Abstract: Objective To study the influence of L-arginine（L-arg） and NG-nitro-L-arginine methyl ester（LNAME）on inducible nitric oxide synthase（iNOS） expression in compressed periodontium during orthodontic tooth movement in rats. Methods 60 male S-D rats were randomly divided into 3 groups and rat models with orthodontic appliances were established. Three groups received respectively subperiosteal injections of L-arg（L-arg group）, normal saline（NaCl group） and L-NAME（L-NAME group） at 2-day intervals. Rats were sacrificed at given
time points. The maxilla tissue samples were collected and sliced up for immunohistochemistry and image analyses. Results All groups showed a similar iNOS expression after orthodontic force load and iNOS expression reached the maximum at day 7. No statistically significant difference was found in iNOS expression between different study groups at the same time point. Conclusion Both L-arg and L-NAME have no effect on the expression of iNOS in periodontal ligament during orthodontic tooth movement in rats. They may affect orthodontic periodontium remodeling and orthodontic tooth movement through some other ways.

Key words: nitric oxide, L-arginine, NG-nitro-L-arginine methyl ester, orthodontic tooth movement, inducible nitric oxide synthase