Dental Casting Alloys Research Articles

Processing and characterization of beryllium free Ni–Cr–Mo biomaterial doped with cerium, boron and titanium for dental applications

Dental restoration has been a major concern of healthcare since centuries. Several alloys are in use for dental prostheses including Ni–Cr–Mo alloy. The Ni–Cr–Mo alloy has advantage of economy and density over other alloys, while possessing equivalent corrosion and biocompatibility characteristics. However, beryllium in Ni–Cr–Mo dental casting alloys has associated health hazards, being carcinogenic. In this research Ni–Cr–Mo alloys with minor additions of boron (0.2 wt %), cerium (0.4 wt %) and titanium (2 wt %), to replace beryllium were developed through vacuum induction melting and investment casting technique. Manufacturing steps are detailed for the alloy development to have medically clean alloy, suitable for biomedical applications. The cast alloy samples were tested for microstructure, phases, melting temperatures, wear and corrosion characteristics. Corrosion and wear test results demonstrate that the composition with minor addition of cerium had a significant effect to have low corrosion rate (25.92 × 10−3 mills per year), low wear rate (0.04 × 10−4 mm3/N.m) and lowest coefficient of friction.

Effect of Artificial Saliva Modification on the Corrosion Resistance and Electronic Properties of Bego Wirobond® C Dental Alloys

Wirobond® C is a commercial dental casting alloy suitable for the fabrication of crowns, bridges, and metal ceramic restorations. This study aims to investigate the effect of ready-to-use Listerine® and Meridol® mouthwashes and sodium fluoride on the resistance of CoCrMo dental alloys to electrochemical corrosion in artificial saliva at 37 °C. SEM, EDS, SKP, and microhardness investigations were carried out to characterize the material under study. The in vitro corrosion resistance of the CoCrMo alloy was conducted using the open-circuit potential method, electrochemical impedance spectroscopy, and anodic polarization curves. The presence of Co 59.8(8) wt.%, Cr 31.5(4) wt.%, and Mo 8.8(6) wt.% was confirmed. The CoCrMo alloy was characterized by a Vickers microhardness value of 445(31) µHV0.3. Based on the EIS data, the capacitive behavior and high corrosion resistance of the CoCrMo alloy were revealed. The kinetics of pitting corrosion in the artificial saliva were lower after being modified with NaF, Listerine®, and Meridol® mouthwashes. The potentiodynamic characteristics revealed the passive behavior of the CoCrMo alloy in all solutions. Based on the SKP measurements of the CoCrMo alloy after corrosion tests, the effect of artificial saliva modification on the electronic properties of Bego Wirobond® C dental alloy was found.

Effect of cerium on mechanical, metallurgical and biomedical properties of NiCrMoB dental alloy

NiCrMo alloys are popular as non-precious dental casting alloys and appreciated specially in developing nations. A number of elements may be alloyed to achieve enhanced characteristics suitable for dental restorations. In this study NiCrMo dental casting alloy was alloyed with cerium to improve mechanical, metallurgical and biomedical characteristics. Three alloys were produced by vacuum induction melting technique. These cast alloys were tested for melting range, phase analysis, microstructure, mechanical and wear characteristics, corrosion behavior, coefficient of thermal expansion and biocompatibility properties. Test results revealed that 0.4% cerium addition in NiCrMoB alloy substantially improved the mechanical, metallurgical and corrosion characteristics of the cast alloy without compromising the biocompatibility and melting characteristics of the alloy. Mechanical testing and tribological results pointed out that the NiCrMoB alloy with 0.4% addition of cerium possessed tensile strength up to 515 MPa with impact strength around 7 J, while average coefficient of friction was calculated to be 0.1715; that was least of the investigated alloys. Corrosion rate for the alloy was found to be 25.92 × 10−3 mils per year that was also the least among the investigated alloy samples.

