Scanning electron microscope study of the healing molar tooth extraction socket in the rat.

Healing molar tooth extraction wounds in rats were examined by scanning electron microscopy from 15 minutes to 40 days following tooth removal. The wound epithelium, which was derived mainly from the gingiva but also from the cheek and hard palate, migrated beneath the superficial socket contents. The contents were lost between 5 to 11 days, thus leaving a central epithelial-lined depression. This decreased in width with time as the level of the wound epithelium approached that of the hard palate but was still present at 40 days. Between 5 and 7 days, the wound epithelium became more regular. However, from 11 days on, it became more irregular with increasing numbers of saucer-shaped depressions, circular defects and circular whorls of epithelial cells. The surface structure of the epithelial cells changed as it migrated and matured. The initially plump, then flattened cells mostly had smooth areas along with variable numbers of irregular microridges and microvilli, although cells derived from the cheek had only smooth surfaces. With further maturation, all cells developed a regular honeycomb surface pattern of interconnecting microridges similar to that on the hard palate. Why the wound epithelium became more uneven after 11 days is not known.