Dental Metal Research Articles

顎顔面領域 MR 画像におけるアーチファクトに関するアンケート調査

Magnetic resonance imaging (MRI) is accepted as a valuable method for evaluating and diagnosing various diseases in medical and dental area. On the other hand, dental magnetic attachments have been applied as one of the most suitable retainers of removable prostheses. The dental magnetic attachment is an advanced procedure for the restoration, whereas the dental magnetic attachment is one of the causes of MRI artifacts and/or distortions. In this study the results obtained by a survey in general hospitals on MRI artifacts caused by dental metals, especially dental magnetic attachments, are reported. The results obtained were as follows ; 1. MRI artifacts are experienced in most hospitals. Most radiologists did not regard the effect of the magnetic alloy as the cause, although they thought dental metals in oral cavity were the main cause of MRI artifact. 2. Although about a half of radiologist were aware of the presence of the magnetic attachments, few of them had little experience in taking pictures of the patients with magnetic attachment or magnetic keepers by using MRI. 3. Even when dental metals and magnetic keepers in oral cavity were considered to produce the MRI artifacts, none of radiologists asked dentists to remove them. They tried to solve the trouble of MRI artifacts by themselves. 4. Prothodontists should give much more information about the dental magnetic attachment to radiologists and medical doctors in addition to improving the magnetic attachment and investigating materials to minimize the effect on MRI.

アトピー性皮膚炎患者における歯科金属除去による臨床症状の変化に関する研究

Objects: The aim of this study was to investigate the role of dental metals in the development of atopic dermatitis (AD).Subjects and method: From 300 patients with refractory AD, who showed positive lymphocyte stimulation test (LST) reactions to dental metal salts, we removed the dental restorations that contained LSTpositive metals and evaluated the improvement of clinical symptoms.Result: Positive LST reactions were observed in 98% to Hg, 95% to Ni, 37% to Au, 27% to Ag, 31% to Pd, and 24% to In, respectively. The ratio of clinical symptom improvement “excellent” and “good” was 70%(211/300).Conclusion: Clinically recalcitrant lesions were improved by dental metal removal. This fact reveals that dental metals play an important role in the pathogenesis of refractory AD.

Biocompatibility evaluation of dental metal alloys in vitro: expression of extracellular matrix molecules and its relationship to cell proliferation rates.

The biocompatibility in vitro of dental biomaterials has been widely studied, with consideration of cell viability and cell proliferation rates. In the present study we evaluated the biocompatibility in vitro of three single-phase dental metal alloys, all provided by the same manufacturer. To this aim, we considered the percentage of proliferating cells revealed by 5-bromodeoxyuridine incorporation in human fibroblast cultures in the presence of these biomaterials, performing a short time test (72 h). These data were correlated with immunocytochemical expression of four molecules of the extracellular matrix, i.e., fibronectin, type I collagen, beta(1)-integrin subunit, and chondroitin sulfate, because the capability of cells to adhere to substrata is widely related to cell proliferation rates. Alloys presenting higher amounts of noble elements were more biocompatible even when they contained significant amount of both Ag and Cu. As regards the expression of the extracellular matrix molecules, the organization level of fibronectin in fibrils was correlated with higher cell proliferation rates, whereas no difference was detected for the expression of the other antigens. On these bases, we assume that expression of fibronectin could be a useful parameter in evaluation of biocompatibility in addition to cell proliferation capability.

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.

金属除去により改善を認めた口腔へん平苔せんの臨床的病理組織学検討

A relation between oral lichen planus (OLP) and oral prosthetic metals has been reported because OLP may improve after their removal. However, the criteria for evaluating their involvement in the clinical and histopathological signs of OLP have not been established.We compared the clinical and histological features of 18 cases of OLP that improved after removal of dental metals with those of 18 cases that did not improve clinically after removal. All patients were positive to dental metals on patch testing and had OLP refractory to conventional therapy. Improved cases of OLP were characterized by unilateral involvement of the buccal mucosa, showing a reticular pattern with the formation of erosions and ulcers.Histologically, most cases had remarkable humoral degeneration of the basal cell layer, lymphocytic invasion of the lamina propria, and spongiosis.