Estimating Ni, Cr, Co, and Mo release from 3 dental casting alloys in saliva and blood at 6 and 12 months by using inductively coupled plasma mass spectroscopy

Statement of problemThe leaching of elements from long-term definitive prostheses, with saliva acting as an electrolyte, poses a biological concern. The approximate concentration in the biological samples that are considered clinically toxic ranges from 1 to 5000 nmol/L for Cr and Co, 1 to 200 nmol/L for Ni, and 1 to 20 nmol/L for Mo. While in vitro studies are available regarding the leaching of elements in artificial saliva, solutions containing protein, solutions of different pH, and different culture media, the in vivo effects of leaching in the biological sample with increasing time are unknown. PurposeThe purpose of this clinical study was to quantify the Ni, Co, Cr, and Mo metals in saliva and blood before and after restoration with prostheses made from 3 different brands of dental casting alloy at 6 and 12 months. Material and methodsThree popular brands of Ni-Cr alloy with different compositions were evaluated. A total of 150 participants requiring a definitive prosthesis were enrolled and divided into 3 groups (n=50). Heavy metal levels from saliva and blood were measured by using the inductively coupled plasma mass spectroscopy method before cementation of the prosthesis and after 6 and 12 months. ResultsThe presence of Ni in saliva was in the range of 10.34 to 12.12 μg/L, Cr was 1.04 to 1.22 μg/L, and Mo was 1.04 to 1.08 μg/L over a period of 6 and 12 months after cementation of the metal prosthesis. The presence of Ni in blood was in the range of 6.35 to 14.45 μg/L and that of Cr was 9.09 to 16.16 μg/L over a period of 6 and 12 months after cementation. Co levels were not detected from any brands in saliva or blood, and Mo was detected only in the saliva samples. ConclusionsIncreased levels of Ni and Cr in saliva and blood from all 3 brands of base metal alloy at 6 and 12 months were observed at higher than threshold values.

Corrosion Behavior of Dental Alloys Under Artificial Saliva Solution with Different pH Values

The purpose of this study was to investigate the corrosion behavior of four different dental casting alloys in artificial saliva solutions with varying pH values. Microstructures were observed using scanning electron microscopy. The corrosion behavior of the experimental alloys in artificial saliva was examined using potentiodynamic polarization measurements. The high noble alloy (Au-8.5Pt-2.6Pd-1.4In) exhibited better corrosion resistance with lower anodic current densities in the pH range of 3–5. The anodic current density of the noble alloy (Au-24.9Pd-19.0Ag-5.5In) decreased as the pH decreased. The noble (Pd-37.7Ag-8.5Sn) and base metal (Ni-25Cr-11.5Mo-1.4Si) alloys exhibited lower corrosion resistance with a relatively high current density at pH 3. Compared with noble alloys, base metal alloys exhibited good corrosion resistance in this study. This makes them a promising material for dental castings considering the complex pH changes in the oral environment.

Effect of Mouthwash on Release of Elements from Dental Casting Alloys: An In-vitro Study

Introduction: Mouthwashes are regularly prescribed as a maintenance phase of treatment by the dentist. The pH of the mouthwash can enhance the elemental release from the cemented prosthesis. Aim: To evaluate the effect of two types (Oral-B and Listerine) of mouthwashes on the release of elements from Nickel-Chromium (Ni-Cr) dental alloys. Materials and Methods: An in-vitro comparative study was conducted in the Department of Prosthodontics, School of Dental Sciences, Karad, Maharashtra, India, from April 2018 to April 2022. A total of 90 crowns were fabricated using three different brands of dental casting alloys (DCA) using lost wax technique. The crowns were immersed into two different mouthwashes (Oral-B and Listerine) in polypropylene test tubes, and then incubated at 37°C to simulate the oral temperature for 1, 4, and 7 days. The leaching of the elements from the fabricated crowns into the mouthwashes was analysed using inductively coupled plasma mass spectrometry (ICP-MS). Data analysis was performed using the t test and repeated measure Analysis of Variance (ANOVA) followed by post hoc Dunnett Multiple Comparisons Test. Results: The Ni and Cr levels in the mouthwashes were significantly elevated in brand I (Ruby, Japan Dentistry Products Pvt. Ltd.), brand II (Dentmark, R&D Impex International), and brand III (BEGO, GmbH & Co KG). Presence of Ni released from all the three brands of DCA in mouthwash over a period of 1, 4, and 7 days was detected to be in the range of 16 to 39.9 µg/L. Cr released from all the three brands of DCA in mouthwash over a period of 1, 4, and days was detected to be in the range of 10.3 to 42.8 µg/L. Conclusion: The Ni and Cr were released in the mouthwash and the release increased with time. The acidic pH of Listerine adds to the increased release of Ni and Cr.

