Using Chlorhexidine Varnish to Reduce Caries Risk
To date, most of the research on 1% chlorhexidine in 1% thymol varnish (CTV) has been conducted on children, examining levels of mutans streptococcus (MS) and lactobacillus in saliva, and levels of MS in fissures in both primary and permanent teeth following varnish placement.
To date, most of the research on 1% chlorhexidine in 1% thymol varnish (CTV) has been conducted on children, examining levels of mutans streptococcus (MS) and lactobacillus in saliva, and levels of MS in fissures in both primary and permanent teeth following varnish placement. The premise for using CTV is that chlorhexidine produces antibacterial effects, including selective effects against MS. Theoretically, if MS levels can be reduced, caries risk should also decrease. Short-term reductions of MS and lactobacillus have been reported, with little differences shown after 3 months to 6 months as compared to placebo. Most studies have not been of sufficient duration to show long-term effects on caries incidence.
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Effects in the Elderly
Investigators in a double-blind clinical trial randomly assigned 102 frail elderly patients to receive either CTV or a placebo varnish. All leathery and soft root lesions were first coated with a fluoride varnish, then the CTV or placebo varnish was applied to the lesions. Patients received their assigned varnish treatment five times over the course of 1 year. At the end of the study, the size and severity of root lesions did not change in patients who received CTV; however, lesions treated with the placebo varnish worsened (eg, increased length, width, and extended closer to the gingival margin). Following CTV application, there was an initial significant reduction in levels of salivary MS; however, at 12 months, there were no differences in salivary MS levels between the two varnish groups. These findings suggest that use of CTV may help to reduce lesion progression, but that antibacterial effects produced by CTV varnish are short-lived.
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Impact on Plaque and Gingivitis
Chlorhexidine is the gold standard antibacterial agent against which other agents are compared for the reduction of supragingival plaque and gingivitis. Thus, investigators have hypothesized that application of CTV could also reduce plaque and gingivitis, especially among older adults with poor oral hygiene. However, a study of 56 institutionalized elderly, ages 64 and older, who were randomly assigned to receive CTV or placebo varnish, twice in the first week, then again at 1 month, 3 months, and 6 months, found no differences in either plaque or gingival index scores with either varnish. Use of CTV did not reduce plaque or gingivitis in this elderly population with poor oral hygiene.
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Oral Hygiene Is Key
Oral health professionals who choose to apply CTV and other varnishes likely do so at routine preventive care visits. In the previously discussed studies, patients received the varnishes at baseline, and then again repeatedly over the course of 3 months to 6 months, but without a change in patients’ usual oral hygiene habits. It is unknown what role oral hygiene status has on influencing efficacy of this treatment.
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Higher Doses May Be Needed
A recent systematic review found that there is no conclusive evidence that the application of CTV is effective when regular professional oral prophylaxis is performed. Higher concentrations of chlorhexidine varnish (40%) were found to provide a greater benefit over control or fluoride varnishes. Lower concentration chlorhexidine varnishes (1% and 10%) may be beneficial for high-risk patients, such as older adults, to help protect against root caries when oral hygiene is poor and in the absence of regular professional oral prophylaxis.
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American Dental Association Speaks Up
In October 2018, the American Dental Association (ADA) issued revised evidence-based guidelines for the nonrestorative treatment of carious lesions. According to the latest ADA recommendation: “to arrest or reverse noncavitated and cavitated carious lesions on root surfaces of permanent teeth, the expert panel suggests clinicians prioritize the use of 5,000 ppm fluoride (1.1% NaF) toothpaste or gel (at least once per day) over 5% NaF varnish (application every 3 months to 6 months), 38% silver diamine fluoride (SDF) plus potassium iodide solution (annual application), 38% SDF solution (annual application), or 1% chlorhexidine plus 1% thymol varnish (application every 3 months to 6 months).”
