Characteristics of Si (C,N) Silicon Carbonitride Layers on the Surface of Ni-Cr Alloys Used in Dental Prosthetics.

Chromium- and cobalt-based alloys, as well as chrome-nickel steels, are most used in dental prosthetics. Unfortunately, these alloys, especially nickel-based alloys, can cause allergic reactions. A disadvantage of these alloys is also insufficient corrosion resistance. To improve the properties of these alloys, amorphous Si (C,N) coatings were deposited on the surfaces of metal specimens. This paper characterizes coatings of silicon carbide nitrides, deposited by the magnetron sputtering method on the surface of nickel-chromium alloys used in dental prosthetics. Depending on the deposition parameters, coatings with varying carbon to nitrogen ratios were obtained. The study analyzed their structure and chemical and phase composition. In addition, a study of surface wettability and surface roughness was performed. Based on the results obtained, it was found that amorphous coatings of Si (C,N) type with thicknesses of 2 to 4.5 µm were obtained. All obtained coatings increase the value of surface free energy. The study showed that Si (C,N)-type films can be used in dental prosthetics as protective coatings.

Shear bond strength of the ceramic veneer to additively manufactured titanium.

OBJECTIVES: The objective of this in vitro study was to evaluate the shear bond strength between the ceramic veneer and additively manufactured titanium with different surface treatments, and to compare with milled titanium. Also, to characterize the surface and the presence of an α-case layer of additively manufactured and milled titanium. MATERIAL AND METHODS: Sixty additively manufactured titanium grade 23, and 20 milled titanium grade 4 cylindrical specimens were divided into four groups based on surface treatments, air-particle abrasion and grinding. After ceramic veneering half of each group were thermocycled. The bond strength was analyzed using a shear bond strength test. The surfaces were analyzed using interferometry and scanning electron microscopy. RESULTS: The grinding procedure and air-particle abrading pressure had no significant effect on the shear bond strength (p = .264 and p = .344). Thermocycling showed a tendency towards an effect but not significant (p = .052). The group with the highest air-abrading pressure showed the highest surface roughness. No presence of an α-case layer was detected in any of the groups. CONCLUSION: Additively manufactured titanium grade 23 may be veneered with ceramics without prior grinding of the surfaces.

Oral Galvanism Side Effects: Comparing Alloy Ions and Galvanic Current Effects on the Mucosa-like Model.

The interaction of different dental alloys with the oral environment may cause severe side effects (e.g., burning sensation, inflammatory reactions, carcinogenesis) as a result of oral galvanism. However, the pathogenesis of side effects associated with oral galvanism is still unclear, and the effects of direct current and alloy corrosion ions are considered potentially contributing factors. Therefore, the aim of this study was to systemically compare the damaging effects of (1) galvanism as a synergistic process (direct current + corrosion ions), (2) direct current separately, and (3) corrosion ions separately on an in vitro mucosa-like model based on a cell line of immortalized human keratinocytes (HaCaTs) to reveal the factors playing a pivotal role in dental alloys side effects. For this, we chose and compared the dental alloys with the highest risk of oral galvanism: Ti64-AgPd and NiCr-AgPd. We showed that galvanic current may be the leading damaging factor in the cytotoxic processes associated with galvanic coupling of metallic intraoral appliances in the oral cavity, especially in the short-term period (28 days). However, the contribution of corrosion ions (Ni2+) to the synergistic toxicity was also shown, and quite possibly, in the long term, it could be no less dangerous.

Clinical Evaluation of Corrosion Resistance, Ion Release, and Biocompatibility of CoCr Alloy for Metal-Ceramic Restorations Produced by CAD/CAM Technologies.

