Effects of nickel-chrome dental alloys used in dentistry on saliva and serum nickel levels, peripheral T-lymphocytes and some other blood parameters

Epidemiological investigations have shown that nickel is a potent sensitivity producing agent. However, it is not known if intra-oral use of nickel-chrome alloys can cause any sensitization reaction. The purpose of this study was to determine if nickel-chrome alloys used in dentistry influence nickel levels in saliva and serum and whether there were associated changes of some blood parameters such as lymphocyte, T-lymphocyte, neutrophil, eosinophil, basophil and monocyte. The study was performed on 10 patients all of whom had no medical and dental history of using nickel containing drugs or restorations. Four unit fixed partial prostheses containing 22.97% nickel and 22.65% chrome were constructed and worn by the patients. Blood and unstimulated whole saliva samples were taken from the patients before insertion of the prostheses and then 1 month and 6 months post-insertion. Hematocrit determinations, total and differential leucocyte count, total T-lymphocyte counts and serum nickel concentrations were determined from the blood samples and salivary nickel concentrations from the saliva samples. It was found that there were no significant changes in circulating T-lymphocyte and monocyte population but a decrease was found in circulating eosinophil and an increase in circulating neutrophil and basophil populations.     

Mechanical properties and soldering of some cobalt base metal alloys

The mechanical properties of 5 cobalt base alloys for porcelain fused to metal and the strength of their solder joints have been determined. The variation in the composition of these alloys is reflected in their mechanical properties. The ranges of the mechanical properties of the materials tested were: (1) ultimate tensile strength — from 647 to 889.5 MPa; (2) yield strength — from 446.4 to 641.4 MPa; (3) modulus of elasticity — from 168.9 to 252.8×10³ MPa; (4) elongation — from 2 to 10%; and (5) hardness — from 350 to 440 VHN. Heat treatment did not have any significant effect on any of the mechanical properties except elongation which showed some variation. In general, stronger joints were made by soldering with a torch than by oven soldering. Also, presoldered joints were stronger than postsoldered ones. So, presoldering with a torch produced the strongest joints.     

Comparison of the bond strength of laser-sintered and cast base metal dental alloys to porcelain

OBJECTIVE: The purpose of this study was to compare shear bond strengths of cast Ni-Cr and Co-Cr alloys and the laser-sintered Co-Cr alloy to dental porcelain. METHODS: Dental porcelain was applied on two cast and one laser-sintered base metal alloy. Ten specimens were prepared for each group for bond strength comparison. ANOVA followed by Tukey HSD multiple comparison test (alpha=0.05) was used for statistical analysis. Fractured specimens were observed with a stereomicroscope to classify the type of failure after shear bond testing. RESULTS: While the mean shear bond strength was highest for the cast Ni-Cr metal-ceramic specimens (81.6+/-14.6MPa), the bond strength was not significantly different (P>0.05) from that for the cast Co-Cr metal-ceramic specimens (72.9+/-14.3MPa) and the laser-sintered Co-Cr metal-ceramic specimens (67.0+/-14.9MPa). All metal-ceramic specimens prepared from cast Ni-Cr and Co-Cr alloys exhibit a mixed mode of cohesive and adhesive failure, whereas five of the metal-ceramic specimens prepared from the laser-sintered Co-Cr alloy exhibited the mixed failure mode and five specimens exhibited adhesive failure in the porcelain. CONCLUSIONS: The new laser-sintering technique for Co-Cr alloy appears promising for dental applications, but additional studies of properties of the laser-sintered alloy and fit of castings prepared by this new technique are needed before its acceptance into dental laboratory practice. SIGNIFICANCE: Laser sintering of Co-Cr alloy seems to be an alternative technique to conventional casting of dental alloys for porcelain fused to metal restorations.     

Casting accuracy of base metal alloys

The effect of investment material on the casting accuracy of five base metal alloys was evaluated. Overall, the fit of the test castings was poor. Individual alloy-investment interaction appears to be significant. Although marketed for use with base metal alloys, it appears that investment manufacturers' recommended techniques require alteration to enhance the fit of base metal restorations.     

Chemical analysis, castability, and tensile properties of twenty-one dental base metal casting alloys for removable dental appliances

A bstract — Twenty-one alloys used in Australia were tested for chemical composition, castability, and tensile properties. Nineteen alloys consisted of mainly cobalt, chromium, and molybdenum, while two Ticonium alloys were mainly nickel and chromium. All alloys passed the British castability test. Six alloys had a combination of strength and ductility superior to the remainder of the alloys tested. Five of these differed from the composition of the main group. The proposed minimum requirements for the Australian Standard on Dental Base Metal Casting Alloys for Removable Dental Appliances of 500 MPa 0.2 per cent offset proof stress and 1.5 per cent elongation, were found to be appropriate for the alloys tested. The best base metal alloys are not superior to Type IV gold alloy for the retentive spring members on partial denture frameworks.     

Galvanic series of some dental alloys

abstract – Galvanic series for different metals in different electrolytes have been published, but never for dental alloys in artificial saline solution. The material classes studied are amalgam, gold alloy, nickel alloy, chromium cobalt casting alloy and temporary crown form. The electrogalvanic potentials were measured and determined in reference to a hydrogen electrode (H₂/H⁺) arbitrarily defined as zero. A galvanic series of the tested materials was arranged in order of their potentials.     

