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11.

PURPOSE

This study evaluated the initial stability of different implants placed above the bone level in different types of bone.

MATERIALS AND METHODS

As described by Lekholm and Zarb, cortical layers of bovine bone specimens were trimmed to a thickness of 2 mm, 1 mm or totally removed to reproduce bone types II, III, and IV respectively. Three Implant system (Brånemark System® Mk III TiUnite™, Straumann Standard Implant SLA®, and Astra Tech Microthread™-OsseoSpeed™) were tested. Control group implants were placed in level with the bone, while test group implants were placed 1, 2, 3, and 4 mm above the bone level. Initial stability was evaluated by resonance frequency analysis. Data was statistically analyzed by one-way analysis of variance in confidence level of 95%. The effective implant length and the Implant Stability Quotient (ISQ) were compared using simple linear regression analysis.

RESULTS

In the control group, there was a significant difference in the ISQ values of the 3 implants in bone types III and IV (P<.05). The ISQ values of each implant decreased with increased effective implant length in all types of bone. In type II bone, the decrease in ISQ value per 1-mm increase in effective implant length of the Brånemark and Astra implants was less than that of the Straumann implant. In bone types III and IV, this value in the Astra implant was less than that in the other 2 implants.

CONCLUSION

The initial stability was much affected by the implant design in bone types III, IV and the implant design such as the short pitch interval was beneficial to the initial stability of implants placed above the bone level.  相似文献   
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Chondrocytes may control the mineralization of the extracellular matrix of condylar cartilage by several mechanisms including the release of microvesicles involved in the initial nucleation, the creation or modification of the local matrix to help propagate or restrict mineralization, and the regulation of the ionic environment at the calcifying foci within the matrix. The plasma membrane Ca2+-Mg2+ ATPase (Ca2+ pump) is known to play a part in the vectorial efflux of calcium in a variety of cells including chondrocytes. The purpose here was to study the distribution of Ca2+-pump protein in mandibular condyles from growing and adult rabbits, and compare the expression of that protein in progressively differentiating chondrocytes whose final stage is associated with a mineralized extracellular matrix. Ca2+-pump antigen was identified immunohistochemically in six growing and six adult rabbit mandibular condyles with a Ca2+ pump-specific monoclonal antibody. The presence of Ca2+-pump antigen was established in hypertrophic chondrocytes, and in osteoblasts and osteoclasts of subchondral bone. Slot-blot analysis of nitrocellulose-immobilized chondrocyte homogenates showed that the amount of Ca2+ pump in growing cartilage was more than twice that in adult cartilage (p < 0.05). The demonstration of Ca2+-pump antigen in the hypertrophic chondrocytes of growing rabbit condyles is consistent with a role for the plasma-membrane Ca2+ pump in the calcification of mandibular condylar cartilage.  相似文献   
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A new radiographic technique was used to compare apical transportation in four Ni-Ti rotary instrumentation sequences. Mesiobuccal canals of 60 extracted mandibular molars were randomly divided into four groups. Groups 1 and 3 were instrumented by crown-down and groups 2 and 4 by step-back technique with 0.06 ProFiles series 29 to size 6. In groups 3 and 4 Greater Taper files were first used in a crown-down manner. The central axes of initial and final instruments were radiographically superimposed to measure loss of working length (WL) and transportation at 0, 0.5, 1, 3, and 5 mm from WL. ANOVA test showed no significant differences among groups regarding degree of transportation or loss of WL. Transportation was negatively correlated with radius of curvature at 0.5 and 5 mm from WL. The results indicate that the operational sequence of ProFiles or preinstrumentation with GT files has no effect on degree of transportation and loss of WL.  相似文献   
16.
OBJECTIVE: The purpose of this research was to compare the Dr. SEDOC toothbrush, tufted with super-tapered bristles, to the ADA standard toothbrush in three laboratory procedures designed to evaluate 1) the cleaning ability of toothbrush bristles at the gingival margin (GMC), 2) interproximal access efficacy (IAE) and plaque removal efficacy, or 3) subgingival access (SA) into, and removal of artificial plaque deposits from under the gingival margin. METHODOLOGY: Efficacy was tested using three published laboratory methods, with pressure-sensitive paper placed around simulated teeth, at a brushing pressure of 250 or 500 g, with horizontal or vertical brushing motions. Twenty-four tests on each toothbrush design were conducted, and results were statistically analyzed using ANOVA. RESULTS: In all three assays, the Dr. SEDOC toothbrush had a significantly superior (p < 0.001) efficacy mean value compared to the ADA toothbrush. CONCLUSION: The Dr. SEDOC toothbrush, with super-tapered bristles, offers the potential for improved cleaning and plaque removal compared to the ADA standard control toothbrush.  相似文献   
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背景 原发性醛固酮增多症(primary?aldosteronism,PA)是继发性高血压的常见病因,PA的分型中以醛固酮瘤(aldosterone-producing?adenoma,APA)和特发性醛固酮增多症(idiopathic?aldosteronism,IHA)最为常见.PA患者与肾上腺无功能瘤(nonfunctional?adrenal?tumors,NFAT)患者血清甲状旁腺激素(parathyroid?hormone,PTH)水平存在差异,不同亚型PA患者血清PTH水平也存在差异.目的 比较PA与NFAT患者以及APA与IHA患者血清PTH水平的差异,并分析影响PTH的因素,探讨PTH在PA及NFAT患者鉴别诊断中的应用价值.方法 收集解放军总医院第一医学中心2016?-2020年收治的PA患者414例[女176例,男238例;平均年龄(50.90?±?10.40)岁;APA患者263例,IHA患者151例]和NFAT患者275例[女112例,男163例;平均年龄(52.74?±?11.20)岁]的临床资料.比较PA与NFAT患者以及APA与IHA患者血清PTH、血电解质、尿电解质、血浆肾素、血浆醛固酮、尿醛固酮水平的差异.采用Pearson相关性分析探讨影响PTH的因素.分析PTH鉴别PA与NFAT以及APA与IHA的最佳切点.结果 PA患者中位PTH水平明显高于NFAT患者[64.82(62.36,67.28)?pg/mL?vs?45.23(35.02,54.74)?pg/mL,P?相似文献   
20.
The basal ganglia–cortical circuits are important for information process to brain function. However, chronic recording of single-unit activities in the basal ganglia nucleus has not yet been well established. We present a movable bundled microwire array for chronic subthalamic nucleus (STN) single-unit electrocorticogram co-recording. The electrode assembly contains a screw-advanced microdrive and a microwire array. The array consists of a steel guide tube, five recording wires and one referenced wire which form the shape of a guiding hand, and one screw electrode for cortico-recording. The electrode can acquire stable cortex oscillation-driven STN firing units in rats under different behaving conditions for 8 weeks. We achieved satisfying signal-to-noise ratio, portions of cells retaining viability, and spike waveform similarities across the recording sections. Using this method, we investigated neural correlations of the basal ganglia–cortical circuits in different behaving conditions. This method will become a powerful tool for multi-region recording to study normal statements or movement disorders.  相似文献   
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