Er:YAG (λ=2.94 µm) Laser Etching of Dental Enamel as an Alternative to Acid Etching

Abstract

. Acid etching is widely used in clinical dentistry to facilitate the mechanical retention of resin-based materials to teeth, in particular enamel surfaces. Several laser systems have been developed with the aim of modifying dental hard tissues and the Er:YAG (λ=2.94 µm) laser may offer a possible alternative to the acid etching technique. This study compares the shear bond strengths of composite beads attached to sound enamel surfaces prepared using either (a) no etching (negative control), (b) acid etching (positive control) or (c) Er:YAG laser etching, either with or without water, at one of three fluences: 15 J/cm2, 18 J/cm2 or 24 J/cm2. A histological appraisal was also conducted using environmental scanning electron microscopy (ESEM) techniques. The mean shear bond strength for acid-etched enamel was 16.6 MPa (SD 4.4, n=10), whereas the best laser-etched mean bond strength obtained was 11.5 MPa (SD 4.1, n=11) using a fluence of 24 J/cm2 with water. These values were significantly greater than those obtained for the negative control (no etching) of 4.4 MPa (SD 0.9, n=8). There was a significant positive correlation between the etching fluence and the shear bond strength, but pitting of the enamel surface at fluences above 25 J/cm2 limited the maximum fluence for etching purposes. Although Er:YAG laser etching enhanced the retention of a resin-based material to an enamel surface when compared to a negative control, the mean shear bond strengths were significantly lower than those obtained using conventional acid etching. The optimal laser etching parameters in this study were shown to be 24 J/cm2 in conjunction with water.