Alcohol-free essential oils containing mouthrinse efficacy on three-day supragingival plaque regrowth: a randomized crossover clinical trial

BACKGROUND: To evaluate the antiplaque effects of an alcohol-free mouthrinse containing essential oils—Listerine Zero (LZ)—and an alcohol-based essential oils mouthrinse (EO+) compared with a positive control of 0.20% chlorhexidine mouthrinse (CHX) and a negative control of a placebo solution (saline), using an in vivo plaque regrowth model of three days. METHODS: The study was designed as a double-masked, randomized, crossover clinical trial, involving 21 volunteers to compare four different mouthrinses, using a three-day plaque regrowth model. After receiving thorough professional prophylaxis at baseline, over the next three days each volunteer refrained from all oral hygiene measures and performed two daily rinses with 15 mL of the test mouthrinses. EO+ was compared with LZ. CHX rinse served as a positive control and a placebo solution as a negative control. At the end of each experimental period, the Plaque Index (PI) was assessed and a panelist completed through a visual analogue scale (VAS) questionnaire evaluating the organoleptic properties of each product. Each participant underwent a 14-day washout period and then there was another allocation. RESULTS: LZ showed the same inhibitory activity on plaque regrowth compared with EO+ in the whole mouth (PI = 1.72 versus 1.65, respectively), but there was less of an effect compared to the CHX (overall PI of 1.07) and a more efficient activity than the saline solution negative control (PI = 2.31). The difference of 0.07 between LZ and EO+ was not statistically significant. CONCLUSIONS: LZ seems to have the same inhibiting effect on plaque regrowth as EO+ and a less inhibiting effect than the CHX control. Both LZ and EO+, as well as the CHX control, show a better inhibiting effect on plaque regrowth than the placebo solution. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02894593. Registered on 4 September 2016. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13063-017-1901-z) contains supplementary material, which is available to authorized users.