Denture base fracture is one of the most annoying problems for both prosthodontists and patients. Denture repair is considered to be an appropriate solution rather than fabricating a new denture. Digital denture fabrication is widely spreading nowadays. However, the repair strength of CAD-CAM milled and 3D-printed resins is lacking. This study aimed to evaluate the effect of surface treatment on the shear bond strength (SBS) of conventionally and digitally fabricated denture base resins. One l heat-polymerized (Major base20), two milled (IvoCad, AvaDent), and three 3D-printed (ASIGA, NextDent, FormLabs) denture base resins were used to fabricate 10 × 10 × 3.3 acrylic specimens (N = 180, 30/resin, n = 10). Specimens were divided into three groups according to surface treatment; no treatment (control), monomer application (MMA), or sandblasting (SB) surface treatments were performed. Repair resin was bonded to the resin surface followed by thermocycling (5000 cycles). SBS was tested using a universal testing machine where a load was applied at the resin interface (0.5 mm/min). Data were collected and analyzed using ANOVA and a post hoc Tukey test (α = 0.05). SEM was used for failure type and topography of fractured surfaces analysis. The heat-polymerized and CAD-CAM milled groups showed close SBS values without significance (p > 0.05), while the 3D-printed resin groups showed a significant decrease in SBS (p < 0.0001). SBS increased significantly with monomer application (p < 0.0001) except for the ASIGA and NextDent groups, which showed no significant difference compared to the control groups (p > 0.05). All materials with SB surface treatment showed a significant increase in SBS when compared with the controls and MMA application (p < 0.0001). Adhesive failure type was observed in the control groups, which dramatically changed to cohesive or mixed in groups with surface treatment. The SBS of 3D-printed resin was decreased when compared with the conventional and CAD-CAM milled resin. Regardless of the material type, SB and MMA applications increased the SBS of the repaired resin and SB showed high performance.

Background: To investigate the effect of zirconium dioxide nanoparticles (ZrO₂NPs) on the shear bond strength (SBS) of hard denture lines bonded to different denture base resins. Methods: Five different denture bases were used in this study: conventional heat-cured resin, IvoCad, AvaDent, NextDent, and FormLabs, in acrylic specimens of 10 × 10 × 2.5 mm³ (N = 150, n = 10). Specimens were centered at the bottom of a silicon mold to create an auto-polymerized holder. Three major groups of reline material were used: no ZrO₂NPs (control), 2 wt.%, and 4 wt.% ZrO₂NPs. Reline was bonded to the resin surface using a customized jig. After polymerization, specimens were stored in distilled water, and 5000 thermal cycles were performed. Each specimen was fixed to an Instron machine, and SBS was tested using a blade loaded (1 mm/min) at the resin interface until failure. Data was collected and analyzed using two-way ANOVA and post hoc Tukey test (α = 0.05). Results: AvaDent showed the highest SBS when compared with other denture base materials (p < 0.001) except for IvoCad. The addition of ZrO₂NPs significantly decreased the SBS of AvaDent (p = 0.003) and IvoCad (p = 0.001), while heat polymerized resin, Formlabs, and NextDent showed no significant change in SBS (p > 0.05). Conclusion: CAD-CAM milled denture base resin showed higher SBS with pure denture reline. The addition of ZrO₂NPs decreased the SBS of reline with CAD-CAM milled denture base resins but did not change bond strength with 3D printed and conventional denture base resins.

