The Effectiveness Of Mouth Rinses:
New Scientific And Clinical Data Indicate Old Ingredients
Can Be Effective In The Control Of Plaque, Inflammation And Caries.
BY: JERRY A. DOUGLAS, D.M.D.
Since well before the 17th century, when Anton van Leeuwenhoek first observed microorganisms and identified them as a source of disease, health care practitioners have recognized the potential value of a prophylactic mouth rinse and have sought an aid in the control of those factors that initiate disease processes in the oral cavity. The earliest mention of mouth rinsing appears as a treatment for diseases of the gums among the Chinese in 2700 B.C. Pliny recommended salty water to the Romans, and Hippocrates prescribed a mixture of salt, alum and vinegar (1).
Although early proponents of mouth rinse may have been unaware of it, we now know that periodontal disease is, as its origins, a microbiological problem that can have a major impact on certain systemic diseases, and that their efforts would have been most effectively directed toward maintaining a normal host/parasite balance in the oral cavity. In that way, the diseases that lead to premature loss of dentition can be prevented, and transient bacterial involvement in systemic diseases controlled more effectively.
Many of today's widely used mouth rinses rely on the antibacterial effect of alcohol for their control of the mouth's microbiota with very limited substance, and on sweeteners to make the concoctions pleasant tasting. They may freshen the breath for a brief period of time, 20-45 minutes, but most do little to aid in maintaining the health of the oral cavity and controlling the pathogenic bacteria. One employs the well-established therapeutic effects of phenol-related essential oils, thymol and eucalyptol in an alcohol base (2). The scientific community is still evaluating the long-term effect of daily use of high alcohol mouth rinse, and published scientific articles suggest monitoring of the continuous frequent use of such rinses. Side effects and disagreeable taste limit the application of still other potentially beneficial mouth rinse agents, particularly in the United States.
But recently, adequate scientific data concerning etiological factors in diseases of the mouth have become available to assist in the formulation of a mouth rinse that has been shown to be effective in our clinical practice. This prophylactic mouth rinse, trade name Prevention, combines four historically valued active ingredients that have established a safety track record – zinc chloride, sodium lauryl sulfate, hydrogen peroxide and sodium citrate – in a water base as an effective aid to the control of plaque, inflammation, and caries. There is also clinical evidence establishing success in treating oral ulcerations. Prevention, unlike the most popular mouth rinse brands, contains only two percent alcohol.
To be judged effective, a mouth rinse must be active in three arenas, pleasant tasting enough to encourage use, and free of serious sequela. First, it should work to control the proliferation of the primarily anaerobic bacteria that are among the most powerful etiological factors in periodontal disease. The second vital area in which a mouth rinse must be effective is plaque control, control plaque qualitatively not quantitatively. Treatment of inflammation, most always present in periodontal disease, is the third requirement. Clinical experience with Prevention mouth rinse strongly supports its effectiveness in these three areas of concern.
Zinc Chloride
Zinc chloride has been tested and accepted as an antibacterial agent since 1884, when its value was first assessed (3). Its ability to control plaque was originally noted in a 1940 study (4) and a 1973 study (5) that, along with others, showed zinc to reduce plaque accumulation by adhering to cell walls, thereby preventing adherence of the microbiota responsible for plaque to the tooth surface (5,6,7).
Considerable data have accumulated to show that its effect persists for several hours after rinsing (8) and that it is most active in individuals with a high rate of plaque growth (9). Giersten, et. al., (10) reported a 40 percent plaque reduction in individuals who used a zinc-chloride based mouth rinse twice-daily for three days. His findings also showed zinc chloride to be effective in reducing acid production by plaque-causing microorganisms, suggesting that the heavy metal inhibits the bacteria's metabolic activity. Further work by Jones, et.al. supports earlier findings with results that show a zinc dentifrice to have reduced plaque growth by 38 percent in a controlled study (11).