Adhesion of adhesive resin to dental precious metal alloys. Part I. New precious metal alloys with base metals for resin bonding

New dental precious metal alloys for resin bonding without alloy surface modification were developed by adding base metals (In, Zn, or Sn). Before this, binary alloys of Au, Ag, Cu, or Pd containing In, Zn, or Sn were studied for water durability and bonding strength with 4-META resin. The adhesion ability of the binary alloys was improved by adding In equivalent to 15% of Au content, Zn equivalent to 20% of Ag content, and In, Zn, or Sn equivalent to 5% of Cu content. There was no addition effect of the base metals on Pd, however 15% of In addition improved adhesion with Pd-based alloys containing equi-atomic % of Cu and Pd. The alloy surfaces were analyzed by XPS and showed that oxides such as In2O3, ZnO, or SnO play an important role in improving the adhesive ability of the alloys.     

Effect of metal primers and tarnish treatment on bonding between dental alloys and veneer resin

PURPOSE

The aim of this study was to evaluate the effect of metal primers on the bonding of dental alloys and veneer resin. Polyvinylpyrrolidone solution''s tarnish effect on bonding strength was also investigated.

MATERIALS AND METHODS

Disk-shape metal specimens (diameter 8 mm, thickness 1.5 mm) were made from 3 kinds of alloy (Co-Cr, Ti and Au-Ag-Pd alloy) and divided into 4 groups per each alloy. Half specimens (n=12 per group) in tarnished group were immersed into polyvinylpyrrolidone solution for 24 hours. In Co-Cr and Ti-alloy, Alloy Primer (MDP + VBATDT) and MAC-Bond II (MAC-10) were applied, while Alloy Primer and V-Primer (VBATDT) were applied to Au-Ag-Pd alloys. After surface treatment, veneering composite resin were applied and shear bond strength test were conducted.

RESULTS

Alloy Primer showed higher shear bond strength than MAC-Bond II in Co-Cr alloys and Au-Ag-Pd alloy (P<.05). However, in Ti alloy, there was no significant difference between Alloy Primer and MAC-Bond II. Tarnished Co-Cr and Au-Ag-Pd alloy surfaces presented significantly decreased shear bond strength.

CONCLUSION

Combined use of MDP and VBATDT were effective in bonding of the resin to Co-Cr and Au-Ag-Pd alloy. Tarnish using polyvinylpyrrolidone solution negatively affected on the bonding of veneer resin to Co-Cr and Au-Ag-Pd alloys.     

An electron microprobe investigation of the extent of microsegregation occurring in base metal dental casting alloys

Standard tensile specimens were cast from a cobalt base commercial partial denture casting alloy, and from a nickel base alloy. Specimens from the castings were examined metallographically. The electron microprobe was used in order to determine the degree of microsegregation present.     

Galvanic series of some dental alloys.

Galvanic series for different metals in different electrolytes have been published, but never for dental alloys in artificial saline solution. The material classes studied are amalgam, gold alloy, nickel alloy, chromium cobalt casting alloy and temporary crown form. The electrogalvanic potentials were measured and determined in reference to a hydrogen electrode (H2/H+) arbitrarily defined as zero. A galvanic series of the tested materials was arranged in order of their potentials.     

The effects of prewetting on postsoldering of base metal alloys

Prewetting the surface of a base metal alloy with solder prior to low temperature soldering produced strong, predictable, oxide-free joints similar to precious metal joints. The positive results were obtained whether the prewet base metal was soldered to other prewet base metal or to precious metals. Soldered combinations of non-prewet base metal showed lower strength, less predictability, and more oxide formation than the prewet counterparts. The prewetting concept was described for use with fixed prosthodontics or removable partial dentures.     

Corrosion of base metal alloys in vitro.

Corrosion of base metal alloys was studied by placing the alloys in artificial saliva for 2 months and then determining the concentration of metal ions in the saliva. The distribution of the attack on the surface was examined. The results indicated that the amount of metal ions in the artificial saliva could be related to the Cr content of the alloy. When the Cr content exceeded 16% very little corrosion was observed. The corrosive attack was located at Cr depleted areas, grain boundaries. The Cr depletion probably resulted from coring during solidification.     

Apparent cytotoxicity of base metal casting alloys.

The cytotoxic potentials of three Ni-Cr based alloys and an Fe-Cr based alloy were assessed. In tissue culture, casting of all four test materials and powders of the Fe-Cr based material did not elicit adverse cellular changes. However, cultures containing Ni-Cr powders showed prominent zones of lysis and cell alteration. The cytotoxic potential of products obtained from the surfaces of casting alloys may offer an expedient means for estimation of long-term clinical toxicity.     

Cell proliferation rates and fibronectin arrangement as parameters for biocompatibility evaluation of dental metal alloys in vitro

A short-term (72-96 hours) biocompatibility evaluation in vitro of four single phase dental metal alloys was conducted by determining cell proliferation rates correlated to the organization of the extracellular matrix protein fibronectin in human fibroblast cultures. Immunocytochemical methods were performed to detect both cell proliferation rates by 5-bromodeoxyuridine (BrdU) incorporation, and fibronectin arrangement, i.e., diffuse in the extracellular matrix, organized in fibrils or in focal adhesions. We showed that cell proliferation rates were related to fibronectin expression. In particular, a higher percentage of cells in the S-phase were related to a predominance of fibronectin organized both in fibrils and in focal adhesions. The alloy with the highest Au content seemed the most biocompatible among those tested, since it behaved in a very similar manner to the controls. On the contrary, fibroblasts exposed to the alloy with the highest percentage of Ag had the most different behavior as compared to the controls. We can assume that a correlation exists between fibronectin organization and the percentage of BrdU-positive cells and that these parameters are varying with the different metal composition of the alloys. The observation of fibronectin arrangement together with cell proliferation rates could be considered a useful tool to determine the biocompatibility of these biomaterials.