口腔内金属修复物的成分分析

目的：测定口腔内金属修复物的成分，确定使用的合金种类，以使牙科金属过敏患者避免再次使用此种合金。方法：用细砂纸及圆锥形抛光磨头，采取微量口腔内金属修复物，通过EDXRF(荧光X线分析仪)测定所含金属成分，确定合金种类。结果：14例可疑牙科金属过敏患者中，牙科金属修复物120个，按照检出频度的高低．排在前10位的金属元素分别是Ag、Cu、Au、Pd、Zn、Sn、Co、Cr、In和Mo。Au-Ag-Pd合金的使用频度为65％，Ag-Sn-Hg合金为2.5％，Ag合金为5.4％，Au合金为14.6％，Ni-Cr、Co-Cr合金为10.1％，其他2.4％。2种以上异种合金共存同一口腔环境中的患者12例,5种合金同时存在者1例。含Hg的银汞合金的使用频度为2.5％，与10年前的使用频度16％相比下降明显。Ni、Cr、Co的使用频度未见明显改变。结论：被疑牙科金属过敏的患者中，异种金属同存的现象严重，提示在口腔科临床工作中，尽量避免使用异种金属及含Hg和Ni等易诱发过敏的金属合金。     

Cytotoxicity of experimental casting alloys evaluated by cell culture tests

The cytotoxicity of a series of 29 experimental alloys and six pure metals was determined with cell culture techniques and succinic dehydrogenase histochemistry. The width of any ring of inhibition, optical density of the histochemically stained cells, and a visual ranking of the intensity of the blue color of the stained cells were compared for determination of cytotoxicity. Twenty-four of the 35 metals and alloys (approximately 70%) had the same rankings by the three methods. Of the pure metals, Au, Pd, and Ti were the least cytotoxic, followed by Ag, then Ni, and finally, Cu. Single-phase alloys with moderately high Cu and without high Pd and Au concentrations had high cytotoxicity, as did multiphase alloys, even when they were high in Au and Ag. High Pd was more effective in maintaining the biocompatibility of alloys containing Cu than was Au. Single-phase alloys with compositions typical of those to be used for porcelain-fused-to-metal restorations showed good biocompatibility, as did those base metal alloys that formed adherent oxide surface layers.     

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.     

Study of the influence of the anodic potential on metal-components dissolution from dental alloys

This study aims to evaluate the influence of the anodic potential on metal-components dissolution from dental alloys and is intended to serve as an aid in the investigation of dental metal eruption (metal allergy). In the experiments, anodic potentials were applied electrochemically to various dental alloys in a 0.9% NaCl solution. Thereafter amounts of metal-component dissolution were measured by means of atomic absorption spectrophotometry. In addition, relations between metal-component dissolution and electrochemical characteristics (anodic polarization and charge transfer calculated from current density-time transients) were considered. Results: 1. Breakdown potentials determined on the basis of anodic polarization profiles agreed with potentials of remarkable increase in component dissolution. 2. Current density-time transients gave good indications of alloys' corrosion tendencies. Correlations between charge transfer and total amounts of metal-component dissolution were comparatively good. 3. Metal-component dissolutions in various alloys at fixed anodic potentials 1) Cu and Zn were found to dissolve slightly from gold alloys (types II and IV) at potentials above 200 mV (vs SCE). 2) Ag, Pd, Cu, and Zn were found to dissolve from the Ag-Pd-Cu-Au alloy at potentials above 100 mV. A comparatively large amount of Zn was released at low potentials. Amounts of Ag and Cu dissolution increased rapidly at 300 mV and 500 mV respectively. Although traces of it were detectable at low potentials, dissolution of Pd increased remarkably at 500 mV. 3) Ag, In, and Zn were found to dissolve from the Ag-In-Zn alloy at potentials above O mV. Amounts of In and Zn dissolution increased above 20 mV. The increase was especially remarkable in the case of In. 4) Sn and Zn were found to dissolve from the Ag-Sn-Zn alloy at potentials above -200 mV; Ag dissolved from the same alloy at potentials above 100 mV. Amounts of Sn and Zn dissolution increased at potentials above 100 mV. This was especially true in the case of Sn. 5) Ni, Cu and Si were found to dissolve from the soft type Ni-Cr alloy (9.0 wt% Cr) at potentials above -100 mV. Cr, Mn, and Fe dissolved from the same alloy at potentials above 0 mV; and Co at potentials above 200 mV. Metal-component dissolution was greater in the case of this alloy than in those of all the other alloys used in this study. A considerable amount fo Ni was released at 0 mV.(ABSTRACT TRUNCATED AT 400 WORDS)     

