Search Results (92)

Pure titanium (Ti) and its alloys are the gold standard for dental implants because a stable titanium dioxide passive film provides excellent corrosion resistance in physiological environments. In this study, we aimed to examine electrochemical interactions between Ti and cobalt–chromium–molybdenum alloy (CoCrMo), and between a novel Ti–magnesium composite (BIACOM TiMg) and CoCrMo, when immersed in everyday solutions representing beverage or oral hygiene exposure. Test solutions included Coca-Cola^®, lemon juice, Elmex^® fluoride gel, Listerine^® Cool Mint, and Sensodyne^® fluoride paste. Immersion experiments paired Ti sticks with CoCrMo sticks and, separately, BIACOM TiMg with CoCrMo sticks, with three measurements per configuration. When galvanically coupled with CoCrMo, immersion in Coca-Cola produced galvanic potential differences of ~983 mV for the BIACOM TiMg-CoCrMo couple and 830 mV for the commercially pure grade 4 (CP4) Ti-CoCrMo couple, indicating significant electrochemical instability. Both materials showed significant potential increases in Elmex fluoride gel. Listerine Cool Mint and Sensodyne fluoride exposure produced electrochemical interactions exceeding 200 mV. Significant differences in corrosion stability were observed between CP4 Ti and BIACOM TiMg. These findings indicate that material pairing and electrolyte environment significantly influence galvanic behavior, with the Ti-Mg composite showing greater susceptibility than CP4 Ti, informing dental/biomedical material selection in oral environments. Full article

Titanium (Ti) and its alloys are widely used in orthopedic applications, including total hip and knee replacements, bone plates, and dental implants, because of their superior biocompatibility, bioactivity, corrosion resistance, and mechanical robustness. These alloys effectively overcome several limitations of conventional metallic implants, such as 316L stainless steel and Co-Cr alloys, particularly with respect to corrosion, fatigue performance, and biological response. However, dense Ti alloys possess a relatively high elastic modulus, which can cause stress shielding in load-bearing applications. This challenge has motivated significant research toward engineered porous Ti structures that exhibit a reduced and bone-matched modulus while preserving adequate mechanical integrity. This review provides a comprehensive examination of powder metallurgy and additive manufacturing approaches used to fabricate porous Ti and Ti-alloy scaffolds, including additive manufacturing and different powder metallurgy techniques. Processing routes are compared in terms of achievable porosity, pore size distribution, microstructural evolution, mechanical properties, and biological outcomes, with emphasis on the relationship between processing parameters, pore architecture, and functional performance. The reported findings indicate that optimized powder-metallurgy techniques can generate interconnected pores in the 100–500 μm range suitable for osseointegration while maintaining compressive strengths of 50–300 MPa, whereas additive manufacturing enables the precise control of hierarchical architectures but requires careful post-processing to remove adhered powder, stabilize microstructures, and ensure corrosion and wear resistance. In addition, this review integrates fundamental aspects of bone biology and bone implant interaction to contextualize the functional requirements of porous Ti scaffolds. Full article

Objectives: This in vitro study aimed to evaluate the effects of three framework orientation (FO) positions on an SLM building platform (Horizontal [H], Diagonal-45° [D45°], Diagonal-60° [D60°]) and two designs (with [B] or without [NB] stabilizing bars) on the fitting accuracy of digitally fabricated Co-Cr RPD frameworks. Materials and Methods: A custom RPD framework CAD was performed on a 3D-printed resin-model of an edentulous maxilla with three geometric tooth forms. A Co-Cr alloy was processed via SLM processing into 24 framework specimens, divided into three FO groups (n = 8: H, D45°, D60°) and two subgroups each (n = 4: B, NB). Qualitative/quantitative fit-evaluation was assessed using virtual framework-to-model seating and a custom digital protocol with GOM Inspect software (2018-Hotfix5, Rev.115656). Mean fitting distances were calculated from 220 equidistant points per specimen. Statistical comparisons were performed using ANOVA-on-ranks, Kruskal–Wallis multiple comparisons, and Bonferroni adjustment. Results: FO Sub-Group medians (Q1, Q3: 25% and 75% Quartiles) (mm) were: H/NB 0.150 (0.140, 0.164), H/B: 0.136 (0.121, 0.152), D45°/NB: 0.230 (0.219, 0.241), D45°/B: 0.144 (0.137, 0.154), D60°/NB:0.238 (0.232, 0.247), D60°/B: 0.171 (0.166,0.176). Pairwise comparisons indicated the following statistically significant (p < 0.05) FO Sub-Group differences: H/B-D45°/NB, H/B-D60°/NB, D45°/B-D45°/NB, D45°/B-D60°/NB, H/NB-D45°/NB, H/NB- D60°/NB. Conclusions: Horizontal orientation improved RPD fit accuracy regardless of bar presence. D45° accuracy is enhanced by stabilizing bars, while D60° accuracy is unaffected by bar addition. Full article

