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The purpose of this study was to test the hypothesis that the increase in fracture toughness of a fluorcanasite-based glass-ceramic is a linear function of crystal volume fraction.A total of 60 specimen bars (20 x 5 x 2 mm(3)) were cut from parent glass blocks, polished, annealed, randomly divided into six groups, nucleated at 680 degrees C/4 hr, and crystallized at the following temperatures and times: (1) 850 degrees C/0.5 hr, (2) 850 degrees C/1 hr, (3) 850 degrees C/3 hr, (4) 750 degrees C/6 hr, (5) 800 degrees C/6 hr, or (6) 850 degrees C/6 hr. Indentation flaws were produced by a microhardness indenter at the center of one surface, and the prepared specimens were subjected to three-point flexure loading with the severely flawed surface under tension at a crosshead speed of 0.5 mm/min. Flexural strength and fracture toughness (K(IC)) were calculated based on the indentation-strength technique. Crystal volume fraction (V(c)) was determined by quantitative stereology of scanning electron images of each group of ceramic specimens. Statistical analysis was performed using ANOVA and Duncan's multiple comparison test (alpha= 0.05).The mean K(IC) and V(c) values ranged from 2.7 to 3.9 MPa m(1/2) and 37% to 71% within the crystallization temperature range of 750 to 850 degrees C. Five statistical subsets of groups 1, 2/4, 3, 5, and 6 were determined as a function of crystallization temperature and holding time (Duncan's multiple comparison analysis; alpha= 0.05). The lowest and highest K(IC) and V(c) values were associated with Groups 1 (850 degrees C/0.5 hr) and 6 (850 degrees C/6 hr), respectively. Fracture toughness increased linearly as a function of crystal volume fraction (correlation coefficient R(2)= 0.67). The fracture toughness increased by 45% when the crystal volume fraction increased by 92%.Mean K(IC) values increased as a linear function of crystal volume fraction in a fluorcanasite-based glass-ceramic within the crystallization temperature range of 750 to 850 degrees C and at isothermal crystallization time range of 0.5 to 6 hours. The control of crystallization temperature and isothermal holding time should be optimized to generate tougher, more reliable ceramic prostheses in the shortest period of time.

The influence of crystal volume fraction on fracture toughness (K IC ) and indentation strength was analyzed for Li 2 O-Al 2 O 3 -CaO-SiO 2 (LACS) and LACS glass-ceramics containing 0.58 mmol% AgNO 3 (LACS-0.58Ag) or 0.78 mmol% AgNO 3 , (LACS-0.78Ag). The mean flexure strength, indentation strength, and K IC values of the LACS-0.78Ag groups increased with volume fraction of crystallinity. To achieve the greatest strength and K IC in LACS-Ag specimens, a high volume fraction of crystallinity (95%) had to be produced. However, the relationship between volume fraction of crystal phase and translucency had to be analyzed to determine the influence of crystallization on the potential esthetic results that are essential for dental applications. Addition of AgNO, to LACS glass produced a change from surface crystallization to bulk crystallization.

The influence of alumina content (0-15 wt% Al2O3) on the indentation strength, fracture toughness (KIc), and crystal structure of fluorcanasite (Al2O3-CaO-F-K2O-Na2O-SiO2) glass-ceramics was analyzed. Increasing the Al2O3 content from 0 wt% (CAN0) to 8 wt% (CAN8) caused the mean indentation strength and KIc values to decrease from 213 ± 14 MPa and 2.7 ± 0.1 MPa·m1/2, respectively, for the CAN0 glass-ceramic to 78 ± 16 MPa and 1.3 ± 0.2 MPa·m1/2, respectively, for the CAN8 glass-ceramic. Increased Al2O3 concentrations (0-15 wt%) significantly affected the crystal size, crystal shape, aspect ratio, and crystal aggregation characteristics of the fluorcanasite glass-ceramics. The addition of greaterthan equal to8 wt% of Al2O3 to fluorcanasite glass caused a transformation from canasite to leucite.

