In vitro evaluation of fluoride-releasing restorative materials for sealing the root canals of overdenture abutments

Purpose: The purpose of this study was to evaluate the ability of newer flu oride-releasing restorative materials to protect the root surface from acid attack. Materials and Methods: The materials used were glass-ionomer cemen t (GIC), resin-modified glass-ionomer cement (RM-GIC), and a compomer (Comp ). A composite resin (CR) was used as the control. The restored teeth were stored in deionized, distilled water for 14 days and subjected to 300 therm ocycles (55 degreesC and 5 degreesC). The teeth were cycled in a deminerali zing solution (pH 5.0 or 4.0) for 6 hours and in a remineralizing solution (pH 7.0) for 17 hours for 10 days. The depths of lesions created by acid ch allenge were measured at the interface of the tooth and the restorative mat erial and then at a distance of 50, 100, and 300 pm from the tooth-restorat ion margin using polarized light microscopy and contact microradiography. R esults: At pH 4.0, there was significant difference in the depth at the int erface between the tooth and the restorative material (P < .001). The GIC a nd RM-GIC were protective, and the lesion depths were significantly shallow er than for Comp or CR. The protective effect varied depending on the dista nce from the interface of the tooth and the restorative material. At pH 5.0 , the GIC and RM-GIC had no lesions at the interface, while the Comp and th e CR had lesions (P < .001). Conclusion: Fluoride-releasing glass-ionomer c ement seems to be an appropriate material to seal the root canals of overde nture abutments, because it has an inhibiting effect on demineralization at the cavity wall in vitro.