Effects of Casting Methods over the Composition Stability of the Dental Casting Alloy

Introduction: Alloys with high nickel content have been increasingly used for dental prostheses. The dental casting machines are regularly used to make dental restorations. The effects of the casting of the base metal alloys using actyleneoxygen flame casting machine and induction casting machine has not much been studied. Aim: To estimate nickel, chromium, cobalt, and molybdenum metals from as-received dental casting alloy of three different brands and to estimate metals from these alloys after fabrication of crown using actylene-oxygen flame casting machine and induction casting machine. Materials and Methods: This in-vitro comparative study was conducted in the Department of Prosthodontics at School of Dental Sciences, KIMSDU, Karad, Maharashtra, India. Total of 15 crowns were fabricated using actylene-oxygen flame casting machine and 15 crowns by induction casting machine from three different brands of Dental Casting Alloys (DCA) by lost wax technique. Elemental estimation was done for the asreceived pellets and for the crowns fabricated by both methods using X-ray Florescence spectrometry (XRF). Unpaired t-test was used for data analysis. Results: Nickel (Ni), chromium (Cr) and molybdenum (Mo) levels in crowns fabricated by both actylene-oxygen flame casting and Induction casting technique were significantly decreased (Ni: -2.01% to -5.14%, Cr:-7.35% to -29.51% and Mo: -15.70% to -95.94%) in all brands of dental casting alloys. Cobalt level was not detected in all three brands of fabricated crowns by XRF by either of the casting methods. Conclusion: These observations indicate that the elemental composition of the fabricated crowns is decreased as compared to that of As-received crowns, which could be due to the burnout of some amount of elements during casting.

Accuracy of 3D Printed Burnout Resin Versus CAD/CAM Milled Wax Castings

Objectives: The purpose of this study is to evaluate the accuracy of 3D printed burnout resin, CAD/CAM milled wax and CAD/CAM PMMA and the effect on die spacing and cementation onto the tooth. Method: Design and manufactured three different type of digital materials, PMMA, milled wax and 3D printed burnout resin (n=4/product). PMMA and milled wax were milled by MC X5 CAD/CAM machine and 3D printed resin was produced by Asiga Max. Scanning the crowns sprayed by Shera scan spray using INEOS extraoral scanner to create STL files exported for comparison with master crown. We invest (90% to 10% Shera to distal water ratio) using Shera Fina 2000 investment material and cast with Sirona PFM dental cast alloy. Devasting and grinding out the excess alloy around the crown with a 3.3 bar pressure sandblasting. Repeating the scanning processes with casted crowns and compare the STL files in cloud-compare software. Using Auto Mesh to cut half the crown to make the result accurate. Comparing both before and after casting crown in STL files using cloud-compare software and get absolute mean and RMS value for each crown. The data points on each crown is already large enough, so we don’t use p value in our study. Results: CAD/CAM milled wax, PMMA and 3D printed burnout resin all found some of the abs mean and RMS value increase before and after casting compared to master crown. Milled wax has the least difference followed by 3D printing and PMMA. PMMA is the least accurate material in this experiment which would vary the amount of die spacer and cementation. Significance: High inaccuracies of PMMA material might affect the actual die spacing and cementation value, whereas milled wax performed the best. Milled wax and 3D printed resin are both within the clinical acceptable value.

