Response of Dental Pulp Cells to Er:YAG Irradiation

Abstract

This study aimed to investigate the response of human dental pulp cells lying on a thin dentin disc to Er:YAG irradiation. Er:YAG laser irradiation has been effectively used for tooth cavity preparation with minimal damage to the dental pulp tissue. However, study of its direct effect on pulp cells has been limited. Primary human dental pulp cells were cultured and allowed to grow on one side of 500-μm-thick dentin discs. An Er:YAG laser at output energies of a 120, 300, or 500 mJ/pulse with a repetition rate of 10 Hz was used to ablate the non-cell surface of the dentin disc for 10 s with cooling irrigation. Twenty-four hours after laser irradiation, light and scanning electron micrographs revealed pulp cells with a normal fibroblastic morphology for the 120 and 300 mJ laser-treated groups. In the 500 mJ laser-treated group, many pyknotic cells with knob-like projections on the cell surface were mostly observed: the number of cells with normal morphology decreased compared to that of the other groups. However, the production of type I procollagen assessed by the enzyme immunoassay increased in the 500 mJ laser-treated group significantly (p < 0.001). The low-energy Er:YAG laser (120 and 300 mJ at 10 Hz) with coolant irrigation did not cause damage to dental pulp cells at critical thickness (500 μm) of dentin, whereas the laser of 500 mJ at 10 Hz induced greater production of type I procollagen with partial damage to the cells.