To evaluate the efficacy of EO as adjuncts to mechanical plaque control (MPC) on the reduction of plaque and gingivitis when compared to placebo or cetylpyridium chloride (CPC).

Randomized controlled trials of at least 6 months of follow-up including systemically healthy individuals with gingivitis were included.

MEDLINE, EMBASE, Lilacs and SCOPUS were searched up to April 2016. From 3045 citations, 16 studies were included. 14 studies assessed the Quigley-Hein Plaque Index (QHI) and 11 studies assessed the Modified Gingival Index (MGI) and were included in meta-analyses and meta-regression.

The analysis of risk of bias suggested that the quality of the studies ranged from moderate to low. Mean QHI (WMD = −0.86, 95%CI −1.05 to −0.66) and MGI (WMD = −0.52, 95%CI −0.67 to −0.37) were lower for EO + MPC than placebo + MPC. Reductions in plaque and gingivitis were, respectively, 32% and 24% larger for EO + MPC than placebo + MPC. The decreases in QHI (WMD = −0.95, 95%CI −1.26 to −0.63) and in MGI (WMD = −0.34, 95%CI −0.53 to −0.15) observed in the EO + MPC group, compared to placebo + MPC in interproximal areas, were significantly different and in favor to EO + MPC. EO + MPC compared to CPC + MPC resulted in clinically lower levels of plaque and gingivitis. High heterogeneity (I² > 95%) was found and explained (MGI − R² = 63.6%; QHI − R² = 80.1%) by differences between studies in the percentage of males, supervision of the mouthwashes and provision of oral hygiene.

EO seems to be superior to placebo + MPC and CPC + MPC for reduction of plaque and gingival inflammation in patients with gingivitis. Expected benefits may be clinically relevant and may also reach the interproximal area.

Mouthwashes containing essential oils should be considered the first choice for daily use as adjuvants to self-performed mechanical plaque control.