[Study on fatigue and fracture resistance of metal ceramic crowns with CAD/CAM-fabricated titanium copings].

Purpose: To compare the fatigue and fracture resistance of metal ceramic crowns (MCCs) with nickel-chromium and CAD/CAM-fabricated titanium copings.
Methods: Twelve premolar MCCs were fabricated with cast nickel-chromium alloy (Ni group) and CAD/CAM-fabricated titanium (Ti group) copings, respectively. To minimize the differences among specimens, the geometric dimensions of the MCCs were tested with a laboratory scanner and digital measurement software and then adjusted. After cemented to identically milled titanium dies, each specimen was subjected to thermocycling (5-55℃, 5000 cycles) and cyclic loading (75000 cycles) test, followed by a static load-to-fracture test to measure the fracture loads(F). The fractures were characterized using stereomicroscope. SPSS13.0 software package was used for statistical analysis.
Results: The mean fracture loads were (1645±356)N for Ni group and (1555±331)N for Ti group. No significant difference was observed (P=0.525). Most of the fractures were confined to the palatal third. The chief failure mode for all specimens from Ni group and most of the specimens from Ti groups was mixed failure. Adhesive failure was noted in 3 specimens from Ti group.
Conclusions: The fracture resistance of MCCs with CAD/CAM-fabricated titanium copings is similar to that of MCCs with nickel-chromium copings.