牙科铸造合金诱发慢性毒副作用细胞机制的研究进展

牙科铸造合金在口腔临床中被广泛应用，而合金修复后在长期使用过程中，由于口腔内复杂微环境的影响，合金在口腔中的腐蚀会引起金属离子析出。大量的研究发现：这些析出的金属离子会对邻近的组织和细胞带来不同程度的慢性毒副作用，主要包括局部不良反应和全身不良反应。由于全身不良反应的发生率较低，相关的数据报道也比较有限，所以对合金中析出的金属离子引起的口腔局部不良反应成为国内外学者研究的热点。本文就铸造合金析出的金属离子对组织和细胞的毒副作用的研究现状及相应的细胞调控机制作一综述。     

Patients with local adverse effects from dental alloys: frequency, complaints, symptoms, allergy

Data on the prevalence of adverse effects from dental cast alloys and on the characteristics of the related patient groups are scarce. Therefore, the aim of the present study was to investigate patients in a defined part of Germany attributing oral complaints or symptoms to dental cast alloys. All dentists in the area of Eastern Bavaria (with 1 million inhabitants) were asked to send corresponding patients to our department during a 3-year period. Out of this collection, patients with complaints or symptoms in the oral cavity were recruited and characterized with regard to number, age and sex distribution, type of subjective complaints and objective intraoral symptoms, and allergy status based on an alloy analysis. Patients reporting to our department with suspected local adverse effects from dental cast alloys represented 0.01% of the population. Thirty-four percent of the patients were 50-59 years old, with females prevailing (76%). A great variety of subjective complaints was reported, which mainly resembles those reported by patients with adverse effects attributed to other dental materials like amalgam or denture base materials. The main objective intraoral symptoms were gingivitis, anomalies of the tongue (lingua plicata, lingua geographica), discoloration of the gingiva, redness of the palate or tongue and lichenoid reactions of the oral mucosa. In not more than 10% of the patients, allergy was diagnosed as contributing to the complaints or symptoms.     

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。     

Allergic palmoplantar pustulosis caused by cobalt in cast dental crowns: a case report

Cobalt chrome alloy is a common material in prosthodontic restorations; however, instances of palmoplantar pustulosis owing to cobalt allergy are rare. Here, we report an unusual case of palmoplantar pustulosis in the hands and feet of a 58-year-old male patient caused by a cobalt allergy. The patient developed palmoplantar pustulosis characterized by redness, pustules, vesicles, and scaly erythema on his hands and feet 1 month after obtaining cobalt chromium alloy cast crowns on his molar teeth. The symptoms persisted for 1 year. He underwent standard patch testing, which showed a strong positive reaction to cobalt chloride. After the crowns were removed, the symptoms disappeared in 3 weeks. This study may serve to remind dental practitioners to be aware of potential allergic reactions to dental materials used in prosthodontic treatment and to enable them to recognize a metal allergy if it appears.     

Root canal treatment on a patient with zinc oxide allergy: a case report

AIM: To describe successful root canal treatment of a patient with a true zinc oxide allergy and to discuss allergic reactions to dental materials. SUMMARY: Dental materials have been reported as aetiologic agents for both local and systemic allergic reactions. It is essential for the oral healthcare provider to recognize the clinical symptoms associated with allergic reactions and to modify dental treatment, if necessary, to prevent these reactions from occurring. This article describes an unusual case of a patient with an allergy to zinc oxide. To our knowledge, this is the first case of successful root canal treatment of a patient with confirmed zinc oxide allergy to be reported in the dental literature. KEY LEARNING POINTS: Medical and dental histories must be evaluated to prevent medical complications secondary to dental treatment. Any patient suspected of having an allergy to dental materials should be referred to a healthcare professional capable of performing and interpreting allergy tests prior to dental treatment.     

