Evidence for Mouthrinses as Adjunctive Therapy

Effective control of oral diseases requires methodical patient assessment, critical thinking, and a thorough understanding of mechanical and chemical biofilm removal modalities.¹ In clinical practice, the addition of appropriate adjunctive therapy, such as therapeutic mouthrinses, may improve patients’ oral hygiene. However, patients need individualized recommendations — and this requires a keen understanding of available products and the clinical effectiveness of their active ingredients. Patients often judge the effectiveness of a mouthrinse by taste or flavor, and may inadvertently choose a product with low efficacy.² Individualized patient education on the complex nature of oral bacteria provides the greatest opportunity for effective disease management.

While the use of mechanical plaque control helps patients maintain adequate levels of oral hygiene, research and clinical experience indicate the level of efficacy with these methods is often lacking.^3,4 The need for adjunctive therapy to support mechanical plaque removal — with the goal of controlling biofilm and preventing caries — provides the foundation for introducing therapeutic mouthrinses.³

Consensus exists on the benefits of fluoride for caries prevention.⁵ While clinicians can choose from a range of fluoride products, the most common formulations include neutral sodium fluoride solutions ranging from 0.05% (200 ppm) to 2% (900 ppm).^5,6 The effectiveness of fluoride stems from its bacteriostatic properties that inhibit enolase enzymes in the glycolytic pathway.⁶

Sodium fluoride mouthrinse inhibits caries disrupting the activity of cariogenic microbes in the oral cavity. It has a neutral pH and bacteriostatic properties that make tooth structure more resistant to acid attacks via the formation of fluorapatite.⁶ As acids from food or drink coat a tooth’s surface, fluoride in the saliva forms fluorapatite and alters the physiochemical properties on the enamel’s surface to make it more resistant to breakdown.⁶ Patients at high caries risk — including those with active coronal and/or root surface caries, an inability to maintain adequate oral hygiene, or orthodontic appliances — are typically best served by a low-potency, high-frequency regimen of 0.05% sodium fluoride rinse used daily. Alternately, clinicians can prescribe a high-potency, low-frequency regimen of 0.2% sodium fluoride rinse.⁷

Patients with xerostomia and symptoms of hyposalivation caused by disease, medications or chemotherapy/radiation treatment will benefit from a sodium fluoride mouthrinse.⁷ Among the various caries prevention methods, therapeutic mouthrinses have been found to be one of the safest and most effective strategies, especially in children age 6 and older, as rinses have the ability to deliver therapeutic ingredients to all accessible surfaces in the oral cavity, including interproximal surfaces.⁴

Previous research often compares the effectiveness of fluoride rinses with fluoride dentifrices.⁸ Current studies assess the efficacy of fluoride mouthrinses as an adjunct to fluoride dentifrices and other fluoride products. A 2014 study investigating the remineralization effects of fluoride rinses observed greater remineralization of proximal caries lesions when the frequency of fluoride mouthrinse use was increased and utilized in concert with fluoride toothpaste.⁸ The use of fluoride rinses as adjunctive therapy has also been shown to be effective in preventing and reversing root caries.⁹

The incorporation of fluoride into antimicrobial mouthrinses — even used once daily — may improve caries control and increase remineralization. Mouthrinses should be used after toothbrushing, as rinsing with water or nonfluoride rinses may remove beneficial residual fluoride.^8,9

ANTIBACTERIAL RINSES

Antiseptic mouthrinses are used to reduce plaque accumulation and inflammation of gingival tissues. They inhibit microbial reproduction and cellular metabolism, resulting in cell death. An antiseptic rinse can be effective throughout the oral cavity — including areas commonly missed in the mechanical disruption of biofilm. However, they are most effectively used as adjuncts to biofilm removal. Research has found some antiseptic rinses are bactericidal in saliva and soft tissues, including the tongue and oral mucosa, which harbor pathogenic bacteria.¹⁰ However, for patients with periodontitis and deep probing depths, rinses will not reach the depth of the pocket.

