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.

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The effect of an antimicrobial-containing varnish on root demineralisation was investigated. The in situ demineralisation effect on the varnish, with or without the active ingredients chlorhexidine and thymol, was measured by means of microradiography in comparison with no application after a 2-week period in vivo. Furhermore, the effect of one or two applications was investigated by the 10 participants who carried sound intact roots in an appliance for four consecutive 2-week periods. In each period, different roots were mounted in the buccal flanges of a lower prosthesis, the experiment being of a randomized cross-over design. The results show that: (1) A single varnish treatment with active ingredients reduced lesion depth and mineral loss by about 77 and 82%, respectively. (2) The control varnish had no effect, and it can be concluded that antimicrobial-releasing varnishes are promising materials for root caries prevention.

In this paper the influence of xylitol on the progress of the demineralization front in enamel is described and discussed. Xylitol reduces enamel demineralization; the influence can be observed mainly at relatively high xylitol contents in solution. Autoradiography with ¹⁴C-labelled xylitol shows that xylitol penetrates fast in demineralized enamel. Most likely xylitol inhibits acid dissolution of enamel by interfering with the transport of dissolved enamel from the lesion to the bulk solution (by lowering the diffusion coefficients of calcium and phosphate ions). The results may be of practical interest for the use of xylitol in, e.g., toothpastes or chewing gums.