Oral Health Group

INFECTION CONTROL: Preprocedural Mouthrinses

October 1, 2000
by R.A.Clappison DDS, FRCD(C) Prosth.

Mouthrinses are used in dentistry for a number of reasons: to freshen breath, to prevent or control tooth decay, to reduce plaque formation on teeth and gums, to prevent or reduce gingivitis, or to deliver a combination of these effects. Given their antiseptic properties, however, some agents also can serve an important function in infection control.

In their 1998 text book Infection Control and Management of Hazardous Materials for the Dental Team, Miller and Palenik write, “The application of antiseptics to the skin or mucous membranes before surgery or injections has been practiced for many years. The goal of such application is to reduce the number of microorganisms on the surface to prevent their entry to underlying tissues, which could cause bacteremia, septicemia, or local harmful infections. The use of an antimicrobial mouthrinse by the patient before dental procedures is based on a similar principle of reducing the number of oral microorganisms. This reduction also reduces the number of microorganisms that may escape a patient’s mouth during dental care through aerosols, spatter, or direct contact.”


Although clinical research has not proven that use of a preprocedure mouthrinse prevents or reduces disease transmission from patients to staff, several research papers have demonstrated that mouthrinsing with an antimicrobial mouthwash can greatly reduce the number of viable microorganisms in the operatory:

Building, on previous findings that a quaternary ammonium compound mouthrinse reduced the initial intraoral bacterial population by 81% over a water-rinse control, Litsky, Mascis and Litsky in 1970 reported the mouthrinse’s effectiveness in decreasing bacterial aerosols created during drilling. They found that the mouthwash rinse created 89.3% less bacteria in aerosols than water-rinse controls.

Another 1970 study, this one by Mohammed and Monserrate, looked at the efficacy of an over-the-counter quaternary ammonium compound mouthrinse in reducing the bacterial counts in dental aerosols produced by an air turbine. They found that the patient’s use of the mouthwash prior to the procedures greatly reduced the number of airborne bacteria.

“A preprocedural mouthrinse should be used to reduce the number of microbes in the patient’s mouth. The mouthrinse should have residual activity to help maintain reduced microbial levels throughout the appointment.”

A 1971 study by Wyler, Miller, and Micik evaluated several oral hygiene measures for their effectiveness in reducing the bacterial content of dental aerosols. They found that toothbrushing reduced bacterial levels by an average of 90% (range: 52-97%; mean: 85%) and toothbrushing with mouthrinsing by 95% (range: 85-99.7%; mean: 96%); a plain water rinse also reduced bacterial counts, but this procedure was the least effective.

Mouthrinsing alone, however, provided the most reliable reductions with an average 97% decrease in recovered bacteria over the narrow range of 92% to 99.5% (mean reduction: 98%). Investigators also looked at individual mouthwashes and their efficacy at controlling bacterial counts. Whether the active ingredient was a quaternary ammonium compound, a phenol, essential oils, or zinc chloride, reductions in bacterial aerosols were substantial. The authors concluded that “use of the rinsing technique can provide between a tenfold and hundredfold reduction in bacteria in the aerosols produced during dental procedures, and thereby [can] have the effect of reducing the dentist’s chance of receiving pathogenic organisms from his patient while providing treatment.”

Research published in 1978 by Muir and colleagues found that a two-minute rinse with chlorhexidine gluconate significantly reduced bacteria in aerosols produced by ultrasonic scalers.

A 1992 study by Fine and colleagues found that, compared baseline levels, rinsing with an essential-oil-based mouthwash produced a 94.1% reduction in recoverable counts of bacteria in aerosols generated during a tenminute ultrasonic scaling. This translated to a 1.23 log reduction in bacterial counts as compared to baseline levels. A control rinse produced a 33.9% reduction compared to baseline. The essential oil containing rinse was significantly more effective than the control rinse.

In a separate study published by Fine, et al. in 1993, preprocedural rinsing with the essential oil mouthrinse resulted in a 93.6% reduction, compared to baseline, in recoverable counts in aerosols generated 40 minutes after rinsing. As before, this reduction was significantly greater than seen with the control rinse.

In 1993, Fine and colleagues reported the results of two clinical trials of preprocedural rinsing with a mintflavored variant of the essential oil mouthrinse. In the first study, the antiseptic mouthrinse reduced recoverable counts by 92.1% compared to the baseline in aerosols generated immediately after rinsing. This was significantly greater than the reduction from the control finse which was only 14.9%. The second study measured reduction in bacterial count from baseline in aerosols generated 40 minutes after rinsing. The essential oil mouthrinse reduced recoverable counts by 91.3% and was again significantly more effective than the control rinse.

A 1995 study by Logothetis and Martinez-Welles looked at the effectiveness of two consecutive 30-second rinses with a chlorhexidine gluconate (CHG) mouthrinse on the bacterial aerosols generated through air polishing. The CHG prerinse delivered significant reductions in the number of bacterial colony-forming units as compared to an essential-oil-based mouthwash and water control.

In 1996, DePaola et al. published a study that showed rinsing with an essential-oil-based antiseptic mouthrinse resulted in a significant reduction (60% to 65%) in intraoral salivary bacteria. The reductions of most organisms were sustained for up to 60 minutes, the time of most dental appointments. The authors concluded that the agent “significantly reduces the level of bacteria in human saliva; and when used prior to dental procedures, may contribute to an overall infection control program.”