口腔金属修复体所致过敏性疾病的临床研究

目的:采用皮肤斑贴试验和口内金属修复体成分检测,探讨患者的临床症状与齿科金属过敏的相关性。方法:对2例可疑齿科金属过敏患者进行齿科金属系列斑贴试验,并同时检查患者金属修复体成分,结合二者判断2例患者的皮肤或者黏膜过敏症状与齿科金属修复体的相关性。结果:2例患者的斑贴实验阳性反应过敏原与口内金属修复体成分相一致,因而推测患者的临床症状与齿科金属致敏性具有相关性。经拆除患者的金属修复体,改用全瓷材料治疗牙列缺损,随访观察发现临床过敏症状好转。结论:齿科金属的致敏性可导致一些口腔黏膜或者皮肤的过敏症状,影响患者的生活质量。口腔科医生在进行修复治疗的时候应充分了解所使用金属合金的致敏率,减少高致敏率合金的临床应用,或在修复前采用斑贴试验,指导患者更安全有效的选择合适的材料。     

Allergic contact stomatitis from a gold alloy--fixed partial denture

Allergic contact stomatitis to gold is rare. To our knowledge, seven cases caused by dental restorations have been previously reported. Each of the patients was female. This report documents an allergic reaction to gold in a fixed prosthesis. A female patient, previously sensitized to gold earrings, experienced an itching and burning pain sensation and ulceration of the oral tissues adjacent to the gold restoration. Patch tests confirmed the allergy to gold. The dentist needs to be aware of the symptoms that are characteristic of the allergic manifestations of gold. Inquiries about allergies to metals and jewelry should be a part of the medical history. Any patient experiencing pain, itching, burning, and ulceration of the mucosa adjacent to a cast gold restoration should be suspected of an allergic contact stomatitis.     

New high-palladium casting alloys: 1. Overview and initial studies.

High-palladium alloys for metal ceramic restorations, based on the Pd-Cu-Ga and Pd-Ga systems, were introduced to the dental profession during the past decade. These alloys have become increasingly popular because they are much less expensive than the gold-based alloys, and recently marketed high-palladium alloy compositions have excellent mechanical properties. A summary of the important melting and casting considerations for these somewhat technique-sensitive alloys is presented together with an overview of important dental materials science aspects and the results of a dental laboratory survey. A maxillary central incisor coping was chosen as the clinically appropriate specimen shape, and the gas-oxygen torch melting technique was found to produce castings with clinically acceptable levels of marginal sharpness and little evidence of microporosity. The etched as-cast high-palladium alloys exhibited fine-scale multiphase microstructures, and a noteworthy finding was that relative proportions of the microstructural constituents frequently varied for thin versus thick sections of the cast specimens.     

In situ microsampling technique for identification of elements of a restoration with exposed metal to identify potential allergens.

STATEMENT OF PROBLEM: For clinical investigations of allergic reactions to dental materials, it is necessary to know the type of metal used in restorations in the mouth of the patient. However, an intraoral method of sampling the dental alloy without removing the metal restoration has not yet been established. PURPOSE: This study attempted to establish a clinically serviceable method for microsampling dental alloy. MATERIAL AND METHODS: A piece of silicone sampling tube is held on the surface of the metal restoration. This surface was ground with a carbide bur through the sampling tube, and the ground metal particles were then recovered from the inner surface of the tube. The recovered sample was subjected to energy-dispersive x-ray microanalysis. The percentage recovery of ground alloy by this microsampling method, which was the ratio of the recovered weight of metal to the total weight of the metal ground, was evaluated using 3 mm diameter x 1 mm thick disk-shaped specimens of Ag-Au-Pd and Ni-Cr alloys. RESULTS: Elemental analysis of the retrieved alloys identified the component elements in the alloy compositions. The percentage recovery by this microsampling method was 75.0% for Ag-Au-Pd alloy and 69.9% for Ni-Cr alloy, respectively. CONCLUSIONS: The microsampling method demonstrated a relatively high percentage recovery of the ground alloy particles. This microsampling method would be of great benefit clinically to patients who have allergic reactions to dental materials.     

