Effect of surface penetrating sealant on wear rate of posterior composite resins

Although posterior composite resins have been improved considerably, secondary caries and wear continue to be a major concern. Recent studies suggested that microstructural defects such as voids and microcracks contribute to a weakened surface. The purpose of this study was to evaluate the effect of an experimental surface-penetrating sealant on the wear resistance of a posterior composite resin. At the end of 1 year, the rate of wear of the treated restorations was one-half of those not receiving the surface penetrating sealant.     

Nanomechanical and chemical characterization of incipient in vitro carious lesions in human dental enamel

OBJECTIVE: The research was designed to examine the growth of in vitro carious lesions in dental enamel using nanoindentation and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). This was intended to give maps of mechanical properties and chemistry over the cross-section of the lesions. METHODS: Incipient carious lesions were grown on the buccal faces of 20 human premolars by exposure to acid for 3, 5, 7 or 14 days. The lesions were then cut in cross-section normal to the exposed surface. The lesions' cross-sections were then examined using nanoindentation and TOF-SIMS. RESULTS: The earliest lesions (3 days of acid exposure) showed little evidence of lesion growth, but the 5, 7 and 14 days of exposure all gave lesions with a weak, demineralized interior, but a stronger, less demineralized surface zone. The thickness of the surface zone was found to diminish with the length of exposure to acid, but it was still present even after 14 days of exposure. CONCLUSION: The results indicate that carious lesions develop subsurface and that the surface zone forms by a coupled diffusion process. Mechanically the lesion has a strong surface layer, but a very weak interior which makes the lesion vulnerable to mechanical loading. However, the presence of a surface zone that retains a high mineral content and is mechanically strong suggests that lesion development can be arrested and possibly reversed even when the lesions are relatively mature.     

The multiple roles of major histocompatibility complex class-I-like molecules in mucosal immune function

The human major histocompatibility complex (MHC) on chromosome 6 encodes three classical class-I genes: human leukocyte antigens (HLA) A, B, and C. These polymorphic genes encode a 43- to 45-kDa cell surface glycoprotein that, in association with the 12-kDa beta2-microglobulin molecule, functions in the presentation of nine amino acid peptides to the T-cell receptor of CD8-bearing T lymphocytes and killer inhibitory receptors on natural killer cells. In addition to these ubiquitously expressed, polymorphic proteins, the human genome also encodes several nonclassical MHC class-I-like, or class Ib, genes that, in general, encode nonpolymorphic molecules involved in various specific immunological functions. Many of these genes, including CD1, the neonatal Fc receptor for IgG, HLA-G, HLA-E, the MHC class-I chain-related gene A, and Hfe, are prominently displayed on epithelial cells, suggesting an important role in epithelial cell biology.     

A comparative study of the strength of aluminous porcelain and all-ceramic crowns

This study compared the breaking strengths of all-ceramic crowns constructed with aluminous porcelain, the Cerestore system, and the Dicor system on an anterior tooth preparation. Fifteen crowns from each group were constructed to comparable dimensions on dies from the same master die. Ten crowns from the same group were cemented on the master die and loaded until catastrophic failure. Five crowns from each group were embedded and sectioned to examine internal adaptation. No significant difference was found between the load necessary to produce failure in the aluminous porcelain and Dicor crowns and the load needed to initiate crack formation in the Cerestore crowns. However, seven of the 10 Cerestore crowns showed a two-phase failure pattern; the difference between crack initiation and catastrophic failure was significant. Within the limitation of this study, neither the Cerestore (high alumina core) nor the Dicor (castable glass-ceramic) produced an all-ceramic crown superior to the current aluminous porcelain crown.     

The influence of glucocorticoid receptor single nucleotide polymorphisms on outcome after haematopoietic stem cell transplantation

Haematopoietic stem cell transplantation (HSCT) remains the only cure for most haematological malignancies, however, the mortality rate remains high. Complications after HSCT include relapse, graft versus host disease (GvHD), graft rejection and infection. Over the last few years several groups, have demonstrated that non‐HLA gene polymorphisms can be predictive of outcome after HSCT. Since the glucocorticoid cortisol is pivotal in the regulation of the immune system, we decided to examine single nucleotide polymorphisms (SNPs; rs6198, rs33388 and rs33389) within the glucocorticoid receptor (GR) and correlate with HSCT outcome. The training set consisted of patients (n = 458) who underwent HSCT for acute leukaemia between 1983 and 2005. In the recipients, the absence of the ACT haplotype and absence of the T allele of rs33388 were associated with decreased OS and the absence of the ACT haplotype, the absence of the T allele of rs33388 and the presence of the ATA haplotype were associated with increased risk of relapse. In addition, the presence of the ACT haplotype in the recipient showed a trend to be associated with increased risk of chronic graft versus host disease (cGvHD). The patients in this cohort received mainly myeloablative conditioning (n = 327). The SNPs in the glucocorticoid receptor were then investigated in a validation set (n = 251) of HSCT patients transplanted for acute leukaemia from 2006. This cohort contained significantly more patients that had received reduced intensity conditioning (RIC). Some of the results could be validated in these patients. However, contrary to the training set, the absence of the haplotype ACT in the donor in this cohort was associated with increased risk of cGvHD. Differences in the conditioning were shown to influence the results. These results are the first to associate GR SNPs with HSCT outcome and demonstrate the inherent problems of replicating SNP association studies in HSCT, due to different pre‐transplant regimens.     

