Fluoride release process of (resin-modified) glass-ionomer cements versus (polyacid-modified) composite resins

The fluoride release of conventional and resin-modified glass-ionomers is reviewed and compared to that of fluoride-releasing (polyacid-modified) composite resins. Each formulation displays a typical fluoride release profile. The cumulative amount of fluoride released is described by [F]c = [F](I)t/(t + t1/2) + beta square root t for glass ionomers whether resin-modified or not, whereas for composite resins this quantity is given by [F]c = [F](I)t/(t + t1/2) + alpha t. Both equations indicate that two kinetic processes are responsible for the fluoride release profiles. The kinetic parameters [F](I), t1/2, beta and alpha depend on the formulation. On the basis of the exchange characteristics for fluoride, an attempt is made to explain the mechanisms responsible for these fluoride release processes.     

A four year study of therapeutical observation of patients with hypertension

We attempt to quantify compliance with hypotension medication regimens in 620 patients with hypertension at the Centros de Salud (community health centers) of Novelda and Elche (in the province of Alicante) and to assess the impact of a mixed-strategy health education program. The method used to evaluate compliance is the self-communicated interview as indicated by Haynes-Sackett. The intervention consisted of individualized instruction, family support, educational leaflets, and written instructions. Among the results obtained, we emphasize the following. First, 64% completed the treatment as prescribed, 16% stopped taking the medication, and 20% followed the regimen in a sporadic fashion, lack of motivation and forgetfulness being the main reasons cited for the latter. Second, 27% of the patients with hypertension--among them, primarily young people and men--do not visit the center for monitoring. Third, the health education program is responsible for a significant increase in blood pressure measurements and in therapeutic compliance, also reducing the number of drop-outs. Fourth, 26% did not come to the unit at the end of the study period (four years) despite phone calls and house visits as reminders.     

Septic complications of total parenteral nutrition. A five year experience

Elevated levels of serum albumin have been noted in patients on chronic methadone maintenance and in heroin addicts. This observation was investigated in rabbits maintained on daily methadone 4 mg per kg of body weight after a period of 3 months on increasing dosage to assure drug tolerance. Albumin distribution and metabolism were measured with tested lots of 125I rabbit albumin. Studies were made before and again after the attainment of the methadone maintenance state. Albumin distribution was altered markedly with a shift of intravascular albumin to extravascular sites. Associated with this change, the serum albumin level rose by an average of 0.5 g per 100 ml. Albumin degradation increased by 32% from 248 to 327 mg per kg per day. The total exchangeable albumin pool increased 35%, or 3.6 g. Since the exchangeable albumin pool increased in the face of an increment in albumin degradation, albumin synthesis must have increased even further to account for this change. Although the specific factors responsible for these alterations in albumin metabolism and distribution are not known at present, to date, this hyperalbuminemic hypercatabolic state is not produceable in any other clinical or experimental situation.     

A descriptive epidemiology of netball injuries during competition: a five year study

As new knowledge is being acquired about the highly polymorphic apolipoprotein (a) gene, studies are also being directed at elucidating the factors involved in the synthesis and maturation of apolipoprotein (a) and the determinants controlling the interactions between apolipoprotein (a) and apolipoprotein B100 in lipoprotein (a) assembly. It is now apparent that apolipoprotein (a) is not only size but also sequence polymorphic and that some of the mutations within the lysine-binding site potentially impair the binding of apolipoprotein (a) to lysine-rich domains, such as those in fibrin(ogen) and apolipoprotein B100. At present, there is little knowledge about the effect of the lipoprotein (a) polymorphism on the mechanisms underlying its atherothrombogenic potential. With the current availability of in-vitro, ex-vivo, and transgenic mice models, this issue should be amenable to productive exploration.     

Public schools and four year olds: A teacher's view.

