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At least 19 recordsLinked to original sources
PubMed1998

Advantages of impact testing over hardness testing in determining physical integrity of tablets.

An investigation of four different tablet strength tests was carried out on four different placebo formulations (differing in Avicel: Pharmatose ratios). The results analysis compared fatigue failure, work of failure, and impact failure to diametrical compression measurements (hardness). The impact results clearly show how different formulations can have the same hardness, yet their impact resistance can vary by as much as 200%. The impact test used in this work and other tests described are useful in tablet development to understand, compare, and mitigate tablet breakage during subsequent unit operations.

Cellulose↗
PubMed1999

Use of a water hardness test kit to measure serum calcium concentration in cattle.

OBJECTIVE: To determine whether a commercially available water hardness test kit could be used to measure total serum calcium concentration and diagnose hypocalcemia in dairy cows. DESIGN: Prospective study. ANIMALS: 30 dairy cows from 19 commercial herds. PROCEDURE: Serum calcium concentration was determined using a water hardness test kit and a standard, laboratory-based method. Simple linear regression was used to determine whether there was a linear relationship between results of the 2 methods, and Spearman's rank correlation was used to calculate correlation between measurements. Sensitivity, specificity, and predictive values of using test kit-derived values for diagnosis of hypocalcemia (laboratory value < 8 mg/dl) were calculated. RESULTS: There was a high correlation and significant linear relationship between results of the 2 methods. Sensitivity, specificity, predictive value of a positive test result, and predictive value of a negative test result were 100, 73, 86, and 100%, respectively. Accuracy was improved by using a test kit-derived calcium concentration of 7 mg/dl as the cut-off for determining hypocalcemia. CLINICAL IMPLICATIONS: Results indicate that a commercially available water hardness test kit can be used as a rapid, inexpensive method of estimating serum calcium concentrations and diagnosing hypocalcemia in dairy cattle. However, the test is not practical for cow-side use, because blood samples must be centrifuged to obtain serum for use in the test kit.

Animals↗
PubMed1999

Nondestructive tablet hardness testing by near-infrared spectroscopy: a new and robust spectral best-fit algorithm.

A new algorithm using common statistics was proposed for nondestructive near-infrared (near-IR) spectroscopic tablet hardness testing over a range of tablet potencies. The spectral features that allow near-IR tablet hardness testing were evaluated. Cimetidine tablets of 1-20% potency and 1-7 kp hardness were used for the development and testing of a new spectral best-fit algorithm for tablet hardness prediction. Actual tablet hardness values determined via a destructive diametral crushing test were used for construction of calibration models using principal component analysis/principal component regression (PCA/PCR) or the new algorithm. Both methods allowed the prediction of tablet hardness over the range of potencies studied. The spectral best-fit method compared favorably to the multivariate PCA/PCR method, but was easier to develop. The new approach offers advantages over wavelength-based regression models because the calculation of a spectral slope averages out the influence of individual spectral absorbance bands. The ability to generalize the hardness calibration over a range of potencies confirms the robust nature of the method.

Algorithms↗
PubMed1989

Hardness tests in highly filled composite resins.

The hardness of seven proprietary, light-cured, posterior composite resins was evaluated by three different hardness testers: the Knoop hardness tester, the Barcol indenter and the Rockwell 15T hardness meter. Specimens were measured after light-curing and 24-hour immersion in 37 degrees C water. Barcol hardness numbers ranged from 79.2 to 85.0. The Rockwell 15T hardness data had a range from 73.3 to 80.3 and the Knoop hardness numbers varied from 39.9 to 79.0. Relatively small variations were determined between results of Barcol hardness numbers and Rockwell 15T hardness data. Great variation was revealed in the results from Knoop hardness numbers. According to the dimensions of the indentations, the results of Barcol and Rockwell hardness represent the bulky part of tested composites rather than superficial hardness. Knoop hardness testing is found to be relatively feasible and a suitable measurement for the determination of superficial hardness of highly filled composite resins.

Composite Resins↗
PubMed1997

Near-infrared spectroscopy as a nondestructive alternative to conventional tablet hardness testing.

PURPOSE: Near-infrared reflectance spectroscopy (NIRS) was used to evaluate and quantify the effect of compression force on the NIR spectra of tablets. METHODS: Flat, white tablets with no orientation (scoring, etc.) were manufactured on a Stokes Rotary Tablet Press. NIRS was used to predict tablet hardness on the following four formulations and one placebo matrix: hydrochlorothiazide (HCTZ) 15% and 20% in a placebo matrix (microcrystalline cellulose and magnesium stearate), and chlorpheniramine maleate (CTM) 2% and 6% in a placebo matrix. Five or six levels of tablet hardness from 2 to 12 kg were used for each formulation. Laboratory hardness data was compared to NIR reflectance data using a NIRSystems Rapid Content Analyzer. Multiple linear regression and partial least squares regression techniques were used to determine the relationship between tablet hardness and NIRS spectra. RESULTS: An increase in tablet hardness produced an upward shift (increase in absorbance) in the NIRS spectra. A series of equations was developed by calibrating tablet hardness data against NIR reflectance response for each formulation. The results of NIRS hardness prediction were at least as precise as the laboratory hardness test (SE = 0.32). CONCLUSIONS: A NIRS method is presented which has the potential as an alternative to conventional hardness testing of tablets.

Chlorpheniramine↗
PubMed1977

Hardness testing of some fissure-sealing materials.

The mechanical properties of fissure-sealing materials are of significant importance for their durability, i.e. their wear resistance. One of the methods of evaluating a material's resistance to attrition is to apply a hardness test. In the present investigation, the surface hardness of some fissure-sealing materials was tested. Sealants made from diluted composite materials and with inclusion of inorganic filler particles appeared to have a considerable higher surface hardness than the other sealing materials tested.

Composite Resins↗
PubMed1996

Bone hardness testing in the trabecular bone of the human patella.

Bone hardness of 10 human patellas in 15 regions and at three depths was measured through in situ indentation tests. Indentation tests were performed perpendicular to the three articular surfaces (lateral and medial facets, and central ridge area) and, thus, parallel to the trabeculae. Multiple regression analysis demonstrated a significant reduction of bone hardness with depth. In addition, the lateral facet had a higher bone hardness than the medial facet, and the proximal and central regions demonstrated higher bone hardness than the distal region. Overall, the proximolateral region of the patella exhibited the highest hardness compared with other regions. As bone hardness is indicative of load bearing, these results may have important consequences for patellar resurfacing and patellar component design.

Aged↗
PubMed1978

Creep and hardness testing of some denture base polymers.

A method of measuring creep, recovery, hardness, and the effect of cyclic loading on denture base polymers using a modified Wallace hardness tester is described. This apparatus is particularly sensitive and is capable of detecting very small variations in these properties of the materials. A representative group of denture base polymers that include heat-cured, pour-type, and other modified materials was tested. The results obtained are in good agreement with those shown by other workers.

Denture Bases↗