Skin Irritaton and Contact Sensitization of Dental Metals in Guinea Pigs

Skin Irritaton and Contact Sensitization of Dental Metals in Guinea Pigs

Corrosion behaviour of dental metals and alloys in different media.

The corrosion tendencies of metals are related with their position in the electromotive series. These electrode potential degrees may change due to the compositions of the alloys, the surrounding media, or due to alterations in the composition because of recurrent casting. Therefore in this research, the electrode potentials and their changes over a period of time were measured in different pH media simulating the oral electrochemical conditions in vitro. The surface structure of the first and second castings of 29 different dental metals and alloys were examined under a scanning electron microscope and their composition in percentage weight was calculated by the Energy-dispersive X-ray Analysor system. Further the current-potential curves of the dental alloys were found by the potentiodynamic method in three different solutions and, in addition, the changes of corrosion potentials over time were also determined. The corrosion rates, corrosion potentials, their changes over time and their cathodic Tafel slopes were determined. All alloys tested showed ion leakage in corrosive media. Titanium exhibited the least, but alloys with tin and cobalt content displayed the greatest corrosion tendencies. Alloys with iron and copper corroded in the acid media, conversely alloys containing chromium, nichel and molybdenum proved to be resistant to corrosion. The recurrent castings were also corrosion resistant.

The effect of pH on the corrosion of dental metal alloys

The aim of this study has been to find out the effects of pH degrees of oral environment on the corrosion of dental metals and alloys which have different composition by electrochemical methods. The surface structure of the first and second casting of dental metals and alloys were examined under the Scanning Electrone Microscope. Their composition were investigated by the Energy Dispersive X-Ray Analysor system. The rotary disc electrode was prepared by these materials. The potential changes of these electrodes by time were established in three different pH solutions, and their current-potential curves were obtained by the potentiodynamic method. In addition the changes of corrosion potentials due to time was also determined.

多数の金属にアレルギー反応を示す患者のチタンによる歯科補綴治療

A case of lichen planus of the buccal mucosa in a 52-year-old female is reported. Her teeth were cemented by a fixed bridge in a dental clinic three years earlier. A few days later, she had a constant pain in her oral mucosa that was worsening. She visited our hospital with this swelling, so the lesion was examined. Lichen planus was recognized in the biopsy specimen of the lesion. She had a medical history of metal allergy. Patch test for dental metal sensitivity was used to investigate the problem. Positive reactions were observed for tin, copper, chromium, gold, and palladium. Investigation was done by metal biopsy of the surface of the resin disk inscribed on her prostheses. The minute amounts of biopsy on the resin disk were analyzed by ESCA. It was found that her prostheses were made of Au-Ag-Pd and Ag-In-Sn alloys. These results suggested that this case may have lichen planus caused by allergy to dental alloys. Therefore, her metal prostheses were removed and a temporary restoration of resin for 10 months was done. Finally, a titanium prostheses was applied. Her condition has remained good without any allergic reaction. It seemedthat this treatment was successful because her lesion recovered.

The influence of dental metal alloys on cell proliferation and fibronectin arrangement in human fibroblast cultures

The biocompatibility of six single-phase dental metal alloys was studied by determining cell proliferation ;rates correlated to the arrangement of fibronectin (FN) in fibroblast cultures. Immunocytochemical methods were used to detect cell proliferation by 5-bromodeoxyuridine (BrdU) incorporation, and FN organization [i.e. diffuse in the extracellular matrix and organized in fibrils or in focal adhesions (FA)] in human fibroblast cultures. Cell proliferation rates were related to FN arrangement and in particular a higher percentage of cells in the S-phase was related to a predominance of FA. The greatest difference in behaviour compared to that of the controls was detected after 120 and 168 hr: at these times, as well as at previous ones, the alloy with the highest Au content seemed the most biocompatible among; those tested, as it behaved in a very similar way to the controls. In contrast, fibroblasts exposed to the other five alloys showed different behaviours from the controls. It is assumed that a correlation exists between FN organization and the percentage of BrdU-positive cells, and that these features vary in the presence of different alloys. The observation of FN arrangement together with cell proliferation rates could be another useful tool in determining the biocompatibility of dental metal alloys.

