• E V Ross, G S Naseef, J R McKinlay, D J Barnette, M Skrobal, J Grevelink, and R R Anderson.
• Wellman Laboratories of Photomedicine, Department of Dermatology, Massachusetts General Hospital, Boston.
• J. Am. Acad. Dermatol. 2000 Jan 1; 42 (1 Pt 1): 92-105.

BackgroundAdvances in laser technology allow for precise tissue removal and minimal thermal damage. However, mechanisms for cosmetic improvement have not been determined. Investigators have suggested that ablation, collagen shrinkage, and new collagen deposition all contribute to the clinical outcome.ObjectiveIn a live farm pig, we examined gross and microscopic effects of thermal and mechanical ablation devices to characterize immediate and long-term mechanisms in skin rejuvenation.MethodsTwo CO(2) lasers, an erbium:YAG laser, a dermabrader, and a dermatome were used to treat flank skin in a farm pig. There were 14 different treatment groups based on device type and working parameters. One to five sites were treated for each group. Wound surface areas were measured before treatment, immediately after treatment, and 7, 17, 23, 30, and 60 days thereafter. Biopsies were performed immediately after irradiation and 2, 7, 17, and 60 days after treatment.ResultsFor the CO(2) laser-induced wounds, surface area measurements showed that immediate and final wound contraction tended to increase with initial residual thermal damage (RTD) for a range of values, above which immediate contraction remained relatively constant. Although there was no immediate wound contraction with mechanical ablation devices, long-term wound contraction in the dermatome and dermabrasion sites increased with depth of ablation. The erbium:YAG laser sites healed in a manner similar to that of mechanically induced wounds. Wound contraction profiles over time were dependent on depth of RTD and depth of ablation. Sixty days postoperatively, histologic examination showed varying degrees of fibroplasia. Overall, there was greater compaction and horizontal orientation of collagen fibers in those wounds with more than 70 microm of dermal RTD. Grossly, all wounds were similar after 60 days, with the exception of the deep dermabrasion sites, at which clinical scarring was observed.ConclusionOur results show that CO(2) laser resurfacing produces short- and long-term wound contraction that is greater than that induced by purely ablative methods for the same total depth of injury. The erbium laser produced wound contraction profiles similar to those produced by mechanical wounding. The data suggest that initial collagen contraction and thermal damage modulate wound healing.

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