Nordic dentists' opinions on the safety of amalgam and other dental restorative materials

The safety of amalgam and other restorative materials has caused concern among dental patients in recent years. The aim of this study was to obtain information on dentists' perceived competence in handling different filling materials and their opinions on the safety of these. A random sample of practising dentists in Denmark, Finland, Norway, and Sweden received a mail question-naire in spring 1990. Answers were received from 1732 dentists (65%). The study showed that the respondents believed that their theoretic knowledge and clinical skills were generally at a high level regarding restorative materials. The risks of the side-effects of gold, ceramic materials, and glass ionomer were considered to be low by about 90% of the respondents. Amalgam was considered to be significantly more hazardous by the Swedish respondents than the others. Interestingly, composite was considered to be associated with a high risk of side-effects by about half of the dentists in all Nordic countries. The dentists' opinions were not found to be greatly influenced by their sex, age, or place of residence but rather by their country and service sector. Against the background of the present lack of scientific evidence on the hazardousness of amalgam or other restorative materials for patients' general health, these findings indicate that dentists are influenced by discussions in the mass media about dental treatment and materials and, of course, by the guidelines given by the health authorities in their own countries. Few dentists were shown to be concerned about occupational risks associated with the use of amalgam, and they had not had their own amalgam fillings replaced. Thus, Nordic dentists seem prepared to continue to use amalgam as one of several dental restorative materials while waiting for technically and biologically more satisfactory ones.     

The effect of dental restorative materials on dental biofilm

To investigate the arrangement of biofilms formed in vivo, volunteers wore splints with slabs of six different dental materials inserted to collect smooth surface plaque. After 5 d of undisturbed plaque accumulation, the specimens were vital stained and analyzed by the confocal laser scanning microscopy (CLSM) to evaluate the percentage of vital biofilm microflora (VF percentage). Further parameters were the area of the specimens covered by plaque (surface coating; SC, %) and the height of the biofilms (BH, pm). The metals amalgam and gold, the compomer, as well as the glass-ionomer cement harboured an almost entirely dead biofilm (VF <8%). Resin composite led to vitality values between 4 and 21%, while a very thin biofilm on ceramic revealed the highest vitality values (34-86%). SC varied from 6% on glass-ionomer cement to 100% on amalgam. BH reached its highest value on amalgam and gold of 17 and 11 microm, respectively, while heights of between 1 and 6 microm were found on the ceramic, resin composite, compomer and the glass-ionomer cement. Within their limits, the present findings indicate that amalgam, gold, compomer and glass-ionomer cement exert an influence against the adhering biofilm. No general relationship could be established between the different parameters VF percentage, SC percentage and BH (microm).     

Attitudes of some European dental undergraduate students to the placement of direct restorative materials in posterior teeth

Summary The aim of this article was to report on the attitudes, opinions and confidences of final year dental students in three European schools towards the restoration of posterior teeth and in particular towards the use of amalgam and resin composite. One hundred and twenty‐eight pre‐piloted questionnaires were distributed to final year dental students in Cardiff, Dublin and Malmö. The questionnaire sought information relating to various opinions and attitudes towards the use of amalgam and resin composite in posterior teeth. Information was returned anonymously. Ninety‐one completed questionnaires were returned (response rate = 71%; Cardiff: n = 40, Dublin: n = 24, Malmö: n = 27). Ninety‐three per cent of Malmö students (n = 24), 67% of Dublin students (n = 16) and 60% of Cardiff students (n = 24) reported that they feel confident when placing posterior resin composites. One hundred per cent of Malmö students (n = 27), 75% of Cardiff students (n = 30) and 33% of Dublin students (n = 8) would prefer to have a resin composite rather than amalgam, placed in one of their own posterior teeth. Eighty‐five per cent of Malmö students (n = 23), 30% of Cardiff students (n = 12) and 25% of Dublin students (n = 6) perceive amalgam as being harmful to the environment. For the restoration of a posterior tooth in a pregnant female, 44% of students (n = 40) would place a resin composite restoration, and 7% (n = 6) would place an amalgam restoration, while 32% (n = 29) would place a temporary restoration. Students at Malmö report that they place more posterior resin composites and have greater confidence at placing posterior resin composites than students at Cardiff or Dublin. There was confusion relating to the choice of restorative materials for pregnant females. Large variations in restorative strategies among graduates must be considered as dental professionals can practice in all countries within the European Union.     

Reasons for replacement of amalgam dental restorations

abstract — Recurrent caries appears to be the most frequently occurring reason for replacement of amalgam dental restorations. Recent developments of amalgam alloys have improved the clinical appearance of such fillings but the possible influence on their durability is uncertain.     

