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Knoop Hardness Number (knoop + hardness_number)
Selected AbstractsA confocal micro-endoscopic investigation of the relationship between the microhardness of carious dentine and its autofluorescenceEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2010Avijit Banerjee Banerjee A, Cook R, Kellow S, Shah K, Festy F, Sherriff M, Watson T. A confocal micro-endoscopic investigation of the relationship between the microhardness of carious dentine and its autofluorescence. Eur J Oral Sci 2010; 118: 75,79. © 2010 The Authors. Journal compilation© 2010 Eur J Oral Sci This study aimed to investigate the null hypothesis that there is no relationship between the microhardness of carious dentine and its native autofluorescence (AF). Six extracted, carious molars were sectioned through natural lesions in the mesio-distal longitudinal plane. The Knoop microhardness (Knoop hardness number, KHN) of the cut surfaces of each sample was recorded at regular intervals through sound and carious dentine. Confocal fibre-optic micro-endoscopic (CFOME) examination of the carious dentine and the sound dentine was carried out at the same intervals using the Cellvizio system (600 ,m wide, flat-end probe) with an excitation wavelength of 488 nm. The blindly collected numerical data were analysed using the original microhardness KHN. The data analysis indicated that the autofluorescence signals increased significantly when the microhardness of dentine dropped below 25 KHN. Therefore, the null hypothesis was disproved, and it was concluded from this investigation that the autofluorescent signal intensity recorded using CFOME could produce an objective and reproducible correlation to the microhardness of carious dentine. Confocal fibre-optic micro-endoscopic examination could have clinical potential as a technology to help delineate the carious dentine that might be excavated in a clinical procedure in vivo. [source] Environmental damage and occlusal contact area wear of composite restorativesJOURNAL OF ORAL REHABILITATION, Issue 1 2002A. U. J. Yap The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in-vivo degradation of composite resins. The resin matrix can be softened and fillers constituents can be leached out when composites are exposed to certain chemicals/food-simulating liquids (FSLs). A reciprocal compression sliding wear device was used to study the effects of the chemical environment on occlusal contact area (OCA) wear of four composite restoratives (Silux Plus, Z100, Ariston pHc and Surefil). The effects of FSL on hardness was also investigated and correlated to wear. Thirty-six hardness/wear specimens of each material were made and stored in artificial saliva at 37 °C for 24 h. The specimens were then divided into six groups of six specimens and stored in the following FSL for 1 week at 37 °C: distilled water (W), 0·02 N citric acid (C), 0·02 N lactic acid (L), heptane (H) and 75,25% ethanol,water solution (E). Conditioning in artificial saliva (S) was used as control. After conditioning, the specimens were wear tested at 20 MPa contact stress against SS304 counter-bodies in the respective FSL/artificial saliva up to 20 000 cycles. Wear depth (lm, n=6) was measured using profilometry. Change in hardness (,KHN, Knoop hardness number) was determined by microhardness testing pre- and post-conditioning. Results of statistical analyses (ANOVA/Scheffe's at significance level 0·05) of wear data were as follows: Silux , S, W > L, H, E and C, L > H; Z100 , S, W > all other mediums and E > H; Ariston , all other mediums > H; Surefil , W, C > S, L, H, E (> indicates significantly more wear). With the exception of Surefil, the greatest wear was observed with conditioning and wear testing in water. This ranged from 93·18 ± 21·96 lm for Z100 to 31·43 ± 2·80 lm for Surefil. For all materials, conditioning in heptane resulted in the least wear. This ranged from 8·9 ± 2·2 ,m for Ariston to 16·5 ± 5·9 lm for Silux. The effects of the different FSL on OCA wear were material dependent. No correlation was observed between ,KHN and wear. [source] Comparative evaluation of secondary heat treatment and a high intensity light source for the improvement of properties of prosthetic compositesJOURNAL OF ORAL REHABILITATION, Issue 4 2000N. Tanoue This study determined the hardness and water solubility of two prosthetic composites polymerized with three curing modes for the purpose of evaluating the influence of secondary heating and a high intensity light source on resulting material properties. Two prosthetic composite materials (Artglass and Dentacolor) were cured with the following methods: (1) exposure by means of a photo-curing unit with a xenon stroboscopic light source (Dentacolor XS) for 120 s; (2) exposure with the xenon unit for 120 s, followed by heating in an oven (KL 100) at 100 °C for 15 min; and (3) exposure by means of a photo-curing unit with two metal halide lamps (Hyper LII) for 120 s. Knoop hardness and water solubility were determined according to standardized testing methods. Although post-cure heat treatment considerably elevated the Knoop hardness number for both materials, the greatest hardness number was generated with the use of the metal halide unit. Water solubility of the Dentacolor material was lowest when the material was cured with the metal halide unit, followed by the secondary heated group, whereas, solubility of the Artglass material was unaffected by the curing modes. This suggests that the use of a high intensity light source is more effective than the application of secondary heating for improving the post-curing properties of composites. [source] Purification and crystal growth of TlBr for application as a radiation detectorCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2004I. B. Oliveira Abstract Thallium bromide is a semiconductor compound with high atomic number and density. It has a CsCl-type simple cubic crystal structure and it is non-hygroscopics. The TlBr crystals are relatively soft with a knoop hardness number of 12. In this work, the TlBr commercial powder was purified by zone refining and the purest material section was used for crystal growth by Bridgman method. Efforts have been concentrated on the purification of the TlBr. The purification efficiency has been evaluated (NAA and ICP-MS) by impurities reduction results after zone refining passes. The crystalline quality was evaluated by X-ray diffraction. The characterized TlBr crystal as a detector has shown good response to gamma radiation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||