Controlling Plaque with Mouthrinses

Mouthrinses have a variety of indications including to freshen breath, to help prevent or control caries, to reduce plaque, to prevent or reduce gingivitis, or to produce a combination of these effects. The American Dental Association (ADA) has recognized two general categories of mouthrinses: cosmetic and therapeutic. Cosmetic mouthrinses may temporarily control or reduce malodor and leave the mouth with a pleasant taste. They mask the undesirable odor and neither kill the bacteria that cause bad breath nor chemically inactivate odor causing compounds. Cosmetic mouthrinses do not claim to reduce plaque, gingivitis, or caries. Therapeutic mouthrinses may reduce plaque, gingivitis, caries, and malodor. Fluoride mouthrinses, which help reduce caries, are therapeutic.

Plaque Control

Periodontal diseases are characterized by plaque-induced inflammation. Therefore, therapeutic intervention and maintenance recommendations are based on plaque removal. Many strategies for plaque removal exist, but the endpoint remains the same—to regularly remove as much plaque as possible. Complete plaque removal is not practical but fortunately, the host response can manage some degree of inflammation.

Carefully performed daily home plaque control combined with professionally delivered plaque removal reduces supragingival plaque and greatly reduces the number of subgingival sites with periodontal pathogens. Plaque control is an effective way of treating and preventing gingivitis and is a critical part of the treatment and prevention of periodontal diseases.¹

Good plaque control practices are particularly important for periodontal patients because they may have active infections, as well as previously treated disease, and a demonstrated susceptibility to periodontal infections. Plaque control efforts for periodontal patients focus on improved brushing and cleaning interproximal areas—tasks that require mastering difficult and time-consuming daily oral hygiene habits. Periodontal patients should completely remove plaque from the teeth at least once every 24 hours because of their susceptibility to disease.

Mechanical plaque removal is the traditional method of plaque control. In theory, mechanical plaque control methods are able to maintain adequate levels of oral hygiene. In actuality, though, most patients do not employ them effectively. The need for additional help in the control of bacterial plaque provides the rationale for the use of mouthrinses with clinically-proven anti plaque and antigingivitis effectiveness as adjuncts to patients’ mechanical oral hygiene regimens.²

Evaluation of Therapeutic Mouthrinses

The clinical effectiveness and safety of mouthrinses are best evaluated by using prospective, randomized clinical trials. In these studies plaque and gingival indexes, the condition of the oral mucosal tissues, and the composition of the oral flora are evaluated when the product is used according to the label directions and as an adjunct to mechanical oral hygiene procedures (brushing and flossing).

Four characteristics are essential to assessing which types of clinical studies are credible:

1. The trial should be controlled with a negative control group to which the test group can be compared.
2. Subjects meeting entry criteria should be assigned randomly to treatment and control groups.
3. The trial should be blinded so that the examiner and all other personnel involved in evaluating data do not know which group a given subject is assigned.
4. The protocol, entry criteria, random assignments, and method of statistical analyses should be determined in advance of the actual treatment phase.

The ADA Council on Scientific Affairs (CSA) has developed guidelines for testing chemotherapeutic products for control of supragingival dental plaque and gingivitis.⁴ The Food and Drug Administration (FDA), the Canadian Dental Association, and the British Dental Association have all adopted these guidelines. Subsequent modifications deal with issues of study design, such as requiring a gingival bleeding component in the assessment of gingivitis; indicating methods for standardization of examiners; specifying elements to be included in the statistical analyses, and establishing a minimum acceptable effect level.

To be considered acceptable, a product should be tested in two independently conducted trials that use either a crossover or a parallel study design and last a minimum of 6 months. There are several reasons for requiring a 6-month study: it is the traditional recall interval in dental practice; it provides sufficient time to determine if the product has any adverse effects, such as tooth staining or mucosal irritation; and it provides enough time to determine whether the mouthrinse will have an adverse effect on the oral flora, such as allowing for the overgrowth of opportunistic pathogens.

The CSA has set a 20% reduction in gingivitis for establishing definite improvement of mean gingivitis scores, which is measured against a placebo agent or inactive control treatment. This requirement is important because studies’ participants who use a placebo agent often show improvement simply because they are in a dental study; have had their teeth, plaque, and gingivae examined; and, subsequently, are more dentally aware.

The CSA also recommends that in addition to measuring plaque quantitatively by any of the traditional indexes, investigators should obtain microbiologic samples from several supragingival sites and clearly characterize the oral flora in a control group as well as in the test group.

