The effect of a mouthrinse containing essential oils on dental plaque and gingivitis

PubMed and the Cochrane Central Register of Controlled Trials were searched up to December 2006 were searched. Only studies published in English were included.

Randomised controlled clinical trials, controlled clinical trials and uncontrolled longitudinal clinical trials were included in the initial search. Studies with a minimum duration of 6 months, healthy subjects >/=18 and gingivitis without severe periodontal disease were included. The effects of plaque and gingivitis were considered the primary outcomes with staining of teeth a secondary outcome.

Studies were screened and data extracted independently by two reviewers. It is unclear whether or not this process was duplicated. Disagreements were resolved by discussion. Heterogeneity of the studies was assessed. Data was pooled for gingivitis and plaque and a weighted means meta-analysis using a random effects model was carried out.

Eleven studies (all randomised controlled trials) met the inclusion criteria. All were of six months duration except one of nine months. There was no meta-analysis between baseline and end trial as the standard deviation could not be calculated. Three studies were not included in the meta-analysis. Meta-analysis of staining was not carried out. There was significant reduction in gingivitis with EO mouthrinses compared to control groups regardless of the measurement index used (Weighted Means Difference (WMD) -0.32 95% Confidence Interval (CI) [-0.46 to -0.19], P< 0.00001; test for heterogeneity: P<0.00001 I(2) =96.7%). A significant reduction in interproximal gingivitis was also noted for EO mouthrinses compared to control (WMD -0.29 95% CI [-0.48 to -0.11] P=0.002; test for heterogeneity: p<0.0001 I(2)=95.8%) and compared to floss (WMD -0.05 95% CI [-0.20 to -0.09] P=0.48; test for heterogeneity: P=0.0001 I(2)=99.7%). Similar results were seen for the effects on plaque with a decrease in total plaque in favour of EO mouthrinse (WMD -0.83 95% CI [-1.13 to -.053] P<0.00001; test for heterogeneity: P<0.00001 I(2)= 96.1%). Significant interproximal plaque reduction, again in favour of EO mouthrinse, was also seen compared to control (WMD -1.02 [-1.44 to -0.60] P<0.00001; test for heterogeneity: P<0.00001 I(2)=96.1% 95% CI) and compared to floss (WMD -0.75 95% CI [-1.15 to -0.363] P<0.0002; test for heterogeneity: P<0.0002 I(2)= 93%).

When used as an adjunct to unsupervised oral hygiene, the existing evidence supports that essential oil provides an additional benefit with regard to plaque and gingivitis reduction compared to placebo or control.