Objectives . The objective of this study was to characterize the influence of various metals, metal compounds, and P 2 O 5 as a nucleating agent on the color and translucency of a Li 2 OAl 2 O 3 CaOSiO 2 glass-ceramic. Methods . Glass frits of Li 2 OAl 2 O 3 CaOCaOSiO 2 (LACS), LACS with 1 mol% P 2 O 5 (LACSP), and/or LACS with one of 16 colorants were melted, poured into a cylindrical graphite mold, cut into disks, annealed, nucleated, crystallized, and annealed again. Ten translucency measurements of each of five disks were made using a tristimulus colorimeter and a D65 standard CIE illuminant. The color of each disk was analyzed using the CIE L ★ a ★ b ★ color space system (1976) as a function of colorant, colorant concentration, and P 2 O 5 . Results . Mean L ★ values of glass-ceramic disks ranged from 63.5 for LACS containing 6.2 mmol% FeCl 3 (LACSP-6.2Fe) to 84.1 for LACS. No significant difference (p > 0.05) was found between the mean L ★ values for LACS, LACSP, and LACS with 0.19 mmol% AgNO 3 (LACS-0.19Ag). The mean contrast ratio of glass-ceramic specimens ranged from 0.42 (LACS and LACS-1.0Fe) to 0.98 (LACS-0.78Ag). Mean color difference values varied from 5.8 (LACSP-1.0Fe vs. LACS) to 36.3 (LACSP-0.78Ag vs. LACSP). Significance . The results of this study indicate that, because certain colorants in glass-ceramics affect opacity as well as hue and chroma, the development of glass-ceramics should be simplified by: 1) employing a nucleating agent that does not affect hue or chroma significantly, 2) controlling fixed levels of translucency consistent with mechanical and physical property requirements, and 3) varying the hue and chroma by means of colorants that do not affect the crystallization process. This implies that the volume fraction and mean size of crystals must be controlled, since the translucency or opacity of glass-ceramics is associated with scattering of light at the interfaces between adjacent crystals, and between crystals and the glass phase because of differences in refractive indices (McMillan, 1979a).

To validate the difference on the prevalence of rheumatic symptoms between north and south parts of the country and to study the associated risk factors of rheumatic complaints in Shantou city, China.A total number of 10 638 people at above 16 years of age from four samples, were surveyed in 1987, 1992, 1995, and 1999. Protocol of International League Against Rheumatism (ILAR)-China collaborative study or WHO-ILAR community oriented program for control of rheumatic disease(COPCORD) core questionnaire was implemented. Data on related rheumatic symptoms were collected and analyzed.The prevalence rate of rheumatic complaints had been increasing in Shantou area during the last decade (in 1987 11.6%, 1992 12.5%, 1995 16.0% and 1999 19.8%) but still lower than that seen in Beijing, China in 1987(40.0%). Rheumatic symptoms were more prevalent in females than in males, in elderly than in young people with most frequently involved site happened in low back area, followed by knee and neck. Lumbar pain was more frequent among rural residents, while neck pain was more prevalent in urban school students. Prevalence of knee pain was significantly higher in people living in multi-storey buildings without elevator than those living in single-storey houses. The peak values of Bone Mineral Density in Shantou population were (0.839 +/- 0.085) g/cm2 in men, and (0.723 +/- 0.064) g/cm2 in women, significantly higher than that reported in 13 other provinces and cities including Beijing. The sense of seeking for medical help was higher in population with higher prevalence of rheumatic symptoms than that in lower complaints group. However, no significant difference was found in the rates of disability among the different populations.The prevalence rate of rheumatic complaints was lower in Shantou than that in Beijing. Socio-economic status, environment, sex, age, occupation, ergonomics, bone mineral density, and awareness of seeking medical care might have been the associated risk factors to the prevalence of rheumatic complaints.

