Purpose
The aim of this study was to review the effect of selective laser melting (SLM) procedure on the properties of dental structures made of Co‐Cr alloys and to evaluate its quality and compare ...it to those produced by conventional casting and milling fabrication techniques.
Materials and Methods
A computerized database search using PubMed and Scopus was conducted for peer‐reviewed scientific research studies regarding the use of SLM in Co‐Cr dental alloys with no restrictions for publication years. The search engines provided hundreds of results, and only 48 scientific research papers, case studies, or literature reviews were considered relevant for this review.
Results
The innovative manufacturing concept of SLM offers many advantages compared with casting and milling fabrication techniques. SLM provides different microstructure from casting and milling with minimal internal porosity and internal fitting, marginal adaptation, and comparable bond strength to porcelain. Mechanical and electrochemical properties of SLM structures are enhanced compared to cast, while clinical longevity of single‐metal ceramic crowns is comparable to Au‐Pt dental alloy.
Conclusion
The SLM technique provides dental prosthetic restorations more quickly and less expensively without compromising their quality compared with restorations prepared by casting and milling techniques. Clinical significance: The current SLM devices provide metallic restorations made of Co‐Cr alloys for removable and fixed partial dentures without compromising the alloy or restoration properties at a fraction of the time and cost, showing great potential to replace the aforementioned fabrication techniques in the long term; however, further clinical studies are essential to increase the acceptance of this technology by the worldwide dental community.
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.
Display omitted
•Trace metals released from dental alloys and titanium are accumulated transiently in peripheral blood.•Trace metals in peripheral blood decrease sharply after removal of dental alloys and titanium.•Ni-Cr and Co-Cr alloys induce transient increment of trace metals and apoptotic effect on liver and kidney.•Trace metals and apoptotic effect on liver and kidney are reduced or terminated by removal of dental alloys and titanium.•Ni- and Co-based alloys and titanium have no effect on histopathology or function of liver and kidney.
Highlights • Heterogeneous macro-micro and nanostructures were formed in the CoCrMo alloys prepared by SLM. • The interlocking of “weld lines” and elongated grains generated 3D textures resembling ...weaved fabrics. • The formed textures compensated the micro-faults making the SLM CoCrMo alloys “defects-tolerant”.
Background
Fixed prosthodontic treatment (crowns, fixed dental prostheses (FDPs), complete arch prostheses) involves the use of several different materials to replace missing tooth structure. ...Traditionally full metal or metal frameworks veneered with ceramic (metal‐ceramic (MC)) have been used. In recent years several different metal‐free systems have become available to clinicians and patients. In general, metal‐free restorations should allow practitioners to better reproduce natural tooth colour, avoiding shortcomings of MC restorations. The comparative in service clinical performance of fixed prosthodontic treatments of different materials is unclear.
Objectives
To assess the effects of metal‐free materials for prosthodontic restorations compared to metal‐ceramic or other conventional all‐metal materials.
Search methods
Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (searched 3 May 2017), Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 4) in the Cochrane Library (searched 3 May 2017), MEDLINE Ovid (1946 to 3 May 2017), and Embase Ovid (1980 to 3 May 2017). The US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials (searched 3 May 2017). No restrictions were placed on the language or date of publication when searching the electronic databases.
Selection criteria
Randomised controlled trials (RCTs) in which the clinical performance of metal‐free fixed prosthodontic restorations was compared with metal‐ceramic (MC) or other conventional restorations in adult patients requiring prosthodontic treatment. RCTs in which the clinical performance of different kinds of metal‐free systems were compared among themselves were also considered.
Data collection and analysis
We used standard methodological procedures expected by Cochrane. Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted independently and in duplicate. Trial authors were contacted for missing information. Available results for the outcomes of interest of the systematic review of the studies included were tabulated as they could not be included in a formal meta‐analysis.
Main results
Nine trials involving a total of 448 participants were included. We judged two trials to be at unclear risk of bias and seven to be at high risk of bias. The majority of items of risk of bias were evaluated to be at unclear or high risk level in more than 50% of the included trials. Each trial except two was addressing a different type of intervention. All evidence was rated as being of very low quality due to problems with risk of bias and imprecision of results, the latter being due to very small sample sizes, low event rates, 95% confidence intervals including the possibility of benefit for both the test and control groups, or combinations of these problems. This means that we are very uncertain about all of the results presented in this review.