The aim of this laboratory study was to evaluate the fitting accuracy of complete-arch implant-supported fixed dental prostheses (ISFDPs) and the occurrence of possible constraint forces after ISFDP fixation using the All-on-four treatment concept. A titanium model was fabricated with support posts for implants in positions 15, 12, 22, and 25. The forces acting on these posts were assessed using strain gauge half bridges. Implants (BEGO Semados^® SCX Implantat 4.1 mm × 10 mm, BEGO Implant Systems, Bremen, Germany) were fixated on top of the support posts. Based on conventional impressions and intraoral scans, two 12-unit monolithic ISFDPs made from cobalt–chromium alloy (CoCr) and zirconia (ZrO₂) were fabricated, jointed with titanium adhesive abutments (PS TiB NH, BEGO), and successively attached to the model. Constraint forces caused by ISFDP fixation were measured for each implant without external force. After testing four ISFDPs with different materials and impression techniques, four new implants were fixated (n = 10 model situations). A standard linear mixed model was used to assess horizontal and vertical constraint forces. The horizontal constraint forces acting on the implants were oriented in the oral direction, indicating that the ISFDPs were too small. The highest constraint forces were measured on implant 22 in the horizontal and vertical directions. Within the limitations of the present laboratory study, the fitting accuracy of complete-arch CoCr and ZrO₂ ISFDPs based on the All-on-four concept was sufficient for clinical use. Restorations made using conventional impressions had better fitting accuracy and reliability than those made using intraoral scans. Full article

The primary goal of this study was to assess the suitability of the proposed method for modifying the surface of cobalt alloys in dental prosthetics, taking into account the specific characteristics of the stomatognathic system during long-term use and their impact on physicochemical properties and the adhesion of cariogenic bacteria such as Streptococcus mutans. Technological factors influencing the quality of the product and its final dimensional characteristics were considered, confirming or ruling out the possibility of iatrogenic errors (related to poorly shaped prostheses) occurring during laboratory fabrication. This study demonstrates that atomic layer deposition of ZrO₂ on CoCr dental alloys results in a chemically stable, uniform, and protective surface layer, reducing ion release and improving surface quality. These improvements address key safety and performance requirements outlined in MDR 2017/745, supporting the use of ALD as a state-of-the-art technique for functionalizing dental prosthetic devices. Such coating development may influence the final quality of the denture and also verify its suitability for use in the oral environment (reducing the likelihood of denture stomatitis). Full article