To validate the differences of the prevalence of rheumatic symptoms between the north and south part of China and to investigate the associated risk factors for rheumatic complaints in Shantou, China.Four samples together comprising 10,638 peopleor = 16 years of age were surveyed in 1987, 1992, 1995, and 1999. The protocol of the ILAR-China Collaborative Study or the WHO-ILAR COPCORD Core Questionnaire was implemented. Data on rheumatic symptoms that were part of these surveys were collected and analyzed.The prevalence rate of rheumatic complaints was increasing in the Shantou area during the recent decade (in 1987 11.6%, 1992 12.5%, 1995 16.0%, and 1999 19.8%). However, it was still lower than the rate in Beijing, China, in 1987 (40.0%). Rheumatic symptoms were more prevalent in women than in men, and were more frequently seen in the elderly than in young people. The most frequently involved site was the low back followed by the knee and neck. Lumbar pain was more frequent among rural residents, while neck pain was more prevalent in the urban school-age population group. The prevalence of knee pain was significantly higher in people living in multi-story buildings without elevators compared with those living in single-story houses. The peak value of bone mineral density (BMD) in the Shantou population was 0.839 +/- 0.085 g/cm2 in men, and 0.723 +/- 0.064 g/cm2 in women, significantly higher than that reported in 13 other provinces and cities of China including Beijing. The sense of seeking a physician's care was higher in the population with a higher prevalence of rheumatic symptoms than that in the group with a lower prevalence of complaints. However, no significant difference was found in the rate of disability among the different population samples.The prevalence rate of rheumatic complaints was lower in Shantou than in Beijing. Socioeconomic status, environmental differences (e.g., Shantou in the southern and Beijing in the northern part of China), sex, age, occupation, ergonomics, BMD, and awareness of seeking medical care might all be risk factors associated with the prevalence of rheumatic complaints.

The purpose of this study was to test the hypothesis that nucleation temperature significantly affects the fracture toughness of a fluorcanasite-based glass-ceramic.Sixty specimens were cut from a glass bar, polished, and randomly divided into six groups for nucleation treatment at temperatures of (1) 520 degrees C, (2) 550 degrees C, (3) 580 degrees C, (4) 610 degrees C, (5) 640 degrees C, and (6) 670 degrees C for 4 hours and a crystallization temperature of 850 degrees C for 6 hours. A precrack was produced at the center of each bar, and the prepared specimens were subjected to three-point flexural loading with the cracked surface under tension using an Instron machine at a cross-head speed of 0.5 mm/min. Fracture toughness was calculated based on the indentation strength technique, and crystal volume fraction was determined by quantitative stereology of SEM images of each group of ceramic specimens.The mean fracture toughness and crystal volume fraction ranged from 2.6 to 3.5 MPa x m1/2 and from 65% to 81%, respectively, within the limits of the nucleation temperatures investigated. ANOVA showed statistically significant differences among the test groups. Based on Duncan's multiple comparison test, significant differences in mean fracture toughness and crystal volume fraction were found among the following statistical subsets: groups 1 to 4, group 5, and group 6.Fracture toughness and crystal volume fraction of a fluorcanasite-based glass-ceramic were strongly influenced by nucleation temperature; the crystals precipitated during thermal processing are thought to be an important factor in increasing fracture toughness.

The aim of this study was to analyze the effect of a nucleation agent (P2O5) and a colorant/nucleation agent (AgNO3) on the chemical durability of Li2O-Al2O3-CaO-SiO2(LACS) glass-ceramics in 4% HAc solution, deionized-distilled water, and in pH buffer solutions of pH 1, pH 9, and pH 11.Glass powder [27.8 mol% Li2O, 2.5% Al2O3, 5.9% CaO, and 63.8% SiO2(LACS)] was melted, poured into a cylindrical graphite mold (16 mm diameter), cooled, cut into 2.2 mm thick disks, polished through 1200 grit SiC, nucleated at 510 degrees C for 3 h, and crystallized at 650 degrees C for 6 h. Dynamic corrosion tests of LACS glass-ceramic, LACS glass-ceramic containing 1.0 mol% P2O5 (LACSP), LACS glass-ceramic containing 0.78 mmol% AgNO3(LACSAg), and Dicor control specimens were performed in a shaker-bath unit at 80 degrees C at a shaker speed of 30 cycles/min for periods of up to 15 d. Differences in mean weight loss and ionic concentration were analyzed for statistical significance (p = 0.05) using ANOVA and the Tukey's Studentized Range Test.The mean weight loss over 15 d in 4% HAc increased in the following order: LACS (0.21 +/- 0.02 mg/cm2), LACSAg (0.25 +/- 0.05 mg/ cm2), and Dicor (0.27 +/- 0.05 mg/cm2). The differences in mean values were not statistically significant (p0.05). The amounts of Li+ leached in 32 mL of pH1 and pH11 buffer solutions were 3.1 +/- 0.3 microgram/cm2/mL and 243 +/- 49.0 micrograms/cm2/mL, respectively, for the LACS group, and 3.0 +/- 0.6 microgram/cm2/mL and 166 +/- 28.0 micrograms/cm2/mL for the LACSAg group. The differences in mean values are not statistically significant (p0.05). The high chemical durability in acidic environments of LACS glass-ceramics without P2O5 and their decreased durability at pH values of 9 and above were confirmed by SEM observations of the exposed surfaces.The weight loss for the three glass-ceramic systems was highest in pH 11 buffer solution, which represents an unlikely in vivo environment. From a toxicological viewpoint, the maximum amount of Li+ released from 28 fully dissolved crowns of LACS glass-ceramic at a temperature of 80 degrees C (which is greater than any temperature experienced in the oral cavity) is approximately 1.2 mg; this amount appears to be below the daily limit of 2 mg allowable from food sources.

