IADR Abstract Archives
Stress Relaxation of Denture Base Materials
Objectives: To evaluate the stress relaxation of different denture materials under constant strain.
Methods: Three denture base materials were examined. HIPA high impact pour acrylic denture base (Dentsply-Sirona), CAD/CAM block Lucitone 199 (Dentsply-Sirona), and 3D printed Dentca denture base II. Five bars/group, 3x9x50 mm3, were fabricated from each material. Lucitone block specimens were sectioned using a Bueheler Isomet saw. HIPA specimens were fabricated by curing the powder/liquid mixture in a silicone rubber mold at 45 °C for 30 minutes at 1.4 bar and then sectioned. 3D printed specimens were fabricated using a Carbon M Series printer. Specimens were polished sequentially to 15 µm grit using a Buehler Ecomet and stored in water at 37°C for 10 days before testing.
An Instron 5566A was used to measure stress relaxation under a three-point bending setup at a controlled temperature of 37°C. Specimens were loaded to 70% of the mean failure stress of each material at 1 mm/min crosshead speed. The crosshead displacement was held for 10 minutes to allow the stress to relax and the load was recorded. The stress relaxation at the end of 10 mins loading and permanent strain after unloading were obtained. The load relaxation with time was analyzed to fit the combined Maxwell and Voigt viscoelastic model to determine the relaxation constant K and of retardation time τ.
Results: All the test data fitting to the viscoelastic model had an average R-square of 0.988. The acquired mechanical parameters and ANOVA post hoc Tukey test results are shown in Table 1.
Conclusions: The traditional HIPA denture base material showed the least permanent deformation after loading. The traditional denture base showed the least retardant time but no statistically significant difference was found. The CADCAM block showed a significantly lower stress relaxation percentage than other denture base materials.
Methods: Three denture base materials were examined. HIPA high impact pour acrylic denture base (Dentsply-Sirona), CAD/CAM block Lucitone 199 (Dentsply-Sirona), and 3D printed Dentca denture base II. Five bars/group, 3x9x50 mm3, were fabricated from each material. Lucitone block specimens were sectioned using a Bueheler Isomet saw. HIPA specimens were fabricated by curing the powder/liquid mixture in a silicone rubber mold at 45 °C for 30 minutes at 1.4 bar and then sectioned. 3D printed specimens were fabricated using a Carbon M Series printer. Specimens were polished sequentially to 15 µm grit using a Buehler Ecomet and stored in water at 37°C for 10 days before testing.
An Instron 5566A was used to measure stress relaxation under a three-point bending setup at a controlled temperature of 37°C. Specimens were loaded to 70% of the mean failure stress of each material at 1 mm/min crosshead speed. The crosshead displacement was held for 10 minutes to allow the stress to relax and the load was recorded. The stress relaxation at the end of 10 mins loading and permanent strain after unloading were obtained. The load relaxation with time was analyzed to fit the combined Maxwell and Voigt viscoelastic model to determine the relaxation constant K and of retardation time τ.
Results: All the test data fitting to the viscoelastic model had an average R-square of 0.988. The acquired mechanical parameters and ANOVA post hoc Tukey test results are shown in Table 1.
Conclusions: The traditional HIPA denture base material showed the least permanent deformation after loading. The traditional denture base showed the least retardant time but no statistically significant difference was found. The CADCAM block showed a significantly lower stress relaxation percentage than other denture base materials.