The Esthetic Repair of Metal Margins on Metal-Ceramic Crowns Using Etched Porcelain Cervical Shields
— Strassler, H.E., Weiner, S.

The difficulties of successfully repairing the fractured porcelain of porcelain fused to metal fixed prostheses is described.  When fractured porcelain involves the gingival margin of a crown, then the repair may involve bonding to porcelain, and metal, and root dentin.  The merits of Den-Mat products for bonding to these surfaces are explained.  

A clinical case report is presented in which a Cerinate porcelain “shield” (a partial veneer) is bonded over the facial surface of a tooth root and a crown with fractured porcelain at the gingival.  The procedure is simple to perform and the results are excellent.