The question of opening public schools to four-year-olds is examined by the president of the National Education Association. Arbitrary, age-based models of appropriate instruction are criticized, and an educational philosophy based on the ideal of lifelong learning is advanced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A four year prospective study of age-related cognitive change in adults with Down's syndrome

BACKGROUND: While neuropathological studies indicate a high risk for Alzheimer's disease in adults with Down's syndrome, neuropsychological studies suggest a lower prevalence of dementia. In this study, cognitive deterioration in adults with Down's syndrome was examined prospectively over 4 years to establish rates and profiles of cognitive deterioration. METHODS: Fifty-seven people with Down's syndrome aged 30 years or older were assessed using a battery of neuropsychological tests on five occasions across 50 months. Assessments of domains of cognitive function known to change with the onset of Alzheimer related dementia were employed. These included tests of learning, memory, orientation, agnosia, apraxia and aphasia. The individual growth trajectory methodology was used to analyse change over time. RESULTS: Severe cognitive deterioration, such as acquired, apraxia and agnosia, was evident in 28.3% of those aged over 30 and a higher prevalence of these impairments was associated with older age. The rate of cognitive deterioration also increased with age and degree of pre-existing cognitive impairment. Additionally, deterioration in memory, learning and orientation preceded the acquisition of aphasia, agnosia and apraxia. CONCLUSIONS: The prevalence of cognitive impairments consistent with the presence of Alzheimer's disease is lower than that suggested by neuropathological studies. The pattern of the acquisition of cognitive impairments in adults with Down's syndrome is similar to that seen in individuals with Alzheimer's disease who do not have Down's syndrome.     

Endothelial study of iris-claw phakic lens: four year follow-up

PURPOSE: To study quantitative and morphometric endothelial changes in phakic eyes implanted with the Worst iris-claw lens to correct high myopia. SETTING: Department of Ophthalmology, University Hospital "La Fe", Valencia, Spain. MATERIAL AND METHODS: This retrospective study involved 111 phakic eyes (73 patients) implanted with the Worst iris-claw lens. Noncontact specular microscopy and computer-assisted analysis was performed preoperatively and 6 months and 1, 2, 3, and 4 years postoperatively. RESULTS: The mean cell loss was 3.85% at 6 months, 6.59% at 1 year, 9.22% at 2 years, 11.68% at 3 years, and 13.42% at 4 years. At 2 years, the hexagonality and coefficient variation in cell size were close to the preoperative levels. No major complications were seen; early postoperative corneal touch required intraocular lens (IOL) removal in 1 case (0.9%). Four eyes (3.6%) needed a reoperation because of poor IOL fixation (2 eyes), traumatic subluxation of the IOL (1 eye), and miscalculation of the IOL power (1 eye). CONCLUSIONS: Although there was a slight progressive cell loss after IOL implantation, the morphometric changes recovered and were close to the preoperative levels. This suggests that endothelial damage occurred primarily during the surgical procedure.     

感应重熔TiC增强Fe-Al金属间化合物复合涂层的显微组织研究

采用Fe粉、Al粉及TiC硬质颗粒等的混合粉料,利用火焰喷涂加感应重熔的方法得到TiC增强Fe-Al金属间化合物复合涂层,涂层中TiC颗粒含量为15%(质量分数)。用X射线衍射仪(XRD)测定复合涂层的物相组成。用扫描电子显微镜(SEM)观察复合涂层的微观形貌,涂层中出现了TiC增强Fe-Al金属间化合物区,TiC硬质颗粒在Fe-Al金属间化合物中呈白色点状分布。用维氏硬度计测得复合涂层的显微硬度为540.4MPa。     

A comparative study of four forms of psychotherapy.

