Etching of Enamel by Laser Energy for Direct Bonding of Orthodontic Appliance and Evaluation of Shear Bond Strength

Abstract

In recent years, there has been growing interest in the laser applications for different dental maladies. Some of the applications of laser irradiation to etch dental enamel in preparation for direct bonding of orthodontic appliances have been studied and compared. Nonetheless, the etching effects of phosphoric acid and tow lasers radiations on the enamel of extracted human teeth had been compared in this study. 40 extracted human teeth were divided into 4 groups of 10 teeth each. Power settings on the laser etching unit were used. For first group: buccal surfaces were etched with an Er:yag laser (λ=2.9μ, W=2.5w), second group: buccal surfaces were etched with a Nd:yag laser (λ=0.532μ, average W=12w, V=25mm/sec), and third group: buccal surfaces were etched with a Nd:yag laser (λ=0.532μ, average W=12w, V=10mm/sec). While for forth group: buccal surfaces were subjected to a 30sec acid etching (35%). After etching, modifications of the enamel surfaces were compared using two microscopes. Microscopically, the laser-ablated surfaces showed the formation of craters. These craters are higher in Er:yag laser. The acid-etched surfaces contained numerous microspaces, for the surface changes seen in the Nd:YAG laser-etched enamel result in a rough porous surface. But, some of the laser beam energy to thermal energy causes thermally-induced and Er:yag laser with lower energy is more useful without side effects of thermal on dental tissues than Nd:yag. The summary means shear bond strengths of the buccal enamel surfaces etched by laser irradiation and by phosphoric acid, along with their standard deviations. It has been suggested that a minimum clinically acceptable bond strength. No significant differences were found between 2.5W laser irradiation and phosphoric-acid etching.