The structure of experimental in vitro lesions around glass ionomer cement restorations in human teeth

Class V cavities were prepared at the amelo-cementum junction in sixty-eight extracted human teeth. Fifty-one were filled with glass ionomer cement (ASPA). 'Secondary carious' lesions were produced around thirty-five of the restorations by exposure to acidified gelatin. Thirty-three teeth served as controls of the effect of the preparation procedure, the conditioner, the ASPA liquid and the filling material proper on the cavity walls. Sixty 120 micrometers-thick longitudinal sections from the teeth with the restorations in situ were studied by polarized light microscopy and microradiography. The glass ionomer cement caused by itself a narrow zone of increased radiopacity in the dentine cavity wall. The 'secondary caries' pattern consisted of a subsurface outer lesion and a subsurface wall lesion as observed previously in corresponding experiments with silicate fillings. Outer lesions in enamel were more frequent than with silicate cement. In the cementum all the experimental teeth showed outer lesions. The wall lesions extended only slightly beyond the level of erosion of the restorations. Between the wall lesions (in dentine) or outer lesions (in cementum/dentine) and the surface of the cavity wall, a zone of increased radiopacity was found, assumed to be due to reprecipitation of Ca and P promoted by release of fluoride from the filling material.