Evaluation of Salvadora persica L. and green tea anti-plaque effect: a randomized controlled crossover clinical trial
In this study, a combination of 0.25 mg/ml Gt and 7.82 mg/ml Sp aqueous extracts mouthwash (test) was able to significantly reduce plaque accumulation as compared to placebo after 24 h re-growth. Interestingly, this formulated mouthwash was also able to significantly reduce plaque quantity compared to the CHX mouthwash. In the authors’ earlier in vitro study, this same combination exhibited anti-bacterial activity comparable to 12% CHX against primary plaque colonizers, i.e. S. mitis, S. sanguinis, and A. viscosus. It also significantly reduced the adherence of those bacteria to saliva covered glass beads which acted as tooth surfaces. When compared the anti-adherence effect of the combination with CHX, fewer primary colonizers adhered but it was statistically non-significant [15].
The initial adherence of primary colonizers to oral surfaces is important as they provide new receptors for subsequent adhesion of secondary bacterial colonizers, thus promoting plaque development [14]. The finding suggested that the significant anti-plaque effect of the test combination was attributed, in addition to its anti-bacterial efficacy, to fewer primary colonizers’ receptors available on tooth surfaces for subsequent secondary colonizers adhesion, therefore resulting in retarded plaque development. This proposed explanation is further supported by earlier reported finding of lower salivary levels of primary colonizers among Sp chewing sticks users than toothbrush users; an effect attributed to chemical constituents of Sp such as thiocynate, sulfate, chloride, and nitrate [9]. Furthermore, polyphenolic tannins were reported to inhibit salivary ?-amylase and bind both salivary histatin and proline-rich protein [20, 21]. Recently, it was reported that rinsing with a fluoride-based mouth rinse results in a slight fluoride accumulation at the surface of the pellicle-coated enamel [22]. Both tannins and fluoride were identified in Sp aqueous extracts [23] and they may bind salivary proteins of the pellicle covering tooth surfaces, modify the pellicle surface and therefore interfere with the adherence of primary plaque colonizers. On the other hand, gargling with Gt polyphenols, catechins, was reported to reduce intra-oral load of primary colonizers including S. sanguinis, S. salivarius, S. mitis and Streptococcus sobrinus [10]. Also, Gt was found to have an anti-adherence efficacy against oral streptococci [24]. These findings might be due to the capability of tea polyphenols to adsorb onto acquired pellicle, subsequently modify its structure, and thus interfere with the bacterial adherence to tooth surface [25].
In this study, the authors considered variations in participants such as gender, thus opted for a crossover design in which each participant would serve as his/her own control to improve the sensitivity for detection of relative changes in plaque accumulation. No mechanical hygiene measures for 24 h protocol was used because the deposition of dental plaque at the gingival margin occurs on all teeth surfaces which can be clinically recognized with or without disclosing agents in less than 24 h [26]. Also, 24 h plaque reformation can be safely measured as previously done [16]. Furthermore, in an earlier in vitro study the test mouthwash was found to exhibit significant anti-bacterial and anti-adherence activities [15]. Thus, the authors used the 24 h plaque re-growth protocol to confirm this in vitro result and to evaluate its impact on plaque formation using only the plaque index. Longer-term protocols, such as 4 days plaque re-growth design, were not been used in this study. This decision was made to avoid inappropriate evaluation of the anti-adherence effect of the test mouthwash, which is believed to be responsible for its anti-plaque effect. This is due to the fact that undisturbed plaque matures after 3 days of no oral hygiene measures [27]. However, the evaluation of the long-term effect of the test mouthwash on gingival tissue is highly recommended using a longer-term protocol and to include the gingival and bleeding indices. Absolute intra-examiner agreement, kappa value of 0.827, was achieved. This enhanced the reliability of the study in which the data was able to be measured in a reproducible manner which in turn improved the discriminative power of the study [18].
Earlier relevant clinical studies have investigated the anti-plaque efficacy of Gt and Sp extracts independently. It was reported that neither commercial Sp mouthwash (PersicaTM) nor its comparator placebo reduced plaque accumulation [28]. In contrast, Al-Bayaty et al. [29] found that rinsing with 10 ml of Sp extract at 100 mg/ml thrice a day significantly reduced plaque scores but did not reach the better effect of CHX. Recent clinical trials reported that rinsing with Gt extracts at 50 and 250 mg/ml significantly reduced plaque accumulation and the anti-plaque effect of both concentrations was comparable to CHX [30, 31]. In conclusion, both Sp and Gt extracts have anti-plaque effect which is in accordance to the current results but at much higher concentrations. The novelty of this study relies on investigating the anti-plaque effect of the combination between Gt and Sp aqueous extracts at lower concentrations than previously studied. Thus, this has the advantage of both cost effect and safety.
In this study, rinsing with the test formulated mouthwash has significantly reduced plaque scores when compared to CHX with an effect size of 1.077. The comparison was powerful (achieved power?=?0.856). This result was not surprising as the authors’ in vitro results had revealed better synergistic anti-adherence effect of the Gt and Sp extracts combination against primary colonizers than CHX, Gt extract and Sp extract alone. Less primary colonizers biofilm adhered to glass beads treated with the combination when compared to CHX after 2 h [15]. Although the difference was not significant, but this might have an effect on the plaque quantity formed after 24 h by providing less binding sites for the secondary plaque colonizers in vivo. On the other hand, less plaque scores were recorded after rinsing with CHX mouthwash compared to placebo with no significance difference. This may be due to small effect size of CHX achieved in this study as shown in Table 4. However, it may need higher sample size of participants to uncover statistical significant difference between CHX and placebo.
In this study, the test formulated mouthwash has significantly reduced supragingival plaque in healthy gingiva participants with no adverse effect detected. The succession of supragingival plaque reformation is similar for both healthy and periodontitis subjects [26]. This clinical finding suggests that the anti-plaque effect could also be seen in periodontitis subjects. Therefore, the test mouthwash can be used by healthy or periodontitis subjects.