Sample size, study location, and target population:
By using t-test and assuming a pooled standard deviation of 0.35 units, the study required a sample size of 15 participants in total, to achieve a 90% power and 1% level of significance (P\<0.05), for detecting a true difference in means between the test and the control group of 0.5 on RMNPI index (Cugini et al 2006). This study is a cross-over study. In other words, participants were their own controls. Therefore, a total number of twenty participants were included in the study (10 males and 10 females).
The staff members of Sydney Dental Hospital were contacted by email to participate in the study. A screening appointment was arranged for interested participants to check for the eligibility criteria.
Study protocol:
One examiner (L.B) examined all participants two or three days a week. One participant was assessed per day. All eligible participants attended the Sydney Dental Hospital for 6 days. On each day, each participant was given a product to use on that day only according to the participant's own randomization list of products. If the day was a control day according to the participant's specific sheet, the participant did not receive anything. Then, the date was documented on each subject's own sheet. A minimum of 3 days wash out period was allowed between experimental days.
The following procedures were performed on each day:
On the control day (no products were used on that day): participants attended one morning appointment (at 8 a.m.) and one evening appointment (at 4 p.m.). Each appointment was about 45 min long.
* In the morning appointment: a disclosing agent (GC Tri Plaque Id Gel: GC America) was used to stain plaque. Then, all participants received a standardized full mouth professional prophylaxis and cleaning using Airflow Prophylaxis Master including Airflow hand piece with erythritol powder and Piezon handpiece to remove any hard deposits if needed (EMS, Switzerland). At that stage, clinical intra-oral photos were taken for all teeth surfaces using the Periodontic Department digital camera (Canon) to show that the mouth is 100% clean. As this is a control day, participants did not receive any of the tested products to be used on that day. They were allowed to practice their normal behaviour during daytime, but they were refrained from brushing, flossing or doing any oral hygiene practice until their evening appointment.
* In the evening appointment: the same disclosing agent was used to stain plaque and clinical intra-oral photos were taken for all teeth surfaces to measure RMNPI. This allowed plaque accumulation for about 7 hours. After that, all participants received the same full mouth professional prophylaxis and cleaning to obtain plaque free mouth.
On the other test days (participants received one test product on each day to use for that day only): similar to the control day, participants had to attend one morning appointment (at 8 a.m.) and one evening appointment (at 4 p.m.). Each appointment was about 45 min long.
* In the morning appointment: the same as the control day was done. In addition, each participant received one of the tested products on each day, according to a computer-generated randomization sequence, to test its effect for that day only. Each product was used twice a day: after tea break at 11 a.m. and after lunch break at 2 p.m., allowing 7 hours of plaque accumulation. Participants' compliance was self-reported. The Products were used according to manufacturer instructions as follows:
* Mouth washes: Vigorously swish 20mL of rinse in your mouth for 30 seconds and then spit out. Do not swallow. Do not dilute. They were dispensed in their original bottles. Participants were given a marked cup to measure the amount of MW.
* Listerine Go Tab: Chew for 10 seconds to activate, swish around the teeth for 30 seconds to clean then swallow.
* Chewing gum: no manufacturer recommendation for the chewing duration, so as done in previous studies, 10 minutes duration was standardized for the chewing duration.
* In the evening appointment: same as control day was done. In addition, VAS was used to record participants' perception of fresh breath and cleanness in their mouth after using the product.
After all participants completed their visits, all photos were assessed to score RMNPI. All data were recorded on an excel sheet that was used to perform the statistical analysis.
Statistical analysis:
Statistical Analysis was conducted using SAS OnDemand for Academics (SAS Institute Inc., Cary, NC, USA). Data was checked for normality using Shapiro-Wilk test. As data proved non-homogeneous and not-normally distributed, Non-parametric Mann-Whitney U test was used to compare medians between groups (pair-wise), and Kruskal Wallis test for multiple groups comparisons. Pair-wise comparisons of significant differences in Kruskal Wallis test were made using the rank-transformed data using Tukey's adjustment to control for type I error. The results in tables are presented as Medians (95% confidence interval). Any differences were considered significant at P\<0.05.
