OBJECTIVE: To compare the retentions of different designs of cobalt-chromium (Co-Cr), pure titanium (CP Ti), and titanium alloy (Ti-6Al-4V) removable partial denture (RPD) circumferential clasps manufactured by selective laser melting (SLM) and to analyze the stress distribution of these clasps during the removal from abutment teeth. METHODS: Clasps with clasp arm size A (1.9 mm width/1.1 mm thickness at the body and 0.8-taper) or B (1.2 times A) and 0.25 mm or 0.50 mm undercut engagement were modeled on a prepared first premolar die, named as designs A1, A2, A3, and A4, respectively. The density and elastic modulus of SLM-built Co-Cr, CP Ti, and Ti-6Al-4V were measured and given to different groups of clasps. The density, elastic modulus, and Poisson ' s ratio of enamel were given to the die. The control group was the cast Co-Cr clasp with design A1, to which the density and elastic modulus of cast Co-Cr alloy were given. The Poisson's ratio of all metals was 0.33. The initial 5 N dislodging force was applied, and the maximum displacement of the clasp along the insertion path was computed. The load was reapplied with an increment of 5 N than in the last simulation until the clasp was completely dislodged. The retentive force range of different groups of clasps was obtained. The retentive forces of the SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with equivalent computed retentive force range to the control group were validated through the insertion/removal experiment. The von Mises stress distributions of these three groups of SLM-built clasps under 15 N loads were analyzed. RESULTS: SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with designs B1 or B2, and Co-Cr clasps with design A2 had higher retentive forces than those of the control group. SLM-built CP Ti and Ti-6Al-4V clasps with design A1 had lower retentive forces than those of the control group. SLM-built Co-Cr clasp with design A1 and SLM-built CP Ti and Ti-6Al-4V clasps with design A2 had equivalent retentive forces to those of the control group. The insertion/removal experiment showed that the measured retentive forces of these three groups of SLM-built clasps were (21.57±5.41) N, (19.75±4.47) N, and (19.32±2.04) N, respectively. No statistically significant measured retentive force difference was found among these three groups of SLM-built clasps (P>0.05). The maximum von Mises stress of these three groups of SLM-built clasps exceeded their responding yield strength except for the Ti-6Al-4V one. CONCLUSION SLM-built Co-Cr circumferential clasps had higher retention than CP Ti and Ti-6Al-4V ones with the same clasp arm size and undercut engagement. The retention of SLM-built circumferential clasps could be adjusted by changing the undercut engagement and clasp arm size. If SLM-built circumferential clasps are used in clinical practice, the Ti-6Al-4V clasp with clasp arm size A and 0.50 mm undercut engagement is recommended considering the long-term use of RPD in the patient's mouth.
Chromium Alloys ; Dental Clasps ; Denture Retention ; Denture, Partial, Removable ; Finite Element Analysis ; Humans ; Lasers ; Titanium

Wet detoxification has traditionally been seen as the most promising technology for treating chromium-contaminated sites. However, the addition of chemicals in the wet detoxification process not only increases the cost but also introduces extra pollutants. Moreover, the chromium-containing slag may be re-dissolved in the form of Cr(VI), and the increased concentration of Cr(VI) results in a serious "returning to yellow" phenomenon in the chromium-contaminated sites, causing undesirable secondary pollution. Microbial remediation is a promising technology to address the re-dissolution of chromium-containing slag after wet detoxification, and this article reviews the advances in this area. Firstly, the toxicity, current situation and conventional technologies for treating the chromium-containing slag were briefly summarized. The mechanisms of the inevitable re-dissolution of chromium-containing slag after wet detoxification were summarized. Three main mechanisms, namely bioreduction, biosorption and biomineralization, which are involved in the environmental-friendly and efficient microbial remediation technology, were reviewed. The variation of microbial species and the succession of microbial community during the bioremediation of chromium-contaminated sites were discussed. Finally, future research directions were prospected with the aim to develop long-term, stable and sustainable technologies for remediating the chromium-contaminated sites.
Biodegradation, Environmental ; Chromium/toxicity* ; Environmental Pollutants/toxicity*

