The objective of this study was to establish whether there is an association between doses of oral simvastatin and a reduction of periodontal attachment loss. This study was approved by the Committee for Human Research of Faculty of Dentistry/Faculty of Pharmacy at Mahidol University. Forty-one patients, age range of 46 to 79 years, of whom 31 were female, were observed. They were taking an oral simvastatin which was prescribed by their physicians.
 Twenty-six patients were taking 5 or 10 mg/day, and 15 patients were taking 20 or 40 mg/day. They were in supportive periodontal treatment for 6 to 24 months. Medical history, medications and supplements, dosage and durations of simvastatin taken, and serum lipid levels were reviewed. Simplified Oral Hygiene Index was measured. Clinical attachment loss was recorded and compared site by site with the records at last maintenance visit. The percentage of sites which changes ≥ 2 mm either reduction or increment were calculated. Two independent sample t-tests, Spearman rank correlation, Pearson correlation, and multiple linear regression were used. P-value < 0.05 was considered significant. The average percentage of sites with clinical attachment loss reductions ≥ 2 mm in the group taking simvastatin doses 5 or 10 mg/day, and 20 or 40 mg/day were 11.18 ± 6.65 and 10.38 ± 6.91 respectively. These were not found to be significantly different nor was there evidence of a dose-response effect. Oral hygiene was found to be related with the reduction. The dose of oral simvastatin is not associated with a reduction of periodontal attachment loss.