The daily disruption of plaque and biofilm is necessary for gingival health. However, mechanical oral hygiene procedures performed at home may be insufficient for completely preventing gingival disease.¹¹ Rinses containing chlorhexidine gluconate (CHX) are shown to reduce Streptococcus mutans and Lactobacillus in saliva.¹² While CHX rinse reduces the presence of certain bacteria, limited studies report its effectiveness for caries control. The bactericidal and bacteriostatic properties make CHX rinses most effective for the disruption of plaque and treatment of gingival disease.¹² Once absorbed, CHX rinse shows a consistent bacteriostatic action lasting 12 hours.¹¹ Daily use of CHX mouthrinse has been shown to be an effective adjunct to mechanical biofilm removal. A 2014 randomized controlled trial by Zimmer et al¹³ found that in conjunction with twice-daily brushing, rinsing even once daily with 0.06% CHX provided greater plaque reduction after eight weeks than toothbrushing alone. While many formulations of CHX rinse contain alcohol, an alcohol-free version is now available, and a recent study showed it has similar efficacy.¹³

When used as an adjunct to oral hygiene, the quaternary ammonium compound cetylpyridinium chloride (CPC) helps reduce plaque and gingival inflammation when compared with toothbrushing alone.¹⁴ With a long history of safe and effective use as an antimicrobial agent, CPC rinse does not disturb the balance of healthy oral microflora.^14,15 It exhibits antimicrobial activity against Gram-positive bacteria by binding to the phosphate groups of lipid cell walls, damaging the membrane and inhibiting the cell’s metabolism.¹⁵ A recent study supports the effectiveness of CPC in reducing Prevotella, a bacterium related to endodontic, gingival, and periodontal infections.¹⁴ Using a CPC rinse three times daily has been shown to significantly reduce plaque scores.¹⁵

Mouthrinses containing essential oils (EO) reduce the bacterial vitality, thickness and density of oral biofilm.¹⁶ Common over-the-counter EO rinses include combinations of thymol (0.064 %), eucalyptol (0.092 %), methyl salicylate (0.060 %) and menthol (0.042%).¹⁷ The effectiveness of EO rinses stems from their ability to disrupt cell wall formation, inhibit enzymatic activity of bacteria, and prevent bacterial aggregation.¹⁷

A 2018 study reports that compared to dentifrice slurries, pathogenic microbes throughout the entire thickness of the biofilm were more susceptible to the antimicrobial activity of an EO mouthrinse.¹⁶ It was found that moving the EO rinse forcefully around the mouth with the cheeks when projecting it onto the biofilm is probably of prime importance for reducing bacterial biofilm vitality.¹⁷ A single application of EO mouthrinse presents high antibacterial activity and penetration capacity, and is an effective adjunctive antimicrobial agent against oral biofilms.¹⁷

PATIENTS WITH XEROSTOMIA

Saliva plays an important role in the protection of the hard and soft tissues of the oral cavity. Xerostomia is a common side effect of many systemic diseases and treatments, such as Sjögren syndrome, chemotherapy/radiation therapy and medication usage. Chronic xerostomia and hyposalivation can lead to significant oral disorders and negatively affect quality of life. Older adults tend to experience xerostomia due to salivary disorders caused by systemic conditions.¹⁸ Additionally, patients with hyposalivation are predisposed to developing mucosal candidiasis, which can present with a pseudomembrane, erythema of the underlying tissues, and/or a burning sensation of the tongue or other intraoral soft tissues.¹⁸

Therapeutic mouthrinses can serve as important adjunctive aids for patients with chronic xerostomia. These individuals are at high risk for caries, so using a sodium fluoride mouthrinse is beneficial. Incorporating a mouthrinse with a neutral pH or rinses containing carboxymethylcellulose may help decrease the effects of xerostomia. Rinses with plant-based ingredients may also provide relief from dry mouth symptoms.^19,20

XYLITOL

Xylitol is a naturally occurring five-carbon organic sugar compound that is found in fruits and vegetables; it is also artificially manufactured from xylan-rich plant materials, such as birch and beechwood.²¹ Approved by the U.S. Food and Drug Administration and American Academy of Pediatric Dentistry, xylitol has been widely researched and globally accepted as a natural sweetener.²² More than 35 countries have approved its use in foods, pharmaceuticals and oral health products, principally in chewing gums, toothpastes, syrups and confectioneries.²¹

The effects of xylitol rinses are multidimensional on oral health. Xylitol reduces the levels of pathogenic microorganisms in plaque and saliva by disrupting their energy production processes. It also reduces the adhesion of microorganisms to tooth surfaces and thus curbs their acid production potential. Because oral bacteria cannot metabolize xylitol, it inhibits microorganism growth by starving the pathogens, resulting in cell death. Xylitol, like other sweeteners, promotes mineralization by increasing salivary flow when used as chewing gum or lozenges.²¹

