[Effect of Aging on the Mechanical Properties of CAD/CAM-Milled and 3D-Printed Acrylic Resins for Denture Bases].

PURPOSE: The purpose of this study was to investigate the mechanical properties of acrylic resins at different aging times for denture bases manufactured using the conventional method, microwave processing, milling, and 3D printing. MATERIALS AND METHODS: A total of 160 rectangular samples (64 Å~ 10 Å~ 3.3 ± 0.03 mm) were prepared, divided among the four main resin groups, and subdivided into four analysis times (T0, T1, T2, and T3), resulting in 10 samples per subgroup. The samples were stored in distilled water at 37° ± 2°C for 24 hours (T0), then subjected to thermocycling at temperatures of 5° ± 1°C and 55° ± 1°C in different numbers of cycles: 5,000 (T1); 10,000 (T2); and 20,000 (T3). The mechanical properties evaluated were surface microhardness, flexural strength, and modulus of elasticity. Statistical differences between resin groups and aging time were evaluated using two-way analysis of variance (P < .05). RESULTS: The 3D-printed resin showed the significantly lowest values of microhardness, flexural strength, and modulus of elasticity compared to other resins (P < .001). CONCLUSIONS: The CAD/CAM-milled denture resin showed mechanical properties similar to those of traditional resins (conventional and microwave-processed). The 3D-printing resin did not show adequate mechanical properties for long-term clinical use. Despite this, new studies are developing better properties of this resin for long-term use.

The role of TiO2 nanotube surface on osseointegration of titanium implants: Biomechanical and histological study in rats.

The nanoscale surface of titanium has been studied to improve the cellular recognition of the biological microenvironment and to increase bone-implant interaction. The aim of this study was to analyze the effect of a titanium oxide (TiO2 ) nanotube surface with a machined surface on osseointegration tibia implants without primary stability. This study used an experimental design, divided into two groups (n = 16): commercially pure titanium machined implants (Cp-Ti Ma) and commercially pure titanium anodized implants (Cp-Ti An). Titanium nanotubes were produced by anodic oxidation, and the topography of surface was analyzed using field emission scanning microscope (FE-SEM). The implants (2.1 × 2.8 mm Ø) were surgically placed in the right tibia (defects with milling drill 2.5 × 3.2 mm Ø) of 32 Wistar male rats (250-300 g). The animals were euthanized at 7 weeks postoperatively. The maximum value of removal torque was measured (N/cm) in the right tibia half of each group (8 animals/8 tibiae); the other half of each group underwent a nondecalcified protocol, stained with Stevenel blue/Alizarin red, and the formation of bone tissue in close contact to the implant was measured. The obtained data were analyzed statistically (t test). Differences were considered statistically significant for α < 0.05. Cp-Ti An implants were significantly higher in removal torque and peri-implant bone healing compared with Cp-Ti Ma implants (p < .01). Within the limitations of this study, it was observed that the surface modification of titanium by anodization (TiO2 nanotubes) can improve osseointegration, and this may be very useful to reduce the time required for peri-implant bone formation.