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Oral and Maxillofacial Surgery Clinics... Aug 2019Nitinol metal alloy that changes shape according to temperature has been in clinical use at select clinics worldwide for the past 2 years and is now released for... (Review)
Review
Nitinol metal alloy that changes shape according to temperature has been in clinical use at select clinics worldwide for the past 2 years and is now released for general use. The Smileloc Abutment and nitinol sleeve enable "cementless," "screwless," crown fastening that saves time and cost with the prospect of replacement of much of the present, sometimes troublesome, anthropic, soon to be anachronistic, technology.
Topics: Alloys; Dental Abutments; Dental Alloys; Dental Implants, Single-Tooth; Dental Prosthesis Design; Dental Prosthesis, Implant-Supported; Humans
PubMed: 31147105
DOI: 10.1016/j.coms.2019.03.006 -
British Dental Journal Jul 2020
Topics: Corrosion; Dental Amalgam; Dental Materials; Mercury
PubMed: 32710031
DOI: 10.1038/s41415-020-1943-6 -
The Journal of Prosthetic Dentistry Aug 2022The forces exerted on teeth and prostheses during mastication are repeated and dynamic, resulting in fatigue damage to dental prostheses. Most fractures of dental...
STATEMENT OF PROBLEM
The forces exerted on teeth and prostheses during mastication are repeated and dynamic, resulting in fatigue damage to dental prostheses. Most fractures of dental restorations are fatigue failure. The 4-point bend fatigue behavior of Co-Cr-Mo-W alloys manufactured by investment casting (CAST) and selective laser melting (SLM) has received little attention.
PURPOSE
The purpose of this in vitro study was to evaluate the 4-point bend fatigue property of dental Co-Cr alloys and determine the relationship between microstructure and the 4-point bend fatigue property of Co-Cr alloys created by traditional casting and SLM. These can guide the use of Co-Cr alloy in dentistry.
MATERIAL AND METHODS
Co-Cr-Mo-W alloys were fabricated with a dimension of 45×2×2 mm by investment casting and SLM. The 3-point bend test measured the ultimate bend strength with 3 specimens in each group. The 4-point bend fatigue test evaluated the fatigue life under various stresses, with 6 specimens in each group. The specimens were mechanically ground, polished, and electrochemically etched. Scanning electron microscopy was used to identify the microstructures of both etched specimens and fracture surfaces. X-ray diffraction investigations were used to determine the phases. Significant differences in the bend strength were analyzed by using the independent samples t test (α=.05), and the fatigue test was analyzed with ANCOVA (α=.05).
RESULTS
The mean ±standard deviation bend strength of SLM specimens was 1837 ±3 MPa, higher than the 1200 ±6 MPa for CAST specimens (P<.05). The maximum bend stress of the SLM specimens without fatigue failure was 735 MPa, which was statistically higher than the 394 MPa for CAST specimens (P<.05). The microstructure characteristics of the SLM alloy contributed to its excellent fatigue performance. In SLM alloy, the γ phase constituted the majority with some ε and Laves phases, while the cast alloy possessed higher ε and Laves phases. The grains of SLM alloy were equiaxed and fine, and the second phases were fine and dispersive. In contrast, the cast alloy possessed clear dendrites, and the second phases were sizable.
CONCLUSIONS
The SLM dental Co-Cr-Mo-W alloy had statistically better 4-point bend fatigue properties than cast alloy, which was associated with an improved microstructure.
Topics: Chromium Alloys; Dental Casting Technique; Lasers; Materials Testing; Microscopy, Electron, Scanning; Surface Properties
PubMed: 35786348
DOI: 10.1016/j.prosdent.2022.05.011 -
European Journal of Oral Sciences Oct 2020The aims of the study were to investigate functional and esthetic properties, the composition of the alloy, and the content of hazardous elements of single dental crowns...
The aims of the study were to investigate functional and esthetic properties, the composition of the alloy, and the content of hazardous elements of single dental crowns with metal skeleton and fired porcelain. Epoxy models made from full mouth impressions taken of a patient with a crown preparation of the right maxillary first permanent molar were used for production of identical polyether impressions, which were distributed to dentists in Norway. The dentists sent the impressions to their regular dental laboratories. All 55 crowns collected were anonymized and examined. Of the crowns received, 35 were made in Norway, 12 were imported, and 8 were of unknown origin. The evaluation of functional properties revealed that 50% of the Norwegian, 42% of the imported, and 25% of the unknown-origin crowns were considered unacceptable. The composition of the alloy was not in accordance with that stated by the manufacturer for 17%, 13% and 20% of the crowns, where this information was provided. The lead content of the alloy exceeded the limit set by the ISO 22674: 2016 for 18% of the crowns in total. The statement that shall follow the work according to EU-regulations was not complete for approximately 75% of the works received.