Evaluation of Patch Tests as a Screening Method for Allergy Associated with Dental Metals

Evaluation of Patch Tests as a Screening Method for Allergy Associated with Dental Metals

ＡｕＣｕ‐Ａｇ擬二元系合金の熱処理が腐食挙動に及ぼす影響

From a viewpoint of dental metal allergy, many investigators have paid attention to the influences of metallic materials on the human body. It has also been required to explain the corrosion mechanism and to establish the evaluation method of corrosion resistance for these materials. The purpose of this study was to obtain fundamental data which explain the corrosion behavior of dental alloys.AuCu-14 at%Ag pseudobinary alloy, simplified component and composition, were heat treated and compared with each datum of corrosion behavior in 1%NaCl solution.In the potential range of ±0.3 V (vs. SCE), assumed intraoral condition, sample aged at 250°C for 100 ks after solution treatment showed significantly higher corrosion activity than other heat treatment conditions (p<0.001).The result showed that dissolution of alloy components from the metallic restoration were influenced by heat treatment. Thus it was suggested that anodic polarization measurement could be used as an evaluation method of corrosion resistance for dental alloys.

補綴臨床の立場からみた金属の選択基準

補綴臨床の立場からみた金属の選択基準

Oxidation Study of Dental Metal-Ceramic Alloys by Surface Characterization Techniques. Part 2. Pd Alloys

Oxidation of commercial Pd-based dental metal–ceramic alloys was studied by multitechnique analyses. The composition and chemical state of alloy components were measured by XPS. The lateral and depth–concentration profiles were studied by SAM combined with ion sputtering. The microstructure was analysed by SEM/EDX and XRD. Various alloying components Cu, Ga, In, Sn and Zn were used to control the oxide structure, which is of primary importance in order to get good porcelain bonding to the alloy. All alloys were oxidized internally. The thickness of the internally oxidized layer was several micrometres. High concentration of the alloying components was observed on the surface. Oxidation of palladium depended on the other oxidizing components of the alloy. For Pd–Ag–Sn–In–Zn alloy the outermost surface layers consisted of a non-oxidized Pd-rich area and an oxidized area rich in Zn, indicating that chemical bonding also contributes to the overall bonding. In general, multitechnique analyses are required to characterize properly the oxide structure of metal–ceramic alloys.

Characterization of a surface‐treated Au–Ag–Cu‐based dental metal–ceramic alloy

AbstractThe oxidation of an Au–Ag–Cu‐based dental metal–ceramic alloy was studied by multitechnique analysis. The elemental spatial distribution of the alloy components was measured by energy‐dispersive x‐ray imaging and scanning Auger microscopy and the depth–concentration profiles studied by XPS and Auger depth profiling. The structure of the oxidized layer was analysed by x‐ray diffraction. Special attention was paid to the pretreatment of the oxidized alloy in order to get a suitable oxide structure, which is known to play an essential role in the porcelain/metal interaction. The studied alloy contained several alloying components, such as In, Cu and Zn, to control melting temperature, strength and porcelain adherence. Oxidation of In could be promoted and that of Cu and Zn inhibited. This is of great importance because In2O3 is known to increase porcelain adherence to noble alloys, whereas CuO tends to cause discolouration of porcelain.

Clinical application of energy dispersive x-ray microanalysis for nondestructively confirming dental metal allergens

Dental metal restorations contain and release allergens that cause metal allergy. Until now it has been a general treatment for dental metal allergy to remove all suspected metal restorations without confirming their chemical composition. This study describes the procedures to examine nondestructively the chemical composition of metal restorations by the use of an energy dispersive x-ray microanalysis system. The present results indicate that this new application of energy dispersive x-ray microanalysis could identify the dental metal restorations that contain elements positive in skin tests for the patient in whom a metal allergy is suspected and that the potential for the clinical use of energy dispersive x-ray microanalysis exists.