A preprocedural mouthrinse can be used before any dental procedure, but its bacteria-inhibiting properties may be most beneficial before prophylaxis with a prophy cup or ultrasonic scaler, since rubber dam cannot be used and, unless a hygienist works with an assistant, high-volume evacuation is not commonly employed. For these procedures, Miller and Palenik acknowledge, mouthrinsing may be the only approach to minimizing contamination from aerosols and spatter. Dr. Stuart Fischman, professor of oral medicine at the State University of New York (Buffalo) agrees: “Unless there is an effective dry field technique, the bacterial aerosol generated by a high-speed turbine or ultrasonic scaling device can produce a significant discharge of bacteria in the face of the professional…. The effect of [preprocedural rinsing] on actual disease transmission has not been determined, but there would appear to be a favorable risk-benefit ratio.”

In selecting an antiseptic mouthrinse for preprocedural rinsing, residual activity is an important consideration, as the agent must be capable of reducing microbial levels throughout the length of the appointment. A rinse with long-lasting antimicrobial activity (such as 0.12% CHG) can effect a prolonged suppression (up to five hours) of oral microorganisms.

Mouthrinses lacking, this substantivity could allow oral microorganisms to return to their original levels before some dental procedures are completed, which would limit their infection control value.

Following is an overview of various mouthrinses used in dentistry.


A bisbiguanide with broad-spectrum antimicrobial activity, chlorhexidine is a symmetrical cationic molecule that binds strongly to hydroxylapatite, the organic pellicle of the tooth, oral mucosa, salivary proteins, and bacteria. Because of this binding, chlorhexidine-containing mouthrinses exhibit high substantivity, with 30% of the drug retained after rinsing and slow release over time. Depending on dose
, the agent can be bactericidal or bacteriostatic. (Interference with bacterial cell wall transport systems cause bacterlostasis; bactericidal concentrations converge in and disrupt the cell wall, which leads to leakage of intracellular proteins.)

Essential oils

A combination of essential oils (eucalyptol, thymol, methyl salicylate, and menthol) in an alcohol base, essential-oil mouthrinses are thought to inhibit bacterial enzymes and reduce the pathogenicity of plaque. Several studies support their value in reducing bacteria in dental aerosols. They are sometimes referred to as phenolics because most are derivatives of chemicals with the basic phenolic molecular ring.


Although fluoride has been shown to dramatically reduce caries in both children and adults and to help remineralize incipient carious lesions, the germicidal activity of the agent is negligible.

Oxygenating agents

Mouthrinses containing oxygenating agents release oxygen as an active intermediate to loosen debris in inaccessible areas of the mouth. Although oxygenating agents also have been reported to damage bacteria by altering cell membrane permeability, the germicidal action of these agents is negligible and their substantivity is poor.

Cosmetic antiseptic mouthwashes

Used to mask oral malodor, over-the-counter cosmetic mouthrinses have a pleasant taste and aroma. Those carrying antiseptic claims may contain a quaternary ammonium compounds (such as cetylpyridinium chloride) or a phenolic base. These agents offer little to no therapeutic effect in treating gingivitis, and their impact in disguising malodor is reported to be transient and ineffective. Research has shown some of these agents to be effective in reducing bacterial counts, but their substantivity is lower than that of some other categories of mouthrinses. They generally have a high alcohol content.

Prebrushing rinses

The concept behind over-the-counter prebrushing rinses is to loosen plaque, although the exact mechanism of action is unknown and somewhat questionable. It has been suggested that surface active agents such as sodium lauryl sulfate and sodium benzoate make plaque soluble and, therefore, easier to remove. A large number of studies on these agents have found no oral hygiene advantage over brushing alone, and they have little to no germicidal activity.

The usual adult dosage for mouthrinses is 10 to 20 ml for therapeutic purposes, and the maximum dose equals what can typically be held in the mouth. Rinsing with water or drinking immediately after rinsing should be avoided to prevent clearance of the antimicrobial agent from the mouth, which could reduce antimicrobial effectiveness. The safety and efficacy of mouthrinse use by pediatric patients has not been established for all available antiseptic agents. In fact, mouthrinses often are not prescribed for young patients because of their tendency to swallow some of the rinse. In addition, reduced doses may be considered for geriatric patients, patients with serious illness or disability, and patients with medical conditions or prescription regimens that alter oral responses to mouthrinses. Adverse reactions to mouthrinses are rare, and most–such as burning, taste alteration, tooth staining–are temporary. Idiosyncratic and allergic reactions account for a small minority of side effects. Caution should be exercised, however, in administering mouthrinses to patients in recovery from alcoholism.

Use of a preprocedural, antiseptic mouthrinse that has been shown to be effective in clinical trials appears to be an effective means of reducing aerosol exposure to microorganisms. Although chlorhexidine gluconate mouthrinses are used for the therapeutic management of periodontal disease, essential oil-based products have also been shown to be effective for the reduction of plaque and gingivitis and as a preprocedural mouthrinse. However, mouthrinses remain only one small part of an effective in-operatory infection control program. To protect the dental worker’s skin and mucous membranes against spatter and debris, full-protection eyewear, high-filtration masks, and quality gloves must be worn. The patient’s eyes also should be protected during spatter- or debris-generating procedures. When possible, some authors suggest using rubber prophy cups in place of polishing brushes to minimize spatter, and appropriate long-sleeved, high-neck protective garments are always required during spatter-producing procedures. Thorough between-patient handwashing with a residual-action antimicrobial handwash helps reduce bacterial levels and inhibit dermatitis for continual glove users. During patient treatment, limit the spread of contamination by avoiding contact between the hands and nose, face, and hair as well as unnecessary contact with operatory surfaces such as the mobile operator’s chair.

References available from the managing editor, Oral Health.

Reprinted with permission of OSAP, a nonprofit organization that provides information and education on dental infection control and office safety. For information, contact: 1-800-298-6727.