Effect of ceramic material type on the fracture load of inlay-retained and full-coverage fixed dental prostheses

Abstract Objective: Ceramic inlay-retained fixed partial denture (IRFPD) is a conservative prosthetic option but the mechanical durability of new high strength zirconia reinforced glass ceramic FPDs is not investigated. The purpose of this study was to compare fracture load of 3-unit ceramic FPDs. Materials and methods: Extracted premolars and molars (N？=？64) were used to create three test groups (IRFPDs) and one control group (full coverage FPD) (n？=？8). The teeth were embedded in PMMA resin with a mesiodistal distance of 6？mm. Premolars had a distal and molars had a mesial inlay preparation (width: 3？mm; height: 4？mm) in the test groups. IRFPDs were made from a zirconia reinforced lithium silicate (VS) or a monolithic zirconia. Zirconia IRFPDs received 2 types of surface treatments: sandblasting (Zr-IRFPD) or internal coating with feldspathic porcelain (ZrC-IRFPD). Control group was made from monolithic zirconia with the same connector size and zirconia surfaces were sandblasted (Zr-FPD). All restorations were cemented using a resin luting cement. After 5000 thermo-cycles, fracture load values (N) were determined with a universal testing machine at a crosshead speed of 0.75？mm/min. Data were analyzed using 1-way ANOVA and Tukey`s post hoc test (p ？ .05). Result: Fracture load (mean？±？SD) of Zr-FPDs, Zr-IRFPDs and ZrC-IRFPDs were 672？±？183, 672？±？123 and 638？±？59, respectively, being not statistically different (p？>？.05). VS-IRFPD exhibited statically lower values (391？±？136). The predominant mode of failure was fracture at the connector area in all groups. Conclusion: The fracture load of 3-unit IRFPD was significantly affected by types of ceramics but the retainer design and surface treatment in Zr groups did not show a significant effect