BACKGROUND: CAD/CAM technologies facilitate using powder CoCr alloys to produce metal-ceramic dental restorations. However, base alloys may induce oxidative stress in the oral cavity due to corrosion and ion release. This study evaluated resistance to corrosion and release of metal ions from 3D printed CoCr dental alloy and their effect on oral oxidative stress. METHODS: Metal-ceramic crowns with 3D printed copings from CoCr alloy EOS CobaltChrome SP2 (EOS, Germany) were fabricated for 35 patients. Inductively coupled plasma mass spectrometry (ICP-MS) was used for measuring the concentration of Co and Cr ions in non-stimulated saliva before prosthetic treatment (BPT), at 2 h and 7 days after the dental treatment (APT2, APT7, respectively). Open circuit potentials (Eocp) were evaluated at APT2 and APT7. Estimating oral oxidative stress, measurements of 8-isoprostaglandin F2-alpha were conducted using liquid chromatography-tandem mass spectrometry (LC-MS/MS) at stages BPT, APT2, and APT7. RESULTS: Salivary Co level increased at APT2 and decreased to the initial levels at APT7. No statistical difference was found between the levels of 8-isoPGF2-alpha measured, and between the Eocp measurements at APT2 and APT7. CONCLUSIONS: The studied alloy showed stable corrosion resistance and the metal ion release did not induce oral oxidative stress.

Metal Ions Release from Welded Co-Cr Dental Alloys.

Cobalt-chromium alloys (Co-Cr) are widely used in dentistry due to their excellent mechanical properties and corrosion resistance. Since prosthetic materials must be permanently stable in the oral cavity, it is very important to determine the release of ions from alloys in the oral cavity. In dentistry today, metals and alloys are mainly joined by laser and tungsten inert gas (TIG) welding. Therefore, in this work, the release of metal ions from six different Co-Cr alloys joined by these two welding methods was quantified to determine the effects of the welding method on an ion release. Static immersion tests, atomic absorption spectrometry and statistical analysis were performed for this purpose. The results showed that laser-welded alloys release a lower amount of metal ions compared to TIG-welded alloys.

Microscopic and Mechanical Characterization of Co-Cr Dental Alloys Joined by the TIG Welding Process.

Due to their good mechanical and other properties, cobalt-chromium alloys (Co-Cr) are often used in prosthetic therapy. The metal structures of prosthetic works can be damaged and break, and depending on the extent of the damage, they can be re-joined. Tungsten inert gas welding (TIG) produces a high-quality weld with a composition very close to that of the base material. Therefore, in this work, six commercially available Co-Cr dental alloys were joined by TIG welding, and their mechanical properties were evaluated to determine the quality of the TIG process as a technology for joining metallic dental materials and the suitability of the Co-Cr alloys used for TIG welding. Microscopic observations were made for this purpose. Microhardness was measured using the Vickers method. The flexural strength was determined on a mechanical testing machine. The dynamic tests were carried out on a universal testing machine. The mechanical properties were determined for welded and non-welded specimens, and the results were statistically evaluated. The results show the correlation between the investigated mechanical properties and the process TIG. Indeed, characteristics of the welds have an effect on the measured properties. Considering all the results obtained, the TIG-welded I-BOND NF and Wisil M alloys showed the cleanest and most uniform weld and, accordingly, satisfactory mechanical properties, highlighting that they withstood the maximum number of cycles under dynamic load.

Comparative Study of the Microstructure and Properties of Cast-Fabricated and 3D-Printed Laser-Sintered Co-Cr Alloys for Removable Partial Denture Frameworks.

Since additive technologies in dentistry are gradually replacing metal casting technology, it is necessary to evaluate new dental constructions intended for the development of removable partial denture frameworks. The aim of this research was to evaluate the microstructure and mechanical properties of 3D-printed, laser-melted and -sintered Co-Cr alloys, and perform a comparative study with Co-Cr castings for the same dental purposes. The experiments were divided into two groups. The first group consisted of samples produced by conventional casting of the Co-Cr alloy. The second group consisted of 3D-printed, laser-melted and -sintered specimens produced from a Co-Cr alloy powder divided into three subgroups, depending on the technological parameters chosen for manufacturing (angle, location and heat treatment). Examination of the microstructure was carried out by classical metallographic sample preparation, using optical microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (EDX) analysis. A structural phase analysis was also performed by XRD. The mechanical properties were determined using a standard tensile test. The microstructure observation showed a dendritic character in the case of castings, while in the case of 3D-printed, laser-melted and -sintered Co-Cr alloys, the microstructure was typical for additive technologies. The XRD phase analysis confirmed the presence of Co-Cr phases (ε and γ). The results of the tensile test showed remarkably higher yield and tensile strength values and slightly lower elongation of the 3D-printed, laser-melted and -sintered samples than those produced by conventional casting.