Introduction Epidemiological studies of rheumatic diseases have been conducted during the past 20 years in China. The aim of this study was to clarify prevalence rates of common rheumatic diseases in China. Methods Relevant reports of population-based surveys conducted from 1980 to 2006 were retrieved. Studies using the World Health Organization-International League of Associations for Rheumatology COPCORD (Community Oriented Program for Control of Rheumatic Diseases) protocol and those that did not employ this protocol but were published in recognized journals were identified and analyzed. Results Thirty-eight surveys including 241,169 adults from 25 provinces/cities were pooled for analysis. The prevalence of rheumatic complaints ranged from 11.6% to 46.4%, varying by locality, study protocol and age of the people surveyed. Prevalence of symptomatic osteoarthritis (OA) varied from 5.1% to 20.8%, with common sites of involvement being the lumbar spine, knee joint and cervical spine. Compared with rates of radiographic and symptomatic knee OA in the USA, elderly men in Beijing exhibited similar prevalence rates and elderly women exhibited a higher prevalence. The prevalence of hip OA and hand OA was much lower in Chinese than in Caucasian populations, but both kinds of OA were more common in coal miners. The prevalence of ankylosing spondylitis ranged from 0.2% to 0.54% among Han ethnic Chinese and were lower among mixed ethnic populations. The prevalence of psoriatic arthritis ranged from 0.01% to 0.1%, and that of reactive arthritis was 0.02%; undifferentiated spondyloarthropathy was identified in 0.64% to 1.2% of the individuals included in the surveys. The prevalence of rheumatoid arthritis (RA) ranged from 0.2% to 0.93%, with the highest rate being reported from a Taiwan urban area. In mainland China there were no significant differences in prevalence of RA between the northern and southern parts of China, or between different ethnic groups. The prevalence of hyperuricemia increased after the 1980s. The prevalence of gout was found to have increased in recent decades from 0.15% to 1.98%, apart from in the Taiwan aborigines, among whom the highest prevalence rate of 11.7% was recorded. The prevalence of primary Sjögren's syndrome in Beijing was 0.77% by the Copenhagen criteria and 0.33% by the San Diego criteria. The prevalence of soft tissue rheumatism was 2.5% to 5.7%. Fibromyalgia was seldom observed in China. Conclusion Rheumatic diseases are common in China. The prevalence of rheumatic complaints varied with the locality surveyed. The prevalence of OA is comparable with that in Western countries but varies in terms of joint involvement. The prevalence of ankylosing spondylitis is similar to that in Caucasians. Except in Taiwan, the prevalence of RA in China is lower than that in developed countries. The prevalence of hyperuricemia and gout increased after the 1980s, but it remains lower than that in developed countries. More studies are required to evaluate prevalence rates among minority groups in the west and northwest parts of China, and further study is needed to address fibromyalgia in China.

A new type of macroporous ellagitannic acid resin (EAR) can be prepared from macroporous crosslinked chloromethylated polystyrene beads and ellagic acid in the presence of NaOH and KI as catalysts. The synthetic route and structure of the polymer were examined. The structure of EAR was confirmed by elementary analysis and IR spectra. The oxygen content of EAR was 7.06%, and the functional group capacity of EAR was 0.441 mol EA/g EAR. The conversion of functional groups was 8.33%. Cu2+, Fe3+, Ce3+, and La3+ can be easily adsorbed by EAR. The adsorption capacities for these metal ions per g EAR were 0.609 mmol Cu2+, 1.523 mmol Fe3+, 0.320 mmol Ce3+, and 1.561 mmol La3+. The influence of pH, acidity, ionic concentration, adsorption time, and temperature on the percentage of adsorption was investigated.