Papers by Keyword: Dental Ceramic

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Authors: Jun Cui, Jun Ou, Yong Lie Chao, Q.P. Gao, Guang Fu Yin, H. Wang, J.F. Shen, Yang Xi Chen
Abstract: Dental ceramic materials do not always show linear expansion behavior. In general, thermal contraction behavior of dental porcelain can be described with the polynomial function: L/L= C+α1 T+α2 T2. In addition, a new method for taking into consideration of nonlinear contraction behavior of dental ceramics is proposed for calculating thermal mismatch value (α) between substrate and veneering materials. Discs of eight substrate/veneer combinations (n=10) were fabricated for thermal shock testing. In this study, a stepwise multiple regression analysis was performed to determine the relationship between thermal shock test results and thermal mismatch value (α) on these combinations. A high degree of correlation was found between αs-b and T. The new method proves to be a reliable one to predict thermal compatibility of multi-layer dental ceramic composites.
1401
Authors: Ling Yin
Abstract: The application of abrasive technology in dentistry dates from 7000–9000 years. How does this ancient technology affect our modern society where the elderly population needs extensive dental care and ageing well and ageing productively is our first priority? Many patients prefer tooth-colored, all ceramics restorations fabricated by dental CAD/CAM systems for reasons of esthetics, biocompatibility and high efficiency. In spite of the advantages of all-ceramic restorations, ceramic prostheses have not always performed as predicted or desired. Catastrophic fracture has been the most frequently reported reason for failure of all-ceramic restorations. This paper gives a brief review on abrasive technology in ceramic restorative dentistry to highlight problems to be solved by our abrasive technology community.
363
Authors: Tomaž Kosmač, Cedomir Oblak
Abstract: The effects of dental grinding and sandblasting on ageing and fatigue behaviour of pressure less sintered biomedical grade Y-TZP ceramics were investigated. Disc-shaped specimens were sintered to high density for subsequent surface treatment and testing. Accelerated aging experiments by autoclaving in artificial saliva were performed under isothermal conditions at 1340C. The amount of monoclinic zirconia in the ground and sandblasted specimens was < 5% and about 15 %, respectively and the corresponding strength values were 920 MPa and 1290 MPa. After autoclaving for 24 hours, the amount of transformed monoclinic zirconia in as-sintered material was increased to 15 %, resulting in about 10% strength reduction. In contrast, no strength reduction was observed with the ground and sandblasted specimens subjected to prolonged ageing. At any ageing condition, the highest survival rate during mechanical fatigue testing was observed with the sandblasted samples and the lowest with the ground samples. The strength of the surviving specimens tested in air corresponded well to the mean flexural strength of the particular group before fatigue testing, whereas lower survival strength values and a larger variability in strength were obtained with specimens that were subjected to prolonged accelerated ageing prior to mechanical fatigue testing in artificial saliva.
817
Authors: Guang Lei Zhang, Guo Qiang Qin, Hui Gao, Chang Tao Shao
Abstract: This paper focused on the properties of Al2O3-rainforced feldspar dental ceramic. The results indicated that the introduced Al2O3 could elevate the density of the sintered feldspar ceramic, where the relative density reached 97.9% under the conditions of 20 wt% Al2O3 additive and 1200°C. On the other hand, Al2O3 additive could remarkably promote the machinability and the ultimate bending strength of the modified feldspar ceramic. The grinding efficiency increased by 260.1% if the content of Al2O3 additive was 5 wt%, while the ultimate bending strength enhanced under increasing Al2O3 additive content. The microstructure analysis revealed a composition of α-Al2O3 as the dominant phase and crystalline calcium aluminum silicate hydrate as the minor phase in the Al2O3-rainforced feldspar ceramic. The feldspar represented totally as glass phase, wherein the Al2O3 grains showed a homogenized dispersion.
390
Authors: Il Seok Park, Se Young Choi, Myung Hyun Lee, Dae Joon Kim, Jung Suk Han
Abstract: Aqueous-based alumina tape, prepared using acrylate emulsion binder, was employed to form 3-unit all-ceramic anterior fixed partial denture core structures. Formability, linear shrinkage, and strength of the tape were optimized by adjusting tape composition to a/(a+b+p)=0.84 and b/(b+p)=0.5. Marginal fitness of the core framework was acceptable for clinical applications when more than two points on lingual side of core structure were placed to touch a plate during sintering. The 3-unit all-ceramic anterior fixed partial denture utilized ceramic tape has functioned successfully for 3 years without any loss of structural integrity and esthetics.
