These results suggest that during the Er,Cr:YSGG laser irradiation, water spray directed at the ablation sites increases the ablation depths and water plays an important role as an initiator of the ablation of dental hard tissues.

The results of this study suggest that Er:YAG laser irradition with and without water mist appears to be more effective for caries prevention.

The results of this study suggest that addition of a fine water mist directed at the ablation sites does not greatly decrease the ablation, and does not cause any carbonization and melting in the surrounding dental hard tissues.

In the present study, the compositional changes and knoop hardness of the cavity floor prepared by Er,Cr:YSGG laser irradiation was compared with that of the conventional bur cavity. Fifteen laser and 15 bur cavities were cross-sectioned, and subjected to atomic analysis by SEM-EDX and knoop hardness test. Statistical analyses were performed using the Mann-Whitney U-test; a value of P < 0.01 was considered significant. Surface characteristics of the prepared cavities were also investigated by light microscopy and scanning electron microscopy (SEM). The results showed that the quantities of Ca (Ca weight %) and P (P weight %) were increased significantly in the laser cavity floor but no significant differences were found between the Ca/P ratio and knoop hardness number of laser and bur cavities. The SEM observation revealed that the lased cavity surface was irregular and there was also the absence of a smear layer; the orifice of dentinal tubules was exposed. Er,Cr:YSGG laser device is considered as one of the most effective and safe devices for cavity preparation because of its many advantages. This includes easy delivery system, minimal thermal damage to the surrounding tissues, minimal thermal-induced changes of dental hard tissue compositions, and favourable surface characteristic.

The results of this study suggested that Er,Cr:YSGG laser irradiation with and without water mist appears to be effective for increasing acid resistance.