The purposes of this study was to define the optimal irradiation conditions of a KTP:NdYAG laser after root planning treatment. The surfaces of 40 single-root human teeth were scaled with conventional tools before lasing. The pulpal temperature increase was measured by means of a thermocouple. The influence of variables of coloration by Acid Red 52, scanning speed, dentin thickness, and probe position, have been analyzed for a constant exposure time of 15 seconds. The temperature was below 3 C for the adjustments, power output: 400 mw, scanning speed of irradiation: 2 mm/sec., and Pw 0.10 m sec, PRR < 60 Hz or Pw: 0.12 m sec, PRR < 55 Hz.