Title:
Essential oil mouthwash (EOMW) may be equivalent to chlorhexidine (CHX) for long-term control of gingival inflammation but CHX appears to perform better than EOMW in plaque control.

Abstract:
For inclusion in this systematic review, studies had to be randomized clinical trials (RCTs) or controlled trials in healthy human subjects comparing the effects of essential-oil mouthwash (EOMW) with chlorhexidine (CHX) on plaque and calculus accumulation, tooth staining, and gingival inflammation. Included studies could be either short-term (< 4 weeks' duration) or long-term (> 4 weeks' duration). Studies were required to include a specific formulation of EOMW (Listerine, Johnson and Johnson). They reportedly selected this standard formula of EOMW because it was representative of essential oil-based mouthwashes and because it has the American Dental Association seal of approval. Conversely, there were no restrictions on the concentration of CHX used in studies. The CHX concentration in studies varied from 0.1% to 0.2%. Studies could include no brushing (de novo model) or brushing in conjunction with EOMW or CHX. The authors identified 390 unique articles from electronic database searches. Twenty-five of these articles were selected for full review. Seven articles were excluded because they did not meet the inclusion criteria. Hand searching the reference list of selected manuscripts resulted in the addition of one article. The final systematic review included 19 articles, with a total of 826 subjects who completed all trials. The systematic review included short-term studies lasting less than 4 weeks and long-term studies of 4 or more weeks' duration. Six of these trials were included in the 7 separate meta-analyses performed, yielding a total of 315 participants. The age of subjects in the trials ranged from 16 to 62 years. The study by Axelsson and Lindhe was included twice in the metaanalysis of plaque index, gingival index, and stain index because CHX was used in 0.1% and 0.2% concentrations. The studies by Haffajee et al and Charles et al were each used in meta-analyses for both plaque index and gingival index. Three separate meta-analyses included assessments for plaque index, whereas 2 involved gingival index and 2 assessed tooth staining index.
The effects of EOMW or CHX used as a monotherapy (alone) or in conjunction with self-performed daily oral hygiene on periodontal health, was measured by assessments for plaque index or calculus index, staining index, gingival bleeding index, or gingival index.
The primary outcomes of this systematic review and meta-analysis were differences in mean plaque index, calculus index, and tooth staining index, gingival index, and gingival bleeding after daily use of either chlorhexidine gluconate or essential oil mouthwash for < 4 or > 4 weeks.
Nineteen randomized or controlled clinical trials were included in this systematic review. In 5 of the 7 studies of plaque index, CHX was found to be significantly better than EOMW at reducing plaque accumulation. Stain development was assessed in 5 long-term brushing trials. CHX was significantly associated with more staining than EOMW in the systematic review. The calculus index was significantly greater among CHX users versus EOMW users. Of the 5 studies that measured gingivitis levels, 4 provided statistical data that could be used in the systematic review. Two of these investigations showed significantly lower gingival inflammation with CHX. Bleeding indices were assessed in 5 short-term and 4 long-term studies. Only one of the short-term studies showed a significant difference, whereas 3 of 4 long-term studies showed no difference between CHX and EOMW. Meta-analyses were included for plaque index, gingival index, and tooth staining index. In 2 of 3 meta-analyses of plaque index trials, CHX was shown to be significantly more effective than EOMW at reducing plaque. One of the significant meta-analyses involved plaque regrowth over 4 days (< 4 weeks) of no oral hygiene measures. The overall weighted mean difference (WMD) for the plaque index (Turesky modification of the Quigley and Hein plaque index was 0.46 (95% confidence interval (CI) = 0.09, 0.84). The other meta-analysis was a comparison of 6-week and 6-month trials (> 4 weeks) in which either daily EOMW or CHX supplemented normal oral hygiene measures. This long-term study of plaque accumulation showed significantly less plaque with CHX than with EOMW. The WMD for the long-term plaque control studies was smaller than for the short-term studies (0.19; 95% CI = 0.08, 0.30). No significant differences were found in meta-analyses for gingival inflammation (gingival index) or stain accumulation (stain index). Significant heterogeneity was identified in 1 of 2 of the meta-analyses for both gingival index and stain index.
The authors concluded that CHX was significantly better at reducing plaque accumulation than EOMW in short-and long-term studies. Staining and calculus accumulation were greater among CHX users compared to EOMW. CHX and EOMW were not different with respect to long-term control of gingival inflammation. They suggested that EOMW might be a reliable alternative to CHX for controlling gingival inflammation in cases where a dental professional deems that anti-inflammatory oral care is beneficial. However, they concluded that CHX remains the first choice when plaque control is the focus of therapy.