Assessment of circular wound healing in rats after exposure to 808‐nm laser pulses during specific healing phases

Background and Objectives Low‐level laser therapy (LLLT), is an important application modality for the advancement of wound healing processes. In this study, histological and morphometric analyses have been made to understand and compare effects of high‐power 808‐nm pulses on circular skin wounds among groups irradiated immediately after wounding and groups irradiated at specific stages of the healing period. Study Design Experimental groups were as follows: Laser Therapy (LT) was received as three sessions of laser irradiation (6.38 J/cm 2 , 1.276 W/cm 2 , 808 nm) immediately after wounding (Inflammatory group, n = 12), 24 hours post‐wounding (Proliferative group, n = 12), and 72 hours post‐wounding (Remodeling group, n = 12); the Control group ( n = 12) received no irradiation. Histological analyses were performed on the 3rd, 7th, and 14th days post‐wounding. Results Mean wound diameters were 5 mm for all groups. On Day 7, wound diameters were measured as 2.99 ± 0.17, 2.95 ± 0.3, 2.52 ± 0.11, and 2.41 ± 0.34 mm for the Control, Inflammatory, Proliferative, and Remodeling groups, respectively. At 2 weeks post‐wounding, dermal tissue in the Inflammatory and Proliferative groups closed superficially, while 1.30 ± 0.1 mm and 1.30 ± 0.06 mm openings remained in the Control and Remodeling groups, respectively. Mean wound healing rates (WHR) for all treatment groups were found to differ significantly from the control group ( P < 0.05). Upon comparing the Proliferative group with the other treatment groups, a significant difference was found. However, no significant difference was found between the Inflammatory and Remodeling groups, with the former having a slightly higher mean value. Conclusion Histological and morphometric results showed that high‐power, low‐energy application has the best effect when first applied 24 hours post‐wounding (late inflammatory, early proliferative stage) as demonstrated by increases in granulation tissue, fibroblasts and collagen deposition, which lead to faster rates of wound contraction and thus accelerated healing. Lasers Surg. Med. 48:409–415, 2016. © 2015 Wiley Periodicals, Inc.