Biomechanical Behavior of Narrow Dental Implants Made with Aluminum- and Vanadium-Free Alloys: A Finite Element Analysis.

Titanium (Ti) alloys used for narrow dental implants usually contain aluminum (Al) and vanadium (V) for improved resistance. However, those elements are linked to possible cytotoxic effects. Thus, this study evaluated the biomechanical behavior of narrow dental implants made with Al- and V-free Ti alloys by the finite element method. A virtual model of a partially edentulous maxilla received single implants (diameter: 2.7 and 2.9 mm; length: 10 mm) at the upper lateral incisor area, with respective abutments and porcelain-fused-to-metal crowns. Simulations were performed for each implant diameter and the following eight alloys (and elastic moduli): (1) Ti-6Al-4V (control; 110 GPa), (2) Ti-35Nb-5Sn-6Mo-3Zr (85 GPa), (3) Ti-13Nb-13Zr (77 GPa), (4) Ti-15Zr (113 GPa), (5) Ti-8Fe-5Ta (120 GPa), (6) Ti-26.88Fe-4Ta (175 GPa), (7) TNTZ-2Fe-0.4O (107 GPa), and (8) TNTZ-2Fe-0.7O (109 GPa). The implants received a labially directed total static load of 100 N at a 45° angle relative to their long axis. Parameters for analysis included the maximum and minimum principal stresses for bone, and von Mises equivalent stress for implants and abutments. Ti-26.88Fe-4Ta reaches the lowest maximum (57 MPa) and minimum (125 MPa) principal stress values, whereas Ti-35Nb-5Sn-6Mo-3Zr (183 MPa) and Ti-13Nb-13Zr (191 MPa) models result in the highest principal stresses (the 2.7 mm model surpasses the threshold for bone overload). Implant diameters affect von Mises stresses more than the constituent alloys. It can be concluded that the narrow implants made of the Ti-26.88Fe-4Ta alloy have the most favorable biomechanical behavior, mostly by mitigating stress on peri-implant bone.

Minimization of Adverse Effects Associated with Dental Alloys.

Metal alloys are one of the most popular materials used in current dental practice. In the oral cavity, metal structures are exposed to various mechanical and chemical factors. Consequently, metal ions are released into the oral fluid, which may negatively affect the surrounding tissues and even internal organs. Adverse effects associated with metallic oral appliances may have various local and systemic manifestations, such as mouth burning, potentially malignant oral lesions, and local or systemic hypersensitivity. However, clear diagnostic criteria and treatment guidelines for adverse effects associated with dental alloys have not been developed yet. The present comprehensive literature review aims (1) to summarize the current information related to possible side effects of metallic oral appliances; (2) to analyze the risk factors aggravating the negative effects of dental alloys; and (3) to develop recommendations for diagnosis, management, and prevention of pathological conditions associated with metallic oral appliances.

Thermal expansion and corrosion resistance of cobalt-chromium alloys fabricated by contemporary manufacturing processes: an in vitro study / Expansión térmica y resistencia a la corrosión de aleaciones de cobalto-cromo fabricadas mediante procesos de abricación contemporáneos: un estudio in vitro

In Purpose: The fabrication technique can influence the mechanical properties of Cobalt-Chromium (Co-Cr) dental alloys. Hence, the present study aims to determine the corrosion resistance and thermal expansion of alloys manufactured using three contemporary techniques. Material and Methods: A total of nine specimens of Co-Cr alloy were prepared according to ISO 22674 by each one of the three manufacturing processes (three in each process); conventional casting, direct metal laser sintering (DMLS) and milling (MIL). All these specimens were tested for coefficient of thermal expansion and corrosion resistance. The data was tabulated and analyzed statistically. Results: The difference in the thermal expansion of alloys fabricated using three techniques was non-significant at almost all the temperatures from 50 ºC to 950 ºC (p>0.05), except 450 ºC and 600 °C. The polarization resistance of specimens manufactured using the conventional method was more compared to DMLS and MIL at pH 5 (Conventional>MIL>DMLS) (p<0.001). Conclusion: The thermal expansion behavior of alloys manufactured using the three selected techniques were similar, whereas, at acidic pH, the corrosion resistance of conventional and MIL were better than the DMLS.

