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Tear Test (tear + test)
Selected AbstractsResistance to tearing of calf and ostrich pericardium: Influence of the type of suture material and the direction of the suture lineJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2004José María García Páez Abstract The tearing of the valve leaflet of a cardiac bioprosthesis can cause early failure of this device, which is employed to replace a diseased native valve. This report involves the study of the behavior of 312 tissue samples (152 of calf pericardium and 160 of ostrich pericardium) treated with glutaraldehyde and subsequently subjected to tear testing. The samples were cut in the two principal directions: longitudinally, or root to apex, and transversely. They included a series of control samples that were left unsutured, and the remaining samples were repaired with the use of two different suture techniques: a running suture in the direction of the load and a telescoping suture perpendicular to the load. Four commercially available suture materials were employed: Pronova®, nylon, Gore-Tex®, or silk. The unsutured control samples of both types of pericardium exhibited a similar anisotropic behavior in the tear test. The mean resistance to tearing of the calf pericardium was 24.29 kN m in samples cut longitudinally and 34.78 kN m in those cut transversely (p = .03); the values were 28.08 kN m and 37.12 kN m (p = .002), respectively, in ostrich pericardium. The series repaired with the telescoping suture always exhibited greater resistance to tearing, with values that ranged between 44.34 and 64.27 kN for the samples of calf pericardium and from 41.65 to 47.65 kN for those obtained from ostrich. These assays confirm the anisotropic behavior of calf and ostrich pericardium treated with glutaraldehyde when subjected to tear testing, as well as the loss of this behavior in ostrich pericardium after suturing. Suturing techniques, such as the telescoping model, that provide a greater resistance to tearing should be studied for use in the design of the valve leaflets of cardiac bioprostheses made of biological materials. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 69B: 125,134, 2004 [source] Effect of Mixing Methods on Mechanical Properties of Alginate Impression MaterialsJOURNAL OF PROSTHODONTICS, Issue 4 2005Gary Frey DDS Background: A commercial mechanical mixer is available to make the mixing of alginate more convenient and more consistent for the practitioner; however, there is very little information on the mechanical properties of alginate mixed with this device as compared with hand mixing. Purpose: To compare the mechanical properties of alginate impression materials mixed with a mechanical mixer (Alginator II, Cadco) and hand mixing. Material and Methods: Three alginate impression materials (Identic, Jeltrate, and Kromopan) were tested. Strain in compression, elastic recovery, and compressive strength were measured according to ANSI/ADA specification no. 18-1992; tear energy was measured using a pants tear test. Five specimens were prepared for each group with 12 groups for the mechanical mixer and 12 groups for hand mixing, for a total of 120 specimens. A two-way analysis of variance and Fisher's PLSD test at the 0.05 level of significance were used to analyze the data. Results: There were statistically significant differences in properties among the materials, but mixing technique had no statistically significant effect on strain in compression and tear energy. Conclusion: The mechanical mixer improved elastic recovery and compressive strength of the alginate impression materials tested and had no effect on strain in compression and tear energy. A mechanical mixer facilitates the mixing of alginate impression materials and improves some mechanical properties. [source] Reduced tear production in three canine endocrinopathies,JOURNAL OF SMALL ANIMAL PRACTICE, Issue 5 2007D. L. Williams Objectives: Previous reports have suggested that hypothyroid and diabetic patients can be predisposed to keratoconjunctivitis sicca. This study aimed to measure tear production in dogs with diabetes, hypothyroidism and hyperadrenocorticism using the Schirmer tear test and to compare these results with Schirmer tear test values for a group of normal dogs. Methods: Schirmer tear tests were performed on 16 dogs with hyperadrenocorticism, 18 with diabetes and 12 with hypothyroidism together with 100 control dogs. Corneal sensitivity was also measured in 12 of the 18 diabetic dogs with a Cochet Bonnet aesthesiometer and compared with age- and breed-matched normal dogs. Results: Schirmer tear test values in dogs with hypothyroidism, hyperadrenocorticism and diabetes were 12·3±3·2, 14·0±4·0 and 12·3±5·3 mm/minutes, respectively. Schirmer tear test values were significantly lower than that for the control group (19·6±4·2 mm/minutes) in all dogs with an endocrinopathy. Only in two hypothyroid dogs and three diabetics, this was manifested as profound keratoconjunctivitis sicca with Schirmer tear test value lower than 5 mm/minutes. Diabetic dogs had significantly reduced corneal sensitivity compared with a matched set of control dogs. Clinical Significance: This study shows a significant reduction in tear production in animals with diabetes mellitus, hypothyroidism and hyperadrenocorticism. Further research is needed to elucidate the mechanisms by which this reduction in tear production occurs. Assessment of tear production should be undertaken in animals diagnosed with these endocrinopathies, as these animals may progress to clinical keratoconjunctivitis sicca. [source] | ||||||||||