Evaluation of Surface Micro-hardness and Fracture Toughness of Conventionally Constructed versus CAD/CAM Constructed Denture Base Materials- an In-Vitro Study.

The purpose of the current study was to evaluate surface micro-hardness and fracture toughness of Acetal Resin and Acrylic Resin (PMMA) constructed either by CAD/CAM milling method or by heat polymerized conventional method (lost wax method).
Materials and methods: Twenty-eight specimens (fourteen of each material); Acetal Resin and Acrylic Resin were constructed in the form of discs of 2mm thickness and 10mm diameter. Discs were divided equally according to the denture base material into two groups, group I for Acetal Resin and group II for Acrylic Resin (PMMA). Each group was subdivided according to the way of construction into; sub-groups (n=7). Sub-groups Ia and IIa for CAD/CAM milled discs and sub-groups Ib, IIb for conventionally constructed discs. Microhardness was measured on sample surface by digital display Vickers Micro-hardness Tester. Fracture toughness was evaluated by axial loading by the indentation technique. Results: Group I (acetal resin group) recorded statistically significant higher microhardness mean values than group II (acrylic resin group). Moreover, group Ib (injection processed group) recorded statistically significant higher microhardness mean values than group IIb (conventionally processed group). Regarding fracture toughness there was statistically insignificant differences between all groups with higher mean values of group Ia,b (acetal resin groups). Conclusion: CAD/CAM constructed acetal resin and acrylic resin denture base materials presented superior mechanical properties than conventionally constructed ones and expected to be more durable denture bases.
Key words: CAD/CAM, Acetal Resin. Acrylic Resin, microhardness, fracture toughness.