Biocompatibility of dental casting alloys: a review

STATEMENT OF PROBLEM. Dental casting alloys are widely used in applications that place them into contact with oral tissues for many years. With the development of new dental alloys over the past 15 years, many questions remain about their biologic safety. Practitioners must choose among hundreds of alloy compositions, often without regard to biologic properties. PURPOSE. This article is an evidence-based tutorial for clinicians. Concepts and current issues relevant to the biologic effects of dental casting alloys are presented. SUMMARY. The single most relevant property of a casting alloy to its biologic safety is its corrosion. Systemic and local toxicity, allergy, and carcinogenicity all result from elements in the alloy being released into the mouth during corrosion. Little evidence supports concerns of casting alloys causing systemic toxicity. The occurrence of local toxic effects (adjacent to the alloy) is not well documented, but is a higher risk, primarily because local tissues are exposed to much higher concentrations of released metal ions. Several elements such as nickel and cobalt have relatively high potential to cause allergy, but the true risk of using alloys containing these elements remains undefined. Prudence dictates that alloys containing these elements be avoided if possible. Several elements in casting alloys are known mutagens, and a few such as beryllium and cadmium are known carcinogens in different chemical forms. Despite these facts, carcinogenic effects from dental casting alloys have not been demonstrated. Prudent practitioners should avoid alloys containing these known carcinogens. CONCLUSION. To minimize biologic risks, dentists should select alloys that have the lowest release of elements (lowest corrosion). This goal can be achieved by using high-noble or noble alloys with single-phase microstructures. However, there are exceptions to this generality, and selection of an alloy should be made on a case-by-case basis using corrosion and biologic data from dental manufacturers.     

Fabrication systems for restorations and fixed dental prostheses made of titanium and titanium alloys

PurposeIn recent years, the application of restorations and fixed dental prostheses to molars by computer-aided design-computer-aided manufacturing (CAD/CAM) with composite resin has been increasing. Titanium and titanium alloy having a high tissue affinity and good biocompatibility are suitable for cases where CAD/CAM fabrications are inadequate, such as allergic reaction to metal. Many studies have reported methods of production with titanium and titanium alloys. The purpose of this review is to survey the clinical application of titanium and titanium alloy restorations and fixed dental prostheses with various fabrication systems.Study selectionA literature search in PubMed was performed for various fabrication systems of titanium and titanium alloy from 2010 through 2019. The search keywords were “titanium”, “titanium alloy”, “CAD/CAM”, “cast”, “fabrication system”, “marginal gap”, “internal gap”, and “clinical performance”. Only relevant studies are summarized and discussed in this review.ResultsWith any fabrication system, titanium and titanium alloy restorations and fixed dental prostheses fabricated with various systems were within the clinically acceptable ranges of marginal gap and internal fit. Additionally, these restorations were considered to have less effect on the periodontal issues. Although metal–ceramic restoration has clinical performance problems, such as ceramic fracture, fabrications with only titanium and titanium alloy were reported to have good clinical performance.ConclusionsRegardless of the fabrication system, titanium and titanium alloy restorations and fixed dental prostheses can be applied clinically. Titanium and titanium alloys are thought to be a promising alternative to the dental metals currently used.     

The relationship of metals to the general health of the patient, the dentist and office staff

Recently a few dental practitioners have asserted that some of the metallic dental restorative materials can be toxic to patients. In particular, nickel from base-metal casting alloys and mercury from silver amalgam have been implicated. Nickel is a strong allergen and a weak carcinogen. However, current evidence does not support the view that the making and use of base-metal cast restorations causes an increased incidence of either of these problems in dental personnel or in patients. Mercury rarely causes allergy but the possibility of such an event must be remembered. Mercury has a strong potential for causing chronic toxicity. Dental personnel must use caution in the handling of free mercury in the process of making amalgam restorations. There is evidence that mercury can be released from dental amalgam restorations, but only in very small quantities. Except for the claims of those practitioners who decry the use of dental amalgam, there is no evidence to support the view that there is a toxic hazard to patients who have amalgam restorations.     