The effect of a combination of xylitol and chlorhexidine on the viability of Streptococcus sanguinis or S. mutans during the early stages of biofilm development has been studied in comparison with xylitol and chlorhexidine alone.²³ The xylitol/chlorhexidine combination inhibited streptococci more when compared with the sole use of either agent. This synergistic action could be used for high-risk caries patients or for reducing mutans streptococci transmission from mother to child. Chlorhexidine alone and xylitol/chlorhexidine solutions are effective against both S. mutans and S. sanguinis. Research shows S. sanguinis was most sensitive to the antiseptic effects of chlorhexidine alone, while S. mutans colonies were more sensitive to the xylitol/chlorhexidine solution.²⁴

Xylitol decreases the incidence of dental caries by increasing salivary flow and pH,²³ and by reducing the number of cariogenic and periodontal pathogens, plaque levels, xerostomia, gingival inflammation, and dentinal erosion.²⁵ Dentifrice with xylitol reduces S. mutans colonies in saliva and helps maintain healthy pH values, thus it has a positive effect on the quality of the oral environment. Low xylitol concentration in fluoride toothpaste has been shown to improve the cariostatic effects on tooth enamel. Synergistic use of xylitol with small doses of fluoride ions aids caries control.

The noncariogenic and cariostatic properties of xylitol have led to its use in various oral hygiene products. Dental professionals can choose multiple delivery forms, as determined by patient need. Irrespective of the xylitol medium (e.g., chewing gum, toothpaste, mouthrinse, lozenges or candy tablets), research has confirmed that continuous and long-term exposure to the dentition is required for effective action.²⁶ Xylitol chewing gum is an effective adjunct to daily mechanical removal of oral biofilm. Studies of the frequency and dosage of xylitol in chewing gum have examined both the short- and long-term effects. The evidence suggests xylitol gum may be most effective in reducing S. mutans when used in shorter intervals at higher daily doses.^27–29

A 2018 study comparing xylitol and sorbitol gum found that xylitol in the amount of 6 g/day was effective in reducing S. mutans counts during short-term use, and exposure three times a day (or more) was necessary for effectiveness.²⁹ The therapeutic properties of the xylitol gum produced a significant decrease in bacteria from one to two months, but at three months returned to baseline.²⁹ A 2006 study of the dose and effects of xylitol gum found similar results in reducing S. mutans levels.²⁷ After five weeks of chewing xylitol pellets four times a day, the groups chewing either 6.88 g/day or 10.32 g/day exhibited 10-times lower S. mutans counts than at baseline.²⁷ While limited research exists on the effectiveness of xylitol gum and periodontal disease, a 2014 study determined chewing xylitol gum when unable to brush, or with an absence of brushing, may have a limited inhibitory effect on bleeding on probing and plaque scores.²⁸ Further studies are needed to determine the effects of xylitol gum on gingival diseases.

Consumption of chewing gum with a high xylitol concentration of 5 g or more per day increases the level of xylitol significantly in saliva, which aids caries reduction.^28,30 While length of time chewing has not been consistently studied, chewing for more than five minutes encouraged participants in past studies to develop a routine.²⁷ A common dose of xylitol found in a 1.08-g piece of chewing gum is 0.72 g, but dosages may differ between products.³¹ For clinicians, the recommendation of xylitol gum as an adjunct to mechanical biofilm disruption may be beneficial to patients with an increased risks for caries. When recommending the use of xylitol gum for caries prevention, it is important to identify products with effective levels of xylitol, and to counsel patients on the frequency of use needed for optimal preventive effects.

ADDITIONAL INGREDIENTS

Other ingredients not found in traditional mouthrinses may address specific needs of individual patients. While not an antimicrobial, delmopinol hydrochloride interferes with the ability of plaque to adhere to the tooth surface. Thus, delmopinol-based rinses may be helpful for patients who have difficulty with plaque control.^32–34

Patients often request a more holistic approach to care and several mouthrinse products are free of preservatives, coloring agents, artificial sweeteners and stabilizers.³² Mouthrinses containing natural botanicals, such as peppermint oil, tea tree oil and aloe vera, may offer oral health benefits. Chitosan-argininamide is a new ingredient in the mouth­rinse realm that is designed to eliminate oral debris and improve periodontal health.^35,36

CONCLUSION

Mouthrinses used as adjunctive therapies may provide benefits by reducing or controlling plaque, gingivitis, caries and xerostomia. The effectiveness of therapeutic mouthrinses is dependent on patient needs and compliance, concentration of the active agent, dosage, substantivity, and interactions with other medications. Oral health professionals are advised to be well versed in therapeutic mouthrinses to be able to make individualized patient recommendations.

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Featured image by ANDREYPOPOV/ISTOCK/GETTY IMAGES PLUS

From Decisions in Dentistry. May 2019;5(5):40–42.