脉冲Nd:YAG激光照射后牙髓碱性磷酸酶的活性

目的 :探讨脉冲Nd :YAG激光照射后牙髓碱性磷酸酶 (ALP)的活性。方法 :选择 4条健康的本地杂种犬 ,进行牙齿过敏模型制备 ,随机分为 3组 ,分别给予 :33J/cm2 、5 6J/cm2 、111J/cm2 激光照射 ,按照即刻、3d、7d和 1月 4个时间段处死试验犬 ,实验牙经过固定、脱钙后 ,进行组织切片、染色、光镜观察、灰度值分级。结果 :3组激光能量照射后 ,牙髓成牙本质细胞均有染色 ,以 3d、7d染色较深 ,1月后染色变浅 ,ALP活性降低 ,接近正常牙髓细胞水平。结论 :在本实验条件下 ,牙髓成牙本质细胞碱性磷酸酶活性在不同的观察期相差显著 (P <0 .0 1) ,与激光能量无关 (P >0 .0 5 )。     

Y-TZP口腔修复材料的低温老化及抗低温老化的相关研究

综合国内外相关研究,了解氧化钇稳定的四方氧化锆多晶陶瓷(Y-TZP)口腔修复材料的低温老化现象,探讨抗Y-TZP修复陶瓷低温老化的方法,展望抗低温老化Y-TZP陶瓷在口腔临床中的应用.抗Y-TZP低温老化的方法包括:稳定剂类型和含量的选择、加工工艺的改善、适宜的表面处理、合成复合陶瓷等,其中Y-TZP/Al2O3复合陶瓷对Y-TZP的低温老化有较大程度的缓解作用,且能明显改善Y-TZP的机械性能,是一种在口腔临床应用中具有发展前景的氧化锆基陶瓷材料.     

The value of extended-setting-time amalgam in pre-clinical practice in undergraduate dental training

This is a single-blind controlled study investigating the advantages of extended-setting time dental amalgam compared to a standard amalgam in the training of undergraduate dental students. 50 dental students were randomly assigned 1 of the 2 alloys for each restoration placed in the study. Each student placed class I and class II restorations in extracted human teeth mounted in typodont arches. 449 completed restorations were available for assessment, 228 restorations in the experimental group and 221 restorations in the control group. The test restorations were overall marginally inferior to those of the control group. There appears to be no advantage in using extended-setting time dental amalgam in undergraduate training.     

Posterior dental restoration material choices in privately insured people in the United States, 2017 through 2019

BackgroundIn the context of evolving dental materials and techniques and a national agenda to phasedown use of dental amalgam, estimates of dental amalgam placement are necessary for monitoring purposes.MethodsNumbers of amalgam and composite posterior restorations from 2017 through 2019 were calculated using retrospective dental claims analysis of privately insured patients. Kruskal-Wallis and multilevel, multivariable negative binomial regression models were used to test for differences in rates of amalgam and composite restoration placement by age group, sex, urban or rural area, and percentage race and ethnicity area distribution. Statistical significance was set at 0.05, with Benjamini-Hochberg correction for false discovery rate.ResultsThe rate of amalgam restorations declined over time from a mean of 6.29 per 100 patients in 2017 to 4.78 per 100 patients in 2019, whereas the composite restoration rate increased from 27.6 per 100 patients in 2017 to 28.8 per 100 in 2019. The mean number of amalgam restorations placed per person were lowest in females compared with males, in urban areas compared with rural areas, and in areas with more than 75% non-Hispanic White residents.ConclusionsAmalgam restoration placements in privately insured people in the United States declined from 2017 through 2019. Amalgam restoration placements may be unevenly distributed by location.Practical ImplicationsAchieving further declines of dental amalgam use may require changes to insurance coverage, incentives, and provider training as well as augmented disease prevention and health promotion efforts. These efforts should focus particularly on groups with high caries risk or higher rates of amalgam placement.     

Potential side effects of dental amalgam restorations

The aim of this study was to explore a possible association between health status and self-reported adverse effects related to dental amalgam restorations. A group of 50 consecutive patients (index group), referred for complaints self-related to dental amalgam restorations, was compared with a control group of individuals matched by age, sex and postal zip code. The patients underwent an oral, stomatognathic, medical and clinical chemistry examination. Mercury levels were examined in blood, urine and hair. The results revealed that somatic diseases were more common in the index group (38% versus 6%). Symptoms related to cranio-mandibular dysfunction were reported by 74% of the patients in the index group versus 24% in the control group, and were diagnosed in 62% and 36%, respectively. The oral health status and the number of amalgam surfaces were similar in the 2 groups. No positive skin patch test to mercury was found in any of the groups. The estimated mercury intake from fish consumption, occupational exposure, and mercury levels in blood and urine were also similar and far below levels, where negative health effects would be expected. The correlation between the number of amalgam surfaces and mercury levels in plasma and urine ( r = 0.43) indicated a release of mercury from dental amalgam restorations in both groups. Since the mercury levels were similar among index patients and controls, mercury was not a likely cause of the impaired health reported by the patients.     

