Ultramorphological Analysis of Surface and Cement-tooth Interfacial Structures of Fluoride-releasing Luting Cements

Abstract

Several types of fluoride-releasing cements are currently used as luting materials. This study evaluated the following properties of five fluoride-releasing luting cements: 1) pH of liquid components, primers and unset mixtures; 2) surface ultrastructural changes following exposure to acetic acid and acetone; 3) ultrastructure of enamel and dentin surfaces treated with primers and unset cement mixtures; and 4) ultrastructure of and fluoride ion distribution along the cement-tooth interface. A glass-ionomer cement (HY-Bond Glasionomer CX, HBG), three resin-modified glass-ionomer cements (Fuji Lute, FL, HY-Bond Resiglass, HBR and Vitremer Luting Cement Fast Set, VT), and an adhesive resin cement (PanaaviaF 2.0,F) were examined. The pH was measured with pH test paper, and the ultrastructure and fluoride ion distribution were evaluated by scanning electron microscopy and electron probe microanalysis, respectively. Results obtained were as follows: 1. The pH of various cements was lower than 4. 2. All materials showed surface deterioration following exposure to acetic acid and/or acetone. These changes were minimal in VT and HBR following exposure to acetic acid and acetone, respectively. 3. Treatment of human enamel and dentin with the primer for PF (ED primer) caused surface demineralization as demonstrated by the exposure of enamel prisms and dentinal tubules, whereas such changes were less apparent following treatment with unset cements (HBG, HBR and VT), and the conditioner for FL. 4. Along the luting cement-dentin interface, HBG, FL and PF showed the formation of a narrow hybrid layer, whereas HBR and VT showed the formation of a gap. 5. All the test luting cements caused fluoride uptake by enamel and dentin, although PF showed comparatively little fluoride uptake. These results suggest that fluoride-releasing luting cements may contribute to the prevention of secondary caries along the restoration margin, although the surface deterioration and incomplete bonding may affect the longevity of restorations.