Influence of the Commercial Mouthwashes on the Corrosion Behaviour of Dental Alloy

Dental alloys are widely used in fabrication of removable partial dentures, particularly as a dental framework. The present study aimed at studying the effect of the commercial mouthwashes on the corrosion behavior of the Co−Cr dental casting alloy. Corrosion behavior was investigated in alcohol-free and alcohol-containing mouthwashes added to artificial saliva solutions at room temperature by electrochemical tests recorded the open circuit potential (OCP) and current density, after the surface analysis of the samples was performed. During the early 250s, the OCP values showed significant changes, with the exception of one test group containing alcohol, where potential decreased continuously during the test, which also recorded the highest current density, different from the other groups. It was observed that the presence of alcohol increased the current density and the corrosion process in this alloy and the mouthwashes had more aggressive action in specimens submitted to solutions with alcohol in the composition.

A fogászati kerámiaanyagok fejlődésének történeti áttekintése

Initially, ceramics - mostly burnt clay - were used to manufacture container pottery. The first porcelain objects reached Europe out of China in the Medieval Ages. The technique of their manufacturing was a mystery for many hundred years, yet Germans succeeded first to produce fine European porcelain at the beginning of the 18th century. Its elegance and hardness woke the dentists’ interest too thus Frenchmen created the first porcelain dentures in the second half of the 18th century. Since then, there has been an increasing demand for esthetic fixed implant dentures instead of removable ones. The development of ceramic materials resulted in better mechanical and optical properties, thus the first fixed porcelain inlays and jacket crowns were introduced already in 1889. The addition of leucite filler crystals to porcelain in the 20th century increased the thermal expansion of the ceramic. It could be fired on common dental casting alloys, so the first porcelain-fused-to-metal (PFM) crown was created in 1962. Several new techniques were developed from the middle of the 1980s to the end of the 1990s to deal with initial shrinkage and achieve better properties. Beyond casting, pressing, and CAD/CAM technology, additive manufacturing opened new perspectives in dentistry several years ago in processing dental ceramics.

Densification and Mechanical and Antibacterial Properties of Low-Cost Powder Metallurgy TiCu Intermetallic Alloy as a Potential Biomedical Material

Ti-Cu intermetallic alloys are considered as a potential substitute for conventional dental cast alloys due to their enhanced mechanical, antibacterial, and biocompatibility behaviors. In this paper, the effects of sintering temperature on the densification, hardness, and antibacterial activity of a Ti-Cu alloy obtained by a solid-state reaction have been studied. The TiCu and Ti2Cu3 phases were identified as the major phases in the microstructure of the synthesized material. The high hardness of ≈ 1000 HV and high antibacterial activity against S. aureus and E. coli were obtained for the Ti-Cu intermetallic alloy. The high hardness of the Ti-Cu alloy was attributed to its nanocrystalline grains, multi-phase structure and the large amounts of hard TiCu and Ti2Cu3 phases in the microstructure, and its antibacterial behavior was due to the release of Cu2+ ions around the sample in culture media of bacteria.

The effects of recasting on the cytotoxicity of dental base metal casting alloys.

