Fracture resistance of different metal substructure designs for implant-supported porcelain-fused-to-metal (PFM) crowns

Background/purposeThis study evaluated the fracture resistance of different metal substructure designs for implant-supported porcelain-fused-to-metal (PFM) crowns.Materials and methodsEighteen PFM crowns were fabricated using different metal substructure designs and were conventionally cemented on an implant abutment analog. The crowns were divided according to the metal substructure design for manufacturing the metal framework into three groups of six specimens each: Group A had a minimum required thickness; Group B had a conventional design; and Group C had a wrinkled design. After applying a load of 200 N at a frequency of 2 Hz with 300,000 cycles of dynamic loading, all specimens were tested for fracture resistance using compression loading on the buccal functional cusp.ResultsAmong these three groups, Groups A and B, respectively, had the minimum and maximum fracture resistance strengths. Respective data for Groups A, B, and C were 111.13 ± 27.15 kg, 236.13 ± 39.21 kg, and 188.63 ± 12.10 kg. Statistically significant differences were observed among the three groups (P < 0.05).ConclusionThese results confirm that the conventional design had the best fracture resistance, and an excessively thick porcelain layer can cause crown fracture. However, there was no obvious proof that the wrinkled design had better fracture resistance than the conventional design. Therefore, the theory that PFM can provide better support requires further corroboration.