Mechanical Properties of Heat-curing Resins by Stress-Strain Diagrams

Objectives: General objectives were based on multidisciplinary research of biomaterials used in dental medicine and are focused on the mechanical properties of dental prostheses. Materials and Method: We evaluated the mechanical properties of heat-cure resins, such as Meliodent (Heraeus Kulzer, Senden, Germany) and Royaldent Plus (Palatinal Foggyarto Kft., Budapest, Hungary). In accordance with complete-denture technology, we made samples from these materials, which were tested with Zwick Roell equipment (testXpert software). Results: There were noticeable differences, depending on material type. Based on tensile tests, we determined stress-strain diagrams for the comparative evaluation of Royaldent and Meliodent mechanical properties: (for Royaldent) ultimate tensile strength, 71.5 MPa; yield strength, 4.24 MPa; total elongation, 8.46 %; Young\'s modulus, 1019.25 MPa; (for Meliodent) ultimate tensile strength, 63.29 MPa; yield strength, 4.22 MPa; total elongation, 7.9 %; Young\'s modulus, 1215 MPa. Based on data tests and processed statistics and diagrams, stress-strain was determined by a theoretical characteristic curve of linear variation according to the equation: (σ - Tensile Stress [MPa]; ε - Strain [%]). To determine a and b parameters, we used the program Table CurveTM 2D, where stress and specific deformation registered values were defined, based on defined data from which we selected, as a theoretical characteristic curve, the diagram that best described the represented points set. Conclusions: The methods allowed for the evaluation of the tensile strength of dental prostheses, and the certification of dental materials\' quality. The registered results showed the brittle characteristics leading to material breaking, illustrated by stress-strain shape diagrams and samples breaking without registering massive plastic deformation. Keywords: heat curing resins, mechanical properties, stress/strain diagrams