surfaces which were treated with CHX solutions (group 7) or chlorhexidine gel (group 9), respectively, showed clear resin tags when the etch-and-rinse system was used.
DISCUSSION In this study, the cavity disinfectants NaOCl, H2O2 and CHX solution decreased the bond strength when used with selfetching bonding system, whereas no adverse effect was observed when used with the etch-and-rinse adhesive. However, irrespective of the bonding system used, CHX gel had no adverse effect on shear bond strength. The Journal of Adhesive Dentistry
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Control 2% CHX 2.5% NaOCl 1% CHX gel 3% H2O2
10 10 10 10 10
20.87 (3.94) 16.36b (2.46) 15.21b (2.36) 20.86a (3.65) 15.02b (2.87)
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opyretigal No CErcan t Table 1 Disinfectant effects on shear bond strength of Clearfil SE Bond and Prime & Bond NT for Pu adhesive systems bli cat ion Group N Clearfil SE Bond mean(MPa) ±SD Prime & Bond NT mean(MPa) ±SD te ss e n c e a a 20.83 (3.79) 21.01a (2.10) 20.87a (2.52) 21.00a (3.53) 20.97a (2.26 )
There was no statistically significant difference in the groups having same superscript letters.
Table 2 Failure modes of the all test groups Group
1 2 3 4 5 6 7 8 9 10
Description
Control/Clearfil SE 2% CHX/Clearfil SE 2.5%NaOCl/Clearfil SE 2%CHX gel/Clearfil SE 3% H2O2/Clearfil SE Control/PBNT 2% CHX/PBNT 2.5%NaOCl/PBNT 2%CHX gel/PBNT 3% H2O2/PBNT
Failure Adhesive (%)
Cohesive (%)
Mixed (%)
20 50 60 30 60 30 40 30 40 40
40 20 20 30 20 40 30 30 40 30
40 30 20 40 20 30 30 40 20 30
Fig 2a SEM micrograph of dentin surface treated with CHX solution in group 2. Dentinal tubules were not clearly observed. DT: dentinal tubule, RT: resin tag, AR: adhesive resin. Fig 2b SEM micrograph of dentin surface treated with NaOCl in group 3. Some empty areas in dentinal tubules were observed. DT: dentinal tubule, RT: resin tag, AR: adhesive resin. Fig 2c SEM micrograph of dentinal tubules filled with resin tags in group 7. Some dentinal tubules were left empty. DT: dentinal tubule, RT: resin tag, AR: adhesive resin. Fig 2d SEM micrograph of dentin surface treated with chlorhexidine gel and an etch-and-rinse bonding system (group 9). All dentinal tubules were completely filled with resin tags. DT: dentinal tubule, RT: resin tag, AR: adhesive resin.
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Within the limitations of this laboratory study, it may be stated that routinely-used disinfectants, except CHX gel, might have an adverse effect on the bond strength of selfetching adhesive systems. Thus, when clinicians decide to use NaOCl, H2O2 or CHX solution as a cavity disinfectant, they should prefer an etch-and-rinse bonding system. However, the use of chlorhexidine gel as a cavity disinfectant may be advisable, as it does not have any adverse effect on the bond strength of self-etching and etch-and-rinse systems. Further in vitro and in vivo studies are still needed to evaluate the effect of chlorhexidine gel for cavity disinfection.
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Due not only to its well-known disinfecting action, but also to its wettability property, NaOCl has been used as one of the most common cavity disinfectants in clinical practice.11,20 Although it has been proposed that the dentin substrate after deproteinization – as it exhibits a remarkably porous structure with multiple irregularities and anastomoses – could promote bond strength, controversial results still exist.8,15,23,24 From various laboratory results, it has been observed that depending on the testing methodology and the adhesive system used, dentin surface treatment with sodium hypochlorite can increase,8,12,23 decrease,5,16 or have no effect1,21 on bond strength. In our study, while NaOCl had a negative effect on bond strength when used with the self-etching system, it had no effect when used with the etch-and-rinse system. This result is in line with the study by Aries et al,1 that NaOCl had no effect on bond strength when the etch-and-rinse technique was used. With its perfect antibacterial activity, CHX has also been used as a good cavity disinfectant for many years.8,10 Because it has a rewetting capacity and a strong affinity to tooth structure,17 it seems that CHX would improve the bond strengths of the adhesive to dentin. However, in our study, the CHX solution exerted an adverse effect on shear bond strength when used with the self-etching bonding system. This observation is in line with results of Gurgan et al,6 that using chlorhexidine prior to or after etching the dentin without rinsing could adversely affect the shear bond strength of the dentin bonding agent. However, in the other studies, it was shown that applying chlorhexidine before acid etching did not significantly affect the bond strength.7,14,19 A similar result was observed in the present study for specimens treated with the etch-and-rinse system and the CHX solution. The use of chlorhexidine gel in this study did not affect the bond strength of composite regardless of which bonding system was used (self-etching or etch-and-rinse). Although our review of the literature did not discover any previous study using CHX gel as a cavity disinfectant, CHX gel’s lack of effect on bond strength might be explained by the limited penetration depth of the material into the dentin structure due to its gel form. On the other hand, the gel form may also limit the affinity of the material to the tooth structure.
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Clinical relevance: Depending on the bonding system used, clinicians should be aware that some cavity disinfectants – with the exception of except of CHX gel – may have a negative effect on shear bond strength.
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