Objective To observe the changes of surface morphology and temperature of dental pulp cavity in vitro after irradiated by Er：YAG laser with different energy and irradiation time. Methods All of the 96 samples from 24 teeth in vitro were collected from dental clinical departments then divided into two groups（group A and group B） randomly. We chose the energy of 20 Hz, and 1, 2, 3, 4, 5, 6 W to treat the samples in group A and group B and the irradiation time was 10 s or 20 s. We recorded the temperature changes of dental pulp cavity by digital thermometer and observe the morphology of tooth enamel by scanning electron microscope（SEM）. Results With the extension of irradiation time and increasing of energy, the temperatures of dental pulp cavity were significantly increased after the treatment of Er：YAG laser. The two groups of tooth enamel surface morphology were changed after irradiated by Er： YAG laser with different energy and irradiation time. However, there was no melting and carbonation on the surface of tooth enamel after the treatment of Er：YAG laser in two groups. Conclusion The temperatures of dental pulp cavity were increased after irradiated by increasing laser energy density fom 1W to 6W. No melting or carbonized phenomenon was found in enamel within the energy of 1 W to 6 W. All the data would provide evidences for clinical treatment of cavity.