In evaluating the efficacy of a chemo therapeutic agent on gingivitis, the CSA recommends that both subjective scoring of gingivae based on tissue color or estimated degree of swelling and objective measures, such as the extent of gingival bleeding on probing or the amount of crevicular fluid flow, should be made.

A mouthrinse that claims to control gingivitis must demonstrate a statistically significant reduction in gingival in – flammation. Two thera peutic mouth rinse ingredients— chlorhexidine and essential oils— are recognized by the ADA as effective against plaque and gingivitis. The FDA has approved chlorhexidine-containing rinses only as prescription products. Essential oil mouthrinses are sold over the counter. However, it is important to note that no mouthrinse has either FDA approval or ADA acceptance to treat periodontitis.

Chlorhexidine

Chlorhexidine is one of the most effective antiplaque agents available.⁵ It is a cationic compound that binds to the hydroxyapatite of tooth enamel, to the pellicle, to plaque bacteria, to the extracellular polysaccharide of the plaque, and especially to the mucous membrane. The chlorhexidine adsorbed to the hydroxyapatite is believed to inhibit bacterial colonization. After binding, the agent is slowly released in active form over 12 hours to 24 hours. This ability of the oral tissues to adsorb an active agent and to permit its slow release in active form over a prolonged period is known as substantivity. Although chlorhexidine is quite effective, it is not active against all relevant anaerobes. A high minimal concentration is necessary for efficacy.

Chlorhexidine has not proved beneficial as the sole method of treating periodontitis with deep pockets. Following root planing, prophylaxis, or periodontal surgery, chlorhexidine irrigation may be effective in helping to control inflammation and subgingival plaque.⁶

The most common side effect associated with chlorhexidine use is stain. Chlorhexidine can cause staining of tooth surfaces, restorations, and the dorsum of the tongue. One study showed that 56% of chlorhexidine oral rinse users exhibited a measurable increase in facial anterior stain after 6 months compared to 35% of control users. In the same study, 15% of chlorhexidine users developed heavy stain compared to 1% of control users.⁷ Stain is more pronounced in patients who have heavier accumulations of plaque. Stain resulting from use of chlorhexidine oral rinse does not adversely affect the health of the gingivae or other oral tissues. Stain can be removed from most tooth surfaces by conventional professional prophylactic techniques.

Some patients may experience an alteration in taste perception while undergoing treatment with chlorhexidine oral rinse. Rare instances of permanent taste alteration following use of chlorhexidine have been reported via post-marketing surveillance. Increased calculus formation, superficial desquamation of tissue, and hypersensitivity have also been noted. Chlorhexidine is inactivated by most dentifrice surfactants, therefore it is not included in dentifrices. Because of this inactivation, it is critical for dental professionals to alert patients not to use chlorhexidine mouthrinses for 30 minutes before or after toothbrushing.

Although chlorhexidine may be more effective than any other current antiplaque agent and has a definite role in preventive and control dental procedures, it is not a “magic bullet.” Its side effects and inadequate activity range somewhat limit its use.⁶

Essential Oils

Essential oil mouthrinse has been used for more than 120 years and was the first overthe- counter antiplaque and antigingivitis mouthrinse accepted by the ADA.⁸ The active ingredients are thymol, menthol, eucalyptol, and methyl salicylate. Flavor variations of the product as well as the original formula have received the ADA Seal of Acceptance. Microorganisms do not develop a resistance to the antibacterial effects of essential oils. In long-term clinical trials, essential oil mouthrinse has been shown to reduce both plaque accumulation and severity of gingivitis by up to 34%.^9,10 A review of 22 studies demonstrated that essential oils are effective as both antiplaque and antigingivitis agents.¹¹ Microbial sampling of plaque in these trials has demonstrated no undesirable shifts in the composition of the microbial flora.¹² Patients are advised to rinse twice daily with 20 ml of an essential oil mouthrinse for 30 seconds in addition to employing their usual oral hygiene regimen.
As with chlorhexidine, rinsing with an essential oil mouthrinse is unlikely to be effective in treating periodontitis because the solution does not reach the depths of the periodontal pockets. Irrigation studies using irrigator tips designed to deliver solutions subgingivally suggest that the essential oils and chlorhexidine may have some value as adjuncts to mechanical therapy.

