The effect of irradiance level in 980-nm diode laser skin welding

Current research aimed to investigate the role of irradiance in skin laser welding.

Optical and thermal responses of tissue to infrared irradiation are highly dependent on both wavelength and tissue type. The desired effect on tissue is created by proper selection of laser power, application time, and spot size.

Full-thickness skin incisions on Wistar rat dorsum were welded with 980-nm diode laser application. Two irradiance levels (200 and 16.6 W/cm(2)) were applied with high (6 W, 400 ms) and low (0.5 W, 5 s) powers of laser with the same spot size (0.03 cm(2)). Subjects were monitored throughout a 21-day recovery period; incisions were sampled for histology and mechanical tests on particular control days (1, 4, 7, 14, and 21). Closure index, thermally altered areas, epidermal thickness, and granulation areas of H&E (eosin) stained samples were calculated. The breaking point during a mechanical tensile test that ran at 5-mm/min crosshead speed was recorded.

In the suture group, there was no closure 24 h postoperation. For laser groups, immediate closure at the surface layers of the incisions was observed: Almost half-thickness (from surface to deep dermis) welding was achieved. Granulation tissue level and epidermal thickness level for all groups were similar on postoperative day 21.

The laser welding technique was found reliable in terms of immediate and mechanically strong closure compared with suture. Low irradiance of a 980-nm laser (16.6 W/cm(2)) yielded noticeably stronger bonds at the end of 21 days of recovery, as well as minimal thermal damage.