Ceramic restorations are appealing because of their esthetics, high hardness and wear resistance. They can replace a composite or amalgam restoration in teeth where buccal and lingual walls remain intact and where excessive isthmus width contraindicates the use of a direct posterior composite restoration. Recent clinical trials have shown that porcelain restorations with margins on the occlusal surface of a posterior tooth tend to fail due to fracture of the porcelain under biting forces.