Investigation of Er:YAG laser etching on enamel–sealant interface in vitro SEM study

Abstract

The purpose of this study was to evaluate the optimal laser energy irradiated on enamel surface and to investigate the application of Er:YAG laser etching on enamel–sealant interface by scanning electron microscope (SEM). The pretest was conducted by using six extracted human premolars and then evaluated the optimal energy level. The buccal surface of each tooth was divided into four sections, each of which was then irradiated with Er:YAG laser at 60, 100, 140 and 180 mJ/pulse, respectively. The result showed that the energy level at 140 mJ/pulse was suitable for altering enamel surface. Twenty-four human premolars from 12 patients were divided into two parts of six patients. One premolar from each patient was etched with 38% phosphoric acid as a control in each part. For the experiment in part I, the enamel surfaces were lased with Er:YAG laser 140 mJ/pulse. In part II, the enamel surfaces were lased with Er:YAG laser and followed by acid etching. Then sealing material was placed on the pit and fissure and light activated. All teeth were demineralized in 10% HCl acid leaving remaining sealing material intact. The enamel–sealant interfaces were investigated under SEM. The results showed that the samples in control groups had numerous resin tags on the enamel surface. In the other samples, there were a lot of interconnecting partitions but disappeared in the area adjacent to the bottom of the pit and fissure, and no resin tags were found on the inclined plane. However, resin tags were observed on the junction between the interconnecting partitions and the bottom of the pits and fissures in the samples, which were lased and followed by etching. In conclusion, this study revealed different patterns between acid etching and laser etching.