We investigated the outcome of conventional periodontal treatment in mouth breathing patients with chronic periodontitis, and compared the efficacy of applying salivary substitute to the anterior sextants as an adjunct to conventional treatment in such patients. In this randomized, investigator-blind, clinical study involving parallel groups, 40 mouth breathing patients were divided into two groups: a control group (CG, n = 20) comprising patients who received scaling and root planing (SRP), and a test group (TG, n = 20) who received salivary substitute as an adjunct to SRP for treatment of chronic periodontitis. The patients were followed up at various time intervals, and improvement of the gingival index (GI) was examined as the primary outcome. Student's t-test, repeated-measures ANOVA and Mann-Whitney U test were applied for statistical analysis. Although periodontal parameters were improved in both groups after 8 weeks of follow-up, the test group showed better improvement in terms of GI and percentage bleeding on probing. Within the limits of this study, our results suggest that the use of salivary substitute has a beneficial adjunctive effect for improvement of periodontal parameters in mouth breathing patients with chronic periodontitis.