Antecedentes: La técnica de fabricación puede influir en las propiedades mecánicas de las aleaciones dentales de cobalto-cromo (Co-Cr). Por lo tanto, el presente estudio tiene como objetivo determinar la resistencia a la corrosión y la expansión térmica de aleaciones fabricadas con tres técnicas contemporáneas. Material y Métodos: Se prepararon un total de nueve probetas de aleación de Co-Cr según ISO 22674 por cada uno de los tres procesos de fabricación (tres en cada proceso); fundición convencional, sinterización directa de metal por láser (DMLS) y fresado (MIL). Todos estos especímenes fueron probados para determinar el coeficiente de expansión térmica y la resistencia a la corrosión. Los datos fueron tabulados y analizados estadísticamente. Resultados: La diferencia en la dilatación térmica de las aleaciones fabricadas con las tres técnicas no fue significativa en casi todas las temperaturas desde 50ºC hasta 950ºC (p>0,05), excepto 450ºC y 600ºC. La resistencia a la polarización de las muestras fabricadas con el método convencional fue mayor en comparación con DMLS y MIL a pH 5 (Convencional>MIL>DMLS) (p<0, 0 01). Conclusión: El comportamiento de expansión térmica de las aleaciones fabricadas con las tres técnicas seleccionadas fue similar, mientras que, a pH ácido, la resistencia a la corrosión de la convencional y la MIL fue mejor que la de la DMLS.

Reacciones Adversas durante el tratamiento de Ortodoncia: Incidencia e Impacto en España / Adverse reactions during orthodontic treatment: Incidence and impact in Spain

Introducción: Las reacciones alérgicas preocupan cada vez más a los profesionales sanitarios en todos los ámbitos debido al incremento de la susceptibilidad de la población a múltiples alérgenos. Se estima que entre 10 y 30% de los ortodoncistas en España han sido testigos de reacciones adversas asociadas a aparatos ortodónticos, adhesivos y otros materiales. Objetivo: Estimar el número de reacciones alérgicas que se producen en la práctica clínica ortodóncica en España y determinar la necesidad de utilizar dispositivos sin níquel en las consultas de ortodoncia en el momento actual. Métodos: Se encuestó a una muestra de 100 ortodoncistas (23 en formato papel y 77 online) para cuantificar retrospectivamente el número de pacientes que habían sufrido reacciones adversas en sus consultas y describir dichas reacciones frente a los aparatos y otros materiales utilizados. Resultados: El 21% de los encuestados refirió haber observado entre sus pacientes alguna reacción alérgica intraoral o extraoral en relación con aparatos ortodónticos y otros materiales. En la mita de los casos, la reacción se presentó como eritema u otros síntomas localizados en la mucosa oral y/o en los labios. Conclusiones: Una quinta parte de los ortodoncistas admiten haber tenido en su práctica clínica al menos un paciente con una reacción alérgica intraoral o extraoral causada por algún aparato de ortodoncia en los últimos 5 años (AU)

Introduction: Allergic reactions are of increasing concern to healthcare professionals in all settings due to the already increasing susceptibility of the population to multiple allergens. It is estimated that between 10 and 30% of orthodontists in Spain have witnessed adverse reactions associated with orthodontic appliances and adhesive materials. Objective: To estimate the number of allergic reactions that occur in orthodontic linical practice in Spain and to determine the need to use nickel-free devices in orthodontic practices at the present time. Methods: A sample of 100 orthodontists was interviewed (23 in paper format and 77 online) to retrospectively quantify the number of patients who had suffered adverse reactions in their practices and to describe these reactions to the appliances used. Results: 21% of the respondents reported having observed an intraoral or extraoral allergic reaction to orthodontic appliances among their patients. In half of the cases the reaction presented as erythema or other symptoms located on the oral mucosa and/or lips. Conclusions: One-fifth of orthodontists admit to having had at least one patient with an intraoral or extraoral allergic reaction caused by any orthodontic appliance in the last 5 years (AU)

Study on the Surface of Cobalt-Chromium Dental Alloys and Their Behavior in Oral Cavity as Cast Materials.

