Chlorhexidine (CHX) is probably the most widely used and the most potent chemical plaque inhibitory agent, whereas fluoride (F−) is the only truly accepted anticaries agent available at present. As they have discrete mechanisms of action, a combination effect of these agents on human dental caries may exist. The inhibitory effect of CHX on the formation of, and acid production in, plaque may reduce a relatively extreme cariogenic challenge sufficiently for it to be overcome by the local F− concentrations achieved by brushing or rinses. The aim of this study was to evaluate the possible caries inhibitory effect of combining 2.2 mM CHX mouthrinses used twice daily with daily 11.9 mM NaF rinses in an in vivo human caries model using plaque‐retaining bands on premolars scheduled for extraction. Nine subjects (a total of 28 teeth) were fitted with the bands for 4 wk. Saliva and plaque samples were collected before and after the study period for bacterial cultures, and the tooth surfaces were analyzed by microradiography after careful tooth extractions. The combination of CHX and F− rinses resulted in enamel mineral loss only slightly higher than that observed in “sound” enamel and clearly less than with F− rinses alone. Both total plaque bacteria and Streptococcus mutans were reduced by CHX rinses, confirming the discrete mechanisms of action.

The effect of copper sulfate applied topically or in drinking water on dental caries was investigated in rats. Two daily topical applications of 0.2 ml of 5.0 mM Cu²⁺ as CuSO₄ ad libitum or 1.0 mM CuSO₄ in the drinking water reduced the caries scores significantly on all tooth surfaces. The number of Streptococcus mutans colonising tooth surfaces was also significantly reduced by 1.0 mM Cu²⁺ in drinking water.

The effect of 3 weeks dietary supplementation, respectively restriction, of sucrose on gingival smooth surface plaque was assessed in 4 caries-inactive adults. Plaque samples collected from discrete tooth sites were monitored for the prevalence of streptococci, actinomycetes, and veillonellae, with special emphasis placed on Streptococcus mutans. At the end of each dietary period, the acidogenicity of plaques on 5 smooth tooth surfaces in each subject was assessed by in situ pH measurements subsequent to sucrose application. Reversible white spot lesions appeared in 2 of the 4 subjects on the sucrose-rich diet. In 3 of the 4 subjects, the pH-depressing capacity of their plaques was greater on the sucrose-rich than on the sucrose-poor diet. In the 4th subject, the acidogenicity of the plaques was similar on the two diets; this subject moreover appeared not to harbor S. mutans in these plaques. In the other 3 subjects, S. mutans occurred with greater frequency in their plaques on the sucrose-rich diet; however, the prevalence of S. mutans did not appear to be affected by diet. Other bacterial changes in plaques on the two diets seemed to be mainly subject-dependent with no consistent pattern from one individual to another.

P. Retenlion of Cu and Zn in the oral cavity following rinsing with aqueous solutions of copper and zinc salts. Scand J Dent Res 1983; 91: 42-5. .Mi^ii .H I Rctciilic)]! oltai and Zn in the uiouth altci' rinses with kuouii vukuncs ol ac|ucous .solutions ol the metal salts was measured by atomic absorption. The mean amounts retained in 10 subjects were 0.02 mg Cu and 0.22 mg Zn. These values represent approximately 31 % of the Cu and 15% of the Zn originally in the rinse. The intraindividual variation (s.d.), esdmated by three mouthrinses at weekly intervals in three subjeets averaged 2.1 % for Cu and 2.3% for Zn. Following a rinse the salivary concentration of Cu and Zn decreased rapidly during the first 4 h, approaching prerinsc levels.

A series of experiments were performed to evaluate the lowest concentration of copper or zinc effective in reducing the acidogenicity of dental plaque in vivo when applied simultaneously with a carbohydrate challenge. The effect of a combination of sub-effective concentrations of these metals was also determined. The results showed a significant reduction in acid production in plaque challenged with glucose solutions containing 0.25 mM CuSO4 or 5.0 mM Zn (C2H3O2).2 as compared to glucose solutions alone. Neither 0.1 mM copper sulphate nor 2.5 mM zinc acetate reduced the acidogenicity of plaque significantly, whereas a combination of these subeffective concentrations was effective. The low metal concentrations causing reduction in acid formation in this study may be explained by the inhibiting substances reaching the bacteria at the same time as the substrate. The synergistic effect of the combination of low concentrations of copper and zinc is consistent with the view that these metals effect dental plaque by the same mechanisms.