Glass-infiltrated alumina, which can be used as an all-ceramic dental crown, was prepared. The glasses in the system of SiO$_2$-B$_2$O$_3$-Al$_2$O$_3$-CaO-La$_2$O$_3$with various amount of $Al_2$O$_3$infiltrated into a porous sintered alumina. The effect of $Al_2$O$_3$on the infiltration characteristics and its mechanical strength were studied. The corrosion of the sintered alumina by infiltrated glasses was prevented by increasing the amount of $Al_2$O$_3$in the glass batches, this increased the bending strength of the glass infiltrated alumina composite. The crack like voids in the sintered alumina was a cause of the deteriorating the mechanical strength of the composite, and this can be eliminated by sintering the alumina at 130$0^{circ}C$. Glass infiltration under the vacuum atmosphere enhanced the hording strength of the composite up to 453$pm$31 MPa.