Adult tooth decay is an infectious disease that afflicts the majority of Americans aged 55 and older and is the most common chronic disease at midlife with an ever growing economic toll. Despite the fact that specific bacteria cause tooth decay, no FDA-approved anti-microbial treatment for decay is available to the American dental professional. The Prevention of Adult Caries Study (PACS) is a study designed to evaluate the efficacy of a topical, temporary, 10% w/v chlorhexidine dental coating in reducing new decay in adult dental patients at risk for decay.

The Prevention of Adult Caries Study (PACS) is a randomized, double-blind, placebo-controlled Phase III clinical trial conducted under F.D.A. Investigational New Drug license #45,466, with a target enrollment of 1000 at four clinical centers with vastly different populations. The centers participating in this proposed research are: Kaiser Permanente's Dental Plan in Portland, Oregon; Tufts University Dental Clinic in central Boston, Massachusetts; Delta Dental Massachusetts' Dental Clinic in Southborough, Massachusetts; and the dental clinic of the Tuba City Regional Health Care Corporation in Tuba City, Arizona. Kaiser Permanente's Center for Health Research in Portland, Oregon will act as the data-coordinating center, and Tufts University will act as the Administrative Center. This study is designed to evaluate the efficacy of a topical, temporary, 10% w/v chlorhexidine dental coating in reducing caries increment in at-risk adult dental patients. This study will treat participants in months 1(4 weekly applications) and 7(1 application) with final outcome measured at 13 months after randomization. Examiners were trained and certified before data collection started and were recalibrated annually. The primary outcome analysis in the intent -to- treat sample compares active to placebo group on the rank-normalized caries increment score, adjusting for examiner, age and age squared. Multiple imputation (data augmentation using MCMC) will be used to replace missing outcome. Planned secondary analysis examine the secondary caries increment outcomes using the same model, as well as parallel analyses in the per-protocol group. Safety of the coating will be evaluated by comparing development of resistant S. mutans or C. albicans as well as incidence of MedDRA-coded adverse events between the two arms.

Inclusion Criteria:

• 18 years of age and older
• at least 20 intact natural teeth, excluding third molars
• 2 or more lesions, of which at least one must be a cavitated D2 or D3
• willing and able to provide informed consent

Exclusion Criteria

• pregnant or planning to become pregnant or planning to become pregnant during the study (breastfeeding is permitted)
• use of fixed orthodontic appliances
• allergic to any of the ingredients of the study medication
• long-term antibiotic therapy
• a history of, or currently active, radiation therapy for cancers of the head or neck
• Sjögren's syndrome
• advanced periodontitis
• consumption of the equivalent of more than five servings of acidic or sugared drinks per day
• having 10 or more lesions requiring restorative care at the time of the screening visit
• remineralization therapy within one month of randomization
• investigator discretion

Adverse events were reported at any time throughout the study and were systematically screened for at the 6-month and 1-year visit.

Systematic assessment of adverse events evaluated during routine completion of standard questionnaire.