OBJECTIVES: At present, removable partial denture is still one of the main restoration methods for dentition defects. However, the trend for digital partial denture is becoming more and more obvious in the field of oral repair. However, there are relatively few studies on digital removable partial denture. The aim of this study is to investigate the effects of 3 processing technologies (precision casting, digital cutting, and 3D printing) on the fitness for the clasps of cobalt chromium alloy and pure titanium removable partial denture, and to provide a theoretical basis for the clinical application of digital removable partial denture. METHODS: Clasps of Co-Cr alloy and pure titanium were produced by 3 different processing technologies (precision casting, digital cutting, and 3D printing). There are 6 groups, including a casting pure titanium group, a casting cobalt chromium group, a cutting pure titanium group, a cutting cobalt chromium group, a printing pure titanium group, and a printing cobalt chromium group ( RESULTS: There was no statistical difference in fitness between the casting pure titanium group and the casting cobalt chromium group ( CONCLUSIONS The cobalt chromium alloy and pure titanium clasps made by precision casting, digital cutting, and 3D printing have good fitness. Under the same process, there is no significant difference between cobalt chromium alloy and pure titanium clasps. The 3D printing pure titanium clasps have better fitness than casting pure titanium and cutting pure titanium clasps, which meet the needs of clinical application.
Chromium Alloys ; Cobalt ; Denture, Partial, Removable ; Titanium

Aims: Chromium salt possesses unique characteristics that render it useful in numerous applications in several industrial processes, especially tanning of animal hides which act as a major source of hexavalent chromium toxicity in environment. This study aimed to evaluate the efficiency of loofah immobilized Cladosporium cladosporioides CEL14 in remediate tannery wastewater which contains hexavalent chromium. Methodology and results: A total of 18 fungal species were isolated from three different sites of tannery wastewater in Egypt, of which C. cladosporioides CEL14 was the most capable species of chromate remediation with 81% after 7 days of incubation as free cells. The experiments were conducted in minimum salt medium supplemented with 200 ppm chromate in the form of potassium dichromate. Different process parameters studies demonstrated that chromate was completely removed at 30 °C, pH 6, 0.1% malt extract and 0.2% glucose after 7 days of incubation with 20% inoculum size. After that, C. cladosporioides was immobilized on a natural support material (loofah). The removal ability of chromate was enhanced through permanent viable immobilization on loofah pieces, which showing complete removal of chromate within 3 days. The toxicity assessment of treated tannery effluents revealed that 74% of Brassica napus seeds were germinated upon exposure to the treated effluent. Conclusion, significance and impact of study This study revealed that C. cladosporioides CEL14 isolate has high potential as bioremediating agent against toxic hexavalent chromium. The removal ability of toxic chromate was enhanced through permanent viable immobilization on loofah pieces. This technology is simple, cost effective, efficient and environmentally friendly. The loofah immobilized with C. cladosporioides CEL14 has potential to be applied in wastewater treatment of small-scale tanneries after onsite trials.
Luffa ; Cladosporium ; Chromium ; Wastewater

There have been few studies investigating the association between atopic dermatitis (AD) and prenatal exposure to heavy metals. We aimed to evaluate whether prenatal exposure to heavy metals is associated with the development or severity of AD in a birth cohort study. A total of 331 subjects were followed from birth for a median duration of 60.0 months. The presence and severity of AD were evaluated at ages 6 and 12 months, and regularly once a year thereafter. The concentrations of lead, mercury, chromium, and cadmium in umbilical cord blood were measured by inductively coupled plasma mass spectrometry. Cord blood mononuclear cells (CBMCs) were isolated and stimulated for analysis of cytokine production using ELISA. Heavy metal levels in cord blood were not associated with the development of AD until 24 months of age. However, a positive correlation was observed between the duration of AD and lead levels in cord blood (p=0.002). AD severity was also positively associated with chromium concentrations in cord blood (p=0.037), while cord blood levels of lead, mercury, and cadmium were not significantly associated with AD severity (p=0.562, p=0.054, and p=0.055, respectively). Interleukin-13 production in CBMCs was positively related with lead and chromium levels in cord blood (p=0.021 and p=0.015, respectively). Prenatal exposure to lead and chromium is associated with the persistence and severity of AD, and the immune reaction toward a Th2 polarization.
Cacao ; Cadmium ; Chromium ; Cohort Studies ; Dermatitis, Atopic ; Enzyme-Linked Immunosorbent Assay ; Fetal Blood ; Interleukin-13 ; Mass Spectrometry ; Metals, Heavy ; Parturition ; Plasma ; Umbilical Cord

