Sarrett 244 The Journal of Adhesive Dentistry
Shear Bond Strength and Physicochemical Interactions of XP Bond Mark A. Latta a Purpose: The purpose of this study was to evaluate the shear bond strength of composite to dentin and enamel using the new etch-and-rinse adhesive XP Bond compared to other adhesives (Optibond Solo Plus, Apder ScotchBond 1 XT, Syntac Classic). Materials and Methods: Shear bond strength (MPa) was measured by shearing a resin cylinder 4.5 mm in diameter from prepared buccal surfaces of human third molars using an Instron Testing Machine equipped with a chiselshaped rod. In addition, micro-Raman spectroscopy was performed to determine if there was a chemical interaction between the resin adhesive and dentin and enamel. Results: Significant differences were observed among the dentin and enamel values generated with the adhesives tested. XP Bond generated statistically similar values to Optibond Solo Plus and Apder ScotchBond 1 XT to both enamel and dentin. Syntac Classic generated significantly lower values to both enamel and dentin. Conclusion: Micro-Raman spectroscopy showed a complete infiltration of resin into the demineralized dentin zone. In addition, it strongly suggested a chemical interaction with XP Bond and components of dentin. It is hypothesized that this interaction is due to the formation of calcium phosphate complexes derived from mineral apatite in the dentin and phosphate esters in the adhesive. Keywords: adhesion, bonding, chemical analysis, Raman spectroscopy. J Adhes Dent 2007; 9: 245-248. Submitted for publication: 15.12.06; accepted for publication: 11.1.07. In spite of significant improvements in dental adhesives in the last decade, achieving a durable bond and seal of resin based restorative materials still remains a challenge. The primary mechanism for bonding to dentin with etch-andrinse adhesives is via the removal of the dentin smear layer and surface mineral followed by infiltration and entanglement of resin monomers into the exposed collagen matrix in the demineralized zone. 2 This resultant mixture of resin, collagen, and mineral is termed the hybrid zone. 4 The exposed collagen fibrils are suspended in water, creating space for a Associate Dean for Research, Professor of General Dentistry, Creighton University School of Dentistry, Omaha NE, USA. Paper presented at Satellite Symposium on Dental Adhesives, Dublin, September 13th, 2006. Reprint requests: Prof. Mark A. Latta, D.M.D., M.S., Associate Dean for Research, Professor of General Dentistry, Creighton University School of Dentistry, 2500 California Plaza, Omaha NE 68178, USA. Tel: +1-402-280-5044, Fax: +1- 402-280-5004. e-mail: mlatta@creighton.edu the penetration of the resin monomers. Drying collagen results in its collapse and may prevent full infiltration of the adhesive resin. 3 Clinically, it is difficult to create the optimal dentin moisture for bonding. However, failure to do so may lead to postoperative sensitivity, bond failure, leakage, and ultimately early failure of the restoration. There are numerous in-vitro testing methods to evaluate the properties of resin adhesives. While bond strength testing does not definitively predict clinical behavior, comparison of new systems with adhesives of known clinical performance can yield valuable information. 1,5,9 Microscopically, the interfacial interaction between adhesive and tooth structure is typically investigated with scanning electron microscopy and transmission electron microscopy. However, there is only limited chemical structural investigation of the resin/tooth interface. The minimal thickness of the tooth/adhesive interface requires an analytical technique with very high resolution. Micro-Raman spectroscopy has been shown to be a very promising technique for investigating the adhesive bond with tooth structure. 7,8,10,11 It has numerous advantages, including the ability to analyze speci- Vol 9, Supplement 2, 2007 245