Purpose: To evaluate the efficacy of SmartMouth Clinical DDS compared with 0.12% chlorhexidine and placebo mouthrinses. Materials and Methods: Seventy-six subjects with gingivitis or chronic periodontitis were enrolled in a double-blind, placebo-controlled, clinical study. Examinations included Gingival Index (GI), Bleeding Score (BS), Plaque Index (PI), Tooth Stain Index (TSI), and Calculus Index (CI). Subjects were given a prophylaxis and oral hygiene instructions at the time of enrolment. Subjects were assigned to one of three groups: SmartMouth Clinical DDS (SM), 0.12% chlorhexidine (CHX), or placebo (PL). Subjects were examined at 3 and 6 weeks. Data were evaluated as differences from baseline for each group. Analysis of variance (ANOVA), t tests or non-parametric alternatives were used to analyse data. Results: The GI, BS and PI decreases from baseline were statistically significant at both 3 and 6 weeks for all three groups (p ≤ 0.025). Differences between groups were not statistically significant, except that the PI decrease for CHX was significantly greater than PL at 6 weeks (p = 0.048). At 6 weeks there was a statistically significant increase in TSI for CHX (p ≤ 0.001). CI decreased significantly for all groups at 3 weeks (p ≤ 0.004) and for PL at 6 weeks (p ˂ 0.001). At 3 weeks and 6 weeks, the percentages for compliance were significantly higher for SM and PL than for CHX (p ˂ 0.001). SM had less taste alteration reported than CHX (p = 0.003). Conclusion: While all three groups were shown to improve GI, BS and PI scores; non-prescription SM resulted in less taste alteration, less tooth stain and better compliance than CHX. Keywords: cetylpyridinium chloride, chlorhexidine, mouthrinse, volatile sulphur compounds, zinc-ion