Compared 4 forms of psychoanalytically oriented psychotherapy involving 3 male experienced psychiatrists and 106 18–56 yr old psychiatric outpatients. Patients received either individual therapy or group therapy that lasted either 6 or 24 mo. A comprehensive set of outcome scores (e.g., a version of the 16PF and the Cornell Index) provided by patients, therapists, and an independent assessor was monitored each 6 mo, including a 6-mo follow-up assessment. Therapy outcome, therapy process as viewed by the therapists, and cost-effectiveness were examined. What emerged as important was the particular form of therapy received, not the general type of therapy or the general duration of therapy when considered as independent dimensions. Results favor long-term group therapy and short-term individual therapy over long-term individual therapy and short-term group therapy. Advantages and difficulties associated with each form of therapy are discussed. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

多壁碳纳米管和氧化铝复合增强铝基复合材料阻尼特性的研究

采用粉末冶金的方法制备了四种不同增强体组分的铝基复合材料,这四种复合材料分别为:10%A l2O3/A l复合材料、1%MWCNT+9%A l2O3/A l复合材料、5%MWCNT+5%A l2O3/A l复合材料、10%MWCNT/A l复合材料.用动态机械热分析仪研究了上述四种复合材料的阻尼特性.     

不同陶瓷颗粒增强铁基复合材料力学性能的研究(英文)

Mechanical properties of iron matrix composites reinforced by different types of ceramic particles(SiC,Cr3C2,TiC and Ti(C,N)) prepared by the two-stage resistance sintering were studied experimentally.It was found that tensile strength of SiC/Fe composite shows the highest among the four types of composites.The elongation of all the composites decreases as increasing of reinforcement volume fraction.The stress-strain curves of the composites were simulated by Eshelby approach modeling to reveal the strengthening mechanisms.The modeling and microstructure observations suggest that the strengthening mechanism of the iron matrix composites relies not only on load sharing of the reinforcements but also on reinforcement increasing matrix strength.     

Panavia/sandblasted resin bonded prostheses: a five year retrospective study

The authors feel that this study suggests that the Panavia/sandblasted retention method, with its low debond rate, is a viable method for luting resin bonded prostheses. The authors wish to acknowledge the services of Ms. Jane Jakobsen (statistician) and Ms. Connie Norton (secretary) who made significant contributions to the completion of this article. Their help was much appreciated.     

A structural study of oxidation in an Al2O3 fiber reinforced titanium aluminide composite

A composite of titanium aluminide, reinforced with ZrO₂ toughened Al₂O₃ fibers, has been produced by pressure casting. The stability of the microstructure during vacuum and air annealing was investigated by scanning and transmission electron microscopy (TEM). Processing resulted in partial dissolution of ZrO₂ of the fiber into the molten metal which solidified into a two phase lamellar α₂ + γ matrix. Vacuum annealing caused dissolution of Al₂O₃ fiber into the matrix, transformation of the matrix into γ and precipitation of ZrO₂ and Al₂Zr within γ. During air annealing diffusion of O through the fiber resulted in the formation of Al₂O₃ coated ZrO₂ nodules extending from the fiber surface into the matrix in some regions and in the other regions the growth of Al₂O₃ into the γ of the lamellar matrix. An A15 phase with the metal composition, Ti₃Al₂, was found between the external oxide scale and the metal matrix.     

牙科光固化复合树脂材料的性能与展望

牙科光固化复合树脂具有色泽美观,强度高,临床操作方便,粘结固位效果好等优点,在牙科修复领域引起了广泛关注.该复合材料是由树脂基体、无机填料和光引发体系组成的,原料混合后经特定波长的可见光照射即可固化.牙科光固化复合树脂虽然已在临床上得到了应用,但在性能方面仍然存在某些不足之处,所以如何进一步提高其性能成为目前研究的热点之一.该文作者综述了树脂基体、无机填料和光引发剂的研究情况,对光固化复合树脂的力学性能、聚合度、吸水性和溶解性等性能及其影响因素进行了评述,并对今后的研究进行了展望.     

Pulsed blue laser curing of hybrid composite resins

Clinical performance of light-curing composite restorations is greatly influenced by the quality of the curing-light. Currently used photopolymerization units have some important drawbacks, such as decreasing light output with time and distance, which results in a relatively low degree of conversion and shallow depth of cure, particularly of darker shades. Experiments with continuous argon laser polymerization showed overheating of the composite sample, as well as increased shrinkage of the material. In this study a pulsed laser, set at 468 nm (the maximum of the camphorquinone absorption coefficient), with 20-ns pulse duration, repetition rate of 10 Hz and energy of 10 mJ per pulse, was used as a light source. The aim of the study was to evaluate the effect of polymerization of light and dark shades of three different hybrid composites cured by pulsed laser at the surface and at 3.0 mm depth. The degree of conversion was measured by Fourier transform infrared spectroscopy (FTIR). Applying pulsed blue laser, significantly better results were obtained for both shades compared to standard polymerization values. Very weak dependence of the degree of conversion, between the surface measurements and those at 3.0 mm, were observed in the case of pulsed laser polymerization due to the piercing nanopulses and the monochromatic light at 468 nm.     

