20 Subjects with clinical diagnosis of adult periodontitis with sites having average pocket depth of 4mm were selected for the study. After scaling and root planing of those sites, 30% minocycline-HCl contained in biodegradable device were inserted in one group, scaling and root planing was carried out in another group and the last group was without any periodontal treatment. the difference between the groups was determined by pocket depth, bleeding on probing, attachment level, distribution of subgingival plaque bacteria. Conclusion was made for the comparisons between baseline and 4 weeks and the groups.

1. In analysis of pocket depth, there was significant difference in scaling and root planing group only.

2. Both the scaling and root planing group and minocycline group showed significant decrease in bleeding on probing.

3. There was significant increase in the attachment level in scaling and root planing group, but no difference was foundbetween the groups.

4. There was significant decrease in the total number of subgingival bacteria in all groups and the number of motile bacteria decreased significantly in the minocycline group.

These results indicate that insertion of Minocycline-HCl at the base of periodontal pocket was useful as an additional aid of mechanical treatment at the point of periodontal pocket, bleeding on probing, attachment level, microbial distribution.