Long junctional epithelium produced by application of bacterial protease in rats.

In the present study, the effect of bacterial protease on the periodontal tissues in rats was investigated histologically and histometrically. In the control group, 0.03 ml distilled water was applied to the lingual marginal gingiva of the mandibular incisor while, in the experimental group, 0.03 ml bacterial protease (distilled water with 300 units, Sigma type XIV) was applied to the same area. Both groups were treated once a day for 1, 3, 6, 9, 15 and 21 d. Histologically, the junctional epithelium in the experimental group showed a marked apical proliferation along the tooth surface, and the gingival connective tissue displayed also a slight inflammatory cell infiltration subepithelially. The remaining periodontal tissues were almost similar to those of the control group. Histometrically, the length of the junctional epithelium between the base of the gingival crevice and the most apical portion of the junctional epithelium in the experimental group at 9, 15 and 21 d were significantly greater (p less than 0.01) than those of the control group, respectively.