Gedalia, et.al. recorded, "a highly significant decrease . . . in the plaque index after the complete rinsing period of five days" (12), from their study of a zinc chloride mouth rinse. They also report prolonged retention of the anti-plaque agents and suggest that zinc inhibits bacteriological growth, binds to the surface of oral bacteria to affect their ability to adhere to the teeth, but does not accumulate in the surface enamel of the teeth. Other researchers have found that zinc chloride effectively reduces structural and metabolic changes in bacteria (13) and reduces the acidogenicity of dental plaque (14, 15). One of the most beneficial attributes of zinc chloride from an oral clinical aspect, is its ability to be bacterial selective. It only attacks the pathogenic bacteria and doesn't disturb the normal oral flora.
Sodium Lauryl Sulfate
Another of the active ingredients in Prevention mouth rinse – sodium lauryl sulfate – is the most widely used synthetic detergent in dentifrices, with the capacity to reduce surface tension and emulsify plaque remnants. It exhibits a high affinity for enamel (16).
Recent research has also shown that such surfactants are effective in limiting the action of certain pathological bacteria by inhibiting enzyme activity in the metabolism of glucose. Results show that sodium lauryl sulfate is effective as an inhibitor of the bacteria Streptococcus mutans, known to be an agent of smooth surface dental caries (17). Others, (18, 19) report that sodium lauryl sulfate interferes with cell integrity of the microbiota and reduces plaque acidity. Barkvoll, Rolla and Lagerlof (20) claim that sodium lauryl sulfate prevents the adhesion of plaque to tooth enamel due to its action of binding electrostatically to the tooth surface, competing successfully for the available binding sites.
ZnCl2 and SLS Combined
Research has documented that zinc salts inhibit the growth of pathogenic bacteria (21); recent studies have shown further that its effect can be greatly increased by combining it with sodium lauryl sulfate. In concert, the two compounds have the capacity to provide a threefold increase in plaque control. Giersten (22) reports that both zinc and sodium lauryl sulfate are successful antibacterials, but that combined they exert an additive inhibitory effect beyond what can be expected from either substance alone. Giertsen tested the combination on two known pathogenic bacteria – Streptococcus sobrinus and Streptococcus sanguis. In both cases, zinc chloride and sodium lauryl sulfate exhibited an additive inhibitory effect on growth.
Hydrogen Peroxide
Many studies have established the value of hydrogen peroxide as a mouthwash ingredient (23) in the years since W.F. Dunlop first introduced the concept of oxygen as an effective agent for controlling growth of anaerobic bacteria (24). Though Dunlop applied oxygen directly and under pressure, the release of oxygen by hydrogen peroxide contained in a mouth rinse has much the same effect.
In one study of adolescents with fixed appliances, by R.L. Boyd (25), results were unequivocal. A control group of 24 that used tooth brushing and a mouth rinse without hydrogen peroxide was compared to a subject group of 34 employing tooth brushing and a mouth rinse containing 1.5 percent hydrogen peroxide. Evaluated at 1, 3, 6, 9, 12 and 18 months, the two groups (which had no significant differences at baseline) showed significantly improved oral health among those using the H2O2 rinse at every interval from 3 months on. Bleeding tendencies and sites with plaque or gingival indices greater than 1 were always significantly lower in the subject group. No mucosal irritation or staining of the tongue or teeth was recorded in either group. Boyd also reports that both groups exhibited excellent compliance with the study protocol.
An earlier study (26) examined the mechanism by which hydrogen peroxide is effective. The researchers sampled bacteria from the oral cavities of two groups of students – one using a placebo mouthwash three times a day, the other rinsing with an H2O2 solution three times a day. The rinses were the only oral hygiene products used during the two-week trial period.
Results showed that hydrogen peroxide effectively limited the growth of the filaments, fusiforms, motile and curved rod bacteria, the microorganisms common in plaque. The authors write that the hydrogen peroxide greatly reduced the amount of plaque formed and significantly retarded the development of gingivitis. The study confirmed the effect of oxygen on the anaerobic bacteria found in earlier work (27, 28) to be relatively more common in gingivitis pockets than in healthy sulci.
