Tabriz University of Medical Sciences Journal of Dental Research, Dental Clinics, Dental Prospects 2008-210X 10 1 2016 03 16 Evaluation of the effects of subgingival injection of Simvastatin on space re-opening after orthodontic space closure in adults 3 7 10.15171/joddd.2016.001 EN Arezoo Jahanbin Mostafa Abtahi Parastoo Namdar Farzin Heravi Fatemeh Sadeghi Hamidreza Arab Hooman Shafaee Journal Article 10.15171/joddd.2016.001 2016 04 03 2016 04 07 Background. This clinical trial evaluated the effect of Simvastatin on space re-opening after orthodontic space closure and its effect on the gingival index (GI) and clinical attachment loss (CAL).Methods. 16 females, 25‒40 years old, with spaces between anterior mandibular teeth due to chronic periodontitis were participated in this study. The patients were randomly divided into control and experimental groups. In the experimental group, 1.2% Simvastatin gel and in the control group, 0.9% sodium chloride as a placebo was injected into the pocket depth of the six anterior teeth. The amount of space reopening, GI and CAL were measured.Results. No serious complications were observed during interventions and follow-up periods. Space re-opening was significantly reduced in patients receiving Simvastatin (P < 0.001). Moreover, GI reduction was significantly greater in Sim-vastatin group compared to the control group (P < 0.001). However, CAL did not demonstrate a significant difference between the groups.Conclusion. Simvastatin may decrease space re-opening after orthodontic space closure in human anterior teeth.