In vitro cytotoxicity evaluation of elemental ions released from different prosthodontic materials

ObjectivesThis study investigated the cytotoxicity of elemental ions contained in four fixed prosthodontic materials (gold, nickel–chromium, stainless-steel alloys and CAD–CAM ceramics).Materials and methodsAccording to the determination of elements released from prosthodontic materials by using inductively coupled plasma mass spectroscopy, similar amounts of elements Pd, Ag, Zn, Cu, Ni, Cr, Mo, Be, Fe, Al, and K were prepared as salt solutions. Wells with a tenfold higher concentration of the tested elements were used as positive controls, while a well without any tested element was used as a negative control. These salt solutions were tested for cytotoxicity by culturing mouse L-929 fibroblasts in the salt solutions for a 7-day period of incubation. Then, the percentage of viable cells for each element was measured using trypan blue exclusion assay. The data (n = 5) were statistically analyzed by ANOVA/Tukey test (p < 0.05).ResultsThe results showed a statistically significant difference for the cytotoxic effect of the tested elements salt solutions. For the released element concentrations the lowest percentage of viable cells (mean ± SD) was evident with Zn, Cu or Ni indicating that they are the highly toxic elements. Be and Ag were found to be intermediate in cytotoxic effect. Fe, Cr, Mo, Al, Pd or K were found to be the least cytotoxic elements.SignificanceZn and Cu released from gold alloys, and Ni released from nickel–chromium alloys, which are commonly used as fixed prosthodontic restorations, show evidence of a high cytotoxic effect on fibroblast cell cultures.     

Metallic pigmentation of human teeth and gingiva: morphological and immunological aspects

The composition of metallic pigmentations in gingiva and dental roots was determined by means of transmission electron microscopy with energy dispersive x-ray microanalysis. The systemic immune response to the metals found in the oral cavity was evaluated in 10 patients by using a modified lymphocyte proliferation test. Immunological results were compared with a group of five controls without metallic materials and pigmentation. Dense particles of various shapes and sizes, as well as of diverse extracellular and intracellular localization patterns, were detected in the pigmented lamina propria gingivae. Metallic deposits consisted predominantly of silver accompanied by selenium or sulfur or both. Besides, Ag, Au, Cr, Ni, Fe, Hg, Cu, and Ti were identified in dentinal tubules of teeth reconstructed with dental alloys. Nine patients with metallic pigmentations had a positive lymphocyte proliferative response to one or more metals present in their own metal reconstructions. Results of this study thus indicated that dental alloys-by virtue of their corrosion process-might pose a significant risk to immunologically susceptible patients.     

New conversion method of metal surfaces for resin bonding. Conversion effects for pure metals in dental precious metal alloys

Excellent adhesion of adhesives to metals can be realized by simply applying liquid Ga-Sn alloy (Adlloy) on the adherend metal surface. This method is only effective on dental precious metal alloys. Five metals, Au, Pt, Pd, Ag, and Cu, included in dental precious metal alloys were converted by this method to determine the most effective pure metal from bonding strength measurements, water durability at the adhesion interface, and ESCA measurements. All metals converted by Adlloy showed excellent bonding strength and water durability, whereas nonconverted metals showed poor water durability. ESCA measurements showed that metal surfaces converted by Adlloy are covered with a 3-6 nm thick Ga and Sn oxide film and that the diffusibilities of Ga in the metals are in the order Ag greater than Au greater than Pt greater than Cu greater than Pd. From the viewpoint of handling, Ag is the most effective metal.     

The influence of the pure metal components of four different casting alloys on the electrochemical properties of the alloys

ObjectivesThe aim of this study was to investigate the influence of the pure metal components of the four different casting alloys on the corrosion behaviors of these alloys tested.MethodsPotentiodynamic polarization tests were carried out on four different types of casting alloys and their pure metals at 37 °C in an artificial saliva solution. The ions released from the alloys into the solutions during the polarization test were also determined quantitatively using inductively coupled plasma-mass spectrometry (ICP-MS).ResultsNi–Cr (M1) and Co–Cr (M2) alloys had a more homogenous structure than palladium based (M3) and gold based (M4) alloys in terms of the pitting potentials of the casting alloys and those of the pure metals composing the alloys. The total ion concentration released from M3 and M4 was less than from M1 and M2. This may be because M3 and M4 alloys contained noble metals. It was also found that the noble metals in the M3 and M4 samples decreased the current density in the anodic branch of the potentiodynamic polarization curves. In other words, noble metals contributed positively to dental materials.SignificanceCorrosion resistance of the casting alloys can be affected by the pure metals they are composed of. Au and Pd based noble alloys dissolved less than Ni–Cr and Co–Cr based alloys.     