歯科用金属アレルギーが原因と思われた頬粘膜形質細胞肉芽腫の１例

Plasma cell granuloma is a pseudotumor characterized by aggregation of plasma cells. It rarely occurs in the oral cavity. A case of plasma cell granuloma of the buccal mucosa in a 42-year-old woman is reported. She suffered from repeated bite wounds of the right buccal mucosa from 18 months previously, and a granulomatous lesion of this region, initially measuring 15×15mm, developed 15 months previously. The lesion came in contact with metal crowns. Inflammatory cell infiltration chiefly by plasma cells was recognized in the biopsy specimen of lesion. Polyclonality of plasma cells was revealed by immunohistochemical staining of kappa and lambda chains. The histopathological diagnosis was plasma cell granuloma. She had a history of metal allergy and a patch test for dental metal was positive. The stimulation index in the lymphocyte stimulation test by palladium was high. Dental metal allergy was thus suggested to be the main cause of this lesion. The metal crowns in contact with the lesion were removed. The lesion gradually disappeared. Since other region of the oral mucosa that were in contact with the metal crown appeared normal, this lesion was suggeted to be caused by local trauma, as well as metal allergy.

Implications of Amalgam and Ceramic Degradation in the Oral Environment

Recent breakthroughs in materials science and technology have led to improved dental restorative ceramics, metals, and resin-based composites. These breakthroughs have been most important since one of the major controversies during this period has centered on allegations of the physiological risks of mercury released from amalgam restorations. Dental amalgams have been used in the United States since 1832, yet not a single well-documented case of dental patient toxicity to mercury from amalgam restorations has been reported in the scientific literature.A particularly extreme position has been adopted by the Swedish government, which has proposed the progressive elimination of amalgam as a dental restorative material by 1997. Among the materials that have been considered as the most biocompatible alternative to amalgam are dental ceramics. New ceramic products and technologies have gained considerable acceptance in Sweden even though their safety and efficacy have not been fully established.Although dental ceramics constitute a much more costly alternative than some other materials, they offer the advantages of esthetics, inertness, durability, low thermal conductivity, and low diffusivity, as compared with amalgams. Although ceramics are generally considered to be inert in the oral cavity, there are certain phenomena associated with their use that may cause significant surface degradation of these materials and subsequent physiological side effects.

Survey of chemical (mostly metals) poisoning cases as reflected in hospital admissions in urban Zimbabwe.

Exposure to heavy metals is mainly an occupational hazard such as in metal mining and refining, in the mechanical and chemical industry. Metals are also used as pesticides (copper and arsenic) and as therapeutic agents (Lithium carbonate, mercurial diuretics), Nylander et al 1987. Amalgams are used in dental treatment and various metals as implants in medicine, (Aronsson et al 1989, Goldwater, 1991). In some various cases the high natural occurrence of metals in food and /or drinking water can be a source of exposure (Gossel and Bricker, 1984). Sometimes the leaching of metals from eating utensils and/or cooking vessels may be a source of exposure. Environmental pollution caused by industrial emission, metals in fossile fuels or metal waste are additional sources of exposure, (Elinder, et al, 1983; Vanter and Lind, 1986). A number of countries now utilise lead-free fuels but in Zimbabwe lead is still blended in motor vehicle fuels and environmental pollution may exist.

金属アレルギーの現状と歯科領域における対応

Sensitization and allergic lesions resulting from metals in our living environment have often been reported. However, dentists have paid little attention so far on sensitization or dermal or mucosal lesions caused by metal restorations. We have established a team of 14 research institutions to perform patch tests with 18 kinds of dental metals and to conduct and epidemiological survey on the patch test positive subjects.Prior to the study, application of the testing solutions and reading of the skin reactions were standardized. Patch tests were done on volunteers and patients with the total of 1, 728 subjects. On those patients who showed positive reactions to the patch tests, metal analysis for the intraoral restorations was done by the method developed by Inoue et al. The analysis results were then compared to the patch test results to investigate the relation between the two.The following data was collected and discussions were made:(1) patch test posit ive/negative rates for the total subjects, (2) their differences regarding sex, age, or a kind of metal, (3) regional dfference, (4) relation between an individual with patch test positive result and his/her intraoral metal restoration (s), (5) types and locations of the lesions, (6) patch test positive rate (overall and of the each metal) for the patient group, (7) difference in the patch test positive rate between the volunteer group and the patient group, (8) comparison between the patch test positive rates among the M-9, M-11 or M-13 series, and among the different concentrations of the testing solutions, (9) comparison of the results between patch tests and their confirmation tests, (10) changes in the patch test reaction during the testing period.From these results, it is considered that careful and adequate measures against the metal allergy should be taken, when the dentist starts the prosthodontic treatment.