Effect of free mercury on the strengths of dental amalgams

A previous study of several different Ag?Sn, Ag?Cu, and Ag?Sn?Cu alloys revealed that some of these alloys were susceptible to mercury embrittlement. The present study was undertaken to determine the extent to which embrittlement of alloy particles in amalgam affects the strength of the material. Specimens of low copper amalgam (O), high copper admixed amalgam (D), and high copper single composition amalgams (S and T) were condensed into 2 mm×4 mm×15 mm molds using a pressure of 14 MPa. After aging the specimens for 7 days at 37°C, mercury was coated on each specimen either by electro-plating mercury or by immersion in mercury. In each method, mercury was applied for 15 s or 1 min. At 30 s after coating, each specimen was placed in a 3-point fracture fixture and immediately loaded at 0.25 and 2.54 mm/min until fracture occurred. As controls, specimens of each amalgam without mercury coating were also tested. Ten specimens per experimental condition were tested. Fractured surfaces were examined using a scanning electron microscope. Strength reductions as high as 60% for O amalgam, 44% for D amalgam, and 31% for T amalgam were found. Two observations suggest that embrittlement of unconsumed alloy particles is primarily responsible for the strength reduction: 1) the amalgams showing susceptibility to mercury embrittlement in the present study contain alloy particles of alloys that were shown to be susceptible to embrittlement in an earlier study, and 2) the amalgam S, which showed the least susceptibility to mercury embrittlement, contains unconsumed alloy particles of an alloy that showed no significant embrittlement in the earlier study. Experimental evidence supports the hypothesis that free mercury released during corrosion or aging of amalgam restorations can contribute to the weakening of these restorations.     

脉冲Nd:YAG激光照射对犬牙髓的影响

目的：探讨Nd：YAG激光对牙髓的安全阈值。方法：选择4条健康的本地杂种犬，先进行过敏模型制备，随机分为3组，分别给予：33J／cm^2、56J／cm^2和111J／cm^2激光照射，按照即刻、3d、7d、1个月4个时间段处死试验犬，实验牙经过固定、脱钙后，进行组织切片、光镜观察、病理分级。结果：牙髓反应均在3级以下，随激光照射能量的升高牙髓组织病理变化明显。在33～56J／cm^2之间，牙髓组织正常或反应轻微。结论：应用Nd：YAG激光进行牙齿过敏治疗时，其热效应可能对牙髓组织产生影响，33～56J／cm^2的激光能量不会对牙髓组织产生损害，能量较高将导致牙髓组织炎症，所以33～56J／cm^2的能量密度应为进行当次牙齿过敏治疗的安全阈值。     

Reasons for restorative therapy and the longevity of restorations in adults

The aim of this study was to obtain information on the restorative dental care of adults in Finland. A random sample of private dentists was drawn from the register, and in spring 2000 they were sent a questionnaire requesting them to record information for each restoration placed during one ordinary working day. A total of 800 dentists were contacted and 548 responded. The dentists reported placement of 3,455 restorations. Of these, 5% were Class I, 36% were Class II, 13% were Class III, 9% were Class IV, 21% were Class V, and 16% were extensive restorations including 4 or more surfaces. Overall, composite resin was the most common restorative material, and it was used in 79% of the restorations, whereas amalgam was used in 5%, compomers in 4%, and glass ionomers (either conventional or resin‐modified) in 7% of cases. In 5% of the cases, the tooth was restored with indirect restorative methods, using either gold or ceramic materials. Of the treatments, 65% were replacements of previous restorations. Secondary caries was the most common reason for replacement (36%, 52%, and 41% for composite, glass ionomer, and amalgam, respectively). Other common reasons were fractures of the tooth or restoration (23%, 11%, and 22% for composite, glass ionomer, and amalgam, respectively) and lost composite restorations (16%). The median age of failed restorations was 15 years for amalgam, 6 years for composite, and 7 years for conventional glass ionomer. Although the longevity of tooth coloured restorations was shorter than that of amalgam, comparisons with our previous studies indicate improved survival periods for tooth coloured materials.     