Elemental composition of brazing alloys in metallic orthodontic brackets

The aim of this study was to assess the elemental composition of the brazing alloy of representative orthodontic brackets. The brackets examined were Gemini (3M, Unitec, Monrovia, Calif), MicroLoc (GAC, Bohemia, NY), OptiMESHxrt (Ormco, Glendora, Calif), and Ultratrim (Dentarum, Ispringen, Germany). Four metallic brackets for each brand were embedded in epoxy resin and after metallographic grinding and polishing were cleaned in a water ultrasonic bath. Scanning electron microscopy and energy-dispersive x-ray microanalysis (EDS) were used to assess the quantitative composition of the brazing alloy. Four EDS spectra were collected for each brazing alloy, and the mean value and standard deviation for the concentration of each element were calculated. The elemental composition of the brazing alloys was determined as follows (percent weight): Gemini: Ni = 83.98 +/- 1.02, Si = 6.46 +/- 0.37, Fe = 5.90 +/- 0.93, Cr = 3.52 +/- 0.34; MicroLoc: Ag = 42.82 +/- 0.18, Au = 32.14 +/- 0.65, Cu = 24.53 +/- 0.26, Mg = 1.12 +/- 0.33; OptiMESHxrt: Au = 67.79 +/- 0.97, Fe = 15.69 +/- 0.29, Ni = 13.01 +/- 0.93, Cr = 4.01 +/- 0.35; Ultratrim: Ag = 87.97 +/- 0.33, Cu = 10.51 +/- 0.45, Mg = 1.29 +/- 0.63, Zn = 1.13 +/- 0.24. The findings of this study showed that different brazing materials were used for the different brands, and thus different performances are expected during intraoral exposure; potential effects on the biological properties also are discussed.     

The adhesion mechanism of dental adhesive resin to the alloy. Adhesive ability of dental adhesive resin to the cleaned metal surface obtained by hydrogen gas reduction method

With the cleaned metal surface without passive film or an oxide layer, chromium, cobalt, and iron show excellent bonding strength, indicating values similar to 18-8 stainless steel. Therefore the existence of a passive film and oxide layer at the interface metal/resin is not essential for metal-resin bonding. The adhesive ability decreases in the order: Cr congruent to Co congruent to Fe greater than Cu greater than Ag greater than Au congruent to Ni greater than Pt greater than Pd.     

pH值对烤瓷工艺处理后的合金耐腐蚀性能的影响

目的研究不同pH值对经过烤瓷处理过的烤瓷合金的耐腐蚀性能的影响。方法制作金合金、纯钛、钴铬合金、镍铬合金试件,常规临床烤瓷,分别置于不同的pH值溶液中,应用电化学综合测试系统和腐蚀分析软件对受试合金行动电位极化扫描,绘制合金在人工唾液中的极化曲线,获得并分析材料的自腐蚀电位(Ecorr)和腐蚀电流密度(Icorr)。结果4种合金临床烤瓷加工后在同一pH值人工唾液中自腐蚀电位负值增加的排序为金合金、纯钛、钴铬合金、镍铬合金;4种合金在pH为5.6±0.04、pH=为.6±0.04人工唾液中均比pH为6.8±0.04中自腐蚀电流密度增大,自腐蚀电位负值增大。结论纯钛与金合金耐腐蚀性能好于钴铬合金,镍铬合金,随pH值下降,非贵金属耐腐蚀性能下降明显。     

镍铬合金在人工唾液中的电化学腐蚀行为

目的 本项研究旨在探讨镍铬合金在体外的电化学腐蚀行为。方法 实验应用极化曲线方法，将镍铬合金浸泡在人工唾液中，温度为36．5℃，pH值为7．0，测量试样的腐蚀电位和自腐蚀电流密度。应用X射线光电子能谱(X-ray photoelectron spectroscopy，XPS)，分析试样表面的元素成分变化。结果 实验结果表明，镍铬合金的点蚀电位为-390mV，钝化电位为-160mV，活性溶解区从-160mV到-270mV。它的自腐蚀电流密度为0．262μAcm^-2。极化曲线试验后，对试片表面进行XPS能谱分析，所得原子峰高图发现，随着氩离子刻蚀的由浅入深，金属元素镍(Ni)、铬(Cr)、钼(Mo)、铁(Fe)的含量逐渐增加，而非金属元素氧(O)、碳(C)的含量则逐渐减少。由于钙(Ca)为介质中的元素，其含量也呈逐渐减少。结论 镍铬合金在人工唾液中，经过电化学极化曲线试验，会发生腐蚀反应，生成腐蚀产物附着于试样表面。     