Oral lichenoid lesions related to dental restorative materials

OBJECTIVES: To determine the effectiveness of replacing restorations considered to be the cause of an oral lichenoid lesion (oral lichenoid reaction)(OLL). DESIGN: Clinical intervention and nine-month follow up. SETTING: The study was carried out in the University Dental Hospital of Manchester, 1998-2002. SUBJECTS AND METHODS: A total of 51 patients, mean age 53 (SD 13) years, who had oral lesions or symptoms suspected to be related to their dental restorations were investigated. Baseline patch tests for a series of dental materials, biopsies and photographs were undertaken. Thirty-nine out of 51 (76%) of patients had their restorations replaced. RESULTS: The clinical manifestations of OLL were variable; the majority of OLL were found to be in the molar and retro molar area of the buccal mucosa and the tongue. Twenty-seven (53%) patients had positive patch test reactions to at least one material, 24 of them for one or more mercury compound. After a mean follow up period of nine months, lesions adjacent to replaced restorations completely healed in 16 (42%) patients (10 positive and 6 negative patch tests). Improvement in signs and symptoms were found in 18 (47%) patients (11 positive and 7 negative patch tests). CONCLUSION: OLLs may be elicited by some dental restorations. Replacing restorations adjacent to these lesions is associated with healing in the majority of cases particularly when lesions are in close contact with restorations. A patch test seems to be of limited benefit as a predictor of such reactions.     

A modified phosphate-bonded casting investment

Abstract – An experimental phosphate-bonded casting investment with negligible setting'expansion and a thermal expansion of 1.6%, sufficient to compensate for the solid thermal shrinkage of conventional dental gold alloys and high-precious alloys for die porcelain fused to metal technique, is described. When used in a ringless casting technique the investment makes it possible to produce cast restorations with a consistent slidefit. In combination with a die spacer technique the new investment makes it possible routinely to produce cast restorations with a consistent and known, degree of loosefu.     

Present status of titanium removable dentures--a review of the literature

Although porcelain and zirconium oxide might be used for fixed partial dental prostheses instead of conventional dental metals in the near future, removable partial denture (RPD) frameworks will probably continue to be cast with biocompatible metals. Commercially pure (CP) titanium has appropriate mechanical properties, it is lightweight (low density) compared with conventional dental alloys, and has outstanding biocompatibility that prevents metal allergic reactions. This literature review describes the laboratory conditions needed for fabricating titanium frameworks and the present status of titanium removable prostheses. The use of titanium for the production of cast RPD frameworks has gradually increased. There are no reports about metallic allergy apparently caused by CP titanium dentures. The laboratory drawbacks still remain, such as the lengthy burn-out, inferior castability and machinability, reaction layer formed on the cast surface, difficulty of polishing, and high initial costs. However, the clinical problems, such as discoloration of the titanium surfaces, unpleasant metal taste, decrease of clasp retention, tendency for plaque to adhere to the surface, detachment of the denture base resin, and severe wear of titanium teeth, have gradually been resolved. Titanium RPD frameworks have never been reported to fail catastrophically. Thus, titanium is recommended as protection against metal allergy, particularly for large-sized prostheses such as RPDs or complete dentures.     

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.     

Clinical findings in patients with orofacial discomfort complaints

In 113 patients with orofacial and general complaints, which they assumed were caused by galvanic currents and/or metallic restorations, clinical dental and medical examinations were performed. Most of the patients had natural teeth with dental metallic restorations. A number of dental diagnoses, such as caries, pulpitis, periapical osteitis and periodontitis, were found. However, 16% were edentulous in one or both jaws and had complete dentures. 69% had possible metal contacts. Some oral mucosal changes were observed, but they were as frequent in patients without as in those with metal contact possibility. Signs of parafunctions and functional disturbances of the masticatory system were extremely frequent. A careful oral examination in these patients thus revealed many clinical dental and oral signs that could be more-or-less related to the complaints. Because of the extremely varying symptoms reported, however, only a small proportion could be fully explained by odontological and/or medical diagnoses, and in 38% of the patients, no clear odontological diagnosis was found that could explain the complaints.     

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.     

Applicability of zirconia dental prostheses for metal allergy patients

The aim of this study was to investigate the applicability of zirconium dioxide (zirconia) as a substitute for metal alloys in a group of metal allergy patients. Fourteen patients (eight women, six men) who had been restored with porcelain-fused-to-metal fixed partial dentures (FPDs) and had exhibited hypersensitivity lesions to dental alloys were enrolled in this study. Patients were previously patch-tested using standard testing substances authorized by the International Contact Dermatitis Research Group. Patients received FPDs with zirconia frameworks and occurrences of oral symptoms were evaluated. No hypersensitivity lesions in the mouth or on the skin were encountered during the follow-up period of 3 years. Zirconia FPDs may be an alternative to porcelain-fused-to-metal FPDs in patients with metal allergies.     

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.