RESUMO
This study aimed to evaluate the effect of scaling and root planning [SRP] alone versus in conjunction with systemic doxycycline on gingival crevicular fluid [GCF] neutral protease activity in refractory periodontitis [RP]. Twenty patients with RP as well as eight healthy volunteers served as controls were enrolled into this study. The patients were randomized into two equal groups: The first group received SRP with adjunctive doxycycline [200 mg loading dose followed by 100 mg/day for fourteen days] and the second group received SRP only. At baseline and one, two, three and six months after treatment; gingival index [GI], pocket depth [DP] and attachment level [AL] were assessed for all patients. Neutral protease activities in GCF were measured by spectrofluorimetric method for the patients. The study concluded that adjunctive doxycycline is capable of improving and stabilizing RP lesions better than SRP alone and the major mechanism of this therapeutic potential might be antimicrobial in such cases. Moreover, GCF neutral protease activity might reflect the periodontal status of RP patients and could be valuable in monitoring the disease activity