Influence of Screw Channel Angulation on the Fracture Resistance of Zirconia Abutments: An In Vitro Study.
- 作者列表："Garcia-Hammaker S","Saglik B","Sierraalta M","Razzoog M
PURPOSE:The aim of this study was to investigate the effect of implant screw channel angulation on the fracture resistance of zirconia abutments without artificial aging. MATERIALS AND METHODS:Ten implant replicas were embedded in a jig of autopolymerizing acrylic resin. Using a surveyor and a metallic platform, the implant replicas were mounted centrally and with an angulation of 30°. A maxillary left central incisor crown was fabricated from pattern resin and scanned. The digital design of a monolithic zirconia implant abutment-crown was completed using a 3D imaging software. For all specimens of this group (ASC25 ), the screw channel was positioned at 25° to the lingual. Following fabrication, the samples were attached onto the embedded implant replicas and manually torqued to 35 Ncm as recommended by the manufacturer. The monolithic zirconia implant abutment-crowns were mounted in a metallic platform, positioned perpendicular to the indenter, and subjected to loading until failure. Crosshead speed was set at 0.5 mm/min for the universal testing machine. Data from a similar in vitro study where straight zirconia custom abutments (ASC0 ) were subjected to static load until failure was used as a control group. An unpaired Student's t-test was used to determine if fracture resistance based on load at failure and maximum load in each group were significantly different from each other (ASC25 vs ASC0 ). Statistical significance level was inferred at p ≤ 0.05 RESULTS: Group ASC25 fractured at a mean (SD) load of 215.49 (47.10) N and a mean (SD) maximum load of 420.50 (17.18) N. Group ASC0 fractured at a mean (SD) load of 534.04 (133.77) N and a mean (SD) maximum load of 762.69 (109.59) N. The difference was statistically significant for both mean load and mean maximum load at failure (p ≤ 0.05). The survival rate of 0° zirconia abutments was significantly higher than that of 25° ASC zirconia abutments. CONCLUSIONS:Within the limitations of this in vitro study the mean fracture load was significantly higher in the group with a straight channel angulation.
目的: 本研究的目的是研究种植体螺钉通道角度对无人工老化的氧化锆基台抗折性能的影响。 材料和方法: 将10个植入物复制品包埋在自聚丙烯酸树脂的夹具中。使用测量员和金属平台，将植入物复制品安装在中心，角度为30 °。由图案树脂制作上颌左中切牙冠并扫描。使用3D成像软件完成整体氧化锆种植体基台-冠的数字化设计。对于该组 (ASC25) 的所有样本，螺钉通道位于舌侧25 ° 处。制造后，将样品附着到嵌入的植入物复制品上，并按照制造商的建议手动扭转至35 ncm。将整块氧化锆种植体基台-冠安装在金属平台中，垂直于压头定位，并进行加载直至失效。万能试验机的十字头速度设定为0.5毫米mm/min。来自类似的体外研究的数据，其中将直氧化锆定制基台 (ASC0) 经受静态载荷直至失效用作对照组。使用未配对的学生t检验来确定基于每组中的失效载荷和最大载荷的抗断裂性是否彼此显著不同 (ASC25 vs ASC0)。统计显著性水平在p ≤ 0.05时推断: ASC25组在平均 (SD) 载荷为215.49 (47.10) N和平均 (SD) 最大载荷为420.50 (17.18) N时断裂。组ASC0在534.04 (133.77) N的平均 (SD) 载荷和762.69 (109.59) N的平均 (SD) 最大载荷下断裂。平均载荷和平均最大载荷在失效时的差异具有统计学意义 (p ≤ 0.05)。0 ° 氧化锆基台的存活率显著高于25 ° ASC氧化锆基台。 结论: 在本体外研究的限制范围内，直道成角组的平均骨折负荷显著较高。
METHODS::The ATP binding-cassette superfamily corresponds the mostly transmembrane transporters family found in humans. These proteins actively transport endogenous and exogenous substrates through biological membranes in body tissues, so they have an important role in the regulation of many physiological functions necessary for human homeostasis, as well as in response regulation to several pharmacological substrates. The development of multidrug resistance has become one of the main troubles in conventional chemotherapy in different illnesses including cancer, being the increased efflux of antineoplastic drugs the main reason for this multidrug resistance, with a key role of the ABC superfamily. Likely, the interindividual variability in the pharmacological response among patients is well known, and may be due to intrinsically factors of the disease, genetic and environmental ones. Thus, the understanding of this variability, especially the genetic variability associated with the efficacy and toxicity of drugs, can provide a safer and more effective pharmacological treatment, so ABC genes are considered as important regulators due to their relationship with the reduction in pharmacological response. In this review, updated information about transporters belonging to this superfamily was collected, the possible role of these transporters in cancer, the role of genetic variability in their genes, as well as some therapeutic tools that have been tried to raise against main transporters associated with chemoresistance in cancer.
METHODS:BACKGROUND:Cholinergic neurotransmission regulates neuroinflammation in Parkinson disease (PD). RESEARCH DESIGN AND METHODS:The authors conducted a delayed-start study of donepezil for cognitive decline in non-demented PD patients. The study consisted of a 96-week randomized placebo-controlled double-blind phase 1, followed by a 24-week donepezil extension phase 2. The primary outcome measure was a change in the Mini-Mental State Examination (MMSE) at week 120. RESULTS:A total of 98 patients were randomly allocated to the early-start (donepezil-to-donepezil) and delayed-start (placebo-to-donepezil) groups. Mean (SD) of the baseline MMSE was 27.6 (2.0) and 28.0 (2.1), respectively. MMSE change at week 120 was better in the early-start group than in the delayed-start group, but the difference was not significant. The MMSE declined in apolipoprotein ε4 carriers, but not in non-carriers, and the factor interaction (intervention × ε4 genotype) was highly significant (P < 0.001). Analyzed with the interaction, the difference was significant (group difference 1.95 [0.33 to 3.57], P = 0.018). The MMSE decline slope in phase 1 was significantly better in the early-start group than in the delayed-start group (P = 0.048). CONCLUSIONS:Cognitive function deteriorated in ε4 carriers, but not in non-carriers, and early-start donepezil may postpone cognitive decline in the former.
METHODS::Since the discovery of dental pulp stem cells, a lot of teams have expressed an interest in dental pulp regeneration. Many approaches, experimental models and biological explorations have been developed, each including the use of stem cells and scaffolds with the final goal being clinical application in humans. In this review, the authors' objective was to compare the experimental models and strategies used for the development of biomaterials for tissue engineering of dental pulp with stem cells. Electronic queries were conducted on PubMed using the following terms: pulp regeneration, scaffold, stem cells, tissue engineering and biomaterial. The extracted data included the following information: the strategy envisaged, the type of stem cells, the experimental models, the exploration or analysis methods, the cytotoxicity or viability or proliferation cellular tests, the tests of scaffold antibacterial properties and take into account the vascularization of the regenerated dental pulp. From the 71 selected articles, 59% focused on the "cell-transplantation" strategy, 82% used in vitro experimentation, 58% in vivo animal models and only one described an in vivo in situ human clinical study. 87% used dental pulp stem cells. A majority of the studies reported histology (75%) and immunohistochemistry explorations (66%). 73% mentioned the use of cytotoxicity, proliferation or viability tests. 48% took vascularization into account but only 6% studied the antibacterial properties of the scaffolds. This article gives an overview of the methods used to regenerate dental pulp from stem cells and should help researchers create the best development strategies for research in this field.