Progressive replacement of epithelial attachment by a connective tissue junction after experimental periodontal surgery in rats.

The purpose of this study was to test the hypothesis that the long junctional epithelium formed during the early stages of periodontal wound healing can become replaced, at least in part, by a connective tissue attachment. A surgical wound was created on the mesial surface of the left maxillary first molar of 4-month-old rats and the mesial root surface curetted free of soft tissue and cementum. The contralateral molar served as an unoperated control. Groups of five to eight animals were killed at intervals of 10 days, 3 and 6 weeks, and 3, 6 and 12 months after surgery. The histometric data demonstrated a progressive apical recession of the entire gingival unit on the unoperated control side during the experimental period. On the operated side, the junctional epithelium became reestablished by migration of epithelium from the wound edge along the cut gingival surface facing the tooth, until contact was established near the apical border of the instrumented root surface. Coronal migration of the epithelium from that level accounted for most of the lengthening of the junctional epithelium observed in 3 weeks. During the balance of the experimental period the junctional epithelium did not change in length significantly. However, the entire epithelial attachment was displaced coronally, primarily at the expense of sulcus depth which decreased with time, and by replacement of the apical portion of the junctional epithelium by a connective tissue junction of increasing dimension. These findings challenge the widely held belief that, once established, the dentoepithelial junction cannot be replaced by a connective tissue attachment.