Bond strength of an etch-and-rinse adhesive to KrF excimer laser-treated dentin.
OBJECTIVE
The aim of this work was to evaluate the effect of KrF excimer laser treatment on the bond strength between dentin and an etch-and-rinse adhesive system.


METHODS
Polished dentin surfaces were subjected to the following treatments: (1) 35% phosphoric acid etching for 15 s; (2) laser surface treatment using KrF excimer laser radiation (1 J/cm(2)); and (3) laser treatment under the same conditions followed by acid etching. After treating the dentin, an etch-and-rinse adhesive (Adper Scotchbond 1 XT, 3M ESPE) was applied and composite (Esthet-X, Dentsply Caulk, Konstanz, Germany) build-ups were incrementally constructed. After 24 h of water storage at 37 degrees C, 1 mm(2) beams were longitudinally cut from the samples. Microtensile sticks were loaded in tension at a crosshead speed of 0.5 mm/min. Bond strength data were analyzed with one-way ANOVA and the Student-Newman-Keuls test (p < 0.05). The dentin surfaces resulting from each surface treatment and the fracture surfaces originated by the bond-strength tests were observed under a scanning electron microscope.


RESULTS
Laser-treated surfaces exhibited a cone-shaped topography with a frank occlusion of dentinal tubules, while acid etching produced a smoother surface with open tubules. Application of 35% phosphoric acid on laser-treated dentin surfaces resulted in the partial dissolution of the surface cones. Mean microtensile bond strengths for acid-etched dentin was significantly higher (33.7 +/- 8.7 MPa) than for laser-treated (13.8 +/- 5.1 MPa) and laser-treated and etched surfaces (19.7 +/- 6.9 MPa). A higher percentage of cohesive failures at the base of the cones occurred in the laser-treated group, whereas mixed failures were predominant on acid-etched samples.


CONCLUSIONS
The cone-shaped texture produced by treating dentin with KrF laser radiation does not improve the bond strength of the tested etch-and rinse adhesive system when compared to the traditional acid-etching technique.
Eugénio
Sónia
S
Department of Materials Engineering, Instituto Superior Técnico, Lisboa, Portugal.
Osorio
Raquel
R
Sivakumar
Manickam
M
Vilar
Rui
R
Monticelli
Francesca
F
Toledano
Manuel
M
D000134:Acid Etching, Dental; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D001840:Dental Bonding / Q000379:methods*; D003799:Dental Stress Analysis; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents; D006801:Humans; D054018:Lasers, Excimer; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008964:Molar, Third; D010755:Organophosphates; D013499:Surface Properties; D013718:Tensile Strength
C489661:Adper Prompt Self-Etch; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C466112:Esthet-X; D010755:Organophosphates; D017438:Bisphenol A-Glycidyl Methacrylate