DTG thermal analyses and viscosity measurements of three commercial agar impression materials

Three commercial agar impression materials, two for clinical uses and one for dental laboratory, were examined for their thermal properties by differential thermogravimetric (DTG) thermal analyses and viscosity measurements. On DTG profiles, an endothermic peak along with weight loss at around 100 degrees C was observed on all three agar impression materials as a result of water evaporation. Two clinical agar impression materials were more susceptible to this trend than the remaining one dental laboratory agar impression material. The viscosity of three agar impression materials could be expressed in the exponential function of temperature. Viscosity at 46 degrees C of one dental laboratory agar impression material far exceeded those of two clinical agar impression materials. Monitoring the viscosity could facilitate the detailed analysis of setting process of agar impression materials upon cooling, and might be useful for future development of agar-based dental impression materials.     

Candida albicans growth on thermal cycled materials for maxillofacial prostheses in vitro

In the present study, the growth of a single isolate of Candida albicans on saliva-, serum-coated or protein free (uncoated), thermocycled (4-70 degrees C for 1 min, respectively; 0, 1000 and 10 000 times) 15 commercial maxillofacial materials was investigated, by monitoring pH changes in growth media. The inhibitory effect of the tissue conditioners on fungal growth was analysed using three parameters viz: (i) delay in the onset of the rapid decline in pH (ii) reduction in the rate of pH change and (iii) the pH minima reached. In the case of control materials (non-thermocycled and uncoated), significant antifungal effect was observed with two products. However, the antifungal effect of the materials was significantly reduced both by thermal cycling (Analysis of covariance [ANOVA]; P < 0.01) and a layer of protein coating (saliva, P < 0.05; serum, P < 0.01). When the interrelation between three parameters of fungal growth and the surface hydrophobicity of the materials were analysed, minimum pH of fungal growth on 10 000-thermocycled materials correlated well with the contact angles of the materials (Student t-test, P < 0.01), suggesting that thermocycling process reduced the unpolymerized components of the materials which showed the antifungal effects, resulted in that the cell growth depends on the surface hydrophobicity of the specimens. These results, taken together, suggest that the ageing of the materials and the biological fluids of the host enhanced the fungal growth on maxillofacial materials.     

Kr:F准分子激光对牙体硬组织的热效应研究

目的：评价Kr:F准分子激光照射牙齿后，对牙体硬组织的影响。方法；通过测量Kr:F准分子激光照射后牙齿硬组织的温度，并与Nd:YAG激光照射组进行比较。结果：10s,60s时，Kr:F准分子激光组牙齿硬组织的温度升高值明显低于Nd：YAG激光照射组（P＜0．01）。在照射10s-60s时间内，Kr:F准分子激光照射后牙齿硬组织的温度变化值也明显低于Nd:YAG激光照射组（P＜0．01）。结论：Kr:F准分子激光牙齿产热较少。     

Alpha- and beta-forms of gutta-percha in products for root canal filling

AIM: This study was undertaken to evaluate which materials were in the alpha-form of gutta-percha as claimed, and which were in the more conventional beta-form, and to explore the effect of heating on the materials. METHODOLOGY: Samples of gutta-percha without chemical additives, and dental gutta-percha formulations which included (i) two products previously studied; (ii) 12 newer products; and (iii) one newer product that had been stored at high temperature, were analysed by simultaneous differential thermal analysis and thermogravimetry. RESULTS: It was found that only four of the newer materials contained the alpha-form; all the rest comprised beta-gutta-percha. No weight loss was found for any material under the conditions of the present experiments. A typical heating cycle up to 130 degrees C caused changes in material behaviour - that is, on reheating fewer endothermic peaks were present. Storage of gutta-percha samples for 10 years under ambient temperature and storage in a heater at 80 degrees C appeared to have no effect on properties. CONCLUSIONS: It was concluded that heating dental gutta-percha to 130 degrees C causes physical changes; this was not seen with chemically pure gutta-percha. The presence of additives in the dental samples altered material behaviour.     