Aim and Objectives:In dentistry, base metal casting alloys are extensively used for the fabrication of inlays, onlays, crowns, bridges, partial dentures, etc. During the casting of these alloys, excess amount of material used than needed will be collected as sprue buttons at the end, which is either added to the fresh alloy during casting and reused or disposed of.Materials and Methods:The aim of the present in vitro experimental study was to investigate the effect of the complete recasting of four commercially available cobalt-chromium (Co-Cr) and nickel-chromium (Ni-Cr) base metal casting alloys on their cytotoxicity. During the study, four groups of alloys were subjected to complete recasting up to twenty times without the addition of new alloy. The cytotoxicity assessment of the selected alloys after recasting (Co-Cr and Ni-Cr alloys) was carried out using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.Results:The results indicated that Co-Cr alloys exhibit superior cell viability compared to Ni-Cr alloys, and cytotoxic potential of the alloys increased with repeated casting and led to increased cell death. The recasting of alloys in the present study did not show high cytotoxicity even after the 20th recasting.Conclusion:From the results of the present study, it can be concluded that the alloys generated as a waste in the dental laboratory can be safely reused up to five times or at least once before they can be disposed, which reduces the cost of the treatment and also helps in conserving the natural resources.

Periodontal clinico-morphological changes in patients wearing old nickel–chromium and copper alloys bridges

Elderly population frequently presents more than one prosthetic restoration realized from different types of dental alloys which, in time, suffer various alterations in the oral environment. Metallic ions are released in saliva due to its electrolytic qualities, interacting with the contact tissues. Studies regarding cytotoxicity of dental alloys are providing contradictory results. Besides biocompatibility, the microbial factor is also greatly influencing the long-term success of the prosthetic rehabilitation. This study’s aim was to assess the response of the gingival tissue to nickel–chromium (Ni–Cr) and copper (Cu)-based dental casting alloys from fixed dentures present in many patients from Romania. Gingival samples were taken from 124 patients wearing fixed dental restorations made from these two types of alloys from injured areas surrounding the abutment teeth; histological specimens were prepared, fixed in 10% neutral buffered formalin, paraffin-embedded and stained with Hematoxylin–Eosin (HE). Histological analysis showed the existence of a chronic inflammatory infiltrate in the gingival chorion, necrosis areas, and vascular congestion. Various morphological alterations appeared, depending on the intensity of the inflammation and the immune response. The surface epithelium suffered a hyperplasic reaction, either limited to acanthosis or involving the whole epithelium, the release of the Cu2+ and Ni2+ ions from the dental alloys used in bridges and crowns being responsible for inducing gingival hyperplasia and a chronic inflammation in the areas situated around the abutment teeth. The immunohistochemical study allowed us to observe an increased number of positive cluster of differentiation 3 (CD3) T-lymphocytes in periodontium, proving that the cellular immune response is rapid and intense.

Chemical, Physical, and Mechanical Properties and Microstructures of Laser-Sintered Co-25Cr-5Mo-5W (SP2) and W-Free Co-28Cr-6Mo Alloys for Dental Applications.

We examined the chemical, physical, and mechanical properties and microstructures of laser-sintered Co–25Cr–5Mo–5W (SP2) and W–free Co–28Cr–6Mo alloys. The tensile and fatigue properties of the laser-sintered Co–Cr–Mo alloys were extremely superior to those of dental-cast alloys. The ultimate tensile strength (σUTS) and total elongation (T.E.) were close to those of hot-forged Co–28Cr–6Mo alloys. The fatigue strengths (σFS) at 107 cycles of the 90°-, 45°-, and 0°-direction-built Co–28Cr–6Mo alloys were ~500, ~560, and ~600 MPa, respectively. The ratio σFS /σUTS was ~0.4. These superior mechanical properties were attributed to the fine π-phase particles in the grains and grain boundaries of the fine face–centered cubic (fcc) matrix formed owing to the rapid solidification. The chemical composition of 20-times-laser-sintered Co–Cr–Mo alloy without the virgin powder added was approximately the same as that of the alloy laser-sintered with the virgin powder. σFS of the 90°-direction-built alloys after laser sintering 20 times was also ~500 MPa. σUTS of hot-forged Co–28Cr–6Mo alloys decreased with increasing annealing temperature, whereas T.E. increased. For the Co–Cr–Mo alloys annealed at 1000 to 1150 °C for 30 min after laser sintering, the rates of decrease in σUTS were small. σFS/σUTS increased to near those of annealed Co–28Cr–6Mo alloys after hot forging. The durability of clasps fabricated by laser sintering was superior to that of dental-cast clasps.

