Anatomic CAD-CAM post-and-core systems: A mastication simulation study

Statement of problem: Few studies have investigated the differences among various post-and-core systems under mastication simulation. Comparing these systems while simulating the clinical environment should provide a more accurate assessment of their performance. Purpose: The purpose of this in vitro study was to evaluate the fatigue resistance of conventional cast metal and prefabricated fiber post systems with computer-aided design and computer-aided manufacture (CAD-CAM) prefabricated nonmetal post-and-core systems. Material and methods: Forty freshly extracted human maxillary premolars were endodontically treated and divided into 4 subgroups (n=10) according to the material: cast metal, zirconia, fiber-reinforced composite resin, prefabricated fiber post. The post-and-core materials were manufactured either conventionally or milled with CAD-CAM technology. All specimens were exposed to simultaneous mastication simulation (1.2 million cycles) and thermocycling (10 000 cycles at 5 degrees C to 55 degrees C) and analyzed based on failure of specimens. Data were analyzed by using the Kaplan-Meier survival analysis and Cox-regression (alpha=.05). Results: Both cast metal and zirconia post-and-core groups had similar fatigue resistance (P>.05) but significantly higher fatigue resistance than the fiber-reinforced groups (P<.05). Fiber-reinforced composite resin and prefabricated fiber post did not survive the mastication simulation, fracturing between 504 000 and 752 000 cycles, with fractures occurring in the cervical portion of the tooth. Conclusions: Cast metal and zirconia post-and-core systems had improved physical properties with high resistance to fatigue when compared with fiber-reinforced post-and-core systems.