TERRI TILLISS, CLIFTON M. CAREY
The question being studied by this systematic review of the literature is how mouthwashes containing essential oils used as adjuncts to daily mechanical plaque control compare to placebo mouthwashes, cetylpyridinium chloride (CPC), or dental floss in reducing plaque and gingivitis among adults with gingivitis. A secondary question is how essential oils compare to these other approaches regarding plaque and gingivitis reduction at interproximal surfaces. Causes of heterogeneity among study findings were also examined.
Main Outcome Measure
The main outcomes were the oral health parameters of dental plaque and gingivitis among subjects with gingivitis. The Quigley-Hein index as modified by Turesky was used to sum- marize dental plaque. Three indices were used to summarize gingivitis: the Gingival Index by Loe and Silness, the Modified Gingival Index, and bleeding on probing. The reported means and standard deviations for these measures were used for further meta-analyses. When possible, the percentage reduc- tion of plaque or gingivitis index scores from the baseline to trial end was calculated from the data provided.
Main Results
Of the 107 relevant articles, 91, or more than a third, were excluded because they had<6 months of follow-up.
Sixteen studies met the inclusion criteria and were reviewed, for a total of 4016 study subjects. All studies were funded by industry, and the majority of studies tested Listerine Antiseptic as the EO-containing mouthwash.
The weighted mean difference (WMD) and the 95% confi- dence interval (CI) between EO and comparison groups were calculated from the mean and standard deviations of each study. In addition, the percentage change from the baseline to the end of study (relative end-of-trial difference) was estimated for comparisons between EO + MPC and placebo + MPC.
Meta-analyses
All 14 studies comparing EO with placebo for plaque score outcomes showed a reduction in plaque with a WMD of -0.86 (95% CI -1.05 to -0.66) in favor of EO.
All 11 studies comparing EO with placebo for gingivitis score outcomes showed a reduction in gingivitis with a WMD of -0.52 (95% CI -0.67 to -0.37) in favor of EO.
All 4 studies comparing EO with CPC for plaque score outcomes showed a reduction in plaque scores with a WMD of -0.75 in favor of EO.
All 4 studies comparing EO with CPC for gingivitis score outcomes showed a reduction in gingivitis with a WMD of -0.52 in favor of EO.
A subgroup of 4 studies that provided information about plaque and gingivitis scores from interproximal areas only was analyzed to compare EO with placebo. EO use resulted in a significant decrease in plaque scores (WMD -0.95, 95% CI -1.26 to -0.63) and gingivitis scores (WMD -0.34, 95% CI -0.53 to -0.15).
Meta-regression analyses were performed to identify sour- ces of effect modification of the pooled WMD. The sources included within the meta-regression analyses were year of publication, source of the sample, age, percentage of male subjects, percentage of smokers, supervision of mouthwash use, provision of oral hygiene instructions before the study, and baseline values of plaque and gingivitis. The regression model was developed by inclusion of these factors one after another on the basis of their P value from lowest to highest. The meta-regression analysis was performed to understand the causes of study heterogeneity.
Meta-regression Analysis
Heterogeneity observed in the plaque scores was mainly due to the percentage of men in the study (P = .01) and supervision of mouthwash use (P = .03). This explained 80.1% of the variation in the final score among groups.
Heterogeneity observed in the gingivitis scores was mainly due to the provision of oral hygiene instruction before the study (P = .04). This explained 63.6% of the variation in the final score among groups.
Conclusions
- Fourteen reviewed studies comparing EO and placebo mouthwashes found that
- EO was statistically significantly better than pla- cebo in reducing plaque and gingivitis.
- Six months of using EO compared with CPC demonstrated statistical superiority of EO for both plaque and gingivitis reduction. - Four reviewed studies comparing EO, placebo solution, and flossing in the interproximal areas found that
- Plaque and gingivitis were significantly reduced in the - EO groups as measured by the Q-H index and the Modified Gingival Index compared with the placebo solution.
- EO in addition to brushing and flossing was supe- rior to brushing and flossing alone for plaque levels but not for gingivitis. - The heterogeneity among the plaque scores in various studies was mainly attributed to the number of men in the study sample. When > 35% of the samples were men, the differences between EO and placebo for plaque were not as strong. For gingivitis, the qualifying factor was whether the rinsing was supervised. When unsupervised, the difference between EO and placebo for gingivitis was diminished.