Cure performance of light-activated composites by differential thermal analysis (DTA)

A technique which utilizes differential thermal analysis and a divided fibre optic system is a valuable aid to the study of the curing behaviour of lightactivated composites. Degree of cure and temperature rise can readily be evaluated as a function of irradiation time. Shade of material, thickness, sample temperature and the presence of porosity all have a significant effect on cure behaviour. The temperature rise for a 60 mm³ sample of material varies between 20°C and 40°C for the materials tested.     

Influence of thickness and cooling rate on development of spontaneous cracks in porcelain/zirconia structures

Background: Clinical studies reporting the outcome of zirconia‐based restorations indicate that the strength of the zirconia frameworks is sufficient to withstand masticatory forces. However, a significant incidence of cohesive fracture of the veneering porcelain has been reported. The aim of this study was to investigate spontaneous crack development (chipping, rupture) in a range of porcelains veneered to a zirconia core as a result of thermal stresses induced by changes in thickness and cooling rate. The hypothesis tested was that crack incidence would increase with increased veneer thickness and faster cooling rates. Methods: Zirconia spheres (diameter 7.8 mm) were veneered with 1.5 gm (thickness ratio 1:2) and 2.5 gm (thickness ratio 1:1) of five nominally compatible commercially available porcelains. The manufacturers’ firing cycles and a rapid cooling firing cycle were followed. Results: Multiple regression analysis showed positive associations between the occurrence of cracks and the three covariates (materials, thickness and cooling rate). The incidence of cracks and rupture of the veneering porcelain increased with a faster cooling rate and increased thickness of the specimens in three porcelain–zirconia combinations. Conclusions: Crack incidence increased with increased porcelain veneer thickness and faster cooling rates in nominally compatible porcelain/zirconia systems in the geometrically configured specimens tested.     

“一带一路”背景下国内外藏药发展现状

目的：探讨“一带一路”背景下国内外藏药的发展现状。方法：利用CiteSpace软件对中国知网（CNKI）和Web of Science核心合集自2014年收录的藏药相关文献进行关键词聚类,总结国内各类研究热点,比较国内外研究关注点及方法的异同。结果：藏药研究年发文量较为稳定,中英文文献发文量最多的研究机构分别是是青海省藏医院、印度科学和工业研究理事会,中英文文献的高频关键词有单味藏药、药理学、治疗应用等。结论：国外藏药研究主要聚焦药理学和治疗应用两个领域,国内藏药研究聚焦分离和提纯、遗传学、药理学、药物作用和治疗应用5个领域,国内外关于藏药的研究各有侧重,在知识和应用层面能够相互补充。     

基于偏序结构和药性理论的“方-药-量-性”共性关联分析

目的 探索藏族医（简称藏医）“方-药-量-性”关系复杂而共性关联突出,难以揭示隐形特异性藏医药临床用药规律等科学问题的解决方法。方法 该研究基于属性偏序结构、“味性化味”矢量结构模型、聚类分析等方法,分析《中华人民共和国卫生部药品标准藏药（第一册）》收载184首藏医临床常用方剂的“方-药-量-性”关系。结果 方-药关系分析发现诃子、红花等11个最大共有属性组方,是分类配伍的关键组方,可以有效分类治疗隆病、赤巴病、血热病等8类方剂,在方剂中三果汤散、六味良药散等调节三因和辅助脏腑功能类组方药物的共有性最强。药-量关系分析发现,诃子、红花、石榴子、余甘子等用量最高,表明这些组方药物一般以君药形式入药,而豆蔻、草果等六味良药散组方药物虽频次较高,但剂量较低,主要起着调节方剂整体药性和保护脏腑的作用,而麝香、牛黄、渣驯等藏医特效药物,频次虽高但剂量很低,具有增强药性,引药患处的作用。量-性关系分析发现属于凉性方剂较多,占75.6%,发现有67首方剂因其组方剂量不同而产生药性与功效不相符的现象。结论 藏医方剂中存在很多共性组方和共性用法,如不对这些共性关联加以处理,会出现任何疾病均以这些共性关联为核心的结果,却无法解开隐性的关键因素。因此,在“方-药-量-性”等多维层面同时注重敏感性和特异性规律,才能更有效地揭示藏医临床用药思想。     

