Meta-analysis of the effect of an essential oil–containing mouthrinse on gingivitis and plaque

Background. Standard recommendations for oral hygiene practices have focused on mechanical methods (toothbrushing and interdental cleaning). Published evidence indicates antimicrobial mouthrinses provide oral health benefits beyond mechanical methods alone. The purpose of this meta-analysis was to evaluate the combined effectiveness of mechanical methods with essential oil-containing mouthrinses (MMEO) versus mechanical methods (MM) alone in achieving site-specific, healthy gingival tissue and reducing plaque and gingivitis. Types of Studies Reviewed. All industry-sponsored clinical trials investigating the antigingivitis and antiplaque effects of essential oil (EO)-containing mouthrinses conducted from 1980 to 2012 were reviewed; 29 of 32 studies met the inclusion criteria of 6 months or longer duration, randomized, observer-masked, placebo-controlled, and with individual-level site-specific data. By-study treatment effects were estimated through generalized linear models for binary data and analysis of covariance for continuous data, and then combined using standard meta-analysis techniques; heterogeneity was also assessed. Results. Summary odds ratios for a healthy gingival site and for a plaque-free site were, respectively, 5.0 (95% confidence interval [CI], 3.3-7.5) and 7.8 (95% CI, 5.4-11.2) for MMEO participants versus MM participants at 6 months. The summary percentage reductions in whole-mouth mean gingivitis and plaque at 6 months were 16.0 (95% CI, 11.3-20.7) and 27.7 (95% CI, 22.4-32.9), respectively. Responder analyses using aggregate individual-level data showed 44.8% of MMEO participants and 14.4% of MM participants achieved at least 50% healthy sites in their mouths at 6 months. Similarly, 36.9% of MMEO participants and 5.5% of MM participants achieved at least 50% plaque-free sites in their mouths at 6 months. Conclusions and Practical Implications. This is the first meta-analysis to demonstrate the clinically significant, site-specific benefit of adjunctive EO treatment in people within a 6-month period (that is, between dental visits).