BACKGROUND: Evidence on associations between occupational diesel exhaust and gasoline exposure and colorectal cancer is limited. We aimed to assess the effect of workplace exposure to diesel exhaust and gasoline on the risk of colorectal cancer. METHODS: This caseecontrol study included 181,709 colon cancer and 109,227 rectal cancer cases diagnosed between 1961 and 2005 in Finland, Iceland, Norway, and Sweden. Cases and controls were identified from the Nordic Occupational Cancer Study cohort and matched for country, birth year, and sex. Diesel exhaust and gasoline exposure values were assigned by country-specific job-exposure matrices. Odds ratios and 95% confidence intervals were calculated by using conditional logistic regression models. The results were adjusted for physical strain at work and occupational exposure to benzene, formaldehyde, ionizing radiation, chlorinated hydrocarbons, chromium, and wood dust. RESULTS: Diesel exhaust exposure was associated with a small increase in the risk of rectal cancer (odds ratio 1/4 1.05, 95% confidence interval 1.02–1.08). Gasoline exposure was not associated with colorectal cancer risk. CONCLUSION: This study showed a small risk increase for rectal cancer after workplace diesel exhaust exposure. However, this finding could be due to chance, given the limitations of the study.
Benzene ; Case-Control Studies ; Chromium ; Cohort Studies ; Colonic Neoplasms ; Colorectal Neoplasms ; Dust ; Finland ; Formaldehyde ; Gasoline ; Hydrocarbons, Chlorinated ; Iceland ; Logistic Models ; Norway ; Occupational Exposure ; Odds Ratio ; Parturition ; Radiation, Ionizing ; Rectal Neoplasms ; Scandinavian and Nordic Countries ; Sweden ; Vehicle Emissions ; Wood

BACKGROUND: Herbs have been used worldwide as complementary and alternative medicines. In Korea, herbs for medical purpose are strictly controlled by the Korea Food and Drug Administration (KFDA). But it does not provide standards for metal antigens. OBJECTIVE: This study conducted to identify the metal contents of Korean herbs and herbal products and to give information on counselling metal allergic patient. METHODS: The concentration of three metal allergens with high antigenicity, cobalt (Co), chromium (Cr), nickel (Ni) was quantitatively determined using inductively coupled plasma with a mass spectrometer after nitric acid (HNO₃) digestion. The herbal objects are as follows: 1) ten kinds of herb plants, 2) ten herbal products sold in Korean drugstores, and 3) ten herbal extracts prescribed by Korean herbal doctors. RESULTS: In 30 samples, Ni and Cr were detected in all items. Co was not detected in two drugstore products. CONCLUSION: Although the levels of metal detected in this study were very low relative to international guidelines and KFDA regulations, the herbal preparations contained similar or higher metal levels than known metal-rich foods. It can cause problems when it added to the daily diet and cause deterioration of skin lesions of metal sensitized person.
Allergens ; Chromium ; Cobalt ; Complementary Therapies ; Dermatitis ; Diet ; Digestion ; Herbal Medicine ; Humans ; Korea ; Metals ; Nickel ; Nitric Acid ; Plant Preparations ; Plasma ; Skin ; Social Control, Formal ; United States Food and Drug Administration

BACKGROUND: Medicines and Healthcare products Regulatory Agency (MHRA) guidance for patients with metal-on-metal (MoM) hip replacements was provided in 2012 and updated in 2017 to assist in the early detection of soft-tissue reactions due to metal wear debris. A large number of MoM hip replacements were undertaken at our hospital trust. A program of recall for all patients with MoM hip replacements was undertaken and MHRA guidelines were implemented. In this study, we aimed to investigate the effectiveness of the revised MHRA guidelines in the detection of early adverse reactions to metal debris and to re-evaluate the indications for metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) and revision surgery. METHODS: Identification and recall of all patients with MoM hip replacements from 2001 were conducted by using theatre logs, patient records, clinical coding information, and consultant logbooks. Two senior arthroplasty consultants reviewed X-rays and patient records. Postal questionnaires were forwarded to patients, together with requests for general practitioners to complete cobalt and chromium blood tests. The two consultant-led review of MOM replacements was undertaken with further radiological investigations (X-rays, MARS-MRI) performed according to the 2017 guidance with support of consultant radiologists. RESULTS: Of 674 identified patients, 297 were available for review: 26 patients did not have MoM implants, 36 were untraceable, 59 refused follow-up, 87 moved out of area, 147 had died, and 22 already had revision. Of 297 patients, 126 were women and 171 were men; age range was 39 to 95 years (mean age, 69 years); 126 had resurfacing and 171 had MoM replacements. Twenty-six patients had elevated metal ions. Thirty-three patients underwent MARS-MRI: MARS-MRI results were positive in 17 and negative in 16. Of 17 patients with positive MARS-MRI, 10 patients were asymptomatic and seven were waiting revision. CONCLUSIONS: Positive MARS-MRI can often occur in the absence of elevated metal ion levels; elevated blood metal ion levels do not mean MARS-MRI will be positive. All patients with MoM replacements were at risk. It is imperative to assess patients regularly for symptoms that may raise clinical suspicion and maintain a low threshold to performing MARS-MRI.
Arthroplasty ; Artifacts ; Chromium ; Clinical Coding ; Cobalt ; Consultants ; Delivery of Health Care ; Female ; Follow-Up Studies ; General Practitioners ; Hematologic Tests ; Hip ; Hospitals, District ; Humans ; Ions ; Magnetic Resonance Imaging ; Male