基于下丘脑-垂体-卵巢轴探讨藏药二十五味鬼臼丸对绝经后骨质疏松症大鼠的干预作用

目的基于下丘脑-垂体-卵巢轴(hypothalamus-pituitary-ovary axis,HPOA)探讨藏药二十五味鬼臼丸对去卵巢大鼠骨质疏松的影响。方法将40只SD雌性未孕大鼠随机分为假手术组、模型组、雌二醇组、二十五味鬼臼丸组,每组10只。除假手术组仅摘取卵巢旁同样大小的脂肪块,其余3组大鼠均摘除双侧卵巢建立绝经后骨质疏松症(postmenopausal osteoporosis,PMOP)大鼠模型。手术1周后开始给药处理,雌二醇组ig0.1mg/kg戊酸雌二醇,二十五味鬼臼丸组ig441mg/kg二十五味鬼臼丸,假手术组和模型组ig等体积蒸馏水,1次/d,连续12周后,ELISA法检测血清雌二醇、黄体生成素(luteinizing hormone,LH)、卵泡刺激素(follicle stimulating hormone,FSH)、促性腺激素释放激素(gonadotropin releasing hormone,GnRH)水平;RT-PCR检测下丘脑、垂体、左侧股骨远端雌激素受体α(estrogen receptorα,ERα)、雌激素受体β(estrogen receptorβ,ERβ)m RNA表达;免疫荧光染色法检测下丘脑、垂体和右侧股骨远端ERα、ERβ蛋白表达;HE染色法观察大鼠右侧股骨远端组织形态变化;Micro-CT检测右侧股骨远端微结构的改变。结果藏药二十五味鬼臼丸能显著降低大鼠体内血清LH、FSH、GnRH水平(P0.05、0.01),并在HPOA轴中显著性上调下丘脑及垂体ERαm RNA及蛋白表达(P0.01),同时显著性上调股骨ERβm RNA及蛋白表达(P0.01),并能显著回调大鼠股骨密度及骨微结构参数(P0.01)。结论藏药二十五味鬼臼丸可有效防治PMOP,其机制可能与药物直接作用骨组织雌激素受体或作用HPOA轴靶器官相关雌激素受体后,通过改变体内性激素的水平间接调控骨代谢有关。     

红外热成像对蚕沙外熨辅助治疗糖尿病胃轻瘫的疗效评价研究

目的 研究采用蚕沙外熨腹部的方法辅助治疗糖尿病胃轻瘫的有效性,探讨治疗过程中红外热成像对临床疗效评价的作用.方法 将110例糖尿病胃轻瘫患者随机分为治疗组55例、对照组55例.其中治疗组脱落3例,完成病例观察52例,脱落率为5.45％;对照组脱落5例,完成病例观察50例,脱落率为9.09％.2组均予基础治疗,治疗组在基础治疗上辅以蚕沙外熨治疗,对照组在基础治疗上辅以热水袋外熨.在入组时、2周及4周随访时进行红外热成像检测及彩超胃排空率检测.比较2组胃脘部、中脘穴、大腹部、左右足三里绝对温度、相对温度以及彩超胃排空率.结果 2组彩超胃排空率在治疗2周时及随访时,与治疗前比较差异均有统计学意义(P<0.05);重复测量方差分析结果显示:T3,△T1,△T4在组别和观察时间的交互作用有统计学意义(P<0.05).2组组间比较显示:治疗组△T3较对照组下降,差异有统计学意义(F组间=6.48,P<0.05).结论 蚕沙外熨法辅助治疗能够改善糖尿病胃轻瘫患者彩超胃排空率,降低红外热成像检测时大腹部的相对温度.红外热成像检测能够评估糖尿病胃轻瘫的临床疗效.