Effect of added calcium phosphate on enamel remineralization by fluoride in a randomized controlled in situ trial
Introduction
Dental caries is still one of the most prevalent diseases affecting humans. The prevention of dental caries and the remineralization of enamel subsurface lesions before restorative intervention is a major challenge and goal of modern dentistry. Fluoride-containing dentifrices and mouthrinses have been demonstrated to decrease caries experience in randomized, controlled clinical trials.1, 2 Fluoride ions promote the formation of fluorapatite or fluorhydroxyapatite in the presence of calcium and phosphate ions and this is now believed to be the major mechanism of fluoride's action.3, 4 The intrinsic sources of calcium and phosphate are from saliva, dissolved tooth structure and to a lesser degree, gingival crevicular fluid.5, 6 Fluoride is the cornerstone of the non-invasive management of non-cavitated caries lesions but the ability of the ion to promote net remineralization is limited by the availability of calcium and phosphate ions.7, 8, 9, 10, 11 The availability of calcium and phosphate ions can be the limiting factor for fluoride retention and for net enamel subsurface lesion remineralization to occur upon the application of topical fluoride ions.7, 8, 9, 10, 11 However, combining calcium phosphate and fluoride ions in oral care products is problematic and can lead to loss of bioavailable fluoride ion due to a reaction between the calcium phosphate phase and the fluoride ion.12, 13
In an approach to overcome this incompatibility of calcium phosphates and fluoride ions, two calcium phosphate technologies have been developed where the manufacturers’ claim that oral care products containing the new technologies are stable in the presence of fluoride ions. The first of these calcium phosphate technologies is casein phosphopeptide-stabilized amorphous calcium phosphate (CPP–ACP) delivered in a product called Tooth Mousse or MI Paste (TM) containing CPP–ACP or Tooth Mousse Plus or MI Paste Plus (TMP) containing CPP–ACP plus 900 ppm F.8 It is proposed that the presence of the casein phosphopeptides (CPP) stabilizes the amorphous calcium phosphate phase to deliver bioavailable calcium, phosphate and fluoride ions to the tooth surface to promote remineralization of enamel subsurface lesions.14 The second technology is functionalized tricalcium phosphate (fTCP) where tricalcium phosphate particles have been ball milled with sodium lauryl sulphate.15 This technology has been included in a tooth crème with sodium fluoride marketed as Clinpro tooth crème (3 M ESPE). The manufacturer claims that the fluoride ion is stable and that this product is superior in its ability to remineralize enamel subsurface lesions.
The aim of this study was to determine the efficacy of these new calcium phosphate technologies together with fluoride and compare them with conventional fluoride products; a 1000 ppm F toothpaste, and a 5000 ppm F product as well as with a placebo product in remineralizing enamel subsurface lesions in a randomized, controlled, double-blind, cross-over in situ trial.
Section snippets
Preparation of enamel subsurface lesions and fabrication of intra-oral appliances
Sound relatively planar buccal and lingual surfaces free of cracks, stains and fluorotic lesions (as viewed under a dissecting microscope) were selected from extracted human third molars obtained from the Royal Dental Hospital of Melbourne and treated for at least 2 weeks in 10% phosphate buffered (pH 7.0) formalin. The teeth were rinsed thrice with Milli-Q water and polished wet to a mirror finish using Soflex (3 M) discs on a slow speed contra-angle dental handpiece. Each polished surface was
Results
The acid soluble calcium, inorganic phosphate and fluoride contents of the study products are shown in Table 1. Only the products TM, TMP and Clinpro were claimed to contain added calcium phosphate however calcium could be detected in all products albeit at low levels except for TM and TMP (Table 1). Inorganic phosphate was not detected in the two fluoride-only products (1000 ppm F and 5000 ppm F). All fluoride-containing products contained fluoride concentrations not significantly different to
Discussion
The results of this study demonstrate that calcium phosphate in the form of CPP–ACP added to a fluoride-containing tooth crème (TMP) can enhance the level of remineralization of enamel subsurface lesions when the product is used in situ. However, no additional benefit in remineralization of enamel subsurface lesions could be observed with the fTCP in this in situ study. The result showing significant enhancement of fluoride ion's ability to remineralize enamel subsurface lesions in situ by
Acknowledgements
This study was supported by the Cooperative Research Centre for Oral Health, Australia. The authors acknowledge Kate Fletcher for her outstanding assistance with preparation of the manuscript and Fan Cai for expert technical assistance.
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Both contributed equally to this work.