Title:  Er:YAG laser effect on removal of carious dentine in primary teeth: an in vitro study

Abstract:  Aim The effectiveness of carious dentine removal in primary teeth using an Er:YAG laser irradiation was compared with that of the conventional mechanical treatment, in vitro. Methods and materials First, one half of the carious dentine of 10 samples was subjected to Er:YAG laser irradiation at 200 mJ pulse energy density (55 J/cm?/pulse) with a pulse repetition rate of two pulses per second (pps). The other half of the carious dentine samples was removed with mechanical burs. Thermal change during each treatment, measurements of the time required for carious dentine removal, and scanning electron microscope (SEM) observations were performed for each treatment. The differences in the times required for each treatment group were statistically analysed by Mann-Whitney U test and a value of p<0.01 was considered significant. Results The time required for carious dentine removal by laser irradiation was two times longer than for the bur treatment. SEM observations revealed microirregularities and an absence of a smear layer after laser irradiation, in contrast to the mechanical bur treatment. Discussion The highly irregular surface of the lased cavity floor without a smear layer appears to provide an advantageous substrate for adhesive bonding composite materials. The opening of dentinal tubules might facilitate the formation of a hybrid zone, as primers and adhesive can penetrate the surface better when the smear layer has been removed. Conclusion It can be concluded that under adequate water spray, cavities without sign of thermal damage to the surrounding tissues as well as dental pulp could be produced. Therefore, cavity preparations with this less traumatic removal system may also be favourable in paediatric dentistry.