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Unlabelled: MATERIAL AND METHOD 1: The first stage of a three-stage in-vitro investigation used 146 maxillary incisors to identify optimum setting parameters for two CO2 and Nd:YAG standard laser systems applied in enamel conditioning for bracket bonding., Results: 31 of the 75 parameter combinations investigated for the Nd:YAG laser and nine of the 71 investigated for the CO2 laser proved appropriate for further investigation of tensile strength. MATERIAL AND METHOD 2: In a second stage, tensile bond strength for the selected laser settings was determined in comparison to the conventional acid-etch technique for a further 210 teeth as the control group., Results: The highest average tensile strength for the Nd:YAG laser was 4.1 MPa, with comparable values of 3.3 MPa for the CO2 Laser and 4.9 MPa for the acid-etch technique. MATERIAL AND METHOD 3: The third stage of the investigation involved comparative scanning electron microscopy of enamel surface morphology following laser application and acid-etching., Results: The CO2 laser was found to produce craters of various dimensions, while the Nd:YAG laser produced honeycomb structures regionally similar to enamel samples from the acid-etch technique., Conclusion: The CO2 and Nd:YAG dental lasers tested produce enamel conditioning and tensile bond strength sufficient to meet the requirements of bracket bonding.

An in vitro study showed that it is possible to alter the surface morphology of root canals with a Nd-YAG Laser. S.E.M. and dye penetration photographs showed these changes in the canal surface morphology. In our opinion when an energy level of 15 IPS/1,5 W is used, the resulting changes are useful and of benefit in root canal treatment.