|Year : 2013 | Volume
| Issue : 2 | Page : 55-59
Effect of salivary contamination on micro-tensile bond strength of self-etch adhesives systems after bonding procedure
Muhammet Yalçin1, Neslihan Simsek1, Ali Keles1, Fuat Ahmetoglu1, Ayse Dündar2, Ibrahim Umar1
1 Department of Restorative Dentistry and Endodontics, Faculty of Dentistry, Inonu University, Malatya, Turkey
2 Department of Restorative Dentistry, Faculty of Dentistry, Abant Izzet Baysal University, Bolu, Turkey
|Date of Web Publication||3-Aug-2013|
Department of Restorative Dentistry, Faculty of Dentistry, Inonu University, 44280 Malatya
Source of Support: None, Conflict of Interest: None
Aims: The purpose of this study was to evaluate the effect of saliva contamination on the micro-tensile bond strength (μTBS) of two self-etching (SE) adhesive systems (Clearfil SE Bond, Clearfil S3 Bond). Materials and Methods: Flat occlusal dentin surfaces were created on 12 extracted human third molar teeth. The two bonding systems and resin composite (Spectrum® TPH® 3) were bonded to the dentin under six surface conditions: Group 1: Tooth samples were randomly divided into three equal subgroups. Clearfil SE 1: This was a control group in which dentin was not contaminated with the saliva (primer/bonding/composite). Clearfil SE 2: Contaminated once (primer/bonding (cured)/saliva/rinsing/drying/primer/bonding/composite). Clearfil SE 3: The samples were contaminated 2 times (primer/bonding (cured)/saliva/rinsing/drying/primer/bonding (cured)/saliva/rinsing/drying/primer/bonding/composite). Group 2: The procedures for Group 2 were similar to Group 1 but did not contain a primer stage. Tooth samples were randomly divided into three equal subgroups (Clearfil S3 1, 2, and 3). After 24 h, the teeth were prepared for microtensile bond testing and tensile bond strength was measured (1 mm/min). The data were calculated as megapascal (MPa) and analyzed using the one-way ANOVA and Tukey's post-hoc test (P < 0.05). Results: The μTBS of the Clearfil S3 3 subgroup was statistically higher than that of the Clearfil S3 2 subgroup and Clearfil S3 1 subgroup. There were no significant statistical differences in the μTBSs between the Clearfil S3 2 subgroup and the control subgroup. There were no statistical differences in μTBSs among the Clearfil SE subgroups. Conclusion: μTBS is not affected adversely from one or two saliva contamination after the bonding procedure.
Keywords: Bond strength, dentin, saliva contamination
|How to cite this article:|
Yalçin M, Simsek N, Keles A, Ahmetoglu F, Dündar A, Umar I. Effect of salivary contamination on micro-tensile bond strength of self-etch adhesives systems after bonding procedure. J Res Dent 2013;1:55-9
|How to cite this URL:|
Yalçin M, Simsek N, Keles A, Ahmetoglu F, Dündar A, Umar I. Effect of salivary contamination on micro-tensile bond strength of self-etch adhesives systems after bonding procedure. J Res Dent [serial online] 2013 [cited 2019 Aug 20];1:55-9. Available from: http://www.jresdent.org/text.asp?2013/1/2/55/116036
| Introduction|| |
We investigated the effect of saliva contamination of the tooth on dentin bonding. However, the results were inconclusive.  The use of adhesive systems necessitates an operative field with controlled humidity that is free of saliva contamination. 
There are many factors that affect adhesion and retention of resin-containing restorative materials in the clinical setting. Moisture, such as gingival fluid, blood, hand-piece oil,  and in the particular saliva, can affect the quality of the bond, leading to micro leakage at the tooth restoration interface.  Quality adhesion between the tooth and restorative material is recognized as playing a crucial role in the success of dental restoration. ,,
Retention of restorative materials at the surface of the tooth structure by means of adhesion is carried out routinely.  Adhesion to dentin has been the subject of debate due to its heterogeneous nature, which contains a much higher organic and water content than enamel.  The hybrid layer is indispensable for the bonding of resin-based dentin bonding agents. The bonding mechanism is via micromechanical interlocking with dentinal the collagen fibrils that have been exposed by demineralization. 
