Abstract
Although the prevalence of caries has decreased dramatically over the past decades, it has become a polarised disease, with most of subjects presenting low caries levels and few individuals accounting for most of the caries affected surfaces. Thus it become evident for the need of clinical approaches directed at these high-risk patients, in order to overcome problems related to compliance and low attendance at dental care centres. Slow-release fluoride devices were developed based on the inverse relationship existing between intra-oral fluoride levels and dental caries experience. The two main types of slow-release devices – copolymer membrane type and glass bead – are addressed in the present review. A substantial number of studies have demonstrated that these devices are effective in raising intra-oral F concentrations at levels able to reduce enamel solubility, resulting in a caries-protective effect. Studies in animals and humans demonstrated that the use of these devices was able to also protect the occlusal surfaces, not normally protected by conventional fluoride regimens. However, retention rates have been shown to be the main problem related to these devices and still requires further improvements. Although the results of these studies are very promising, further randomised clinical trials are needed in order to validate the use of these devices in clinical practice. The concept of continuously providing low levels of intra-oral fluoride has great potential for caries prevention in high caries-risk groups.
Highlights
Dental caries is caused by acids produced by bacteria in dental biofilms, which slowly but progressively demineralise the enamel
Among various caries-preventive strategies, which include education in oral health, chemical and mechanical control of dental biofilms, the use of fluorides has proved to be the most clinically effective according to a large number of clinical trials, literature reviews and more recently meta-analyses demonstrating the ability of F in controlling dental caries in studies involving the use of rinses, gels, varnishes and dentifrices[29,30,31,32]
The ability of fluoride to retard or prevent the development of dental caries appears to involve several mechanisms including a reduction in the acid solubility of enamel, the promotion of enamel remineralisation, inhibition of glucose uptake and utilization by acidogenic bacteria, and possibly bacteriostatic or bactericidal effects[21,24]
Summary
Dental caries is caused by acids produced by bacteria in dental biofilms, which slowly but progressively demineralise the enamel. As the current scientific consensus regards a constant supply of low levels of fluoride, especially at the biofilm/ saliva/dental interface, as being of the most benefit in preventing dental caries[18,49], it is reasonable to expect a positive effect on caries prevalence of a treatment able to raise intra-oral F concentrations at constant rates, without relying on patient compliance. This concept is reinforced by the findings of Shields, et al.[47] (1987), who showed that irrespective of water fluoridation status, caries-free children had salivary F levels of 0.04 ppm or more whereas those with carious dentitions had 0.02 ppm or less. Similar findings were obtained in a study employing the copolymer membrane device, for a period of one month[37], as well as in another study conducted with primates[46]
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