Survival analysis of mandibular complete dentures with acrylic‐based resilient liners

doi: 10.1111/j.1741‐2358.2012.00658.x Survival analysis of mandibular complete dentures with acrylic‐based resilient liners Objective: The purpose of this long‐term randomised controlled trial was to compare the longevity of dentures constructed using a conventional acrylic resin (CAR) to that of dentures constructed using an acrylic‐based resilient liner (ARL). Materials and methods: The follow‐up study was essentially carried out by annual telephone calls to each of the 67 participants. The Kaplan–Meier method and life‐table analysis were used for univariate analyses. The Cox proportional‐hazards test was used as a final model for statistically adjusting predictor variables such as sex, clinician type, mandibular denture type and age at denture delivery. Results: The denture type was likely to affect the survival time of the dentures, while the sex and clinician type were not. The group using acrylic‐based resilient denture liners had twice the risk of having shorter denture‐survival times than those using conventional acrylic resin dentures. Younger participants were likely to have a reduced risk of having shorter denture‐survival times than older participants. Conclusion: We conclude that mandibular complete dentures constructed using ARL are twice as likely as dentures constructed using CAR to have shorter denture survival times, mainly because of material deterioration.     

In vivo biofilm formation on a soft denture liner in elderly patients with controlled diabetes

doi: 10.1111/j.1741‐2358.2010.00428.x In vivo biofilm formation on a soft denture liner in elderly patients with controlled diabetes Objectives: This in vivo study evaluated the influence of controlled diabetes on biofilm formation on a soft denture liner in elderly patients. Background: Soft denture lining materials are more susceptible to microbial colonisation than denture base acrylic resins. Especially in the elderly, several predisposing factors may accumulate leading to an increased probability of biofilm development that may result in candidiasis, a significant clinical oral disease. Materials and methods: Volunteers wearing complete dentures were divided into two groups (n = 20): diabetic patients with controlled glycaemia, and healthy patients. In both groups, a silicone‐based soft liner was placed in a recess created at the base of the maxillary dentures. Subjects cleaned the prosthesis three times a day. Biofilm formed on the liner was quantified at various time points (baseline, two, four and six weeks). Data were analysed by two‐way repeated measures anova and Tukey’s test (α = 0.05). Results: There was no statistical difference in biofilm formation for any of the time points between controlled diabetes patients and healthy patients. Conclusion: The results suggest that the control of diabetes in elderly patients provides the same levels of biofilm formation when compared to healthy individuals.     

The Influence of Hydraulic Gradient and Rate of Erosion on Hydraulic Conductivity of Sand-Bentonite Mixtures

The use of sand-bentonite mixtures as liner materials for waste disposal is very common. In the laboratory, this study investigated hydraulic conductivities of such mixtures at different hydraulic pressure (hydraulic gradient), dry unit weights, and bentonite contents. The bentonite content and the dry unit weight of the samples were both important factors, significantly affecting the hydraulic conductivity of the liner material. A bentonite content of 5% was found to be sufficient in reaching a hydraulic conductivity under 10^?9 m/s, when the liner material was compacted under near optimum moisture content. Nevertheless, hydraulic conductivity was found to increase with hydraulic pressures, especially for the 5% bentonite mixtures subjected to pressure above 40 kPa, suggesting some degree of internal erosion (washing out of particles).

Therefore, this paper discuses the influence of internal erosion of the mixtures under a given hydraulic gradient, on the final value of k. The internal erosion of the tested mixtures was found to be influenced mainly by porosity, which can be reduced by properly selecting the sand particle size distribution and the bentonite percentage. Furthermore, this study proposed an empirical expression to predict the risk of internal erosion in the sand-bentonite mixtures, and therefore of k being higher than planned. This expression can be used for designing bentonite content and compaction to achieve very low permeability.     

Compartments for the Management of Municipal Solid Waste

Despite technological developments and improved liner-material applications, heavy metals in landfill leachate still penetrate the soil profile, polluting the soil and ground-water. An alternative approach therefore must be explored to reduce heavy-metal migration in soil-bentonite landfill liners. By considering the interaction of different heavy metals and their synergetic and antagonistics behaviors, such an approach could be developed. Low mobility metals such as Cu²⁺, and Pb²⁺ inhibit the adsorption of Cd²⁺ which is a moderate-mobility metal and Cu²⁺ sorption is decreased by the presence of Zn²⁺ and Cd²⁺. Therefore, Zn²⁺, a low-mobility metal, cannot be grouped with Cu²⁺. This way, four compatible metal groups have been identified: (1) low mobility: Pb²⁺, Cu²⁺, and Ag, (2) low mobility: Zn²⁺ and Cr³⁺; (3) moderate mobility: As²⁺, Fe²⁺, and Ni²⁺; (4) high mobility: Cd²⁺ and Hg²⁺. Cd²⁺ with a moderate mobility pattern is synergetic to Fe²⁺ and is more mobile with Ni²⁺. Therefore, Cd²⁺ is separated from the moderate-mobility group and is consigned with Hg, a high-mobility metal. The liner materials suitable for Hg²⁺ are assumed to be suitable for Cd²⁺ as well. Based on this concept, and to reduce heavy metal mobility, wastes should be segregated on compatibility basis according to their heavy metal contents before being disposed in different individual compartments. For wastes containing several incompatible heavy metals, sorting should be based on the heavy-metal with the highest concentration. Another solution is the manufacturing of products using compatible heavy metal combinations and then labeling them accordingly. Such waste segregation and landfill compartmentalization lowers risks of groundwater contamination and liner cost.     