929
Authors: B. Uyulgan, I. Ozdemir, Ç. Tekmen, M. Toparlı, E. Çelik
2005
Authors: Eleana Kontonasaki, A. Sivropoulou, Lambrini Papadopoulou, P. Garefis, Konstantinos M. Paraskevopoulos, Petros Koidis
Abstract: The effect of fibronectin (FN) on human periodontal ligament fibroblasts (PDLF) attachment and proliferation on Bioglass® (PerioGlas® Synthetic Bone Graft Particulate, US Biomaterials) modified dental ceramics, was investigated in vitro. FN introduced limited alterations in cell attachment on Bioglass®-modified dental ceramics in comparison with the corresponding non-FN-coated specimens but had a profound positive effect on Bioglass®-coated specimens that weakly supported both cell attachment and proliferation. The amount of protein adsorbed on the specimens was not proportional to its biological activity, i.e. cell attachment, spread and proliferation, probably due to surface energy variations and FN conformational changes induced by differences in surface composition and morphology of the different dental ceramics modifications.
727
Authors: Jun Cui, Yi Fan Chen, Yong Lie Chao, Chun Xia Chen, Jun Ou, Lei Sui, Wei Qun Zhang
Abstract: The purpose of this study is to determine the bi-axial flexural strength, weibull modulus and fracture mode of bilayered alumina glass-infiltrated core and the veneering porcelain. Forty disk specimens were fabricated from alumina glass-infiltrated core (HSDC-A) and veneer porcelain (Vintage AL). The specimens were equally divided into four groups as: MV, monolithic specimens of veneer material; MC, monolithic specimens of core material; BV, bilayered specimens with the veneer in tension; BC, bilayered specimens with core material in tension. Mean flexure strength, standard deviation and associated Weibull modulus were determined using bi-axial flexure (ball-on-ring) for each group. Both optical and scanning electron microscopy were employed for identification of the fracture mode and origin. The surface loaded in tension influenced the bi-axial flexural strength and reliability of the composites. The frequency of specimen delamination, Hertzian cone formation and sub-critical radial cracking in the bilayered discs are also dependent on the surface loaded in tension.
1556
Authors: Bao Hui Su, Jing Chun Su, Jun Guo Ran, Bao Yue Su
Abstract: HA/ß-TCP is one kind of important bone tissue engineering scaffold materials. In order to improve the biological performance of materials, HA/ß-TCP ceramics were modified by the cold plasma technique in this paper. The biological performances of treated materials were evaluated by the results of bone-like apatite formation in SBF, the coculture of the C2C12 cell line and HA/ß-TCP, cell proliferation experiments, observations of the electron microscopy and fluorescence staining and the animal intramuscular implantation experiments. The results showed that after immersion, compared with untreated HA/ß-TCP, treated materials were more conducive to form bone-like apatite; modified HA/ß-TCP could promote the cell proliferation more; the cells grew in the course of nature on the treated scaffold and modified HA/ß-TCP had better bone-forming performance in vivo. It was concluded that modified HA/ß-TCP had better biological performance; the cold plasma technique could improve the biological performance of dental biphasic calcium phosphate ceramics.
1264
Authors: Yi Wen Hu, Xin Zhang, Yin Wu, Wen Jie Si
Abstract: Zirconia ceramics are now widely used in dental restorations. The veneering porcelain chipping happens sometimes in zirconia-porcelain all-ceramic system. The objective of this study was to evaluate the bonding strength between the zirconia core and various commercial veneering ceramics. The shearing and bending methods were used to evaluate the bonding strengths of zirconia core and four veneering ceramics. Meanwhile, as surface treatment will play an important role for the bonding strength, the influence of 3 kinds of surface treatment was investigated. The results indicated that both the shearing and bonding strengths of Cercon ceram kiss is better. Moreover sand blasting is the most useful method of surface treatment.
528
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