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The influence of drastic dietary carbohydrate restriction on the occurrence of Strep. mutans, Strep. sanguis and iodophilic polysaccharide-producing bacteria in the dental plaque of 6 subjects was studied. During a carbohydrate-free period of 17 days, the percentage that Strep. mutans constituted of the total cultivable flora decreased to a very low or undetectable level, while simultaneously the percentage Strep. sanguis increased. The percentage IPS-producing bacteria was also lower during this period. Reinstitution of the normal diet, after periods of added glucose and sucrose to the carbohydrate-free diet, resulted in a return of Strep. sanguis to its original proportions and of Strep. mutans and the IPS-producers to levels that were significantly higher and slightly higher respectively than before the experiment. During the study an inverse relationship between the occurrence of Strep. mutans and Strep. sanguis was observed.

A longitudinal study of children from ages 7 to 18 showed that, if enamel lesions were included, the overall number was the same in fluoridated and non-fluoridated areas. However, a significant reducing effect of pre-eruptive fluoride could be seen in the number of dentinal lesions in a fluoridated area, provided that fluoride was also consumed post-eruptively for a considerable period of time. A precise estimation of both pre- and post-eruptive effects was obtained when teeth were classified according to their eruption time as related to the onset of water fluoridation. About 66% of the greatest reduction in pit and fissure caries came from pre-eruptive fluoride, while in smooth surfaces, this effect was reduced to 25%. In approximal surfaces, the reduction was due half to pre- and half to post-eruptive fluoride. Post-eruptive fluoride became more important with decreasing severity of caries attack. Thus, assuming a continuing decline in dental caries, the majority of such populations will benefit most from the use of topical fluorides. However, in high-risk groups, supplementation of pre-eruptive fluoride can still be of major importance.

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