Topics: Crowns; Dental Porcelain; Dental Prosthesis Design; Humans; Metal Ceramic Alloys; Molar; Norway
PubMed: 32805064
DOI: 10.1111/eos.12724 -
Journal of Endodontics Aug 2022Instruments' mechanical strength and flexibility are traditionally tested by running cyclic fatigue, torsional, bending, buckling, and microhardness tests. Several... (Review)
Review
Instruments' mechanical strength and flexibility are traditionally tested by running cyclic fatigue, torsional, bending, buckling, and microhardness tests. Several cyclic fatigue test models have been used in endodontics, all capable of providing a curved trajectory for the instrument to rotate. Cyclic fatigue testing allows the identification of conditions that may affect the fatigue strength outcomes, such as the canal radius and degree of curvature, handpiece static versus dynamic motions, test temperature, kinematics, instrument previously wear and sterilization cycles, or instrument's size and metal alloy features. Because of the international test specifications for both torsional and bending tests, the variations of their models are not as many as for cyclic fatigue. These tests have also identified conditions capable of affecting the outcomes, such as kinematics, instruments' preloading, cross-sectional diameters, or alloy heat treatments. Buckling and microhardness are less common, with the metal alloy being considered to have a major influence on the results. Instruments' mechanical testing, having all these individual conditions as independent variables, allowed the understanding of them and molded the way the technical procedures are performed clinically. Even though the artificiality and simplicity of these tests will hardly mimic real working situations, and independent of being capable of producing cornerstone knowledge, these tests are also associated with inconsistency, a lack of reproducibility, and low external validity. Several attempts have been made to increase the generalizability of the outcomes by adding test settings that intend to mimic the clinical condition. Although pertinent, these settings may also add variabilities inherent to their concepts and practical applications in the laboratory environment. Although the actual studies should be seen as laboratory mechanical tests that measure very specific parameters under very particular conditions and that by far do not mimic the clinical condition, the lower validity drawback seems to be possible to be minimized when achieving a comprehensive understanding of the instrument behavior. A finite element method and/or a multimethod research approach may lead to superior data collection, analysis, and interpretation of results, which when associated with a reliable confounding factor control and proper study designs may be helpful tools and strategies in order to increase the reliability of the outcomes.
Topics: Alloys; Dental Alloys; Dental Instruments; Equipment Design; Materials Testing; Mechanical Tests; Nickel; Reproducibility of Results; Root Canal Preparation; Stress, Mechanical; Titanium; Torsion, Mechanical
PubMed: 35667567
DOI: 10.1016/j.joen.2022.05.007 -
Materials (Basel, Switzerland) Aug 2021Nickel-based and cobalt-based metal alloys are frequently used in dentistry. The introduction of various elements in the alloy changes its characteristics, and a...
Nickel-based and cobalt-based metal alloys are frequently used in dentistry. The introduction of various elements in the alloy changes its characteristics, and a thorough study of each alloy should be completed to determine its appropriate corrosion resistance and biocompatibility in contact with physiological fluids. There are scarce investigations on these widely used dental alloys in Ringer solution, and findings in this research bring new experimental data and information. The present study evaluated and compared the corrosion behavior of six NiCr- and two CoCr-based dental materials in Ringer solution, using the following techniques: potentiostatic polarization curves (chronoamperometry), microstructural analysis, and EIS (electrochemical impedance spectroscopy). The results obtained in this investigation showed that in the NiCr-based specimens Ni4, Ni5, and Ni6 the stability of the passive layer was destroyed after polarization and a development and growth of stable pits was found in the microstructural analysis after electrochemical treatment. In terms of susceptibility to corrosion, two different groups of specimens were derived from this investigation. A first group which included the two CoCr (Co1 and Co2) and three of the six NiCr alloys studied (Ni1, Ni2, and Ni3). A second group with the other NiCr alloys investigated Ni4, Ni5, and Ni6.
PubMed: 34501039
DOI: 10.3390/ma14174949 -
Materials (Basel, Switzerland) Sep 2023(1) Background: In dentistry, a reduction in surface roughness is established mostly by conventional mechanical polishing to hinder biofilm adhesion. This is time- and...
(1) Background: In dentistry, a reduction in surface roughness is established mostly by conventional mechanical polishing to hinder biofilm adhesion. This is time- and labor-intensive. Plasma electrolytic polishing is believed to be an effective finishing method due to the reduced treatment time and materials used for applications in dentistry. (2) Methods: Co-Cr-Mo dental alloy samples were sandblasted and prepared with either plasma electrolytic or conventional mechanical polishing. Evaluation of the polishing methods was obtained by atomic force microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. (3) Results: The sandblasted samples showed the highest surface roughness (Heraenium Sun 991 ± 288 nm; Wironit 1187 ± 331 nm). Our results show that with plasma electrolytic polishing, Co-Cr-Mo surfaces can be polished with a surface roughness in the nanometer range, comparable to those achieved by conventional mechanical polishing. Conventional mechanical polishing (Heraenium Sun 134 ± 23 nm; Wironit 114 ± 11 nm) provided lower surface roughness values compared to plasma electrolytic polishing (Heraenium Sun 288 ± 94 nm; Wironit 261 ± 49 nm). We anticipate our pilot study as a starting point for future studies to refine process parameters and quantitative microbiological assays. (4) Conclusions: Plasma electrolytic polishing might have a promising future for polishing dental alloys.