Background: Candida albicans adhesion to denture base materials is a primary contributor to denture stomatitis. To address this issue, numerous studies have explored the incorporation of various additives into denture base resins to enhance their antifungal properties. Titanium tetrafluoride (TiF₄) is an inorganic fluoride compound that has proven antimicrobial properties but has not yet been tested with denture materials. This study aimed to evaluate the effect of TiF₄ addition into different denture base materials on antifungal activity, surface roughness, hardness, and color properties. Methodology: A total of 200 disc-shaped specimens were prepared—100 heat-polymerized acrylic resins and 100 3D-printed NextDent resins. Four different concentrations of TiF₄ were incorporated: 1 wt%, 2 wt%, 3 wt%, and 4 wt% for both resins, while one group of each resin remained unmodified as a control. All specimens were subjected to thermal cycling for 5000 cycles, and four tests were conducted: Candida albicans adherence, surface roughness, hardness, and color change. A scanning electron microscope (SEM) was used to prove Candida albicans colonies’ adhesion on the specimens’ surfaces, and Fourier-transformed infrared (FTIR) analysis was performed to show the presence of TiF₄ in the resin material; data were analyzed using one-way ANOVA followed by a post hoc test (α = 0.05). Results: TiF₄ significantly reduced the Candida albicans adhesion to heat-polymerized specimens (p < 0.001). Compared to the control group, the incorporation of TiF₄ resulted in a substantial reduction in C. albicans colony counts, with reductions of approximately 97.6% in 1HP, 97.2% in 2HP, 97.4% in 3HP, and complete inhibition (100%) in 4HP. However, there was no significant difference between the 3D-printed ones (p = 0.913). Surface roughness, hardness, and color change of heat-polymerized groups were not significantly affected by TiF₄ (p > 0.05) except the color of the group treated with 4% (p < 0.05). For the 3D-printed groups, no significant differences were detected between the groups regarding candida count, hardness was significantly increased at 2% TiF₄ compared to the control (p = 0.002), and roughness was least with 4% TiF₄, while the color varied significantly between the groups (p < 0.001). Conclusions: TiF₄ addition decreased Candida albicans adhesion to heat-polymerized denture base materials but showed no antifungal effect on the 3D-printed resin. While roughness remained low in 3D-printed groups at higher concentrations. Hardness was not significantly altered in the heat-polymerized resin, whereas it increased significantly in the modified 3D-printed resin. Color stability was compromised at higher TiF₄ concentrations, particularly in the 3D-printed groups. The type of denture base material and TiF₄ concentration both influenced antifungal activity and denture surface properties.

Purpose: To evaluate the impact of different surface treatments on shear bond strength (SBS) of hard and soft denture liners bonded to CAD-CAM and conventional denture base resins. Methods: A total of 300 acrylic denture base specimens were fabricated with dimensions of 10 × 10 × 3 mm, with five different denture base materials: two milled (AvaDent and IvoCad), two printed (NexDent and FormLabs), and one heat-processed acrylic resin. The specimens underwent 5,000 thermal cycles both before and after the reline procedures, and each specimen was treated using one of three surface treatment methods: sandblasting, bur roughening, or no treatment (control). The reline procedure was performed with either a soft liner or a hard liner ( n = 10). Shear bond strength was tested using a universal testing machine with a crosshead speed of 1 mm/min until failure. Data were analyzed by two-way ANOVA ( α = 0.05). Results: Sandblasting significantly increases the SBS of hard liners to AvaDent, IvoCad, NextDent, and conventional resins compared to both the control and bur roughening groups ( p ≤ 0.0001). For FormLabs, sandblasting significantly improved SBS compared to the control group only ( p ≤ 0.01). In the case of soft liners, bur roughening significantly enhanced SBS for AvaDent, IvoCad, and conventional resins, while no significant improvement was observed for NextDent and FormLabs. Conclusion: Sandblasting is recommended to enhance the shear bond strength of hard liners across various denture base resins, whereas bur roughening is more effective when using soft liners.

Background: With the advancement of technology for digitally fabricated removable dental prostheses, protocols for the disinfection of three-dimensional (3D)-printed dentures are lacking. Therefore, this study aimed to assess and compare the effects of different disinfection protocols on the flexural strength (FS) of 3D-printed denture base resins. Materials and methods: A total of 200 bar-shaped samples (64 × 10 × 3.3 mm) were fabricated via two types of 3D-printed denture base resins: DentaBase (DB) and Denture 3D+ (D). According to the disinfectant method, each resin sample was divided into five groups ( n = 20). The samples were then further subdivided based on the duration of disinfection, either 90 days or 180 days. One control group was kept in water, while the other four groups were disinfected using a effervescent denture cleanser tablets (EDC), microwave (MW), ultraviolet light (UV), or ultrasonic (US). The flexural strength (FS) was measured. The collected data were statistically analyzed via three-way ANOVA, and post hoc Tukey’s test was used for data analysis (α = 0.05). Results: For Denture 3D+, FT significantly reduced FS at 90- and 180-day intervals ( p < 0.05). UV disinfection maintained the highest FS at 90 days (72.1 MPa, p < 0.013); however, both the US and MW methods resulted in significant reductions by 180 days ( p < 0.05). In the DentaBase, FT and MW disinfection caused significant FS reductions at 90 days ( p < 0.001). By 180 days, FT, US, and MW disinfection methods led to significant decreases in FS ( p < 0.001). However, UV light did not have a significant effect on FS at either point ( p = 0.22). Conclusion: UV disinfection proved to be the most suitable method for maintaining the mechanical integrity of 3D-printed denture base resins, while chemical, microwave, and ultrasonic methods should be used with caution due to their deteriorating effects on flexural strength.