This study presents the correct processing of Co-Cr alloys as a method of preserving the properties of the materials as-cast, and therefore they can be safely placed in contact with the oral cavity tissues as resistance frameworks. The basic materials analyzed in this study were five commercial Co-Cr dental alloys with different components obtained in three processing steps. The analysis of the electrochemical behavior at the surface of the Co-Cr alloys was performed by electrochemical measurements: impedance spectroscopy (EIS), open circuit electrical potential (OCP), and linear polarization (LP). In terms of validation, all five alloys had a tendency to generate a stable oxide layer at the surface. After the measurements and the graphical representation, the alloy that had a higher percentage of tungsten (W) and iron (Fe) in composition showed a higher tendency of anodizing. After the application of the heat treatment, the disappearance of the hexagonal phase was observed, with the appearance of new phases of type (A,B)2O3 corresponding to some oxide compounds, such as Fe2O3, Cr2O3, (Cr,Fe)2O3, and CoMnO3. In conclusion, the processing of Co-Cr alloys by melting and casting in refractory molds remains a viable method that can support innovation, in the context of technology advance in recent years towards digitalization of the manufacturing process, i.e., the construction of prosthetic frameworks conducted by additive methods using Co-Cr powder alloy.

Insight Into Corrosion of Dental Implants: From Biochemical Mechanisms to Designing Corrosion-Resistant Materials.

Purpose of Review: Despite advanced technologies to avoid corrosion of dental implants, the mechanisms toward the release of metals and their role in the onset of peri-implant diseases are still under-investigated. Effective knowledge on the etiopathogenesis of corrosive products and preventive strategies mitigating the risks for surface degradation are thus in dire need. This review aimed to summarize evidence toward biocorrosion in the oral environment and discuss the current strategies targeting the improvement of dental implants and focusing on the methodological and electrochemical aspects of surface treatments and titanium-based alloys. Recent Findings: Recent studies suggest the existence of wear/corrosion products may correlate with peri-implantitis progress by triggering microbial dysbiosis, the release of pro-inflammatory cytokines, and animal bone resorption. Furthermore, current clinical evidence demonstrating the presence of metal-like particles in diseased tissues supports their possible role as a risk factor for peri-implantitis. For instance, to overcome the drawback of titanium corrosion, researchers are primarily focusing on developing corrosion-resistant alloys and coatings for dental implants by changing their physicochemical features. Summary: The current state-of-art discussed in this review found corrosion products effective in affecting biofilm virulence and inflammatory factors in vitro. Controversial and unstandardized data are limitations, making the premise of corrosion products being essential for peri-implantitis onset. On the other hand, when it comes to the strategies toward reducing implant corrosion rate, it is evident that the chemical and physical properties are crucial for the in vitro electrochemical behavior of the implant material. For instance, it is foreseeable that the formation of films/coatings and the incorporation of some functional compounds into the substrate may enhance the material's corrosion resistance and biological response. Nevertheless, the utmost challenge of research in this field is to achieve adequate stimulation of the biological tissues without weakening its protective behavior against corrosion. In addition, the translatability from in vitro findings to clinical studies is still in its infancy. Therefore, further accumulation of high-level evidence on the role of corrosion products on peri-implant tissues is expected to confirm the findings of the present review besides the development of better methods to improve the corrosion resistance of dental implants. Furthermore, such knowledge could further develop safe and long-term implant rehabilitation therapy.

