Monolithic zirconia crowns are produced from a single block of pure zirconia using computer-aided milling (CAD/CAM), and no external porcelain layer is fired on top. Thanks to these structural properties, they possess incredibly high mechanical strength (approximately 1200 MPa), completely eliminating the risk of porcelain chipping during chewing; however, their light transmittance is lower, and they may appear slightly more matte aesthetically, making them preferred for posterior teeth. In porcelain-over-zirconia crowns, zirconia is used only as a durable core (substructure), and traditional dental porcelain layers are applied on top to provide aesthetic depth. This combination offers excellent, natural light transmittance and aesthetics in anterior teeth; however, there is a risk of the top porcelain layer separating and breaking from the zirconia substructure in case of hard impact or microleakage.
