Early Phase Gingival Wound Healing Following Low-Level Er:YAG Laser Irradiation: In Vitro and In Vivo Studies

Background: Low-level laser irradiation (LLLI) can promote wound healing. However, the biological effects of the erbium-doped yttrium aluminum garnet (Er:YAG) laser on gingival wound healing remain unclear. Objectives: To assess the effects of low-level Er:YAG laser irradiation on endothelial cell activity in vitro and on early phase gingival wound healing in vivo. Methods: In vitro, human umbilical vein endothelial cells were irradiated with a low-level Er:YAG laser (30 mJ/pulse, 10 Hz, 20 and 30 s, defocused, no water spray) and assessed for viability, cytotoxicity, and migration. Standardized bilateral wounds (4 × 1 mm) were created in the palatal gingiva of 14 male mice using a scalpel and curette. The wounds were irradiated for 20 s under the same irradiation settings, using a contact tip (diameter 800 μm) to induce superficial blood surface coagulation, while contralateral sites were assigned to controls in a split-mouth design. Postoperative wound area and mRNA expression of IL-6, TNF-α, VEGF, FGF-2, and TGF-β1 were analyzed after 48 h. Results: In vitro, LLLI significantly enhanced cell proliferation with/without increasing cytotoxicity. In the wound healing assay, the LLLI significantly promoted cell migration compared with the control. In vivo, the reduction in residual wound area in the laser group was comparable to that in the control group. IL-6 and TNF-α expressions were significantly downregulated, whereas VEGF was significantly upregulated in the laser group. Conclusions: Low-level Er:YAG laser irradiation enhances anti-inflammatory and pro-angiogenic effects, suggesting its potential in promoting gingival wound healing.