Cyclic Fatigue Resistance and Surface Roughness of Rotary NiTi Instruments after Simulated Clinical Use in Curved Root Canals - An Atomic Force Microscopy Study

Abstract Objective: To examine the cyclic fatigue resistance and surface topography of TruNatomy and ProTaper Gold nickel-titanium rotary files and evaluate the presence of alterations to surface topography following instrumentation in simulated curved canals. Material and Methods: Twenty-four nickel-titanium instruments, twelve each of TN and PTG file systems, were evaluated for cyclic fatigue resistance. The rotary files were rotated in a simulated root canal with standardized diameter, angle of curvature, and radius of curvature in a custom-made cyclic fatigue testing device until the instrument fracture occurred. The time to fracture for each instrument was recorded with a stopwatch; in seconds in each group. Fractured instruments were subjected to atomic force microscopy analysis measuring the average roughness and the root mean square values to investigate surface features of endodontic files. Mean values and standard deviation were calculated. Data were analyzed using the Mann-Whitney U test. Results: Time to fracture was marginally higher in PTG instruments than in the TN file systems. PTG files exhibited higher surface roughness when compared with TN files (p<0.05). Conclusion: TN file system had a higher cyclic fatigue resistance than PTG. Cyclic fatigue causing file breakage did affect the surface topography of the files. PTG files showed a higher surface porosity value than the TN files (AU).

Additively Manufactured Commercial Co-Cr Dental Alloys: Comparison of Microstructure and Mechanical Properties.

Laser-powder bed fusion (LPBF) is one of the preferred techniques for producing Co-Cr metal structures for dental prosthodontic appliances. However, there is generally insufficient information about material properties related to the production process and parameters. This study was conducted on samples produced from three different commercially available Co-Cr dental alloys produced on three different LPBF machines. Identically prepared samples were used for tensile, three-point bending, and toughness tests. Light microscopy (LM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) analyses of microstructure were performed after testing. Differences were observed in microstructures, which reflected statistically significant differences in mechanical properties (one-way analysis of variance (ANOVA) and Scheffé post hoc test (α = 0.05)). The material produced on the 3D Systems DMP Dental 100 had 24 times greater elongation ε than the material produced on the Sysma MySint 100 device and the EOS M100 machine. On the other hand, the material produced on the EOS M100 had significantly higher hardness (HV0.2) than the other two produced materials. However, the microstructure of the Sysma specimens with its morphology deviates considerably from the studied group. LPBF-prepared Co-Cr dental alloys demonstrated significant differences in their microstructures and, consequently, mechanical properties.

Effect of Titanium Hardness on the Integrity and Stress Concentration of External Hexagon Dental Implants

ABSTRACT: The aim of this study was to evaluate the influence of overtorque on integrity, strength and stress on external hexagonal implants (EH), with two different grades (N=10): conventional (C), grade 4; and modified (M), grade 4 with thermal treatment. The dimensions of EH were 3.75 x 13 mm; the specimens were fixed and submitted to SEM analysis and image acquisition. The abutment was then retained with 70 N/cm, re-analyzed by SEM, and a second image was obtained. The images were analyzed by Image J software (1.44o- NIH, USA) for dimensional variations measurement on surface of the hexagonal area. The finite element method was applied with a similar compliance to calculate the resultant stress (MPa) during the torque. Results were statistically analyzed with t-student test (5 %). The dimensional accuracy of M (0.22 mm2) was statistically significant (p<0.05). Minimum principal stress and von-Mises stress of C (-19.95 MPa, -19.94 MPa), were lower than M values (-55.83 MPa, -55.96 MPa), respectively. However, the M group showed lower deformation than C group. Therefore, more rigid titanium alloy is a promising alternative to avoid plastic deformation of prosthetic connec tions even concentrating higher stress magnitude on its structure.

