Seventeen subjects with more than 3 × 105 mutans streptococci per millilitre of saliva completed this randomised, cross-over study. Four different chewing-gums, containing: (1) 70% xylitol, (2) 35% xylitol+ 35% sorbitol, (3) 17.5% xylitol+ 52.5% sorbitol, and (4) 70% sorbitol, were tested. The participants used 12 pieces of each gum per day for 25 days. During the four experimental periods, they wore a removable palatinal plate containing two demineralised enamel samples, and brushed their teeth with a non-fluoridated toothpaste. The results showed that an increased concentration of xylitol in the gum resulted in a lower number of mutans streptococci in both saliva and dental plaque, although the decreases were only significant in the saliva samples (p < 0.01). The pH drop in plaque, measured in vivo after a 1-min mouthrinse with a 10% sorbitol solution, was least pronounced after the 70% xylitol gum and most pronounced after the 70% sorbitol gum period (p < 0.01). No significant differences were found after a mouthrinse with a 10% sucrose solution. All demineralised enamel samples lost mineral during the experimental periods. However, the lesion depth as well as the mineral loss values, assessed microra-diographically, did not differ significantly between the four chewing-gums.

In eight subjects who were initially highly colonized with Streptococcus mutans and who used a 1% chlorhexidine gel, the numbers of this organism were suppressed in both plaque and saliva. Bacterial plaque samples were obtained from all tooth surfaces, and the recolonization pattern of S. mutans was studied over a 26-week period. At baseline, 83% of all surfaces harbored S. mutans with buccal surfaces colonized in higher frequency than the others. After chlorhexidine treatment, the proportion of tooth surfaces colonized by S. mutans was reduced to a low level. Re-appearance was slow. S. mutans was first recovered from the most posterior teeth in the mouth, the molar surfaces were recolonized earlier than were those of pre-molars and anterior teeth, and the buccal surfaces were recolonized more readily than were the other tooth surfaces. The data show that there is a specific recolonization pattern of S. mutans after chlorhexidine treatment, and that the re-emergence of S. mutans is most probably due to regrowth of bacteria which have not been eradicated.

The relationship between the salivary concentration of mutans streptococci and their prevalence on different tooth surfaces was studied in 114 subjects. Plaque samples were obtained from all tooth surfaces in the dentition and the infection magnitude of mutans streptococci was determined. The salivary concentrations of mutans streptococci correlated significantly with the number of colonized tooth surfaces and with the infection level of mutans streptococci for individual teeth or groups of tooth surfaces. The highest correlation values were found for buccal and approximal surfaces and for molars followed by premolars and anterior teeth. The 10 tooth surfaces best reflecting the salivary levels of mutans streptococci were 5 buccal and 5 approximal sites, 6 of them localized on maxillary posterior teeth. A significant positive relationship was noted between the prevalence of mutans streptococci in saliva and on the dorsum of the tongue.

The effect of sugar restriction on the oral levels of mutans streptococci was studied in 20 subjects fulfilling three criteria: (1) having more than 300,000 CFU mutans streptococci/ml saliva, (2) harbouring both Streptococcus mutans and Streptococcus sobrinus in saliva, and (3) eating sugar frequently. The subjects were randomly divided into a test group (n = 12), who were asked to refrain from using sugar-containing foods between meals and to reduce sugar in main meals for 6 weeks, and a control group (n = 8), who did not receive any dietary advice. Saliva and plaque samples were collected at baseline and at 3, 6 and 12 weeks. The results showed that the levels of S. mutans and S. sobrinus decreased in saliva and plaque during the 6-week sugar restriction period. The decrease in mutans streptococci was more pronounced on buccal than on approximal tooth surfaces. Both species seemed to react in a similar way to the sugar restriction in saliva as well as in dental plaque. At the follow-up examination at 12 weeks, i.e. 6 weeks after completing the sugar restriction period, the numbers of S. mutans and S. sobrinus had increased again, but were still lower when compared to the baseline values.

The aim of the present study was to compare the use of toothpicks with other sampling methods for determination of mutans streptococci on different tooth surfaces. In nine persons with > 10(5) CFU per ml saliva of mutans streptococci, plaque samples were taken from 90 buccal and lingual surfaces, 108 occlusal surfaces and 90 approximal surfaces with toothpicks. The prevalence of mutans streptococci on these tooth surfaces was compared with samples taken at four 1-week intervals on the same tooth surfaces with a carver (buccal/lingual surfaces), a needle (occlusal surfaces) or a dental floss (approximal surfaces). Each sample was plated on MSB agar and the presence of mutans streptococci was expressed on a scale varying from 0 to 4. On two of the sampling occasions the amount of plaque, mirrored by total viable counts on blood agar, was also determined. Only for buccal/lingual plaque samples was a difference in total counts between methods noted and then with higher total recoveries obtained after sampling with toothpicks. More surfaces were found to be positive for mutans streptococci when samples were taken with a toothpick than with a carver, needle or floss. On surfaces positive for mutans streptococci the colonization score was higher in samples taken with a toothpick than with a carver or a needle while samples taken with a floss showed a tendency to higher levels of mutans streptococci than samples collected with a toothpick. The data indicate that the results indicate that the results obtained by using toothpicks for evaluating the prevalence of mutans streptococci on individual tooth surfaces compare favorably with the other methods tested.