[Role of attached gingiva in the extension of gingival inflammation. An experimental study in monkeys].

The purpose of this study was to evaluate the inflammatory response in dento-gingival units with or without attached gingiva in monkeys. Two different types of dento-gingival units with or without attached gingiva were established in premolar and first molar areas of three monkeys. In the experimental group, a part of the keratinized gingiva was removed with periodontal scissors following mucoperiosteal flap procedure, while in the control group, sham surgery was performed. After the surgery, plaque control was performed by mechanical tooth cleaning procedures three times a week for 3 months. As baseline examinations, width of the keratinized gingiva, probing pocket depth, position of the gingival margin, and the clinical attachment level were recorded and oral photographs were taken. Following these examinations silk ligatures were placed around the neck of the teeth to induce gingival inflammation in both the experimental and control groups. A soft diet which allowed plaque accumulation on the teeth was given during the experimental periods. The clinical examinations were carried out at 0, 1, 2, 3, 5 and 12 weeks and all monkeys were sacrificed for histological examination. The results obtained were as follows: 1. The use of silk ligature and a soft diet produced moderate to severe gingival inflammation in the monkeys. 2. The degree of gingival inflammation was greater in the experimental group which was characterized by the absence of the attached gingiva. 3. Marked marginal tissue recession with an apical shift of the attachment level was found in the gingival units of the experimental group at 12 weeks. 4. Histologically, a distance between the level of notch on the root surface and the most apical position of epithelial cell was greater in the experimental groups at 5 and 12 weeks, compared with the pre-experimental level. 5. The degree of alveolar bone resorption was higher in the experimental group at 5 and 12 weeks. These results suggest that an attached gingival tissue plays a certain role as a barrier against the extension of gingival inflammation.