Mechanical properties and shear bond strength of denture teeth to different denture base materials
Alsulaimani, Othman Saleh
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OBJECTIVES: The aim of this in vitro study is to investigate the mechanical properties and bond strength of denture teeth to recently introduced denture base materials. MATERIALS AND METHODS: From high-impact pourable acrylic HIPA (Dentsply Sirona), DSDM Lucitone 199 puck (Dentsply Sirona), and digitally printed (Dentsply Sirona) denture base materials, bar specimens were fabricated for flexural testing (10 × 3.3 × 64 mm3) and fracture toughness testing (8 × 4 × 39 mm3). Tensile strength specimens were fabricated to form dumbbell-shaped specimens (3 × 6 mm cross-section) with a central bar. Micro-tensile specimens were fabricated into 10 × (1.5 ± 0.2) × (1.5 ± 0.2) mm3 bars. The treated specimens were subjected to thermal cycling. Square plates (3 × 18 mm2) were prepared for bonding to IPN denture teeth rods (3.85 mm) for evaluation of shear bond strength after surface treatment with airborne particle abrasion of 50 m aluminum oxide powder. The means were compared using an ANOVA Tukey HSD test, paired Student’s t-test, and contingency test (α = 0.05). RESULTS: DSDM had statistically higher flexural strength (p < 0.0001) than the other tested materials, as determined by one-way ANOVA. However, all denture base materials’ flexural moduli were not statistically different (p = 0.22). The effect of thermal aging on flexural strength (p = 0.18) and moduli of tested materials (p = 0.83) was not statistically significant. DSDM demonstrated statistically higher fracture toughness values (p = 0.0013) than the other materials. HIPA, however, had statistically higher work of fracture values than the other materials tested (p < 0.0001). The effect of thermal aging on Kmax and fracture work of all tested materials (pooled) was statistically different (p = 0.0002 and p = 0.0132, respectively). DSDP had the statistically highest tensile strength, followed by DSDM, and HIPA had the lowest (p < 0.0001). The effect of thermal aging on tensile strength (pooled) was statistically different (p <0.0001). The HIPA material’s mean micro-tensile strength was significantly lower than the DSDM and DSDP materials (p < 0.0001). Furthermore, the effect of thermal aging on the micro-tensile strength of all tested materials (pooled) was statistically different (p = 0.0005). Each paired Student’s t-test showed that surface abrasion increased the shear bond strength of DSDM, DSDP, and HIPA materials significantly (p < 0.0001, p = 0.0037, and p = 0.0035, respectively). Contingency analysis of the effect of the surface abrasion on each material’s failure mode revealed a 100% adhesive failure mode in DSDM. In DSDP, 5% of the failure mode was mixed. In contrast, the analysis showed 40% cohesive, 50% adhesive, and 10% mixed failure modes in HIPA material, although this finding was not statistically significant (p = 0.32). CONCLUSIONS: DSDM had higher flexural strength than the other tested materials and maximum stress intensity factors. However, HIPA performed better in terms of flexural modulus work of fracture. DSDP material had higher tensile strength values than the other materials. Thermocycling increased flexural strength, modulus values, and fracture toughness values, except for DSDP material which its work of fracture reduced after thermocycling. The tensile strength values of all tested materials was reduced after thermocycling. Air abrasion treatment enhanced the bonding strength between denture teeth and denture base material. Fractographic analysis of fragmented HIPA and DSDM specimens revealed varying degrees of plastic deformation, while DSDP material exhibiting less plastic deformation.