[Effects of pulsed Nd:YAG laser irradiation on shear bond strength of composite resin bonded to porcelain].
OBJECTIVE
To evaluate the shear bond strength of composite resin bonded to pretreated porcelain surfaces by use of a pulsed Nd:YAG laser irradiation and by use of 8% hydrofluoric etching.


METHODS
Surfaces of porcelain were roughened with coarse diamonds until the opaque body porcelains were exposed. The samples were divided into four groups. Samples of the first group were etched with 8% hydrofluoric acid for 3 min by following the manufacter's instructions. Samples of the 2nd, 3rd and 4th groups were separately irradiated by a pulsed Nd:YAG laser of three energy parameters of 15 Hz, 40 mJ; 0.6 W; 15 Hz, 60 mJ, 0.9 W and 15 Hz, 80 mJ, 1.2 W different respectively, each specimen was irradiated for 1 min. Then, silane coupling agent was equally placed on the treated surfaces for 3 min, the activator was used on each surface. The adhesive was applied and light-cured. The composite resin material was finally bonded to the treated porcelain surface, forming a 3 mm x 3 mm x 2 mm resin mass. Samples were then tested for shear bond strength between the treated porcelain and composite resin by using a SWD-10 electric universal testing machine with a crosshead speed of 1 mm/min until fracture. At the end of testing, the data was evaluated by using a two-way analysis of variance (ANOVA) comparing the shear bond strength. On the other hand, characteristic morphology of laser irradiated surfaces of porcelain was prepared and observed by a scanning electron microscopy.


RESULTS
The shear bond strength of laser groups of 0.6 W, 0.9 W, 1.2 W and etching group was respectively 8.61, 14.07, 11.22 and 13.47 MPa. There was no significantly difference among groups of laser 0.9 W, 1.2 W and the etching group. This suggested that irradiated on surfaces of porcelain by Nd:YAG laser at the above laser energy could attain the same effectiveness as hydrofluoric acid etching. But the shear bond strength of laser 0.6 W group was significantly lower than the etching group. It suggested that shear bond strength would obviously decrease when laser energy was 0.6 W or lower than this parameter, and had no use in treatment on porcelain surfaces comparing to acid etching. SEM showed that porcelain surfaces irradiated by Nd:YAG laser exhibited rough, umbilicate, lava crater-like structure. This structure helped to produce mechanical retention between resin composite and porcelain.


CONCLUSIONS
The pulsed Nd:YAG laser could replace etching method to pretreat the fracture porcelain surfaces for bonding with composite resin at appropriate energy parameters.
Li
R
R
Department of Stomatology, 3rd Affiliated Hospital, Sun Yat-San Medical University.
Ren
Y
Y
Han
J
J
D003188:Composite Resins; D001840:Dental Bonding / Q000379:methods*; D003776:Dental Porcelain; D007834:Lasers; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D033081:Shear Strength
D003188:Composite Resins; D003776:Dental Porcelain