Shear Bond Strength of Repair Composite Resin to an Acid-Etched and a Laser-Irradiated Feldspathic Ceramic Surface

Abstract

The purpose of this study was to evaluate the shear bond strength of a repair composite resin to a feldspathic ceramic surface that had been either etched with 9.5% hydrofluoric acid (HFA), irradiated by an Er:YAG or Nd:YAG laser, or etched with 9.5% HFA after being irradiated by each laser type. New findings have shown that combined laser irradiation and acid etching of a ceramic surface can be used to roughen ceramic surfaces. Seventy-eight feldspathic ceramic discs were assigned to six surface treatment groups (n = 13): C, no treatment; HFA, 9.5% HFA etching; ER, Er:YAG laser irradiation; ND, Nd:YAG laser irradiation; ER + HFA, Er:YAG laser irradiation followed by HFA etching; ND + HFA, Nd:YAG laser irradiation followed by HFA etching. The surface of one disc from each treatment group was examined under a scanning electron microscope. After the surface treatments and silanization, a repair composite resin was applied to each disc using a commercial ceramic repair kit. Shear bond strength testing was then done after storing the specimens in distilled water for 24 h at 37 degrees C and thermocycling. Each ruptured specimen was examined under a stereoscopic light microscope. The highest shear bond strength was found after HFA etching, and the lowest was found after Er:YAG laser irradiation. HFA etching also caused the most pronounced changes of all the surface treatments. When HFA was applied after either laser irradiation, the fissures and cracks were larger than those seen on the only laser-irradiated surfaces. HFA etching is the most effective surface treatment for increasing the shear bond strength between a repair composite resin and a feldspathic ceramic surface. The shear bond strength after laser irradiation can be increased by HFA etching, but the strength of the bond is still smaller than that after HFA etching alone.