Number of sessions of applications of laser photobiomodulation therapy interferes with the viability of skin flap: an experimental study in rats

Purpose: Several parameters influence the effectiveness of photobiomodulation therapy (PBMT) in improving skin flap viability, yet the role of the number of treatment sessions remains underexplored. This study aimed to evaluate the effect of different numbers of laser PBMT sessions on skin flap viability. Methods: Thirty-two Wistar rats were randomly divided into four groups: G1 (PBMT simulation), G2 (PBMT for 2 consecutive days), G3 (PBMT for 5 days), and G4 (PBMT for 7 consecutive days). Treatment began immediately after surgery with the following parameters: 90 J/cm² fluence, 40 mW output power, 90 seconds application time, and 3.6 J of energy per point, with irradiation at three points and 24-hour intervals between sessions, according to each group’s protocol. On the 7th postoperative day, tissue was collected from the irradiated area for analysis of necrotic area, vessel and mast cell morphometry, and immunohistochemistry for angiogenesis markers. Results: G2 showed the smallest necrotic area, and a higher percentage of VEGF- and HIF-1α-positive cells compared to G1. Conclusion: These results suggest that the number of PBMT sessions influences skin flap viability, with two applications providing the most beneficial outcome.