Long junctional epithelium: epithelial reattachment in the rat

The mesial gingiva of mandibular first molars of Sprague-Dawley rats were subject to irritants for 1, 2 or 3 months. The irritants were then removed for periods of 2 to 4 weeks before sacrifice (healing phase). The keratinized sulcular epithelium tended to remain stable while the junctional epithelium became very reactive demonstrating three responses: (1) Proliferation occlusally, (2) Proliferation apically and (3) Proliferation into the inflamed connective tissue. In approximately half of the rats the depth of the cuff epithelium did not change during the experimental procedures demonstrating the resistence of the rat to local irritation. In approximately 25 % of the animals (Group A) deepened sulci occurred with subepithelial connective tissue inflammation. In the remaining 25 % of the rats (Group B), the cuff epithelium proliferated apically but an increase in epithelial reattachment occurred (38 %) reducing the sulci to normal depths with reduced subepithelial areas of inflammation. Within the limitations of these results, this model system can be used to study the dynamics of the long epithelial attachment.