2010 Volume 53 Issue 2 Pages 147-158
The purpose of this study is to examine the influence of laser irradiation of dental hard tissues and to confirm the optimum irradiation conditions (output energy, repetition rate and ratio of water/air) with an Er, Cr: YSGG laser. The Er, Cr: YSGG laser apparatus used in this study was a Waterlase™ MD® (Biolase Technology, USA). Extracted human molars without a carious region were collected from the Department of Oral Surgery, Osaka Dental University Hospital and stored frozen before the experiment. The enamel and dentin surface of the thawed teeth was ground to #2,000. Initially, we fixed the ratio of water at 30%, and air at 60%. The Er, Cr: YSGG laser was irradiated for one second at an irradiation distance of 1mm to the ground enamel and dentin surfaces at repetition rates of 0.25, 1.00, 3.00 and 5.00W at output energies of 10, 20 and 50Hz. The irradiated mass of the removed teeth (caliber, depth and removal volume) and the tooth quality were observed. Next, based on previous results, the output energy was increased to 5.00W in enamel and 3.00W in dentin with a repetition rates at 20Hz in both the enamel and dentin. The Er, Cr: YSGG laser was irradiated for one second, at an irradiation distance of 1mm to the ground enamel and dentin surfaces at various ratios of water and air. The irradiated mass of the removed teeth (caliber, depth and removal volume) and the tooth quality were observed. The results were as follows: 1. In both the enamel and dentin, the amount of removal was increased by raising the output energy and lowering the repetition rate. 2. In both the enamel and dentin, cracks indicating the influence of heat were observed. 3. Effective removal was possible at an output energy of 5.00W with a repetition rate of 20Hz in enamel and 3.00W in dentin, and with a repetition rate of 10Hz in dentin. 4. Effective removal was possible with 95% water for enamel and 75% for dentin, and 100% air for both enamel and dentin.