Nd：YAG激光用于狗牙直接盖髓术的实验研究

目的：观察Ｎｄ：ＹＡＧ激光照射暴露牙髓后的盖髓术疗效。方法：用肉眼和组织学切片法。结果：１０７个狗牙露髓面用３个不同参数（１５９２ｍＪ／ｍｍ２、３１８５ｍＪ／ｍｍ２、４７７７ｍＪ／ｍｍ２）Ｎｄ：ＹＡＧ激光照射５ｓ后用氢氧化钙盖髓，与单纯氢氧化钙组比较，发现：低能量Ｎｄ：ＹＡＧ激光有刺激照射区和侧方修复性牙本质形成、促进创伤愈合作用，而高能量Ｎｄ：ＹＡＧ激光照射则可能引起牙髓变性坏死。结论：低能量Ｎｄ：ＹＡＧ激光有一定的促进创伤愈合作用，但在Ｎｄ：ＹＡＧ激光用于照射露髓面牙髓前，还应该对促进牙本质桥形成的Ｎｄ：ＹＡＧ激光照射条件进行更详细研究。     

A case of high mercury exposure from dental amalgam

This report describes a patient who suffered from several complaints, which by herself were attributed to her amalgam fillings. Analysis of mercury in plasma and urine showed unexpectedly high concentrations. 63 and 223 nmol/l. respectively. Following removal of the amalgam fillings, the urinary excretion of mercury became gradually normalized, and her symptoms declined.     

Controversy of silver amalgam as a restorative material

Silver amalgam contains mercury leading to concerns about the potential toxic effects of amalgam on the health of dental patients. The debate over the toxicity of silver amalgam restorations has divided the dental profession for over a century. The use of amalgam restorations for anterior teeth have been declining worldwide due to patient’s safety concerns and preference for tooth colored restorations. Nevertheless, amalgam has served the dental profession for decades and benefited hundreds of millions of patients because of its longevity as a dental restorative material. Amalgam is still the World’s most widely used restorative material for posterior teeth.     

Corrosion of zinc-containing dental amalgam

Abstract – The γ₁ lattice constant of amalgams with and without zinc kept under corrosive and non-corrosive conditions was determined at different times after trituration. Zinc disappeared during 1 d from the γ₁ phase of an amalgam made from 0.9% Zn alloy and during 30 d from an amalgam made from 4% Zn alloy, when powdered amalgam was in contact with a 1% NaCl solution.     

Use of potentiodynamic polarization technique for corrosion testing of dental alloys

Abstract— The number and in particular the diversity in types and composition of alloys used in dentistry are increasing, thus enhancing the need for predictive corrosion testing. No corrosion test is generally accepted as being both applicable to and relevant for all dental alloys. However, some methods have gained a certain recognition, and among these are the potentiodynamic polarization techniques. The purpose of the present work was to study the application, the reproducibility and the influence of some methodological variables on the results of potentiodynamic polarization corrosion testing. Embedded specimens of 18 different dental alloys, representing all major types, were subjected to anodic polarization scan within the potential range of – 700 mV to 1000 mV (SCE). Artificial saliva, with and without organic compounds, and sodium sulfide solution were used as electrolytes. The results were processed on a microcomputer using locally developed software. The curves of current density versus potential showed fair reproducibility, with great differences between some of the alloys, showing a clear relationship to nobility or passivity of the alloy. There were marked differences between the results obtained in artificial saliva and in sodium sulfide solution, while addition of organic components to the artificial saliva only had a minor effect. The potentiodynamic polarization corrosion test supplies detailed information such as anodic charge, and open circuit, rupture, and passivation potential. Furthermore, it indicates the passive range and sensitivity to pitting corrosion. These are all useful when evaluating the corrosion properties of a dental alloy. An analysis of variance of the results in this study showed that possible differences between the alloys were clearly detectable with this method. However, for alloys releasing non-ionic products during corrosion/degradation, the method may be inappropriate. It is thus concluded that the method appears applicable as an in vitro corrosion test for most dental alloys, with the possible exception of amalgams.     

Nd:YAG激光对猴牙牙髓的影响

目的：观察Nd：YAG激光对猴牙牙髓的影响，比较牙面涂布60g／L美蓝和经常规硝酸银脱敏后对激光照射效果的影响情况。方法：以1592、3185、4777mJ／mm^23种能量水平的Nd：YAG激光照射3只猴的30个牙面，用组织病理学方法观察牙髓变化情况。结果：1592mJ／mm^2照射组，不论牙面经何种处理，牙髓反应均与对照组相似，为0级；3185mJ／mm^2照射组，牙髓出现轻度改变；大能量、高频率的4777mJ／mm^2照射则出现广泛性成牙本质细胞变性、坏死。照射面色素的存在增加了激光对牙髓的刺激，氨硝酸银加丁香油酚还原成银沉淀，隔绝了外界刺激对牙本质和牙髓的影响，同样参数的Nd：YAG激光造成的牙髓损害在3组中最小。结论：大能量Nd：YAG激光可造成牙髓组织损伤性反应，照射面经不同的处理可影响Nd：YAG激光的照射效果。