RESUMEN: El objetivo de este estudio fue evaluar la influencia del sobrepar en la integridad, la fuerza y la tensión en los implantes hexagonales externos (EH), con dos grados diferentes (N = 10): convencional (C), grado 4; y modificado (M), grado 4 con tratamiento térmico. Las dimensiones de EH eran 3,75 de diámetro x 13 mm de longitud; las muestras se fijaron y se sometieron a análisis SEM y adquisición de imágenes. A continuación, el pilar se retuvo con 70 N / cm, se volvió a analizar por SEM y se obtuvo una segunda imagen. Las imágenes se analizaron con el software Image J (1.44o-NIH, EE. UU.) Para medir las variaciones dimensionales en la superficie superior del área hexagonal, que fue causada por un par excesivo. El método de los elementos finitos se aplicó con un cumplimiento similar para calcular la tensión resultante (MPa) durante el par. Los resultados se analizaron estadísticamente con la prueba t-student (5 %). La precisión dimensional de M (0,22 mm2) fue estadísticamente significativa (p <0,05). La tensión principal mínima y la tensión de von-Mises de C (-19,95 MPa, -19,94 MPa), fueron inferiores a los valores de M (-55,83 MPa, -55,96 MPa), respectivamente. Sin embargo, el hexágono del grupo M mostró menor deformación que el grupo C. Por lo tanto, la aleación de titanio más rígida es una alternativa prometedora para evitar la deformación plástica de las conexiones protésicas incluso concentrando una mayor magnitud de tensión en su estructura.

Ti-Ions and/or Particles in Saliva Potentially Aggravate Dental Implant Corrosion.

The corrosive titanium products in peri-implant tissues are a potential risk factor for peri-implantitis. There is very limited information available on the effect of the corrosion and wear products on the dental implant corrosion. Therefore, we determined the influence of Ti-ions and Ti-particles on Ti corrosion. Eighteen commercially pure-Ti-grade-2 discs were polished to mirror-shine. Samples were divided into six groups (n = 3) as a function of electrolytes; (A) Artificial saliva (AS), (B) AS with Ti-ions (the electrolyte from group A, after corrosion), (C) AS with Ti-particles 10 ppm (D) AS with Ti-particles 20 ppm, (E) AS with Ti-ions 10 ppm, and (F) AS with Ti-ions 20 ppm. Using Tafel's method, corrosion potential (Ecorr) and current density (Icorr) were estimated from potentiodynamic curves. Electrochemical Impedance Spectroscopy (EIS) data were used to construct Nyquist and Bode plots, and an equivalent electrical circuit was used to assess the corrosion kinetics. The corroded surfaces were examined through a 3D-white-light microscope and scanning electronic microscopy. The data demonstrated that the concentration of Ti-ions and corrosion rate (Icorr) are strongly correlated (r = 0.997, p = 0.046). This study indicated that high Ti-ion concentration potentially aggravates corrosion. Under such a severe corrosion environment, there is a potential risk of increased implant associated adverse tissue reactions.

Metal Alloys in Dentistry: An Outdated Material or Required for Oral Rehabilitation?

ABSTRACT: The present study aims to describe through a literature review, the main types of noble and non-noble alloys in dentistry looking to identify the adhesion mechanisms, compositions and mechanical properties, and its applicability as a rehabilitation resource nowadays. A bibliographic search was conducted in the main health databases PUBMED (www.pubmed.gov) and Scholar Google (www.scholar.google.com.br), in which studies published from 1971 to 2021 were collected. Laboratory studies, case reports, systematic and literature reviews, which were developed in living individuals. Articles that did not deal with metal alloys and its use in dentistry were excluded. Through the review, it was possible to ver ify that all works presented the metal alloys and their main properties, indicating that they are divided into three main types: hi gh noble alloys, noble alloys and base metal alloys differing in their levels of constituent noble metals. Several alloys and meta ls are available for the dental market each presenting advantages and disadvantages, mainly based on its specific composition.Continuous research and development are resulting in the production of new technologies and products, giving dental surgeons even more options in the design and manufacture of restorations using metal alloys and understanding that these resources will still be viable alternatives in oral rehabilitations. However, further studies on metal alloys are needed to better understand this subject.