安太堡矿区复垦地植被恢复过程多样性变化

植被生态系统的重建是矿区复垦地恢复的主要环节之一。通过群落调查和实验分析,采用丰富度指数、物种多样性指数和均匀度指数,结合DCCA排序、多元线性回归和相关分析,研究了平朔安太堡矿区复垦地植被恢复过程中多样性的变化。群落多样性分析结果表明:(1)直接种植植被演替后期的植物种大大加速了原始植被演替进程;(2 )多样的人工配置群落比单一的人工配置群落更能促进群落向正向演替的方向发展;(3)能够适应矿区特殊生境的植被配置方式在恢复进程中与自然植被表现出一定的差异,这种差异只持续发生植被恢复的前3a,3a之后群落的演替与自然植被的演替表现出趋同性;(4)森林群落是较灌丛群落更适合安太堡矿区特殊生境的植被配置方式,其中刺槐和油松的混交效果较好。物种多样性的分析表明:(1)多样性偏高的群落与有机质和时间联系较为紧密,而多样性偏低的群落则与锰的联系较为紧密;(2 )制约矿区物种多样性变化的主要因素是土壤水分和演替时间;(3)锌对各多样性指数都有一定的影响(4)有机质、时间与丰富度指数相关显著;(5 )海拔与综合多样性指数相关显著;(6 )铜对均匀度指数的影响较大。方法的比较结果表明:(1)多元线性回归的灵敏度比相关分析高;(2 ) DCCA可以作为对定量分析的补充,解释那些在定量分析中不显著的因     

Culture of cells in beem capsules: A new technique for electron microscopic study of monolayer cultures

Summary A method is described for the monolayer cultivation of primary cell suspensions and established cell lines directly in carbon-coated BEEM capsules. BEEM capsules are routinely employed by electron microscopists in tissue embedding procedures; growing monolayer cultures directly on the lids of inverted BEEM capsules presents the obvious advantage of maintaining cell to cell to substratum contacts with a minimum of stress and damage in the preparative steps for electron microscopy. This work was supported by grant AM 17631 from the National Institute of Arthritis, Metabolism, and Digestive Diseases, grant CA 11339 from the National Cancer Institute. The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

不同纬度产地纽荷尔脐橙果实品质状况初步研究

以纽荷尔脐橙为试材,分析了我国甜橙优势区域内不同纬度地区纽荷尔脐橙果实主要的品质指标。结果表明,纽荷尔脐橙果实的多数品质指标随纬度的变化呈现有规律的变化;线性回归分析结果显示,纽荷尔脐橙果实几项品质指标与纬度的相关性为:可溶性固形物含量呈显著线性正相关,可滴定酸含量呈极显著线性正相关,固酸比呈极显著线性负相关,果皮黄色度和着色强度呈极显著线性负相关,色调角呈显著线性负相关,VitC含量与纬度的线性关系接近显著程度。     

Experiments on in vivo biofilm formation and in vitro adhesion of Candida species on polysiloxane liners

doi:10.1111/j.1741‐2358.2009.00329.x
Experiments on in vivo biofilm formation and in vitro adhesion of Candida species on polysiloxane liners Objectives: Microorganisms may colonise polysiloxane soft liners leading to bio‐deterioration. The aim of this study was to investigate in vitro adhesion and in vivo biofilm formation of Candida species on polysiloxane surfaces. Methods: The materials used in this study were Molloplast B, GC Reline soft, Mollosil Plus, Silagum Comfort and Palapress Vario. The in vitro retention of clinical isolates of Candida albicans to the relining and denture‐base materials by microscopic (scanning electron microscopy, SEM), conventional culturing methods and antimicrobial properties of these materials were studied. Candida found on materials and mucosa following long‐term use were identified and quantified, and biofilms covering the surfaces were investigated by SEM. Results: There was a significant decrease in the number of cells attached in vitro to saliva‐coated surfaces compared with non‐treated surfaces. An oral Candida carriage of 78% was found. Candida albicans, C. glabrata, C. intermedia and C. tropicalis were identified. In vivo biofilm formation on the liners appeared as massive colonisation by microorganisms. Conclusions: The results of the in vitro experiments suggest that salivary film influences early colonisation of different C. albicans strains. The film layer also minimises the differences among different strains. The Candida carriage of these patients was similar to denture‐wearing patients without soft liners.     

近17年陕西榆林植被指数的时空变化及影响因素

植被指数是研究区域植被变化的重要手段。基于MODIS/Terra NDVI遥感影像数据,对陕西榆林市2000—2016年8月份NDVI进行像元尺度的时空变化及影响因素分析。结果表明,榆林有96.44%的区域植被指数是增加的,增加值在0—0.02/a区域面积占榆林的93.63%,呈显著增加趋势的面积占榆林的80.72%。复直线回归分析显示,气象因素对植被生长、演化起到了促进作用,人类活动使得植被指数等级变得更加均匀。人类活动抑制植被生长演化的区域占榆林总面积的45.04%,主要分布在榆林市最北部的府谷县、榆林市南部及西部的大部分区域;人类活动促使植被指数增加的区域占榆林总面积的54.96%,说明有一半以上的区域,人类活动对植被生长起到了促进作用,这些地区的封山育林、退耕还林、退牧还草等措施的实施效果较好。