THERMAL EFFECTS ASSOCIATED WITH THE ND-YAG DENTAL LASER

The heat produced at the dentinal pulpal wall opposite the irradiation site was measured during etching of dental enamel with an Nd:YAG lase r in preparation for direct bonding of orthodontic appliances. Forty e xtracted human teeth were randomly divided into four groups of 1 0 tee th. Within each group, the buccal surfaces of 5 teeth and the lingual surfaces of the other 5 teeth were laser treated for 12 sec. Irradiati on was performed with a commercial Nd:YAG laser at the power settings of 80mJ, 1W, 2W and 3W. Prior to irradiation, an occlusal access prepa ration was made into the pulp in order to facilitate the placement of a thermocouple for measurement of temperature changes at the dentinal pulpal wall opposite the irradiation site. The thermocouple was held a gainst the dentinal pulpal wall and the resulting temperature changes were recorded. Heating effects at the dentinal pulpal wall on both buc cal and lingual surfaces showed an increase in heat as a function of t he increase in power output from the laser unit (p<0.01). The temperat ures measured at power levels 1-3W appeared to be of sufficient magnit ude to cause at least localized pulpal inflammation and possible irrev ersible damage to the pulp tissue immediately opposite the site of las er irradiation.