Study of resin-bonded calcia investment. Part 3: Hardness of titanium castings. (33/368)

The Vickers hardness of the cross-sectioned area of titanium castings made from an experimental resin-bonded calcia investment and three commercial investments was evaluated. The microstructure and element distribution of the surface zone were analyzed using an EPMA. The results showed that the high hardness of the casting surface could be decreased using the experimental investment. The hardness of the castings made from the experimental investment at a 25-50 microm depth was lower than those from the other investments, and the thickness of the hardened casting surface was 125 microm. Layered structures with fewer layers were formed on the surfaces of the castings made from the experimental investment. The layered structures were influenced by both the investment components and the mold temperature at casting. The less contaminating nature of the experimental investment components and the technology of the room temperature mold contributed to the improved surface properties of the resulting castings.  (+info)

Effect of calcium supplementation on the risk of large bowel polyps. (34/368)

BACKGROUND: Clinical trials have shown that calcium supplementation modestly decreases the risk of colorectal adenomas. However, few studies have examined the effect of calcium on the risk of different types of colorectal lesions or dietary determinants of this effect. METHODS: Our analysis used patients from the Calcium Polyp Prevention Study, a randomized, double-blind, placebo-controlled chemoprevention trial among patients with a recent colorectal adenoma. Nine hundred thirty patients were randomly assigned to calcium carbonate (1200 mg/day) or placebo. Follow-up colonoscopies were conducted approximately 1 and 4 years after the qualifying examination. We used general estimating equation (GEE) and generalized linear regression analyses to compute risk ratios and 95% confidence intervals (CIs) to assess the effect of calcium treatment versus placebo on the risk of hyperplastic polyps, tubular adenomas, and more advanced lesions. Additionally, we used GEE analyses to compare the calcium treatment effects for various types of polyps with that for tubular adenomas. We also examined the interaction between calcium treatment and baseline intake of dietary calcium, fat, and fiber. All P values were obtained using Wald tests based on the corresponding models. All tests of statistical significance were two-sided. RESULTS: The calcium risk ratio for hyperplastic polyps was 0.82 (95% CI = 0.67 to 1.00), that for tubular adenomas was 0.89 (95% CI = 0.77 to 1.03), and that for histologically advanced neoplasms was 0.65 (95% CI = 0.46 to 0.93) compared with patients assigned to placebo. There were no statistically significant differences between the risk ratio for tubular adenomas and that for other types of polyps. The effect of calcium supplementation on adenoma risk was most pronounced among individuals with high dietary intakes of calcium and fiber and with low intake of fat, but the interactions were not statistically significant. CONCLUSION: Our results suggest that calcium supplementation may have a more pronounced antineoplastic effect on advanced colorectal lesions than on other types of polyps.  (+info)

Treatment of hyperphosphatemia in patients with chronic kidney disease on maintenance hemodialysis: results of the CARE study. (35/368)

Most patients with end-stage renal disease develop hyperphosphatemia because their dietary intake exceeds phosphorus elimination by intermittent thrice-weekly dialysis. Inadequately treated hyperphosphatemia plays a central role in the pathogenesis of secondary hyperparathyroidism and extraosseous calcification. Moreover, in the last 15 years, this biochemical abnormality has become increasingly important following the publication of two epidemiologic studies that demonstrated an association between elevated serum phosphorus and increased mortality risk in patients with end-stage renal disease. As a result, the National Kidney Foundation Kidney Disease Outcome and Quality Initiative (K/DOQI) Bone Metabolism and Chronic Kidney Disease Guidelines recommend that serum phosphorus levels be maintained between 3.5 and 5.5 mg/dL. Unfortunately, cross-sectional studies have shown a mean serum phosphorus of 6.2 mg/dL in the maintenance hemodialysis population in the United States. An alarming 60% of patients have serum phosphorus in excess of the 5.5 mg/dL level recommended by K/DOQI guidelines. In order to achieve this new target for serum phosphorus, the most efficacious and cost-effective phosphate binders currently available should be utilized. In this review, we discuss the results of the Calcium Acetate Renagel Evaluation (CARE study), which clearly demonstrated the superiority of calcium acetate over sevelamer hydrochloride for controlling serum phosphorus and calcium-phosphate product to the levels recommended by the K/DOQI guidelines.  (+info)

Disposable diaper to collect urine samples from young children for pyrethroid pesticide studies. (36/368)

Disposable diapers are widely used in the US and many other areas in the world; therefore, they are ideal media for urine collection for measurement of young children's exposure to pesticides. However, disposable diapers normally contain polyacrylate polymers that make the extraction and analysis of urine very difficult. The objectives of this paper were to evaluate whether disposable diapers that contain polyacrylate granules can be extracted using salt solutions, and whether they can be used for the collection and quantitative measurements of selected urinary pyrethroid pesticide metabolites and creatinine. The storage stability of the metabolites and creatinine in a wet diaper at body temperature and at refrigeration temperature was also evaluated. Salt solutions including calcium chloride dihydrate, magnesium sulfate, ammonium acetate, and sodium chloride solutions were tested for efficiency of polymer shrinkage. Pyrethroid metabolites 3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (DCCA), 3-(2,2-dibromovinyl)-2,2,dimethyl-(1-cyclopropane) carboxylic acid (DBCA) and 3-phenoxybenzoic acid (3-PBA) were analyzed using LC/MS/MS and evaluated for recoveries in the urine released from the diapers. The study found calcium chloride dihydate to be satisfactory in releasing urine and metabolites from the polymers. The percent recoveries for the three tested pyrethroid metabolites were mostly in the range of 65-130. The percent recoveries for creatinine were in the range of 71-133. The detection limit for each of the three metabolites was 0.1 microg/l. The pyrethroid metabolites and creatinine were stable on the diaper for at least 72 h. We concluded from this study that calcium chloride dihydrate can successfully release urine and metabolites from polyacrylate-containing diapers, and the method is promising for studies of pyrethroid metabolites.  (+info)

