Fit accuracy of metal partial removable dental prosthesis frameworks fabricated by traditional or light curing modeling material technique: An in vitro study

Objective

The aim of this study was to compare the fit accuracies of metal partial removable dental prosthesis (PRDP) frameworks fabricated by the traditional technique (TT) or the light-curing modeling material technique (LCMT).

Materials and methods

A metal model of a Kennedy class III modification 1 mandibular dental arch with two edentulous spaces of different spans, short and long, was used for the study. Thirty identical working casts were used to produce 15 PRDP frameworks each by TT and by LCMT. Every framework was transferred to a metal master cast to measure the gap between the metal base of the framework and the crest of the alveolar ridge of the cast. Gaps were measured at three points on each side by a USB digital intraoral camera at ×16.5 magnification. Images were transferred to a graphics editing program. A single examiner performed all measurements. The two-tailed t-test was performed at the 5% significance level.

Results

The mean gap value was significantly smaller in the LCMT group compared to the TT group. The mean value of the short edentulous span was significantly smaller than that of the long edentulous span in the LCMT group, whereas the opposite result was obtained in the TT group.

Conclusion

Within the limitations of this study, it can be concluded that the fit of the LCMT-fabricated frameworks was better than the fit of the TT-fabricated frameworks. The framework fit can differ according to the span of the edentate ridge and the fabrication technique for the metal framework.     

Altered tissue content of trace metals in diabetic hyperinsulinaemic sand rats (psammomys obesus)

Summary The concentrations of zinc, copper, and chromium in liver, kidney, muscle, bone and serum from control normoinsulinaemic and hyperinsulinaemic sand rats (Psammomys obesus) and from untreated spontaneously hyperinsulinaemic-hyperglycaemic sand rats were compared. A chronic hyperinsulinaemic-hyperglycaemic state was associated with a significant reduction (p<0.01) of zinc concentration in the liver, kidney and muscle but an elevation of zinc content in bone and of chromium in the liver. A hyperinsulinaemic-normoglycaemic state was not associated with similar changes in zinc concentration in the liver, kidney, muscle and bone. We conclude that in hyperinsulinaemic-hyperglycaemic sand rats there is a tendency to zinc depletion in several tissues. This depletion is not solely the result of a hyperinsulinaemic state but may be related to accompanying hyperglycaemia.     

佩戴镍铬合金烤瓷冠对尿镍铬水平影响的前瞻性随访研究

目的探讨镍铬合金烤瓷冠的佩戴是否会导致机体尿镍铬水平升高。方法对33例镍铬合金烤瓷冠佩戴者进行佩戴前和佩戴2月后的尿镍和尿铬重复测量,并采用配对t检验和重复测量数据线性回归分析探讨尿镍铬水平的变化与镍铬合金烤瓷冠佩戴的关系。结果镍铬合金烤瓷冠佩戴2月后,机体尿镍水平（67.6 μg·mol-1肌酐）略高于佩戴前（46.4 μg·mol-1肌酐）,但差异无统计学意义（P=0.063）;女性患者佩戴前为44.8 μg·mol-1肌酐,佩戴后为73.7 μg·mol-1肌酐（P=0.068）。佩戴2月后,机体尿铬水平（99.4 μg·mol-1肌酐）明显高于佩戴前（57.0 μg·mol-1肌酐）（P=0.024）,这种差异仅在女性中明显（佩戴前为59.8 μg·mol-1肌酐,佩戴后为124.4 μg·mol-1肌酐,P=0.023）。重复测量数据的线性回归分析显示机体尿镍铬的排泄与是否佩戴镍铬合金烤瓷冠、佩戴数量及金属裸露面积有关。结论镍铬合金烤瓷冠的佩戴可导致机体尿镍和尿铬水平增加。     

In vivo assessment of stent recoil of biodegradable polymer-coated cobalt–chromium sirolimus-eluting coronary stent system

IntroductionImmediate and acute stent recoil has been observed following balloon deflation in normal and diseased coronary arteries, and the degree varies by stent design.MethodsA total of 19 patients, who underwent elective stent implantation for single de novo native coronary artery lesions, were enrolled: all patients treated with the biodegradable polymer-coated sirolimus-eluting cobalt–chromium coronary stent system (Supralimus-Core^®). The immediate, acute and cumulative stent recoil was assessed by quantitative coronary angiography. The cumulative stent recoil was measured at 24 h of stent implantation.ResultsThe absolute late loss due to recoil was found 0.08 ± 0.19 mm for Immediate Stent Recoil (ISR), 0.05 ± 0.21 mm for Acute Stent Recoil (ASR) and 0.11 ± 0.25 mm for Cumulative Stent Recoil (CSR) respectively.ConclusionsIn vivo acute stent recoil of the Supralimus-Core^® has higher radial strength compared to other available standard drug-eluting stents.     