Saliva is a principal fluid in the mouth. The different components of saliva modulate oral pH, cleanse the oral tissues, provide buffering, prevent demineralization of the teeth, and serve as an antibacterial agent. ,
Matrix metalloproteinases (MMPs) can be released by acids (inorganic and organic) and activated by small integrin-binding ligand n-linked glycoproteins,  proteins, and organic acids in the oral environment or in the bonding adhesives.  The loss of bond strength is caused mainly by the degradation of the hybrid layer at the dentin-adhesive interface.  Activated MMPs may find their way to the hybrid bond layer interface via micro leakage or nanoleakage at bond gaps, from MMPs in saliva or crevicular fluid, and via dental tubule fluid from the pulp over time. ,
Several types of contamination can affect the structural and chemical properties of dental restorative materials.  If collagen fibrils are left exposed in the hybrid bond layer that is unprotected by resin, they can be degraded by activated MMPs. 
Self-etching (SE) adhesives can be subdivided into SE primers that require a separate application of adhesive and all-in-one SE adhesives that combine etchant, primer, and adhesive.  SE adhesive systems do not require acid etching and removal of the smear layer and smear plugs. This reduces the potential for postoperative sensitivity and bonding problems associated with movement of dentinal fluid through patent dentinal tubules. Technique-sensitivity associated with bonding to a dehydrated collagen matrix is also eliminated.  SE adhesive systems provide increased user reliability, with faster application and a reduced number of components and application steps.  Although this reduces the risk of saliva contamination, it may sometimes be impossible to maintain a dry operative field after the SE adhesive application.
There are a number of studies related to saliva contamination; most of these address dentin contamination with saliva. ,, In this study, we focused on saliva contamination occurring after the bonding process, i.e. after the formation of the hybrid layer. The purpose of this study was to evaluate the effect of saliva contamination on the microtensile bond strength (μTBS) of two different SE dentine-bonding systems between resin-dentin interfaces.
| Materials and Methods|| |
Twelve caries-free unrestored human third molars, which had been stored in distilled water, were selected as tooth specimens. Soft tissues were removed with a scalar (H6/H7 Scaler; Hu-Friedy, Chicago, IL, USA). After cleaning the teeth with pumice, each tooth was embedded in an autopolymerizing acrylic resin (Palapress Vario; Heraeus Kulzer GmbH, Wehrheim, Germany) in a cylindrical plastic mold of 20 mm height and 20 mm diameter. Occlusal flat dentine surfaces were exposed by cutting of occlusal enamel, using a low-speed diamond saw (Isomet; Buehler Ltd, Lake Bluff, IL, USA) with cooling water. The standard smear layer was obtained with 600-grit silicon carbide paper under wet conditions.
Two commercially available "SE" adhesives (Clearfil SE Bond [CSEB], Clearfil S3 Bond) and one resin composite (Rc) were used. Composition and manufacturers of these products are listed in [Table 1]. A direct composite resin (Spectrum® TPH® 3) was built up incrementally to create a flat crown with a height of approximately 4 mm for the μTBS test.
Specimens were randomly divided into two main groups based on the SE adhesive and then placed in subgroups based on the method of contamination [Table 2].
Tooth samples were randomly divided into three equal subgroups. Natural saliva required for this study was obtained from research assistant.
Clearfil SE 1
This was a control group in which dentin was not contaminated with saliva. Both Clearfil SE primer and CSEB were applied to the dentin according to the manufacturer's instructions, and the Rc restoration was placed (primer/bonding/composite).
Clearfil SE 2
This bonding procedure was similar to the control; however, fresh saliva was applied with a disposable brush to the dentin-bonded layer after light curing; saliva was then rinsed with a water stream from an air-water syringe for 10 s and dried with a gentle air blast for 5 s. CSEB was applied again and light cured for 20 s. The composite was built on the prepared dentin surfaces (primer/bonding (cured)/saliva/rinsing/drying/primer/bonding/composite).
Clearfil SE 3
This procedure was similar to Clearfil SE 2. After the first contamination and decontamination, CSEB was again applied and light cured for 20 s. Saliva was immediately applied to recontaminate the bonding surface and the second decontamination procedure was the same as the first, and the CSEB was applied similarly. The Rc was built on the prepared dentin surfaces (primer/bonding (cured)/saliva/rinsing/drying/primer/bonding (cured)/saliva/rinsing/drying/primer/bonding/composite).
The procedures for Group 2 were similar to Group 1 but did not contain a primer stage. Tooth samples were randomly divided into three equal subgroups (Clearfil S3 1, 2, and 3).
