In vitro anti-caries effect of fluoridated hydroxyapatite-coated preformed metal crowns

Abstract

Aim: To synthesise fluoridated hydroxyapatite (FA) crystals directly on preformed metal crowns (PMCs) and evaluate the anti-cariogenic properties in an in vitro model.

Methods: FA crystals were grown on etched PMCs and stainless steel discs and characterised by SEM. FA-coated discs allowed fluoride release to be assessed from a known surface area of FA crystals. Discs were divided into four groups (n = 6/group) and exposed to solutions at pH 4-7. Fluoride levels in solution were measured after each exposure. Twelve FA-coated and 12 non-coated PMCs were cemented onto human molars using glass ionomer (GI) or unfilled resin, making four groups of six teeth; FA-coated + GI, FA-coated + resin; non-coated + GI and non-coated + resin. Teeth were exposed to acidified gelatin (pH = 4.3) for 9 weeks.

Results: SEM showed FA crystal growth on interior and exterior of the crowns. Average fluoride release from FA-coated discs was 0.16 mg/L/cm² at pH < 5.0. Teeth were sectioned through the lesion. Polarised microscopic examination revealed significantly smaller lesions in FA-coated crown groups compared to non-coated crown groups.

Conclusion: FA-coated PMCs demonstrated carious lesion preventing effects, i.e. fluoride release and reduction of demineralisation at crown/tooth interface. FA-coated crowns could be an aesthetic, inexpensive and caries preventive alternative in clinical dentistry.

Fig. 1

Images of the preformed metal crown (PMC) before and after crystal coating (a), and scanning electron microscopy images of the surface of the fluorapatite crystal-coated PMCs at low (b) and high magnification (c)

Fig. 2

Mean depths of the acid gel-induced lesions. Teeth were sectioned through the lesions. Lesions into enamel were measured on each tooth section at two sites, the buccal and lingual surfaces. Fluorapatite (FA)-coated and non-coated crowns were compared using glass ionomer (GI) and resin cement

Fig. 3

Polarised microscope photomicrographs of tooth sections at the crown margins from samples of preformed metal crowned teeth after exposure to acidified gelatin for 9 weeks. FA-coated crown + GI cement (a), non-FA-coated crown + GI cement (b). Sound enamel (A), dentine (B), caries-like lesion (C)