This study demonstrates that effervescent denture cleansers can influence the electrochemical behavior of cobalt–chromium (Co-Cr) alloys, with a particular focus on their corrosion resistance. The findings underscore the importance for dental professionals of selecting cleansers compatible with Co-Cr prostheses to minimize material degradation and enhance clinical durability. Corrosion resistance was evaluated using open-circuit potential (OCP), corrosion current density (i_corr), and passivation current density (i_pass). Surface morphology and elemental composition were analyzed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Forty specimens (n = 5 per group) were individually immersed in one of ten test solutions: distilled water (DW), artificial saliva (AS), and eight commercial denture cleansers—Polident 3 minutes™ (P3M), Steradent™ (St), Polident for Partials™ (PP), Efferdent™ (Ef), Corega Tabs™ (CT), NitrAdine™ (Ni), Fixodent™ (Fi), and Kukident™ (Ku). Each specimen was exposed a single solution to avoid cross-contamination. Results showed St, Ef, and Ku had higher OCP values than DW and Ni (p < 0.05), indicating better corrosion resistance. AS exhibited lower OCP values compared to St (p = 0.034), Ku (p = 0.023), and P3M (p = 0.050). DW had higher i_corr than PP (p = 0.030), CT (p = 0.005), and P3M (p = 0.003). For i_pass, DW had lower values than Ef (p = 0.025) and Ku (p = 0.016). SEM and EDS revealed no significant surface alterations. Understanding the underlying corrosion mechanisms in different solutions provides valuable insights into optimizing material performance and ensuring durability in clinical applications. The corrosion resistance of Co-Cr depends on the stability of the passive oxide layer, which can be degraded by chloride ions, reinforced by sulfate ions, and influenced by active ingredients in denture cleansers. Overall, the Co-Cr alloy demonstrated acceptable corrosion resistance, underscoring the importance of selecting suitable cleansers for prosthesis longevity. Full article

Cobalt–chromium (CoCr) alloys are frequently used to produce customized dental applications such as crowns, bridges, or prostheses. These medical products have anatomical forms, and can be effectively manufactured using the laser-based powder bed fusion (PBF-LB/M) technique. A major disadvantage of this approach is the extended time required to refine the resultant surface. The purpose of this research is to reduce the surface roughness of PBF-LB/M/CoCr dental crowns by adopting drag finishing (DF) technology. To evaluate the impact of this automatic post-processing, surface roughness measurements and geometrical investigations were undertaken. The microstructure was characterized using scanning electron microscopy (SEM), and the chemical composition was verified by energy-dispersive X-ray spectroscopy (EDAX). On outside surfaces, the DF post-processing decreased the initial surface roughness by 70–90%. The dental crown’s surface roughness value after DF post-processing was comparable to that of the basic form (cylinder). The lowest roughness was obtained with DF3 post-processing (Ra~0.60 μm). The inner surfaces were limitedly finished. The 3D surface texture showed that the DF method reduced the height of peaks, uniformizing the surfaces. CMM work compared the deviations between the virtual model and the printed samples before and after DF post-processing. This analysis revealed that dimensional deviations were reduced on the outside crown walls, ranging from +0.01 to +0.05 mm. The laser parameters and the heat treatment applied increased the hardness of CoCr crowns to 520 HV, but the proper DF conditions identified reduced the surface roughness and improved the accuracy. Full article

Background/Objectives: Corrosion resistance of dental alloys, indicated by metal ion release, is a significant concern. The aim of this study was to investigate the impact of various sandblasting methods on the corrosion resistance of Co-Cr-W alloy samples in an artificial saliva solution. Materials and Methods: Co-Cr-W samples, obtained by additive manufacturing (selective laser melting) and subjected to different processes, were evaluated using electrochemical corrosion tests on potentiostat equipment in Carter–Brugirard artificial saliva. All measurements were conducted at a temperature of 37 °C. The morphology of the samples was analyzed using scanning electron microscopy to highlight changes in roughness and the effects of the electrolyte solution on the surface of the samples. Results: The corrosion current density values decreased as surface processing increased, dropping from an average of 38.5 μA/cm² in non-sandblasted samples (group A) to 0.74 μA/cm² in samples sandblasted with both Al₂O₃ and glass particles (group C), while the corrosion rate of group A (434.8 mm/year) was significantly higher than that of group C (8.08 mm/year). Conclusions: The results demonstrated different behaviors between sandblasted and non-sandblasted samples, which could be attributed to surface morphology differences influencing the corrosion process. Full article

