Effect of an antibacterial adhesive on the bond strength of three different luting resin composites

Summary

Objectives

Effect of a dentin adhesive system containing antibacterial monomer-MDPB (Clearfil Protect Bond) on the shear bond strength of all-ceramic-IPS Empress 2 restorations luted with three different dual-polymerizing systems (Variolink 2, RelyX ARC and Panavia F 2.0) to dentin was investigated.

Methods

One hundred and eight all-ceramic discs (2×3 mm; IPS Empress 2) were fabricated and ultrasonically cleaned. The buccal surfaces of 108 non-carious extracted human premolars were flattened to expose dentin and subsequently polished with 600-grit wet silicon carbide paper. Three dual-polymerizing luting systems had test groups and control groups consisting of 18 samples each. For the test groups Clearfil Protect Bond was applied to the exposed dentin surfaces. Control groups received the original bonding procedures of each adhesive system. After the all-ceramic samples were luted to the teeth, thermocycling was performed 5000 times. Shear bond strengths were tested using Shimadzu Universal Testing Machine until failure. Analysis of fractured dentin surfaces were performed using Optical Microscope at ×10 and ×1000 magnifications and the images were analyzed with Image Analyzer. Data was analyzed with one-way ANOVA and Bonferroni test at a significance level of p<0.05.

Results

Mean shear bond strength data of the groups in MPa were; Variolink: 20.45±4.75, Variolink+Clearfil Protect Bond:29.32±2.37, RelyX ARC:18.82±3.19, RelyX ARC+Clearfil Protect Bond:25.58±4.05, Panavia F 2.0:17.11±2.98, Panavia F 2.0+Clearfil Protect Bond:24.40±7.46.

Application of the antibacterial adhesive increased the shear bond strengths of all three dual-polymerizing systems to dentin (p=0.00). The surface analysis showed that most of the specimens showed the adhesive failure mode between the dentin and the composite luting agent interface.

Conclusion

The antibacterial adhesive system Clearfil Protect Bond can be safely used to prevent the potential risk of complications resulting from bacterial activity regardless of affecting the bond strength of IPS Empress 2 restorations luted with the dual-polimerizing systems used in this study.

Introduction

Due to an increasing interest in esthetics and concerns about toxic and allergic reactions to certain alloys, patients and dentists have been seeking metal-free tooth-colored restorations.¹ Recent progress in the technology of new all-ceramic materials has broadened the choices for esthetic restorations. The long term success of all-ceramic crowns depends mainly on the strength and durability of the bond of the luting composite to the tooth and the ceramic substrates.²

IPS Empress 2 (Ivoclar Vivadent, Schaan, Liechtenstein) glass ceramic is a heat-pressed, leucite-reinforced material using the ‘lost wax’ technique. This all-ceramic material has been introduced for single unit restorations as well as for three-unit fixed partial dentures of the anterior region extending to the second premolar. The final restoration, made of a lithium disilicate framework ceramic, offers clinical benefits in terms of machinability, polishability, reduced wear of opposing tooth structure with the advantages of increased biocompatibility, natural appearance and superior esthetics.³

Adhesion between tooth structure and the restoration is one of the most important factors determining the success of a restoration. Dentin bonding systems are designed to produce a hermetic seal between a composite restoration and surrounding dentin. Adhesive composite resin luting systems are now recommended for the cementation of many all-ceramic systems.4, 5, 6 Most modern resin cement kits contain both a dentin bonding agent for bonding to the tooth structure and a dual-polymerizing cement (resin composite) for bonding to the restoration. When bonding ceramic to tooth structure, two different interfaces need to be considered the dentin/adhesive interface and the ceramic/cement interface. The bond strength at both of these interfaces should be optimized, because the lower one will determine the final bond strength of the cemented restoration.⁷ Unfortunately, the bonding performance of resin cements is not so reliable as that of adhesives for direct composite resin restoration.5, 8, 9 Several reports are available which have demonstrated the formation of microgaps at the interface between the dentin and resin of various proprietary adhesive systems applied to human teeth in vivo.8, 9 These findings indicate that even the latest adhesive systems are not capable of providing a complete seal in clinical situations. If a proper adhesion cannot be achieved, microleakage, defined as the passage of bacteria, fluids, chemical substances, molecules, and ions between the tooth and its restoration, can occur, which would threaten clinical performance and longevity of the restoration, contributing to staining, recurrent caries, adverse pulpal response and postoperative sensitivity.¹⁰ It has been reported that when resin cements were used, practitioners saw post-operative sensitivity within the first year after cementation in about 37% of their patients, and up to 11% of the teeth required endodontic treatment within the first year.¹¹ Brännström¹² has also stated that about 5–24% of crowns and fixed partial dentures may in time result in pulpal complications and periapical inflammatory lesions.

The problems associated with microleakage can be magnified by incomplete sterilization of the preparation from all infected materials,¹³ especially if a carious lesion exists in the prepared tooth. It has been shown in numerous experiments that infection is the main cause of pulpal damage. Tissue fluids from the pulp as well as organic substances within the dentin and enamel provide sufficient substrate for microbial growth under restorations.¹⁴

The indirect restoration technique generally requires removal of more tooth substance than in the case for direct restoration technique. When the restoration walls are completely in enamel, excellent clinical performance can be obtained since the seal would be nearly perfect.15, 16 On the other hand where dentin is exposed, the application of etchants will increase the permeability of the tubules, resulting in bacterial invasion which will increase the possibility of pulpal irritation or damage and lead to sensitivity.² Since there is always cut dentin to be bonded to the all-ceramic material, expectations of higher risks of sensitivity leading to these complications should be the concern of the prosthodontist practicing with all-ceramics. Therefore, using restorative materials possessing antibacterial activity is considered to be beneficial in eliminating the harmful effects caused both by bacteria remaining after tooth preparation and by microleakage.¹⁷

The application of a disinfectant after tooth preparation and before inserting the restoration is recommended to overcome the consequences of bacterial activity.13, 18, 19 A potential problem in the use of disinfectants with dentin bonding agents is the possibility of an adverse effect on the bond strength of the restorative material to dentin.19, 20, 21 Furthermore, some clinicians believe that the cavity disinfection step is a time consuming and unnecessary procedure during routine restorative treatments. In addition a recent in vitro study indicates that self-etching adhesive system containing antibacterial monomer 12-methacryloxy dodecyl prydinium bromide (MDPB) is found to be more effective in antibacterial activity than cavity disinfectant solutions.²²

However, as this product was only recently introduced to the market there is a lack of literature about the effect of dentin adhesive system containing MDPB, Clearfil Protect Bond (Kuraray, Osaka, Japan) on the bonding performance of luting resin composites used in the cementation of all-ceramic systems. Therefore, the null hypothesis of the present study was that Clearfil Protect Bond would not adversely effect the shear bond strengths to dentin of an all ceramic system-IPS Empress 2 bonded with three different dual-polymerizing systems Variolink 2 (Ivoclar Vivadent, Schaan, Liechtenstein); RelyX ARC (3M ESPE, St Paul, MN, USA) and Panavia F 2.0 (Kuraray, Osaka, Japan).