五种全冠修复合金材料的细胞毒性研究

目的 检测和比较五种全冠修复合金材料的细胞毒性作用。口腔修复合金材料在口腔环境中析出金属离子,合金材料通过这些金属离子对临近组织及远隔组织器官产生影响。方法 采用ＭＴＴ方法检测乳酸脱氢酶活性来测定合金析出离子对体外培养细胞的影响,比较五种合金包括贵金属和贱金属合金的毒性作用。用流式细胞检测仪分析合金析出离子是否诱导Ｌ－９２９细胞凋亡。结果 软质铬钴合金的细胞毒性最大,镍铬合金、银钯合金其次,钯合金     

Comparison of metal release from new and recycled bracket-archwire combinations

Most orthodontic brackets and archwires made from stainless steel or nickel (Ni)-titanium (Ti) alloys can release metal ions into the saliva. This study measures the amounts of metal released from simulated fixed orthodontic appliances. Sixty simulated fixed orthodontic appliances were manufactured in different ways and divided into four equal groups as follows: new brackets and new archwires (group 1 controls), new brackets and recycled archwires (group 2), recycled brackets and new archwires (group 3), and recycled brackets and recycled archwires (group 4). The bracket bases coated with adhesives were heated at 350 degrees C for 30 minutes. Recycled archwires were sterilized by autoclaving. Each appliance was soaked in artificial saliva of pH 7 at 37 degrees C for 45 days. At the end of this period, a sample of the artificial saliva was collected for analysis. Concentrations of Ni, chromium (Cr), iron (Fe), manganese, copper (Cu), and Ti ions were measured by atomic absorption and recorded in micrograms per liter. Analysis of variance and the Duncan multiple-range test indicated significant differences among the groups (P < .001). The study revealed the following: (1) group 4 released higher amounts of Cr, Fe, and Ti than any of the other three combinations; (2) Ni release was similar in groups 1 and 2 and in groups 2, 3, and 4; (3) the amounts of Cu, Cr, and Ti ions released from groups 3 and 4 were significantly greater than the amounts released from the other two combinations.     

牙科低贵合金腐蚀后表面成分分析

目的 通过分析牙科低贵合金腐蚀后的表面成份，探讨腐蚀机理。方法 运用静态浸泡试验评价Ag-Pd合金的腐蚀性能并与常用牙科修复合金Co-Cr、Cu-Al比较。腐蚀介质为Fusayama人工唾液（37℃，pH=5)。采用扫描电镜、电子能谱分析腐蚀产物。结果 铜铝合金的腐蚀大于银钯合金和钴铬合金（P＜0.05)；银钯合金主要以银和铜腐蚀为主，铜选择性释出。结论 低贵合金的腐蚀源于多相结构之间电位差引起的原电池反应。     

Shear bond strength of luting agents to fixed prosthodontic restorative core materials

Background: Bonding properties of luting cements are important for retention of restorative core materials. The aim of this study was to compare the bonding performance of a resin‐modified glass ionomer cement and a self‐adhesive resin cement to various fixed prosthodontic core materials. Methods: Cylindrical specimens with a thickness of 2 mm and a diameter of 5 mm were fabricated from Au‐Pd‐Ag, Co‐Cr, Ni‐Cr‐Mo, Ni‐Cr‐Fe alloys, titanium, zirconia and Empress II (n = 20). Each group was divided into two subgroups to be luted with two different luting agents. Composite resin blocks were cemented onto specimens with RelyXUnicem and FujiCem. A shear bond strength machine with 50 kg load cell and 0.50 mm/min crosshead speed was used. Kruskal Wallis test, Dunn’s Multiple Range test and Mann‐Whitney‐U test were used for statistical analysis. The results were evaluated in a confidence interval of p < 0.05. Results: The highest bond strength was obtained between Ni‐Cr‐Fe‐RelyXUnicem (8.22 ± 2.15 MPa) and the lowest was between Empress II‐FujiCem (1.48 ± 0.9 MPa). In FujiCem groups, Co‐Cr and Ni‐Cr‐Fe showed significantly higher bond strength than Au‐Pd‐Ag and Empress II. In RelyX Unicem groups, Ni‐Cr‐Fe showed higher bond strength than Empress II. Conclusions: The types of luting agents and restorative core materials may have a significant influence on bond strength.     