Interaction of Saliva with Cobalt-Chromium-Based Dental Alloys in Casted Prosthetic Pieces

Cobalt-chromium-based (CoCr) alloys are more frequently used in dental field compared with the precious metal alloys because they are cheaper, resistant to corrosion and compatible with dental ceramic that is used as aesthetic component of prosthetics. The physical properties of CoCr based alloys available on the dental materials market are variable, depending on the concentrations of elements such as tungsten (W) and molybdenum (Mo). This study assessed the corrosion behavior and surface properties of five commercially available CoCr alloys with different contents of W and Mo. Firstly, the alloy casted samples were analyzed from the corrosion's point of view in artificial saliva (Ringer Solution). A current potential was applied to the surfaces for 120min, in an open circuit. Secondly, the specimens of dental casting alloys (CoCrMo, CoCrMoW and CoCrW alloys) were oxidized at high-temperature. All the samples were analyzed with a scanning electron microscope (SEM) and microscopic images of the oxide films on the alloys surface were captured. The high content W alloys showed a linear and stable anticorrosion tendency in an open circuit current potential applied to the surface, in artificial saliva compared with the alloy without W, whose passive layer broke and recreated at the same potential. The SEM analyses showed that the CoCr-based alloys with 15% wt. content of W had created a stable oxide layer, with a higher density than the alloy without W. In conclusion, the stability and resistance of oxide passive layer on CoCrW alloys surface had better anti-corrosion properties than the CoCrMo alloys. CoCr-based alloys with W content can be used as a single casted alloy for prosthetics dental structures, avoiding bimetallism and the corrosive effect in contact with saliva.

Interaction of Saliva with Cobalt-Chromium-Based Dental Alloys in Casted Prosthetic Pieces

Cobalt-chromium-based (CoCr) alloys are more frequently used in dental field compared with the precious metal alloys because they are cheaper, resistant to corrosion and compatible with dental ceramic that is used as aesthetic component of prosthetics. The physical properties of CoCr based alloys available on the dental materials market are variable, depending on the concentrations of elements such as tungsten (W) and molybdenum (Mo). This study assessed the corrosion behavior and surface properties of five commercially available CoCr alloys with different contents of W and Mo. Firstly, the alloy casted samples were analyzed from the corrosion's point of view in artificial saliva (Ringer Solution). A current potential was applied to the surfaces for 120min, in an open circuit. Secondly, the specimens of dental casting alloys (CoCrMo, CoCrMoW and CoCrW alloys) were oxidized at high-temperature. All the samples were analyzed with a scanning electron microscope (SEM) and microscopic images of the oxide films on the alloys surface were captured. The high content W alloys showed a linear and stable anticorrosion tendency in an open circuit current potential applied to the surface, in artificial saliva compared with the alloy without W, whose passive layer broke and recreated at the same potential. The SEM analyses showed that the CoCr-based alloys with 15% wt. content of W had created a stable oxide layer, with a higher density than the alloy without W. In conclusion, the stability and resistance of oxide passive layer on CoCrW alloys surface had better anti-corrosion properties than the CoCrMo alloys. CoCr-based alloys with W content can be used as a single casted alloy for prosthetics dental structures, avoiding bimetallism and the corrosive effect in contact with saliva.

Considerations on determining the castability of dental casting alloys

Castability is, along with biocompatibility, one of the most important characteristics of metallic materials used for dental prosthetic applications. In addition, the characteristics and performance of the employed casting machine are also decisive for the end result of the casting, especially when dealing with titanium or a titanium alloy. Starting from a critical analysis of the existing methods for determining the castability of dental alloys, the current paper presents a new method (and associated pattern) for determining the castability. Also, given the castability’s dependence on the type of casting machine, the paper includes an analysis of suitable casting machines and suggests some possible improvements.

