Evaluation of the tie-over method in wound healing of rat skin.

We evaluated wound healing methods during the tie-over method for repair of oral mucosal defects in rat skin. (Methods) We made epidermal defects 20mm in diameter in rat skin (the first group). After the placement of silk suture at the margin of the defect, sheets of gauze were retained (the second group). After the placement of silk suture on the healthy area 5mm outside the margin of the wound, sheets of gauze were retained (the third group). After the placement of silk suture on the healthy area 5mm outside the margin of the wound, a chitin wound dressing 20mm in diameter was applied, and sheets of gauze were retained (the fourth group). After the placement of silk suture on the healthy area 5mm outside the margin of the wound, a chitin wound dressing 30mm in diameter was applied, and sheets of gauze were retained (the fifth group). We compared these five groups. The fifth group showed the greatest epidermal regeneration, and the second group showed delayed wound healing as compared with that in the nontreated group. The second and fourth groups histologically showed delayed cauterization because sheets of gauze strayed into the dermis in the second group, and sheets of gauze and the chitin dressing strayed into the dermis in the fourth group. The fifth group histologically showed emerging thin collagen fibers in the early stage and a higher degree of cauterization than in the other groups. The rate of epidermal regeneration on postoperative day 21 in the fifth group was significantly higher than that in the fourth group. These results indicate that wound healing during the tie-over method for the repair of skin and oral mucosal defects is achieved by first placing silk suture on the healthy area 5mm outside the wound margin, and then applying a chitin sheet slightly wider than the wound, followed by sheets of gauze.