Dentures and epitheses are mostly made from poly(methyl methacrylate) (PMMA), which does not show antimicrobial properties. They present reservoirs of microorganisms grown in biofilms. The aim of this study is to prepare a PMMA enriched with gold nanoparticles (AuNPs)-PMMA/AuNPs and the examination of its physical, mechanical and antimicrobial properties. The AuNPS were synthetized from HAuCl₄ using the ultrasonic spray pyrolysis method with lyophilization. The PMMA/AuNP samples were compared to PMMA samples. Density was measured by pycnometer. Microhardness was evaluated using the Vickers hardness test. Monomicrobial biofilm formation (Streptococcus mitis, Candida albicans, Staphylococcus aureus and Escherichia coli) was measured by colony-forming units (CFUs) and MTT test and visualized by SEM. AuNP release was measured indirectly (the CFUs of the medium around the sample). The density and microhardness of the PMMA/AuNPs were similar to those of the PMMA. CFU and MTT values for the biofilms formed on the PMMA for each of the tested species were higher than those of the biofilms formed on the PMMA/AuNPs. The CFUs of the medium around the sample were similar for both materials. PMMA/AuNPs showed a significant reduction in the monomicrobial biofilms of all tested species. AuNPs are not released from PMMA/AuNPs. Density, indirect measurement of residual monomer and dentures weight were similar between PMMA and PMMA/AuNPs. Microhardness, as a measure of the wear resistance, was also similar between tested discs.

Variations in the corrosion behavior of biomedical NiTi alloys in Cl⁻ containing and acidic environments present a problem with their biological implantation. The objective of this research was to evaluate the synergy of the microstructure, the corrosion behavior, and the biocompatibility of novel continuous-cast NiTi alloys and to compare them with commercial NiTi alloys. The two alloys have a practically identical nominal chemical composition, but they differ in production technology. The continuous casting technology involved vacuum induction melting of the basic components and vertical continuous casting, while the commercial NiTi alloy was produced through a process of casting, hot rolling, and forming into square shapes. The microstructure was revealed to determine the surface area and size of grains. The corrosion of a commercial nickel–titanium alloy and one prepared by a novel continuous casting method in acidic and chloride-containing solutions was studied via analytical and electrochemical tests. Localized corrosion characteristics related to oxide properties, when exposed to 9 g L⁻¹ NaCl solution, were examined with focused ion beam analysis and subsequent microchemical analysis of the formed corrosive products. Corrosion potential over time and the oxide film resistance were analyzed using linear polarization measurements. To obtain a preliminary estimate of biocompatibility, human fibroblast cells were used in indirect contact, i.e., alloy conditioning medium. The continuous casting method resulted in a reduction in the average grain size in comparison to the commercial sample and better corrosion stability of the sample in an acidic environment. Also, in a solution of 9 g L⁻¹ NaCl the commercial sample showed high values for the corrosion current density (j_corr = 6 μA cm⁻²), which indicated low corrosion resistance, while the continuous casting sample possessed much better corrosion stability and lower values for the corrosion current density (j_corr = 0.2 μA cm⁻²). In line with that, elemental analysis of the corroded surfaces showed higher Cl⁻ ion deposition over the surface layer of the commercial sample, suggesting local oxide breakdown. Moreover, NiTi_cc reached a value three times higher for polarization resistance (R_p = 270 kΩ cm²) over time in comparison to the commercial sample (R_p~100 kΩ cm²). Biocompatibility evaluation showed that human fibroblast cells exhibited altered metabolic activity. An MTT assay showed that cells’ mitochondrial activity dropped below that of control cells in the presence of both materials’ supernatants.

Nickel-titanium alloys are the most common shape memory alloys (SMA) widely used in dentistry. The attractive properties of Ni-Ti BioSMAs (shape memory effect, superelasticity, good corrosion, wear resistance, and good biocompatibility) make them highly desirable candidates for the design of implants, prosthetic components, orthodontic wires, and endodontic files. The aim of this chapter is to present the advantages of Ni-Ti alloy in dentistry through a selection of optimal chemical composition and various surface treatments (mechanical polishing, electrochemical polishing, chemical etching in acid solutions, heat treatment). The osteoconductivity of the Ni-Ti alloy on human bone cells and the anticorrosive and antibacterial effects of nanocoating orthodontic wires were tested. The results on human bone cells suggested good adhesion and proliferation of osteoblast-like cells to nickel-titanium surfaces, which could improve osseointegration of the potential dental implants. A study of magnetron sputtering method (MS) with TiN-Cu-nanocoatings on orthodontic archwires showed favorable results in corrosion resistance and antibacterial properties. Future improvement of mechanical properties is focused on applying various methods of surface modifications, especially applying coatings with antibacterial properties.

This study aimed to analyze the frequency and type of technical complications in different categories of removable dentures. We examined clinical health records of 637 denture wearers who presented for repair and collected information on fracture type (tooth, base, clasp), arch location (maxilla vs. mandible), and denture type. Tooth fractures were the most common complication in both arches. In the upper arch, complete dentures showed the highest incidence of base fractures (20.1%), while in the lower arch, the most common complication was acrylic partial denture clasp fractures (56,7%), followed by base fractures (48.4%). Because the prevalence and distribution of denture fractures vary significantly by denture type and arch location, our findings emphasize the critical role of material selection and reinforcement techniques in extending the service life of removable dentures.

Statement of problem: The stereo-optical method can be used for assessment of strains and deformations of different fixed or removable prosthodontic constructions. Material and methods: The study used two master casts of a lower jaw with bilateral terminal edentulous seats. Their topography was identical, with missing lower molars, the left lower second premolar, and the right canine and incisors, indicating a partially edentulous lower jaw according to Eichner's B3 (and C2) classification (i.e. Kennedy class 1). The control cast had conventional oval copings for overdenture. The experimental cast was almost the same as the control, with the exception of the surfaces simulating three specific milled copings covering the remaining tooth substance. Controlled loading was measured using a gnathodynamometer. Loading stages were at 400, 800, and 1000 N. Measurements of strain and displacement were provided by the Digital Image Correlation Method and the associated software. ‘Wilcoxon Lambda’ two sample tests based on the simple linear rank statistics were used in the analysis of differences in the displacement and deformation between the control rounded and experimental milled copings under loading numerical values. Results: It was found that smaller values of deformations are measured on milled copings when compared to the controls. There were statistically significant differences in displacement between the control rounded and experimental milled copings (Pr > |Z| = 0.001) as well as in deformations (Pr > |Z| = 0.0298). Conclusions: Experimental milled copings are less susceptible to deformation compared to the control conventional oval copings. These findings may have clinical significance in improvements of primary and secondary retention of overdentures on milled copings.