BACKGROUND Periodontitis is an inflammatory disease that results in bone resorption creating bony defects, which may cause tooth loss. Various drugs have been studied using local delivery to improve the periodontal health and to achieve periodontal regeneration. Simvastatin (SMV) is a specific competitive inhibitor of 3-hydroxy-2-methyl-glutaryl coenzyme A reductase. The present study was designed to investigate the effectiveness of SMV, 1.2 mg, in an indigenously prepared biodegradable controlled-release gel as an adjunct to scaling and root planing (SRP) in the treatment of chronic periodontitis. METHODS Sixty patients were categorized into two treatment groups: SRP plus placebo (group 1) and SRP plus SMV, 1.2 mg (group 2). Clinical parameters were recorded at baseline before SRP and at 1, 2, 4, and 6 months; they included modified sulcus bleeding index (mSBI), probing depth (PD), and clinical attachment level (CAL). At baseline and after 6 months, radiologic assessment of intrabony defect (IBD) fill was done using computer-aided software. The mean concentration of SMV in gingival crevicular fluid was estimated by reverse-phase high-performance liquid chromatography. RESULTS All subjects tolerated the drug, without any postapplication inflammation. Both therapies resulted in significant improvements. The decrease in mSBI score at 6 months was greater in group 2 (2.3267 +/- 0.8017) compared to group 1 (0.5033 +/- 0.6815). The mean decrease in PD from baseline to 6 months was 1.20 +/- 1.24 mm and 4.26 +/- 1.59 mm in groups 1 and 2, respectively. Mean CAL gain from baseline to 6 months was 1.63 +/- 1.99 mm and 4.36 +/- 1.92 mm in groups 1 and 2, respectively. In group 2, there was greater decrease in mean IBD (1.41 +/- 0.74 mm or 32.54%) compared to group 1 (0.09 +/- 0.58 mm or 2.16%). CONCLUSIONS There was a greater decrease in gingival index and PD and more CAL gain with significant IBD fill at sites treated with SRP plus locally delivered SMV in patients with chronic periodontitis.