RESUMEN
<p><b>OBJECTIVE</b>To discuss the unsuccessful reasons and the preventive methods of the unsuccessful clinic cases.</p><p><b>METHODS</b>The retrospective analysis was carried on the 80 prosthesis in 70 patients from 1994 to 2001 which were suffered with unsuccessful results after the restoration of the metal crowns and bridges.</p><p><b>RESULTS</b>There were 68 teeth which had collapsed or broken. 20 teeth had the post loosing or shedding. Root breaking, food impaction, unharmony colors of porcelain and the changing color of gingival were 3, 3, 6 and 2 teeth.</p><p><b>CONCLUSION</b>It is necessary to select suitable repairing materials and operate correctly for preventing the occurring of the unsuccessful results in the porcelain-fused-to-metal-crowns and bridges.</p>