RESUMEN: El presente trabajo tuvo como objetivo describir a través de una revisión de la literatura, los principales tipos de aleaciones nobles y no nobles utilizados en odontología buscando identificar los mecanismos de adhesión, composiciones y propiedades mecánicas, así como reflejar su aplicabilidad como recurso rehabilitador en la actualidad. Realizamos una búsqueda bibliográfica em las principales bases de datos de salud PUBMED (www.pubmed.gov) y Scholar Google (www.scholar.google.com.br), en la que se recopilaron estudios publicados desde 1971 hasta 2021. Estudios de laboratorio, informes de casos, revisiones sistemáticas y bibliográficas, que se desarrollaron en individuos vivos. Sin embargo, se excluyeron los artículos que no trataban sobre aleaciones metálicas y su uso en odontología. Se pudo observar que todos los trabajos presentaban las aleaciones metálicas y sus principales propiedades indicando que se estas dividen en tres tipos principales: aleaciones altamente nobles, aleaciones nobles y aleaciones de metales base que difierenen sus niveles de metales nobles constituyentes. Hay varias aleaciones y metales disponibles para el mercado dental, cada uno presenta ventajas y desventajas, principalmente en función de su composición específica. La investigación y el desarrollo continuo están dando como resultado la producción de nuevas tecnologías y productos, brindando a los cirujanos dentistas aún más opciones en el diseño y fabricación de las restauraciones, utilizando aleaciones metálicas y, permite concluir que estos recursos seguirán siendo alternativas viables en los tratamientos de rehabilitación. Sin embargo, se necesitan más estudios sobre el tema abordado en el trabajo, para una comprensión más profunda del tema.

Experimental Study Regarding the Behavior at Different pH of Two Types of Co-Cr Alloys Used for Prosthetic Restorations.

Cobalt-chromium (Co-Cr) alloys are widely utilized in dentistry. The salivary pH is a significant factor, which affects the characteristics and the behavior of dental alloys through corrosion. This study aimed to evaluate the corrosion behavior in artificial saliva with different pH values (3, 5.7, and 7.6) of two commercial Co-Cr dental alloys manufactured by casting and by milling. Corrosion resistance was determined by the polarization resistance technique, and the tests were carried out at 37 ± 1 °C, in Carter Brugirard artificial saliva. After the electrochemical parameters, it can be stated that the cast Co-Cr alloy has the lowest corrosion current density, the highest polarization resistance, and the lowest speed of corrosion in artificial saliva with pH = 7.6. In the case of milled Co-Cr alloy, the same behavior was observed, but in artificial saliva with pH = 5.7, it recorded the most electropositive values of open circuit potential and corrosion potential. Although both cast and milled Co-Cr alloys presented a poorer corrosion resistance in artificial saliva with a more acidic pH value, the milled Co-Cr alloy had better corrosion behavior, making this alloy a better option for the prosthetic treatment of patients suffering from GERD.

Correlation between microhardness and wear resistance of dental alloys against monolithic zirconia.

PURPOSE: The aim of this study is to compare the hardness according to the conditions of metal alloys. Moreover, the correlation between the cast crown hardness before and after wear testing and the degree of wear for each dental alloy was assessed. MATERIALS AND METHODS: Cast crowns of three metal alloys (Co-Cr, gold, and Ni-Cr alloys) opposing smooth-surface monolithic zirconia were used. The Vickers microhardness of the ingot (which did not undergo wear testing) and the cast crown before and after wear testing were measured for each alloy. Two-way ANOVA and Scheffé tests were used to compare the measured hardness values. Moreover, the Pearson correlation coefficient was used to evaluate the relationship between the surface hardness and the wear of the cast crown (α=.05). RESULTS: There was no significant difference in the hardness before and after wear testing for the gold alloy (P>.05); however, the hardness of the worn surface of the cast crown increased compared to that of the cast crown before the wear tests of Ni-Cr and Co-Cr alloys (P<.05). Furthermore, there was no correlation between the wear and hardness of the cast crown before and after wear testing for all three metal alloys (P>.05). CONCLUSION: There was a significant difference in hardness between dental alloys under the same conditions. No correlation existed between the surface hardness of the cast crown before and after wear testing and the wear of the cast crown.