Fluoride concentration in plaque and saliva and its effects on oral ecology after intake of fluoridated milk

Sammanfattning: According to WHO, the addition of fluoride to milk could be considered as an alternative to water fluoridation for community-based caries prevention in childhood. School-based schemes in developing as well as industrial countries have demonstrated substantial benefits on oral health, but there are limited data available on the local events in the oral cavity after consumption of fluoridated milk. The general aim of the present investigations was to investigate the concentration of fluoride obtained in saliva and dental plaque after ingestion of Fmilk and to explore the possible effects on the oral ecology. A series of controlled studies were performed in vivo in which samples of saliva and dental plaque were collected and analysed with respect to fluoride content, microbial composition and acidogenicity. An in vitro study evaluated the effect on enamel lesion formation. In paper I, significantly increased concentrations of fluoride (p<0.05) were disclosed in saliva 15 minutes after drinking the fluoride-containing water or milk. In the plaque samples however, the F-increase remained significantly elevated still after 2 hours. The availability of fluoride from milk was generally somewhat lower than from water but the differences were not statistically significant in either plaque or saliva. In paper II, the fluoride concentration in plaque was further explored after a single intake or habitual consumption of fluoridated milk together with a regular meal. The results showed that cariesinhibiting levels of fluoride persisted up to 4 hours after intake. There were no significant differences between the single intakes when compared with repeated intakes. In paper III, the influence of fluoridated milk on the salivary microorganisms associated with dental caries was evaluated. No significant alterations of the microflora were found compared with baseline. There was a slight reduction in the proportion of mutans streptococci after 2 and 4 weeks during consumption with fluoridated milk but the difference failed to reach statistical significance. In paper IV it was demonstrated that fluoridated milk significantly (p<0.05) could counteract the lactic acid formation in dental plaque as initiated with sucrose. In paper V, laser fluorescence technique was used to monitor the effect of fluoridated milk on enamel lesion formation in an experimental caries model. The results reinforced previous research and showed a hampering effect of fluoridated milk. No side effects were reported in any of the investigations. The findings of this thesis substantiate that milk is a suitable vehicle for fluoride administration and contribute to the understanding and possible explanations for the anti-caries properties of fluoridated milk. The main conclusions were: a) intake of fluoridated milk resulted in significantly elevated fluoride levels in saliva within the first 15 minutes and up to 4 hours in dental plaque when fluoridate milk was consumed together with meal, b) no significant alteration of the salivary microflora was disclosed after habitual intake of fluoridated milk but a delayed carbohydrate-mediated lactic acid formation in suspensions of dental plaque could be demonstrated, c) the fluoride concentrations in plaque were not negatively influence by the food intake, and d) the in vitro findings advocated that fluoride added to milk reduced enamel lesion formation as assessed by laser fluorescence technique in an experimental caries model.According to WHO, the addition of fluoride to milk could be considered as an alternative to water fluoridation for community-based caries prevention in childhood. School-based schemes in developing as well as industrial countries have demonstrated substantial benefits on oral health, but there are limited data available on the local events in the oral cavity after consumption of fluoridated milk. The general aim of the present investigations was to investigate the concentration of fluoride obtained in saliva and dental plaque after ingestion of Fmilk and to explore the possible effects on the oral ecology. A series of controlled studies were performed in vivo in which samples of saliva and dental plaque were collected and analysed with respect to fluoride content, microbial composition and acidogenicity. An in vitro study evaluated the effect on enamel lesion formation. In paper I, significantly increased concentrations of fluoride (p<0.05) were disclosed in saliva 15 minutes after drinking the fluoride-containing water or milk. In the plaque samples however, the F-increase remained significantly elevated still after 2 hours. The availability of fluoride from milk was generally somewhat lower than from water but the differences were not statistically significant in either plaque or saliva. In paper II, the fluoride concentration in plaque was further explored after a single intake or habitual consumption of fluoridated milk together with a regular meal. The results showed that cariesinhibiting levels of fluoride persisted up to 4 hours after intake. There were no significant differences between the single intakes when compared with repeated intakes. In paper III, the influence of fluoridated milk on the salivary microorganisms associated with dental caries was evaluated. No significant alterations of the microflora were found compared with baseline. There was a slight reduction in the proportion of mutans streptococci after 2 and 4 weeks during consumption with fluoridated milk but the difference failed to reach statistical significance. In paper IV it was demonstrated that fluoridated milk significantly (p<0.05) could counteract the lactic acid formation in dental plaque as initiated with sucrose. In paper V, laser fluorescence technique was used to monitor the effect of fluoridated milk on enamel lesion formation in an experimental caries model. The results reinforced previous research and showed a hampering effect of fluoridated milk. No side effects were reported in any of the investigations.The findings of this thesis substantiate that milk is a suitable vehicle for fluoride administration and contribute to the understanding and possible explanations for the anti-caries properties of fluoridated milk. The main conclusions were: a) intake of fluoridated milk resulted in significantly elevated fluoride levels in saliva within the first 15 minutes and up to 4 hours in dental plaque when fluoridate milk was consumed together with meal, b) no significant alteration of the salivary microflora was disclosed after habitual intake of fluoridated milk but a delayed carbohydrate-mediated lactic acid formation in suspensions of dental plaque could be demonstrated, c) the fluoride concentrations in plaque were not negatively influence by the food intake, and d) the in vitro findings advocated that fluoride added to milk reduced enamel lesion formation as assessed by laser fluorescence technique in an experimental caries model.