Oxidation State and Local Structure of Chromium Ions in LaOCl

LaOCl doped with 0–10 mol% Cr was synthesized by thermal decomposition of chlorides. X-ray diffraction (XRD) analysis revealed that incorporation of chromium results in a decrease of the lattice parameter a and a simultaneous increase of the lattice parameter c. The local structure of chromium ions was studied with X-ray photoelectron (XPS), X-ray absorption (XANES), multifrequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy techniques. It was determined that synthesis in oxidizing atmosphere promotes the incorporation of chromium ions predominantly in the 5+ oxidation state. Changes of chromium oxidation state and local environment occur after a subsequent treatment in reducing atmosphere. Spin-Hamiltonian (SH) parameters for a Cr⁵⁺ and two types of Cr³⁺ centers in LaOCl were determined from the EPR spectra simulations.     

Dermatitis from a chromium dental plate

Systemic absorption of metal or metallic salts from dental and orthopedic surgical implants can produce a cutaneous allergic dermatitis in susceptible individuals. Mercury, nickel and cobalt are the most common metals to elicit such systemic allergic reactions from chronic internal exposure. A case is presented of a generalized eczematoid dermatitis apparently caused by allergy to chromium liberated from a metal dental plate.     

Utilization of Tires Waste-Derived Magnetic-Activated Carbon for the Removal of Hexavalent Chromium from Wastewater

The present study focuses on fabrication of magnetic activated carbon (M-AC) using tire waste and its potential investigation for adsorption of Cr (VI) from wastewater. The composite material (M-AC) was synthesized by pyrolysis followed by in situ magnetization method, and characterized by FTIR, FESEM, EDX, and XRD analysis. The maximum adsorption of Cr (VI) ion over composite adsorbent was found (~99.5%) to occur at pH 2, sample volume 10 mL, adsorbent dose 100 mg, contact time 30 min. The adsorption process was endothermic, feasible, spontaneous, and was found to follow pseudo second order of the reaction. The Cr ion could be completely desorbed (~99.3%) from the composite adsorbent by using 20 mL of 2 M NaOH solution. The composite adsorbent was regenerated by continuous adsorption and desorption for 5 consecutive cycles by using 10 mL 0.1 M HCl solution. M-AC also performed well in case of tannery wastewater by removing about 97% of Cr (VI).     

Elevated tissue Cr levels,increased plasma oxidative markers,and global hypomethylation of blood DNA in male Sprague‐Dawley rats exposed to potassium dichromate in drinking water

Hexavalent chromium [Cr (VI)] is prevalent in ground water in some areas, but evidence on the toxic effects of Cr (VI) via ingestion through drinking water remains insufficient. The aims of our study were to investigate the toxic effects of Cr (VI) through oral water ingestion on oxidative stress and DNA methylation. Thirty‐two Sprague‐Dawley rats were randomly divided into four groups, and exposed to porassium dichromate (K₂Cr₂O₇; 0, 30, 100, and 300 mg/L) in drinking water for 4 weeks. Mean body weight gain, mean water consumption, clinical chemistry determinations, and oxidative stress levels in plasma were measured. Global DNA methylation changes and DNA methylation status at the promoter of p16 gene were also detected. After 4 weeks, mild anemic effects and increased plasma malondialdehyde (MDA) levels occurred in rats exposed to 100 mg/L or 300 mg/L of Cr (VI). Plasma glutathione peroxidase (GSH‐Px) activity decreased in all exposed groups. Global DNA methylation levels were reduced in 100 mg/L and 300 mg/L exposure groups. However, DNA methylation status at the promoter of P16 gene remained unchanged in all K₂Cr₂O_7‐treated groups. The correlation analysis indicated that increased MDA levels were closely correlated to global DNA hypomethylation. Our results indicated that oral ingestion of Cr (VI) through drinking water caused not only oxidative stress in plasma, but also global DNA hypomethylation in blood cells from male rats, and a good correlation was found between increased MDA levels and reduced global DNA methylation. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1080–1090, 2016.     

A metallurgical approach to metal contact dermatitis

It is well-known that some metals/alloys are sensitizing on skin contact, but it is not so well appreciated that sensitization is dependent on the reaction of the metal/alloy with sweat. The first step in skin sensitization by metals/alloys is a corrosion process and the formation of soluble metal ions. The nature of this process has implications with respect to occurrence of metal contact dermatitis, to testing techniques and to classification of metals/alloys as skin sensitizers.