To increase the mechanical and improve the operational properties of the AlSi25Cu4Cr and AlSi25Cu5Cr alloys, combinations of the alloying elements Ni, Co and Mo were used. The AlSi25Cu4Cr alloy was additionally alloyed with both Ni and Mo and Ni, Co and Mo, and the AlSi25Cu5Cr alloy was alloyed with Co and Mo in different concentrations. The dental alloys “wiron light” and “wironit” were used to introduce the elements Ni, Co, Mo, as well as additional amounts of Cr into the composition of the base compositions. The thermal analysis recorded a decrease in the liquidus and solidus temperatures of the base alloys, as well as a narrowing of their crystallization temperature range as a result of the added alloying elements. The influence of the used chemical elements on the phase composition of the alloys was established by X-ray diffraction. The elements Cr and Mo do not form secondary strengthening phases but dissolve in the α-solid solution. The results of the corrosion tests conducted in 1 M HCl solution and 1 M H₂SO₄ solution for 336 h and 504 h show that the elements Ni, Co and Mo improve the corrosion resistance of the alloys. Full article

This study aimed to investigate the release of metallic ions from cobalt–chromium (Co-Cr) alloys fabricated by additive manufacturing (AM) for comparison with dental casting. Co-Cr alloys were fabricated via AM using selective laser melting (SLM) and electron beam melting (EBM) in powder-bed fusion. Polished and mechanically ground specimens were prepared. Each specimen was analyzed using an electron probe microanalyzer (EPMA). Each specimen was immersed in an acidic saline solution for 7 days in accordance with ISO 10271: 2020. The EPMA indicated the segregation of some elements in the as-prepared SLM and EBM specimens, whereas the polished and ground specimens exhibited a homogenous elemental distribution. The total amount of ion release from the SLM and EBM specimens was confirmed to be less than 7 μg/cm², which was less than 42 μg/cm² for the cast specimen. The polished and ground specimens exhibited an even lower ion release than the as-prepared specimens. The amount of ions released from the Co-Cr alloy was less than the 200 μg/cm² requirement of ISO 22674: 2022. Co-Cr alloys fabricated by SLM and EBM could provide superior corrosion resistance to cast specimens. AM could be a valuable method for fabricating appliances and denture frameworks in dentistry. Full article

Introduction: Metal ions, released from dental alloys due to corrosion, come in contact with the cells of the surrounding tissues and may spread throughout the body via the gastrointestinal system, thus inducing dose-dependent cytopathological effects. This study aimed to assess and compare the salivary cobalt and chromium concentrations in individuals aged 18–65 years with and without dental restorations containing metal alloys. Methods: Participants were divided into two main groups according to the existence of metal alloys in the oral cavity—18 patients had fixed prosthetic restorations made of metal alloys, and 17 patients had no metal objects in their oral cavity. Each main group was subdivided into two subgroups according to the type of saliva sample—with or without additional stimulation. Salivary cobalt and chromium concentrations were measured by inductively coupled plasma mass spectrometry. A non-parametric Mann–Whitney test and Spearman’s rank correlation coefficient were applied, and the level of significance was set to p < 0.05. Results: The results showed that the chromium level in non-stimulated saliva was higher in the group of patients with metal dental restorations. No statistical difference was found in cobalt levels. There was no statistical difference in Co or Cr concentrations in stimulated saliva between the studied groups. A positive correlation was found between Cr and Co concentrations in non-stimulated saliva and between cobalt concentrations in stimulated and non-stimulated saliva. Conclusions: Metal alloys in the oral cavity induced elevated chromium levels in non-stimulated saliva, and a correlation between chromium and cobalt ion concentration was found. A detailed examination of patients and their medical history prior to prosthetic treatment is advisable in order to avoid any undesired health effects. Full article

Residual stresses and anisotropic structures characterize laser powder bed fusion (L-PBF) products due to rapid thermal changes during fabrication, potentially leading to microcracking and lower strength. Post-heat treatments are crucial for enhancing mechanical properties. Numerous dental technology laboratories worldwide are adopting the new technologies but must invest considerable time and resources to refine them for specific requirements. Our research can assist researchers in identifying thermal processes that enhance the mechanical properties of dental Co-Cr alloys. In this study, high cooling rates (quenching) and annealing after quenching were evaluated for L-PBF Co-Cr dental alloys. Cast samples (standard manufacturing method) were tested as a second reference material. Tensile strength, Vickers hardness, microstructure characterization, and phase identification were performed. Significant differences were found among the L-PBF groups and the cast samples. The lowest tensile strength (707 MPa) and hardness (345 HV) were observed for cast Starbond COS. The highest mechanical properties (1389 MPa, 535 HV) were observed for the samples subjected to the water quenching and reheating methods. XRD analysis revealed that the face-centered cubic (FCC) and hexagonal close-packed (HCP) phases are influenced by the composition and heat treatment. Annealing after quenching improved the microstructure homogeneity and increased the HCP content. L-PBF techniques yielded superior mechanical properties compared to traditional casting methods, offering efficiency and precision. Future research should focus on fatigue properties. Full article