一氧化氮对人肝癌细胞SMMC-7721辐射敏感性的增强效应

目的:观察一氧化氮对肿瘤细胞SMMC-7721辐射敏感性的作用效果。方法:实验于2005-06/09在兰州大学生命科学学院和中科院近代物理研究辐射医学实验室进行。处于对数生长期的肝癌细胞SMMC-7721,在用X射线照射前4h,换入含有0.1mmol/L硝普钠(一氧化氮的前体)的培养液,与对照组(不加硝普钠)一起,在200cGy/min的剂量率下,分别照射0,1,2,4,6,8Gy,换为正常培养液培养。用集落形成法计算细胞的存活率,用吖啶橙/溴乙啶双染法检测细胞的死亡情况,用流式细胞仪检测细胞周期。结果:①存活曲线细胞存活率随照射剂量增加而减少,硝普钠组细胞的克隆形成率低于对照组(2Gy时,P<0.01)。②细胞死亡百分率(坏死细胞与凋亡细胞总数/总细胞数):与照射剂量呈正相关,硝普钠组高于对照组(P<0.05)。对照组从(9.95±3.53)%(0Gy)逐渐升至(58.74±3.46)%(6Gy),而硝普钠组则从(18.53±12.02)%(0Gy)迅速升至(61.57±9.53)%(2Gy)。③细胞周期检测结果:对照组细胞经过X射线照射后,出现了G2/M期阻滞[从0Gy时(12.50±5.76)%逐渐增加到8Gy(40.36±2.74)%],而硝普钠组细胞在低剂量时主要表现为G0/G1期阻滞[0Gy:(16.06±7.19)%;2Gy:(17.93±0.92)%],而G2/M期阻滞仅在高剂量时明显[8Gy时为(50.10±3.93)%,P<0.05]。结论:经硝普钠产生的一氧化氮,通过与X射线协同作用,减少了肝癌细胞SMMC-7721的细胞存活率,促进细胞死亡,阻止细胞被阻滞至G2/M期,是一种有效的辐射增敏剂。     

External validation of compliance to perfusion quality indicators

PURPOSE: There exists a significant gap between the expected and delivered level of quality received in America's hospitals. As a result, clinical outcomes of critical services such as coronary artery bypass graft (CABG) surgery have received unparalleled scrutiny. Medical information technology companies like Solucient and insurance carriers such as Blue Cross of California have identified and published a list of hospitals that demonstrate superior quality and patient outcomes for CABG procedures. These 'benchmark' programs serve as a reminder that closing the quality gap is possible. Unfortunately, none of these rankings (report cards) provide programs that fail to achieve benchmark status with detailed information on the processes or methods necessary to improve performance. METHOD: After identifying hospitals within the Fresenius Medical Care Extracorporeal Alliance (FMCEA) system that were judged as top performers (benchmark programs) by either Solucient ('100 Top Cardiovascular Hospitals', Evanston, IL 60201) or Blue Cross of California ('Centers of Expertise', Newbury Park, CA 91320), 12 months of continuous collection of CPB-related quality indicator data were analyzed for compliance to the FMCEA evidence-based Quality Indicator Program (QIP). A comparison of compliance to the FMCEA CPB indicators was made between the benchmark FMCEA hospitals and the FMCEA peer group hospitals. RESULTS: Seven CPB process indicators were compared: 1) lowest sustained mean arterial pressure, 2) lowest sustained cardiac index, 3) lowest sustained mixed venous oxygen saturation, 4) lowest sustained hematocrit, 5) lowest activated clotting time, 6) highest sustained arterial blood temperature and 7) average sodium bicarbonate administered. Analysis of hospitals in the FMCEA system designated by Blue Cross of California as 'Centers of Expertise' revealed statistically significantly greater compliance (p < 0.05) in all but one CPB indicator. Hospitals in the FMCEA system designated by Solucient's '100 Top Cardiovascular Hospitals' listing revealed statistically significantly greater compliance to all but three CPB quality indicators. CONCLUSIONS: Successful compliance with the majority of FMCEA CPB process indicators correlates with external recognition from two report card systems demonstrating superior hospital performance. Analysis of compliance to process indicators may provide useful guidelines to improve the standard of care in CABG surgery in many hospitals.