Healing of experimental excisional wounds in the rat palate. (I) Histological study of the interphase in wound healing after sharp dissection.

Healing of standardized, excisional wounds in the rat palate has been studied in 40 rats for a period of 3 weeks. The excisional wound were made with a specially constructed biopsy instrument with a diameter of 3 mm. The soft tissue was removed by sharp dissection and uncovered bone tissue was left for secondary healing. 5 rats were killed at 0, 1, 3, 5, 7, 19, 14 and 21 days after the surgical procedure. Photometric measurements were made of the wound at the different control times and serial sections from blocks including the palate, alveolar process and teeth were subjected to light-microscopical examination. Clinical healing was completed within 3 weeks. Photometric measurements showed an almost 50% reduction of the defect between the 7th and 10th days. Histological examination initially revealed a pronounced inflammatory reaction both in the sub-epithelial connective tissue and in the haversian canals of the bone tissue. The epithelialization progressed from the wound borders, the epithelial cells trying to avoid interference with the inflammatory cell infiltrate. Reduction of the wound surface proceeded by contraction of the wound margins as well as by epithelial cell migration. Empty osteocyte lacunae in the surface layer of the bone tissue beneath the wound and the presence of small nectrotic bone fragments indicated that damage to the bone tissue had occurred during the exposure period. After 3 weeks, the defect was completely covered with epithelium although epithelial rete pegs had not yet developed in the central part of the former defect.