The present invention relates to dental composites comprising at least one nanoparticulate mixed oxide (a) of SiO.sub.2 with X-ray-opaque metal oxides of one or more elements selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu which has been prepared by flame spraying.