Legislative framework addresses the issues of alloy corrosion, demanding the restricted use of probable carcinogenic, mutagenic, and toxic-for-human-reproduction (CMG) metals like nickel, cobalt, and chromium and demanding the development of new biomaterials. The aim of this research was to evaluate and compare the ion release of standard dental alloys and their hypoallergenic equivalents. Six types of orthodontic alloy wires (nickel–titanium (NiTi), coated NiTi, stainless steel (SS), Ni-free SS, and cobalt–chromium (CoCr) and titanium–molybdenum (TMA) were immersed into artificial saliva of pH 5.5 and 6.6. Release of metal ions was measured by inductively coupled plasma–mass spectrometry after 3, 7, 14 and 28 days. The data were analyzed using analysis of variance, and results with p < 0.05 were considered significant. NiTi released more Ti and Ni ions compared to the coated NiTi; SS released more iron, chromium, and nickel compared to the nickel-free SS. CoCr released cobalt in a high concentration and low amounts of chromium, nickel, and molybdenum compared to the molybdenum and titanium released by TMA. Release of metals from dental orthodontic alloys in vitro was overall lower at pH 6.6 and for the hypoallergenic equivalents when compared to standard dental alloys. Full article

Surface modifications not only improve the corrosion resistance of Co-Cr-Mo dental alloys (Bego Wirobond^® C) but also ensure their long-term performance and reliability in dental applications. This paper describes the preparation of single-layer TiO₂-ZrO₂ sol–gel coatings on the Co-Cr-Mo dental alloy using the method of dip-coating. The TiO₂-ZrO₂ sol–gel coatings were sintered at 300 and 500 °C. SEM analysis shows that sintering at 300 °C produces a uniform, slightly dense structure without micro-cracks, while sintering at 500 °C results in a denser structure with micro-cracks due to higher stress and shrinkage. EDS confirms that sintering temperature affects the elemental composition of the coating, with higher temperatures causing the volatilization or diffusion of Ti and Zr. Roughness measurements indicate that the Ra value increases with the sintering temperature, meeting dental application requirements. Electrochemical measurements by open-circuit potential, EIS, and cyclic potentiodynamic curves demonstrate that sintering temperature and saliva composition affect corrosion resistance, with NaF and mouthwashes (Listerine Total Care Teeth Protection^® and Meridol^®) generally increasing charge transfer resistance and double-layer capacitance. The ceramic TiO₂-ZrO₂ coatings significantly reduce pitting corrosion susceptibility at physiological and acidic pH, with the 500 °C sintered coating showing better protective properties. These findings highlight the potential of TiO₂-ZrO₂ coatings in enhancing the performance of Co-Cr-Mo dental alloys. Full article

This research explores how variations in laser powder bed fusion (LPBF) parameters—laser power (P), scanning speed (v), and base plate preheating temperature (ϑ_p)—affect the mechanical properties of the EOS Co-Cr SP2 dental alloy. A central composite design (CCD) was used to optimize the process parameters. Mechanical testing focused on crucial properties for dental applications, including yield strength (Rp_0.2), elongation (ε), toughness (KV_a), and flexural strength (R_ms). Microstructural analysis was conducted using light and electron microscopy, while XRD identified microstructural phases. Statistical analysis (ANOVA, Scheffé post hoc test, α = 0.05) revealed significant effects of P, v, and ϑ_p on the mechanical properties. Response surface models (RSMs) were developed, and optimal parameters were determined to achieve maximum toughness and flexural strength. Maximum values were obtained with laser power above 205 W and base plate preheating at 310 °C. The mathematical model predicted toughness values with less than 5% deviation from experimental results, indicating high accuracy. Full article