One trial compared metal‐free single crowns (full contour zirconia) to cast gold single crowns in 224 participants and found insufficient evidence of a difference in failure rate after one year, but after five years there was some evidence of a benefit for the gold crowns. There was insufficient evidence of a difference for crown complications at either time of assessment.
One trial compared three‐unit metal‐free FDPs (lithium disilicate) to three‐unit metal‐ceramic FDPs in 37 participants. There was insufficient evidence of a difference in bridge failure at one and six years, but some evidence of a benefit for the lithium disilicate group in terms of bridge complications at six years. One trial compared zirconia‐ceramic FDPs to metal‐ceramic FDPs in 34 participants but found insufficient evidence of a difference in bridge failures (i.e. no failures in either treatment group), bridge complications or patients' aesthetic evaluation at any time of assessment up to three years.
One trial compared metal‐free cantilevered FDPs to metal‐ceramic cantilevered FDPs in 21 participants. There was insufficient evidence of a difference for any primary outcome: bridge failures (i.e. no failures in either treatment group), bridge complications, or patients' aesthetic evaluation at any time of assessment up to three years.
One trial compared metal‐free implant‐supported screw retained single crowns (zirconia veneered with feldspathic ceramic) to metal‐ceramic implant‐supported screw‐retained single crowns in 20 participants. There was insufficient evidence of a difference for any primary outcome: crown failures (i.e. no failures in either treatment group), crown complications, or satisfaction/aesthetic evaluation at any time of assessment up to two years.
Two trials compared metal‐free implant abutments (zirconia) to metal implant abutments both supporting single crowns in 50 participants. There was insufficient evidence of a difference in abutment failure at one year.
One trial compared metal‐free implant‐supported FDPs made of two different types of zirconia ceramic in 18 participants. There was insufficient evidence of a difference in failures at any time of assessment up to 10 years (i.e. no failures in either treatment group). There was some evidence of a benefit for the zirconia‐toughened alumina group in terms of complications (chipping).
One trial compared metal‐free tooth‐supported FDPs made with two different veneering techniques (pressed versus layered) in 40 participants. There was insufficient evidence of a difference for failures (i.e. no failures in either treatment group) or complications at any time of assessment up to three years.
Authors' conclusions
There is insufficient evidence to support or refute the effectiveness of metal‐free materials for fixed prosthodontic treatment over metal‐ceramic or other type of standard restorations. The overall quality of existing evidence was very low, therefore great caution should be exercised when generalising the results of the included trials. Until more evidence becomes available clinicians should continue to base decisions on which material to use for fixed prosthodontic treatment on their own clinical experience, whilst taking into consideration the individual circumstances and preferences of their patients. There is urgent need of properly designed RCTs.
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.
Display omitted
•Binary and ternary Ti alloys were developed.•Ti–Zr alloys exhibited enhanced hardness and electrochemical stability.•Ti–Nb–Zr alloys presented an elastic modulus closer to that of ...bone.•The experimental alloys were not detrimental to albumin adsorption.•The experimental alloys may be considered a suitable candidate for dental implants.
The aim of this study was to develop binary and ternary titanium (Ti) alloys containing zirconium (Zr) and niobium (Nb) and to characterize them in terms of microstructural, mechanical, chemical, electrochemical, and biological properties.
The experimental alloys — (in wt%) Ti–5Zr, Ti–10Zr, Ti–35Nb–5Zr, and Ti–35Nb–10Zr — were fabricated from pure metals. Commercially pure titanium (cpTi) and Ti–6Al–4V were used as controls. Microstructural analysis was performed by means of X-ray diffraction and scanning electron microscopy. Vickers microhardness, elastic modulus, dispersive energy spectroscopy, X-ray excited photoelectron spectroscopy, atomic force microscopy, surface roughness, and surface free energy were evaluated. The electrochemical behavior analysis was conducted in a body fluid solution (pH 7.4). The albumin adsorption was measured by the bicinchoninic acid method. Data were evaluated through one-way ANOVA and the Tukey test (α=0.05).
The alloying elements proved to modify the alloy microstructure and to enhance the mechanical properties, improving the hardness and decreasing the elastic modulus of the binary and ternary alloys, respectively. Ti–Zr alloys displayed greater electrochemical stability relative to that of controls, presenting higher polarization resistance and lower capacitance. The experimental alloys were not detrimental to albumin adsorption.