Histomorphological response of dogs' dental pulp capped with white mineral trioxide aggregate. (37/368)

This study was conducted to observe the response of dogs' dental pulp to white mineral trioxide aggregate (MTA) when used as pulp capping material. The pulp of 15 dogs' teeth was experimentally exposed and capped with white MTA. The animals were sacrificed two months later and the specimens were prepared for histomorphological study. The pulp capped with white MTA showed a healing process with complete dentin bridge formation in all samples. In some cases, there was not a tubular dentin shape, but only a structure with an interesting morphological aspect sealing the exposure site. Only 2 specimens exhibited pulp inflammation. In conclusion, the data obtained in this study showed that white MTA has the necessary properties of a pulp capping material.  (+info)

Mineral trioxide aggregate as a pulpotomy agent in primary molars: an in vivo study. (38/368)

The retention of pulpally involved deciduous tooth in a healthy state until the time of normal exfoliation remains to be one of the challenges for Pedodontists. A scientific noise has been generated about several materials some of which have been popular pulpotomy medicaments. Concerns have been raised about the toxicity and potential carcinogenicity of these materials, and alternatives have been proposed to maintain the partial pulp vitality, however to date no material has been accepted as an ideal pulpotomy agent. Mineral trioxide aggregate (MTA) is a biocompatible material which provides a biological seal. MTA has been proposed as a potential medicament for various pulpal procedures like pulp capping with reversible pulpitis, apexification, repair of root perforations, etc. Hence the present study was done to evaluate the efficacy of MTA as a pulpotomy medicament. A clinical and radiographic evaluation was done on children where MTA was used as pulpotomy medicament in primary molars for a period of 6 months and it was found to be a successful material.  (+info)

Consequences and management of hyperphosphatemia in patients with renal insufficiency. (39/368)

Consequences and management of hyperphosphatemia in patients with renal insufficiency. Progressive renal insufficiency leads to hyperphosphatemia, hypocalcemia, and secondary hyperparathyroidism. Bone demineralization in secondary hyperparathyroidism may induce fractures, while joint and subcutaneous precipitations of calcium pyrophosphate limit mobility, and may cause crippling. Strategies to preempt bone and joint destruction in chronic kidney disease and end-stage renal disease have focused on limiting dietary phosphorus, intra-gut binding of ingested phosphorous, enhancing calcium absorption, and limiting parathyroid hormone secretion. Deciding which regimen is most effective to meet these treatment objectives challenges nephrologists; they often uncover conflicting evidence about which abnormal metabolite should be the prime treatment objective. Especially vexing is the question of whether hypercalcemia is a cardiotoxic consequence of calcium-based phosphate binders.  (+info)

Treatment of hyperphosphatemia in patients with chronic kidney disease on maintenance hemodialysis. (40/368)

Treatment of hyperphosphatemia in patients with chronic kidney disease on maintenance hemodialysis. Hyperphosphatemia in patients with ESRD leads to secondary hyperparathyroidism, renal osteodystrophy, and is independently associated with mortality risk. The exact mechanism by which hyperphosphatemia increases mortality risk is unknown, but it may relate to enhanced cardiovascular calcification. National Kidney Foundation K/DOQI bone metabolism and disease guidelines recommend maintenance of serum phosphorus (P) below 5.5 mg/dL, and Ca x P product less than 55 mg(2)/dL(2). Although calcium-based phosphate binders (CBPB) are cost effective, long-term safety concerns relate to their postulated role in progression of cardiovascular calcification. Sevelamer hydrochloride has been recommended as an alternative noncalcium phosphate binder. Results from the Calcium Acetate Renagel Evaluation (CARE study) indicate that calcium acetate is more effective than sevelamer in controlling serum phosphorous and Ca x P product in hemodialysis patients. In the Treat-to-Goal study, dialysis patients treated with sevelamer had slower progression of coronary and aortic calcification than patients treated with CBPB. The mechanism underlying the beneficial effect of sevelamer is unknown, but may relate to decreased calcium loading or to dramatic reductions in LDL cholesterol in sevelamer-treated patients. At present, evidence incriminating CBPB in the progression of cardiovascular calcification in ESRD remains largely circumstantial. As calcium acetate is more efficacious and cost effective than sevelamer, it remains an accepted first-line phosphate binder. In this review, we will examine these issues and provide rational guidelines for the use of calcium-based phosphate binders in patients on maintenance hemodialysis.  (+info)