The Effect of Recasting on the Castability of Prepared Nickel-Chromium Dental Base-Metal Casting Alloy

Background: Evaluation the effect of recasting process on the castability value of prepared Ni-Cr dental base-metal casting alloy and compare it with other conventional alloy.Materials and methods: The prepared Ni-Cr alloy was locally prepared in Iraq by Al- Khafagy (2003), while the CB Blando Ni-Cr was used as conventional alloy. A wax mash of 1mm opening and (10*10) segments square was invested in phosphate-bonded investment and casted by using induction casting machine. The number of complete cast segments was counted, divided by (220) and multiplied by (100) to obtain a percentage designated the castability value (Cv).Results and discussion: The prepared Ni-Cr alloy samples were showed lower castability values than the conventional alloy, this may be related to unalloyed silicon and manages and loss the role of these elements in improvement of castability of prepared Ni-Cr alloy. The castibility value was decreased as the percentage of used alloy increased, however, ANOVA test revealed a non significant differences within the groups. Practically, the experimental and conventional alloys could be recastd if the recasted process will not affect the other properties of such alloys.

Effect of recasting on element release from base metal dental casting alloys in artificial saliva and saline solution.

Aim:The aim of this study was to quantitatively estimate the concentration of ion release from recasted base metal alloys in various pH conditions using atomic absorption spectroscopy (AAS).Materials and Methods:Specimens of commercially available dental casting alloys (cobalt [Co]-chromium [Cr] and nickel [Ni]- chromium [Cr]) were prepared using lost-wax casting techniques and were stored in the test solution for 1 week and 4 weeks, and ions released during chemical corrosion were detected using AAS.Results:An increase in the quantity of ion release was observed with recasting. These changes were higher after twice recasting in Ni-Cr alloy.

Immunostimulatory capacity of dental casting alloys on endotoxin responsiveness

Statement of problemOral metal exposure has been associated with systemic and local adverse reactions, probably due to elemental release from the alloys. Although supraphysiological concentrations of salts from dentally applied metals can activate innate cells through TLR4 (Ni, Co, Pd) and TLR3 (Au), whether direct exposure to solid alloys can also trigger innate immune reactivity is still unknown. PurposeThe purpose of this in vitro study was to determine whether dental cast alloy specimens can activate innate cells and influence their responsiveness to bacterial endotoxin. Material and methodsHuman monocyte-derived dendritic cells (MoDC) and THP-1 cells were cultured on top of different alloy specimens (Ni-Cr, Co-Cr, Pd-Cu, Pd-Ag, Ti-6Al-4V, amalgam, gold, and stainless steel) or in alloy-exposed culture medium with or without endotoxin (lipopolysaccharide [LPS]; Escherichia coli 055:B5). Interleukin-8 (IL-8) production was used as the parameter for innate stimulation and evaluated by enzyme-linked immunosorbent assay after 24 hours of culture. The statistical significance of the effects of various casting alloys on the secretion of IL-8 was analyzed by using the nonparametric Wilcoxon rank sum test (α=.05). ResultsDental cast alloys induced IL-8 production in MoDC and THP-1 cells, with Au and Pd-Cu providing the strongest stimulation. The alloy-exposed culture media tested contained sufficient stimulatory metal ions to induce detectable IL-8 production in THP-1 cells, except for the Ni-Cr and stainless steel exposed media. Au and Pd-Cu alloys were also most effective in potentiating LPS responsiveness as measured by IL-8 production. ConclusionsUsing an in vitro culture system to expose MoDC and THP-1 cells to different alloy specimens this study showed that contact with the solid alloys, in particular when they contain Pd or Au, can trigger innate immune responses and augment responsiveness to bacterial endotoxin.