Prostate cancer is the second most common cancer in men worldwide. There are many occupational factors that have been suggested to cause prostate cancer. Our aim was to evaluate the evidence for causality by a literature review of occupational factors. We searched literature in Medline and SCOPUS from 1966 to June 30, 2015 to identify occupational risk factors for prostate cancer. The following risk factors were selected: farmers/agricultural workers, pesticides – whole group, and separately organophosphate and organochlorine pesticides, carbamates and triazines, cadmium, chromium, cutting fluids, acrylonitrile, rubber manufacturing, whole body vibration, shift work, flight personnel, ionizing radiation, and occupational physical activity. For each factor a literature search was performed and presented as meta-analysis of relative risk and heterogeneity (Q and I² index). A total of 168 original studies met the inclusion criteria with 90,688 prostate cancer cases. Significantly increased risks were observed for the following occupational exposures: pesticides (metaRR = 1.15, 95% confidence interval [CI] = 1.01–1.32; I² = 84%), and specifically group of organochlorine pesticides (meta relative risk [metaRR] = 1.08, 95% CI = 1.03–1.14; I² = 0%), chromium (metaRR = 1.19, 95% CI = 1.07–1.34; I² = 31%), shift work (metaRR = 1.25, 95% CI = 1.05–1.49; I² = 78%) and pilots (metaRR = 1.41, 95% CI = 1.02–1.94; I² = 63%) and occupational physical activity in cohort studies (metaRR = 0.87, 95% CI = 0.81–0.94; I² = 0%). The literature review supports a causal association for a few of the previously suggested factors.
Acrylonitrile ; Cadmium ; Carbamates ; Chromium ; Cohort Studies ; Epidemiologic Studies ; Humans ; Male ; Motor Activity ; Occupational Exposure ; Pesticides ; Population Characteristics ; Prostate ; Prostatic Neoplasms ; Radiation, Ionizing ; Risk Factors ; Rubber ; Triazines ; Vibration

Dietary supplements are popular worldwide and their use has been increasing. The purpose of this study was to evaluate the mineral contents of multi-vitamins and minerals (MVMs) in most commonly sold among dietary supplements. Ninety popular MVM supplements sold in South Korea were surveyed regarding their characteristics and ingredients including minerals listed on the labels through off-line and on-line search. Daily mineral contents of the MVM supplements were compared with Korean Dietary Reference Intakes (DRIs) by target populations. The average price of 90 MVM supplements was $41.3 per bottle, with a price of $0.9 per day and the average number of minerals contained per supplement was 4.7. A total 14 minerals were found in the MVM supplements including calcium, phosphorus, sodium, potassium, and magnesium. Nine minerals (e.g. calcium, magnesium, and iron) were included in more than 30% of the MVM supplements examined. When daily mineral dose of MVMs was compared to DRIs, calcium was the lowest (34.0% of recommended intake [RI]) and chromium was the highest (218.7% of adequate intake [AI]), and zinc, copper, selenium, and chromium were also higher than their RI or AI levels. The daily mineral contents of the 90 MVM supplements were below the tolerable upper-intake level, but some minerals were higher than RI or AI with high variance among products. Therefore, there is a great need to educate the public for the adequate selection and use of MVM supplements based on the contents of MVM supplements and individual's mineral intake derived from the diet.
Calcium ; Chromium ; Copper ; Diet ; Dietary Supplements ; Health Services Needs and Demand ; Korea* ; Magnesium ; Minerals* ; Miners* ; Phosphorus ; Potassium ; Product Labeling ; Recommended Dietary Allowances ; Selenium ; Sodium ; Zinc