Fluoride uptake and release characteristics of glass ionomer cements

The aims of this study were firstly to investigate the fluoride-releasing characteristics of five commercial glass ionomer materials: Ketac Fil, Chemfil Superior, Fuji II LC, Aquacem and Vitrebond. The second aim was to assess the fluoride uptake and subsequent release from the same range of materials. In both tests, ten discs, 6 mm in diameter with a thickness of 1.5 mm, were made for each material. The initial fluoride release was assessed over a 60-day period for all materials. Each disc was immersed in 2 ml of de-ionised water within a plastic vial. The solutions were changed daily up to day 15, and thereafter every 3 and 4 days until the end of the test. All of the materials released measurable amounts of fluoride throughout the test period, with a considerable range on day 1 (15.3-155.2 ppm F). The concentration of fluoride released on the 2nd day fell sharply for all materials (range 6.3-44.3 ppm F). By day 60 all materials continued to release fluoride, albeit to a lesser extent (range 0.9-3.99 ppm F). With regard to the uptake and release of fluoride, a similar protocol was employed, although all samples were immersed in 1 litre of de-ionised water for 60 days to allow the majority of the fluoride to leach out from the materials. The ten pellets for each material were divided into two groups, five samples as control and five samples as test. Each day over a 20-day period all test samples were exposed to a 1000-ppm F solution for 2 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

A histopathologic study of direct pulp-capping with adhesive resins

The concentration of heat-shock proteins of 70 kD (HSP70) in heart tissue has been shown to increase during transient myocardial ischaemia and to persist during several hours of reperfusion. In this study the relationship between the local myocardial HSP70 concentration and blood flow was addressed for control physiological conditions and acute myocardial ischaemia. A specific aim of this study was to address the question of whether low flow areas under control physiological conditions have undergone a transient ischaemia during the preceding hours and thus may be in a state of hibernation or stunning. In 12 anaesthetized, open-chest beagle dogs (6 control and 6 with 60-min coronary artery stenosis) heart rate, mean aortic pressure, mean arterial partial pressure of O2 and partial pressure of CO2 averaged 85+/-16 beats/min, 94+/-14 mmHg, 102+/-17 mmHg and 39+/-6 mmHg, respectively. Regional HSP70 and myocardial blood flow (RMBF) were measured using an HSP70-enzyme-linked immunosorbent assay and the tracer microsphere technique, respectively, in samples of 250 mg wet mass. In the control group the mean RMBF was 1.06+/-0.59 ml.min-1.g-1 and the local HSP70 concentration was 7.08+/-1.03 microg/mg cytosolic protein. Myocardial HSP70 showed a blood flow-independent regional biological heterogeneity, equivalent to a coefficient of variation of 0.31. Local HSP70 concentrations did not differ (P>0.05) between control low and high flow samples, 6.16+/-1.0 vs 6.08+/-0.75 microg/mg cytosolic protein, respectively. However, after 60 min of coronary artery occlusion the local HSP70 concentration increased from 7.08 +/-1.03 to 13.43+/-3.19 microg/mg cytosolic protein (P<0. 001). There was a significant inverse relationship between the percent reduction of local blood flow and HSP70 (r=-0.56, P<0.001). From these results it is concluded that: (1) low flow samples under control physiological conditions are unlikely to be in a state of hibernation or stunning since their HSP70 concentration is normal and (2) the increase in the local HSP70 concentration during myocardial ischaemia reflects the degree of impairment of O2 delivery.