The experimental alloys are suitable options for dental implant manufacturing, particularly the binary system, which showed a better combination of mechanical and electrochemical properties without the presence of toxic elements.
Removable or fixed dental frameworks are usually made of CoCr alloys. The CoCr dental alloys are produced traditionally by lost‐wax casting. However, alternative processing routes, such as ...hot‐pressing, are being studied for dental applications. The purpose of the present work was to assess the corrosion resistance of CoCrMo dental alloy produced by conventional lost‐wax casting and hot‐pressing. The corrosion behavior was studied in artificial saliva at 37°C by potentiodynamic polarisation tests. Immersion tests were performed to evaluate the growth of the passive film where electrochemical impedance spectroscopy was used at different immersion periods. Results showed slightly better corrosion resistance in terms of ipass for CoCrMo samples obtained by hot‐pressing. On the other hand, the immersion tests showed a more stable and thicker passive film formed on hot‐pressed CoCrMo dental alloy, pointing out that hot‐pressing may be considered a promising technique to produce CoCrMo dental structures.
The influence of the processing method (conventional lost‐wax casting and hot‐pressing) of CoCrMo dental alloy on the corrosion behavior was studied in artificial saliva at 37°C by potentiodynamic polarisation, and electrochemical impedance spectroscopy through different immersion periods. Results show that hot‐pressing led to the formation of a more stable passive film.
•Platinum and nine noble metal dental alloys were investigated according to ISO 10271.•The different electrochemical parameters in 0.9 % NaCl were determined and discussed.•Based on the ...electrochemical behavior, alloys were classified according to the noble metal (Au, Pt and Pd) content.•The classification was proposed using classification of of the American Dental Association.
Platinum and nine commercial dental alloys with the contents of noble metals ranging from 27 wt.% to 97.6 wt.% were investigated by the procedure described in the Standard ISO 10271:2009, Electrochemical testing was performed in an argon purged solution of 0.9 % NaCl at pH = 7.2. The obtained values of the characteristic determined parameters of the alloys with different noble metal content, treating only Au, Pt, and Pd as noble, were compared with the American Dental Association (ADA) classification system. Based on the obtained results, the considered noble metal dental alloys were classified into three groups.
Implant-associated infections (IAIs) are a dreaded complication mainly caused by biofilm-forming staphylococci. Implant surfaces preventing microbial colonization would be desirable. We examined the ...preventive effect of a silver-coated titanium-aluminum-niobium (TiAlNb) alloy. The surface elicited a strong, inoculum-dependent activity againstStaphylococcus epidermidisandStaphylococcus aureusin an agar inhibition assay. Gamma sterilization and alcohol disinfection did not alter the effect. In a tissue cage mouse model, silver coating of TiAlNb cages prevented perioperative infections in an inoculum-dependent manner and led to a 100% prevention rate after challenge with 2 × 10(6)CFU ofS. epidermidisper cage. InS. aureusinfections, silver coating had only limited effect. Similarly, daptomycin or vancomycin prophylaxis alone did not preventS. aureusinfections. However, silver coating combined with daptomycin or vancomycin prophylaxis thwarted methicillin-resistantS. aureusinfections at a prevention rate of 100% or 33%, respectively. Moreover, silver release from the surface was independent of infection and occurred rapidly after implantation. On day 2, a peak of 82 μg Ag/ml was reached in the cage fluid, corresponding to almost 6× the MIC of the staphylococci. Cytotoxicity toward leukocytes in the cage was low and temporary. Surrounding tissue did not reveal histological signs of silver toxicity.In vitro, no emergence of silver resistance was observed in several clinical strains of staphylococci upon serial subinhibitory silver exposures. In conclusion, our data demonstrate that silver-coated TiAlNb is potent for prevention of IAIs and thus can be considered for clinical application.
Dental implants are often made of titanium alloys. Implant therapy currently promises a good long-term result without impacting health; however, its success depends on many factors. In this article, ...the authors focus on the most common risk factors associated with metallic surgical implants. Titanium-induced hypersensitivity can lead to symptoms of implant rejection. Corrosion and biofilm formation are additional situations in which these symptoms may occur. For medical purposes, it is important to define and discuss the characteristics of metals used in implantable devices and to ensure their biocompatibility. To avoid hypersensitivity reactions to metallic dental implants, precautionary principles for primary prevention should be established.
PDF