Much data has accumulated implicating anaerobic bacteria in plaques, gingivitis and periodontitis (29). Investigators demonstrated a marked change on bacterial populations during the period of no tooth brushing. For the control group, bacteria populations went from 90 percent coccoid cells and straight rods on day 0 to only 40 percent on day 14. For the subjects rinsing with the hydrogen peroxide mouthwash, the characterization of the bacteria remained as it had been on day 0. The authors conclude that, "a mouthwash which releases hydrogen peroxide effectively prevents the colonization of filaments, fusobacteria, mobile and curved rods and spirochetes in developing plaque."
Another study, conducted with 171 subjects over four years, showed improvement in oral hygiene and periodontal disease when participants employed a slurry of hydrogen peroxide, baking soda and salt. Another group and the controls also showed improvement, however (30).
Additional research (31), has also shown marked improvement in oral health and a distinct bacteriacidal effect for hydrogen peroxide. And it has been shown that cells of the body's immune system, responding to pathogens, employ an oxidative burst characterized by a sharp increase in oxygen uptake (32), and that tissues treated with hydrogen peroxide show an increase in oxygen consumption.
In the chemical process of releasing oxygen for its short period of activity, hydrogen peroxide also exerts a mechanical action of bubbling and foaming that may carry away food particles and microbiota from gingival sulci and dental plaque. It is likely that this mechanical action cleans the pit and fissure anatomy of the clinical crown, affecting a reduction in the caries process. Hydrogen peroxide has been approved by the Food And Drug Administration for use in the oral cavity up to concentrations of two percent.
Sodium Citrate
Little is known about the precise action of the astringent sodium citrate, but recent research has shown it to be an effective agent in reducing dentin sensitivity. One study reported that a dentifrice containing sodium citrate reduced pain for 46 percent of the patients who use it (33). The problem of sensitivity is substantial, with an estimated 15 percent of all dental patients suffering pain from dentin sensitivity. Perhaps 40 million North Americans suffer sensitivity at some time, and another 10 million suffer chronically (34).
In studies of sodium citrate's capacity for reducing ulceration and inflammation, positive results have been reported. Although the precise mechanisms by which it acts are not yet known, and the results must be extrapolated to the oral environment, the work suggests that sodium citrate is an effective inhibitor of enzyme release. That fact alone seems to afford an explanation for its positive effect of ulceration (35). Research has shown that heavy metal ions when mixed with sodium citrate complexes the sodium citrate, giving it the ability to inhibit the production of chemo toxic agents by the polymorphonuclear leukocytes that are responsible for the initiation of inflammation (36).
Summary
A mixture of hydrogen peroxide, zinc chloride, sodium lauryl sulfate and sodium citrate, blended in appropriate proportions in a de-ionized water base, enhances a patient's chances of eliminating the etiological factors responsible for host/parasite imbalance and subsequently pathology of the oral cavity, as well as potentially exhibiting a positive affect on certain systemic diseases. The antimicrobial effect of the combined elements operates selectively against the anaerobic bacteria that have been implicated in plaque formation, gingivitis and periodontitis. Prevention mouth rinse has been clinically effective in reducing the plaque, inflammation and caries characteristic of an oral cavity with a pathogenetic balance of microbiota, and proven to help control and prevent oral ulcerations (36).
The clinical results in our practice support the combined effectiveness of the ingredients that the literature suggests. Hydrogen peroxide is an oxygen liberator that palliates inflammation and reduces plaque formation through its bacteriacidal effect on anaerobic microorganisms. Zinc chloride reduces plaque and decalcification via its extra- and intra-cellular attachment, disrupting the metabolic activity of the microbiota responsible for plaque. The surfactant sodium lauryl sulfate enhances the activity of the zinc chloride and adds its own antimicrobial properties, and sodium citrate serves as a desensitizer that also complexes the metals, enhancing their activity on the enzymes of the microbiota. The four ingredients work together to reduce etiological factors, microbiota and their by-products, plaque and decalcification. In this way, they combine to aid in the maintenance of a normal host/parasite balance.
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Prevention Mouth Rinse