PubMed: 37763500
DOI: 10.3390/ma16186222 -
Chemosphere Mar 2020To determine whether the potential effects on liver and kidney caused by dental alloys could be reduced or terminated by the removal of nickel-chromium (Ni-Cr) alloy,...
To determine whether the potential effects on liver and kidney caused by dental alloys could be reduced or terminated by the removal of nickel-chromium (Ni-Cr) alloy, cobalt-chromium (Co-Cr) alloy, and commercially pure titanium (CP-Ti), they were placed in the cheek pouches of Syrian hamsters according to ISO 10993-10. Then, the peak/plateau and end times of trace metals in the blood were determined with or without the removal of the dental alloys. Based on these time points, the trace metals and their effects on liver and kidney were examined. We found that trace metals released from these dental alloys and titanium were accumulated transiently in the blood, liver, and kidney but had no effect on the histopathology of the liver or kidney. Although the functions of the liver and kidney were compromised, the function of these tissues seemed to be clinically acceptable compared to those in control Syrian hamsters. In addition, the apoptotic effect on renal cells was terminated by removing the Ni-Cr and Co-Cr alloys, and that on hepatocytes was also eliminated by removing the Ni-Cr alloy. In contrast, the effect of the Co-Cr alloy on hepatocytes was temporary and recovered by itself. Taken together, Ni- and Co-based dental alloys and titanium have no effect on the histopathology or function of liver and kidney. Moreover, Ni-Cr and Co-Cr alloys induce transient trace metal accumulation and apoptotic effects in liver and kidney, which can be reduced or terminated by the removal of the alloys, while CP-Ti shows favorable biocompatibility.
Topics: Alloys; Chromium Alloys; Dental Alloys; Kidney; Liver; Materials Testing; Titanium
PubMed: 31726262
DOI: 10.1016/j.chemosphere.2019.125205 -
British Dental Journal Apr 2022
Topics: Composite Resins; Dental Amalgam; Dental Restoration Failure; Dental Restoration, Permanent
PubMed: 35396427
DOI: 10.1038/s41415-022-4163-4 -
The International Journal of Oral &...To examine and compare stress values of implants, highest tensile and compressive values, and their distribution in cortical and trabecular bone near and around the...
PURPOSE
To examine and compare stress values of implants, highest tensile and compressive values, and their distribution in cortical and trabecular bone near and around the implant region using different materials (aramid fiber, glass fiber, polyethylene fiber, carbon fiber, and cobalt-chromium [Co-Cr] alloy). Four dental implants were placed in the maxillary crest with two different location scenarios, and the 3D finite element analysis method was used to evaluate stress characteristics.
MATERIALS AND METHODS
Two maxillary models were created in which the implants were placed in different locations (lateral and first premolar, canine and second premolar). Four implant-supported overdenture prostheses were reinforced, applying Co-Cr alloy, glass fiber, aramid fiber, and carbon fiber. Static loads of 200 N were applied on the first molar region using the food stuff method. Stresses around the implants and denture-bearing areas and compression and tensile stresses on the cortical and trabecular bone were evaluated.
RESULTS
In all tested models, the highest von Mises stresses on implants and prostheses were observed in aramid fiber-reinforced overdentures. This was followed by glass fiber, Co-Cr alloy, and carbon fiber groups, respectively. It was observed that the lowest tensile and highest compression stress values in cortical and trabecular bone occurred in prostheses supported with carbon fiber. In all infrastructure materials, the design in which the implants were placed bilaterally in the lateral teeth and the first premolar region was found to be advantageous in terms of stress levels and distribution.
CONCLUSION
High elastic modulus fiber-reinforced overdenture prostheses transmitted less stress to implants and surrounding tissues than Co-Cr alloy. Anteriorly placed implant design illustrated lower stress values in the prosthesis, implant, and cortical and trabecular bone, and this placement design may increase the survival rates of both dental implants and overdentures. In light of this study, fibers can be recommended for clinical use and securely applied as an alternative material to metal support. Int J Oral Maxillofac Implants 2023;38:523-532. doi: 10.11607/jomi.9946.
Topics: Dental Implants; Denture, Overlay; Finite Element Analysis; Carbon Fiber; Dental Prosthesis, Implant-Supported; Chromium Alloys; Dental Stress Analysis; Stress, Mechanical
PubMed: 37279217
DOI: 10.11607/jomi.9946