Release of elements from some gold alloys and amalgams in corrosion

The release of Au, Ag, Cu and Zn elements from six commercially available gold alloys and three amalgam alloys was studied. The polarizing electropotential system with modified Fusayama solution was used. The cycle process was repeated 500 times between +/- 1000 mV during a period of 5 h 22 min. During the process samples of solution were analyzed in order to follow the release of elements. Results revealed rapid release of Zn from most alloys, release of Ag from most alloys and release of Au from two alloys. Also, rapid release of Cu was found from amalgams but not from gold alloys. Release of Ag from gold alloys showed very good passivation up to 3 h, after which it was released in varying amounts.     

Studies on high temperature oxidation of noble metal alloys for dental use (I). Formation of oxide layers and oxidation rate (author's transl)]

Eight commercial and two experimental alloys were examined. The cast specimens were polished metallographically and oxidized at 700 degrees and 800 degrees C in air. An electron probe X-ray microanalyser and a microthermobalance were employed to investigate the oxidation behavior of the alloys. The results obtained were as follows: 1. The copper in the alloys was selectively oxidized and the scales formed on the alloys consisted of two layers, CuO overlying Cu2O. 2. The oxide particles in the internal oxidation zone (subscale) on the alloys containing only Cu as the base metal were Cu2O and on the alloys containing Zn, Cd, and Ni with Cu were ZnO, CdO, and NiO, respectively. 3. The size of the ZnO and CdO particles in the subscale increased with the penetration into the specimen. 4. The ZnO particles in the metal-subscale interface showed preferential precipitation at the grain boundaries. 5. When the oxide particles in the subscale did not develop remarkably, the oxidation rate at constant temperature conformed with the parabolic law. 6. In the 18 carat gold alloy, the oxidation rate at 800 degrees C was about 10 times that at 700 degrees C. 7. Owing to preferential oxidation of the Cu in the alloys, Cu concentration in the outer layer of the metal decreased remarkably and Au, Pt, Ag and Pd concentration increased.     

The release of elements of dental casting alloys into cell-culture medium

Ten dental casting alloys were tested for alloy-element release into cell-culture medium, and this release was related to alloy composition, alloy microstructure, and alloy cytotoxicity (previously determined). Cell-culture medium was analyzed for alloy elements by flame atomic absorption. Concentrations of elements in the medium were normalized by dividing them by their atomic abundance in the alloy, giving element medium-alloy ratios (EMA ratios). Results showed that Au, In, and Pd generally did not dissolve into the medium, but that Ag, Cd, Cu, Ga, Ni, and Zn frequently dissolved. Comparison of EMA ratios for Ag, Cu, and Zn showed that each element retained a behavioral identity in diverse metallurgical environments, but that these environments influenced the release behavior to some degree. Some EMA ratios in multiphase alloys were greater than those in solid solutions, and EMA ratios showed great diversity within all the alloys. Nominal composition seemed to be of little value in the prediction of metal release unless the composition supported multiple-phase formation. In addition, release of alloy elements did not, in itself, completely predict alloy cytotoxicity measured previously. However, cytotoxicity was associated with metal release in each case. The commercial alloys used in this study exhibited more complex and less predictable release behavior than did the simpler ternary alloy systems used by previous investigators. It is believed that the use of commercial preparations is necessary for their in vivo behavior to be modeled.     

Metal content of biopsies adjacent to dental cast alloys

Single case reports indicate that components of dental alloys accumulate in the adjacent soft tissue of the oral cavity. However, data on a wider range of dental alloys and patient groups are scarce. Therefore, the aim of the present study was to examine the metal content of oral tissues adjacent to dental alloys showing persisting signs of inflammation or other discoloration (affected sites) and of healthy control sites with no adjacent metal restoration in 28 patients. The composition of the adjacent alloys was analyzed and compared to the alloy components in the affected sites. Tissue analysis was performed using atomic absorption spectroscopy. Alloy analysis was performed with energy-dispersive X-ray analysis. In the affected sites, the metals Ag, Au, Cu, and Pd prevailed compared to control sites, reflecting the frequency distribution of single metals in the adjacent alloys. In most cases (84%), at least one of the analyzed metals was a component of the alloy and also detected in the tissue. Metal components from almost all dental cast alloys can be detected in adjacent tissue.