The susceptibilities of 379 clinical mutans streptococcal isolates to chlorhexidine (CHX) were tested by agar dilution according to the standards of the National Committee for Clinical Laboratory Standards. Isolates were obtained from saliva samples of 34 young mothers who had high or moderate salivary levels of mutans streptococci at baseline. Samples were collected on three occasions, before childbirth, when each child was 6 months old, and 1 year later. Of these isolates, 50% were inhibited at 1 microgram of CHX per ml, 90% were inhibited at 2.0 micrograms/ml, and all were inhibited at 4.0 micrograms/ml. The MICs for Streptococcus mutans isolates (serotypes c, e, and f) were lower than those for Streptococcus sobrinus isolates (serotypes d and g). In some subjects, the MICs for isolates of the same serotype were different. This phenomenon was studied by ribotyping isolates (n = 45) from selected subjects (n = 7). It was found that if there were intraindividual differences in the MICs for isolates of the same serotype, then the ribotypes of these isolates were different. In order to decrease the mutans streptococcal infection risk for children, 24 mothers (test group) brushed their teeth periodically with a gel that contained 0.3% CHX digluconate and 0.2% NaF, pH 5.8, between the second and third sampling occasions. The gel was used twice a day for the first 10 days of each month. Development of resistant strains during CHX-NaF gel use was not detected. The serotype distribution of isolates from the test group after 1 year of periodic CHX-NaF gel use did not differ from that at baseline. Periodic CHX-NaF gel brushing did not lead to lower salivary mutans streptococcal counts.

– In order to find out if it is possible to prevent caries and gingivitis by periodical use of chlorhexidine‐fluoride mouthrinses with or without strontium, and to find out what effects they have on salivary mutans streptococci and lactobacilli counts, a total of 243 schoolchildren aged 11 yr with high DMFS scores were randomly divided into four groups. One group (C) served as a basic control. Subjects in the second group (GXF) rinsed their mouths twice a day every third week with a rinsing solution containing 0.05% chlorhexidine gluconate and 0.04% NaF. In the third group (CXFS) the rinsing solution contained 500 ppm Sr during the first and second year and 15 ppm during the last 6 months, in addition to chlorhexidine and fluoride. In the fourth group (CX) the solution contained only 0.05% chlorhexidine gluconate. All the rinsing solutions had pH 5.8 buffered with succinic acid‐NaOH buffer. After 2 yr and 9 months, the mean DMFS (SD) increments in the C, GXF, GXFS, and GX groups were 3.8 (5.7), 2.5 (3.2), 3.5 (4.8), and 3.4 (5.5), respectively. The percentage of subjects with bleeding gingival units had decreased from initial to final values as follows: C, 81–38; GXF, 88–42; GXFS, 89–56; GX, 89–37. The number of lactobacilli and mutans streptococci in saliva remained virtually unchanged throughout the study. For caries increment and gingival bleeding, the differences between groups were not statistically significant. The chlorhexidine‐fluoride combination tended to prevent caries, but the effect on gingival bleeding and salivary counts of mutans streptococci and lactobacilli was negligible.

This follow-up of the oral health of children and young adults in Espoo, Finland, has been carried out using annual check-ups done by dentists at the Espoo Health Center. There was about 80% participation in municipal dental care by 3- to 18-yr-olds. Each age group included 1700-2300 individuals. The DMFT-index for 12-yr-olds was 6.9 initially and only 2.2 at the end of the 12-yr follow-up. The reduced DMFT and increased number of clinically caries free children is probably the cumulative effect of various preventive measures adopted during the follow-up period. The proportional influence of each procedure is unknown.

– In order to find out whether microbes can be detected in the incipient rat caries lesions underneath the visibly intact enamel surface, the maxilla of OM‐rats, fed a cariogenic diet, were fixed and partially bisected sagittally with a thin saw. The individual teeth were finally split with a knife to get a crack surface from the fissure region. Selected tooth halves showing slight carious changes at the dentin‐enamel junction were prepared for SEM and examined. In many preparations, colonies of organisms were found firmly attached to the crack surface. Single, predominantly coccus‐like organisms and a few rods could be seen mostly located in the interprismatic furrows at varying depth throughout the enamel. Somc lacuna‐like hollows, with or without the occupant organisms, could be seen carved in the prism structure. The enamel side of the DEJ in the lesion area could be completely covered by the microbes. In samples representing arrested caries, amorphous precipitates were found at the interprismatic substance of the DEJ region.

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