THE JOURNAL OF - Dentsply

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-
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