Quaternary Ammonium Compounds

Quaternary ammonium compounds, such as cetylpyridinium chloride (CPC), are capable of reducing surface tension and adsorbing to negatively charged surfaces. Several over-the-counter mouthrinses contain cetylpyridinium chloride, benzethonium chloride, or domiphen bromide at concentrations of 0.025% to 0.075%. Studies performed on quaternary ammonium compounds report moderate plaque reduction compared to placebo rinses.¹³ Side effects can include oral ulceration and a mild burning sensation of the tongue. Quaternary ammonium compounds may also have a lingering bitter taste. As of yet, no products containing quaternary ammonium compounds have received the ADA’s Seal of Acceptance for plaque reduction.

Preprocedural Rinsing

For the dental professional, it may be important for patients to use a mouthrinse prior to aerosol-generating procedures. Unless an effective dry-field technique is used, the bacterial aerosol generated by a high-speed turbine in a 30-second period is roughly equivalent to the patient sneezing in the dental professional’s face. One study¹⁴ found that even a preliminary water rinse temporarily reduced the bacterial aerosol population by 61%, brushing alone by 85%, and an antibacterial mouthrinse by 97%. Another study¹⁵ showed that preprocedural use of an antimicrobial mouthrinse resulted in a 93.6% reduction in the number of viable bacteria in a dental aerosol produced by ultrasonic scaling. The effect of this reduction on actual disease transmission has not been determined.

Alcohol

Alcohol is an ingredient in most mouthrinses. All ADA-accepted mouthrinses contain pharmaceutical grade denatured alcohol as a vehicle to deliver the antimicrobial ingredients. More than 40 years ago, anecdotal reports suggested a link between mouthrinses containing alcohol and oral cancer.¹⁶ Epidemiologic studies followed and a 1995 literature review concluded that there is no causal relationship between mouthrinses and oral cancer.¹⁷ A further review in 2009 concluded that a link between alcohol-containing mouth – rinses and oral cancer is not substantiated by scientific evidence.¹⁸

The FDA,¹⁹ National Cancer Institute (NCI), and ADA all agree that there is no evidence of a causal relationship between alcohol-containing mouthrinses and oral cancer. The ADA has stated, “According to a statement from the NCI, it is premature to make recommendations about any alcohol- containing mouthwashes. In the meantime, the association suggests that patients continue to use the therapeutic mouthrinses accepted by the ADA…and recommended by their dentists.”²⁰

Conclusion

Plaque control is one of the key elements of oral health. Without plaque control, optimal oral health through periodontal treatment cannot be attained or preserved. Every patient in every dental practice should be educated about daily plaque control and encouraged to adopt it. Mouthrinses are an important part of the armamentarium to control plaque as are conscientious toothbrushing and flossing. Good plaque control facilitates the return to health for patients with gingival and periodontal diseases, prevents tooth decay, and preserves oral health for a lifetime.

References

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4. Guidelines for acceptance of chemotherapeutic products for the control of supragingival dental plaque and gingivitis. J Am Dent Assoc. 1986; 112: 529-532.
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13. Newbrun E. Antiplaque/antigingivitis agents. In: Yagiela JD, Dowd FJ, Neidle, EA. Pharmacology and Therapeutics for Dentistry. 5th ed. St. Louis: Elsevier; 2004:743-755.
14. Wyler D, Miller R, Micik R. Efficacy of self-administered preoperative oral hygiene procedures in reducing the concentration of bacteria in aerosols generated during dental procedures. J Dent Res. 1990;124:556-58.
15. Fine D, Yip J, Furgang D, Barnett M, Olshan AM, Vincent J. Reducing bacteria in dental aerosols: pre-procedral use of an antiseptic mouthrinse. J Am Dent Assoc. 1993;124:56-58.
16. Cole P, Rodu B, Mathisen A. Alcohol-containing mouthwash and oropharyngeal cancer: a review of the epidemiology. J Am Dent Assoc. 2003;134:1079-1087.
17. Gagari E, Kabani S. Adverse effects of mouthwash use: a review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1995;80:432-439.
18. LaVecchia C. Mouthwash and oral cancer risk: An update. Oral Oncology. 2009;45:198-200.
19. Oral health care drug products for over the counter use; Antigingivitis/antiplaque drug products. Fed Register. 2003;68:32241-32243.
20. Ciancio S. Alcohol in mouthrinse: lack of association with cancer. Biol Ther Dent. 1993;9:1-2.

From Dimensions of Dental Hygiene. November 2009; 7(11): 42, 44-45.