Following storage in distilled water at 37°C for 24 h, specimens were sectioned mesiodistally and faciolingually by using a water-cooled low-speed Isomet 1,000 diamond microslicing saw (Buehler, Lake Bluff, IL, USA) to obtain an average of 1 mm 2 thick and 6 mm long rods with the dentin-composite interface located at the center. Between five and nine rods were obtained for each tooth. Subsequently, each rods were attached to a customized microtensile jig with cyanoacrylate adhesive (Pattex, Henkel KGaA, Düsseldorf) so that the composite-dentin interface was perpendicular to the axis of the testing assembly. The μTBS of all specimens were tested using a microtensile tester, (Bisco, Schamburg, Illinois, USA) with a crosshead speed of 1 mm/min.
One-way ANOVA was used to evaluate the statistical significance of the mean tensile bond strength. A Tukey's post-hoc multiple comparison test was used to determine the significance of the deviations in the bond strength among the test subgroups after different treatments. Level of statistical significance was set at P = 0.05. Forty specimens from each subgroup were tested. Statistical analysis was performed with SPSS (SPSS 14.0J for Windows;). Descriptive statistics, including the mean, standard deviation, median, and minimum and maximum values of bond strength were calculated for each of the six groups.
| Results|| |
The μTBSs of the adhesives to dentin are summarized in [Table 3]. One-way ANOVA indicated that dentin bond strength was influenced by the number of contaminants (P < 0.05). The μTBS of the Clearfil S3 3 subgroup (twice contaminated) was statistically higher than that of the Clearfil S3 2 subgroup (contaminated once) and Clearfil S3 1 (control) subgroup. There were no significant statistical differences in the μTBSs between the Clearfil S3 2 subgroup and the control subgroup. There were no statistical differences in μTBSs among the Clearfil SE subgroups, nor were there any statistical differences in μTBSs between the Clearfil S3 and CSEB bond in the control groups.
|Table 3: The mean of micro-tensile bond strength of adhesives to dentin (*MPA)|
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| Discussion|| |
Perchance salivary contamination or presence of moisture is overlooked in the operative field. With inadequate rubber dam isolation in the application area, bond strength decreases dramatically between the resin and the contaminated surface and can cause partial or total loss of the composite restoration within a short time. 
Significant factors in the survival of restoration include behavior of the patient, saliva control, operator, age of patient, time of placement, and arch. Saliva control difficulties also increased risk of failure to bond. In the present study natural saliva was preferred as the contaminant because artificial saliva can provide misleading results. Adequate isolation from salivary contamination has long been recognized as being important to bonding success.  The SE adhesive systems used in this study might be less sensitive to moisture because they use a water-based solvent.  The hydrophilic monomers present in contemporary bonding agents increase surface wetting and resin penetration. 
We found no differences in bond strength between S3 and SE groups. In addition, neither S3 nor SE groups showed a significant decrease in bond strength under contaminated conditions. This result was somewhat surprising because saliva contamination has been reported to decrease the quality of the dentin-adhesive interface with some adhesive systems. , However, SE systems are not considered to be sensitive to moisture and are thus resistant to contamination with saliva. ,,
The hybrid layer is an important part of the bonding mechanism in adhesive systems.  Most SE adhesive systems yield a thin hybrid layer,  but the bond strength in some cases is higher than with total etch systems;  however, hybrid layer thickness is not necessarily correlated with bonding strength to dentin. ,, In this study we showed that bond strengths are not related to the thickness of the hybrid layer, which can be increased by multiple adhesive coatings.
Saliva contamination of dentine has been reported as having no adverse effect on the bonding efficiency of one-bottle adhesive systems. ,, However, some researchers have shown that saliva contamination of the dentine surface produces a significant decrease in bond strength. ,, An interesting finding in the Clearfil S3 group was that the bond strength obtained in the subgroup where the bonding agent was reapplied after being contaminated twice with saliva was higher than the control and Clearfil S3 2 subgroups. The increased bond strength may be a result of multiple adhesive coatings.
Dentine bond strengths of all-in-one adhesives have been reported as being reduced when contaminated with the saliva, and reapplication of the adhesive after cleaning the saliva from the dentine surface is an experimental recommendation for restoring bond strength. , Ghavan and Pour; however, showed that saliva contamination of a single bottle system after curing the adhesive did not decrease the bond strength compared to the control group.  Our results document that the saliva contamination does not adversely affect the bond strength of SE adhesives.
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[Table 1], [Table 2], [Table 3]