Effects of metal surface grinding at the porcelain try-in stage of fixed dental prostheses

PURPOSE

This study was to evaluate the effect of grinding of the inner metal surface during the porcelain try-in stage on metal-porcelain bonding considering the maximum temperature and the vibration of samples.

MATERIALS AND METHODS

Ninety-one square prism-shaped (1 × 1 × 1.5 mm) nickel-chrome cast frameworks 0.3 mm thick were prepared. Porcelain was applied on two opposite outer axial surfaces of the frameworks. The grinding was performed from the opposite axial sides of the inner metal surfaces with a low-speed handpiece with two types of burs (diamond, tungsten-carbide) under three grinding forces (3.5 N, 7 N, 14 N) and at two durations (5 seconds, 10 seconds). The shear bond strength (SBS) test was performed with universal testing machine. Statistical analyzes were performed at 5% significance level.

RESULTS

The samples subjected to grinding under 3.5 N showed higher SBS values than those exposed to grinding under 7 N and 14 N (P<.05). SBS values of none of the groups differed from those of the control group (P>.05). The types of bur (P=.965) and the duration (P=.679) did not affect the SBS values. On the other hand, type of bur, force applied, and duration of the grinding affected the maximum temperatures of the samples, whereas the maximum vibration was affected only by the type of bur (P<.05).

CONCLUSION

Grinding the inner metal surface did not affect the metal-porcelain bond strength. Although the grinding affected the maximum temperature and the vibration values of the samples, these did not influence the bonding strength.     

2型糖尿病患者跟腱病变的超声特征

目的利用剪切波弹性成像(SWE)评估2型糖尿病(T2DM)跟腱截面积、周长、厚径及生物学弹性的变化,并探讨T2DM患者跟腱剪切波速度与糖化血红蛋白水平之间的相关性。方法收集T2DM患者及健康体检志愿者各50例。测量跟腱中段横截面积、周长及厚径,剪切波弹性成像测量该处跟腱弹性的剪切波速度(SWV),记录T2DM患者的入院糖化血红蛋白值,绘制剪切波速度与T2DM患者糖化血红蛋白水平的相关性散点图。结果受试者左、右侧中段跟腱弹性对比及性别间对比均无统计学意义(P>0.05);对照组跟腱各参数较A组均无统计学意义(P>0.05),较B组仅SWV值有统计学意义(P<0.05),较C组跟腱周长、厚径、截面积及SWV均有显著差异,且差异有统计学意义(P<0.05);A组较B组仅SWV有统计学差异(P<0.05),A组较C组除周长无统计学意义外,其余参数均有统计学差异(P<0.05);B组较C组截面积与SWV值两参数统计学差异显著(P<0.05)。相关性分析显示,糖化血红蛋白水平与跟腱SWV值显著相关(r=0.601,P<0.05),糖化血红蛋白值越高对跟腱生物学弹性的影响也就越大。结论SWE技术可定量评估T2DM患者跟腱生物学弹性的改变,为临床医师在预防糖尿病下肢病变的过程中提供参考。     

Maximal strength performance,efficiency, and myoelectric responses with differing intra-set rest intervals during paired set training

IntroductionThe purpose of this study was to investigate the effect of different rest intervals within paired sets (PS) on total work and training volume, efficiency (training volume load/session duration time), and myoelectric activity.MethodFifteen trained men participated in this study. Four experimental protocols were applied: P30 (30 s rest), P60 (60 s rest), P90 (90 s rest), and P120 (120 s rest). The PS bout consisted of a bench press (BP)/lat pull down (LPD), 30° incline bench press (BP30)/wide-grip seated row (SR), and triceps extension (TE)/biceps curl (BC) exercises. Surface electromyography (sEMG) activity of the biceps and triceps brachii were recorded.ResultsVolume load (repetitions x number of exercise sets x loads) was significantly lower for the P30 (5385.8 ± 1224 kg) versus the P60 (6755.6 ± 1398.5 kg), P90 (7358.3 ± 1490.3 kg), and P120 (7463 ± 1310 kg) protocols. No significant differences in sEMG activity was noted between protocols. The efficiency (kg·min⁻¹) of P30 (633.6 ± 144) was significantly higher versus P60 (397.4 ± 82.2), P90 (288.5 ± 58.4), and P120 (219.5 ± 38.5).ConclusionShort intra-set rest intervals (60 s) within PS may be a potential alternative for increasing the volume load, since longer intra-rest (90 s and 120 s) intervals do not provide additional benefits.     

Feasibility and preliminary efficacy of a hypopressive exercise program on postmenopausal cancer survivors: A pilot study

BackgroundCancer-related fatigue (CRF) is a common symptom during and after cancer treatment that negatively affects the patient's quality of life. Exercise is one of the most effective non-pharmacological treatments for CRF. Multimodal exercise therapy programs that include hypopressive exercises, relaxation and myofascial release may be beneficial for CRF. The aim of this pilot study was to evaluate the feasibility and efficacy of a multimodal program on CRF and lower limb functional strength in postmenopausal women diagnosed with cancer.Methods7 postmenopausal women (age = 55.28 years; BMI = 26.05 kg/m2) who had a cancer diagnosis participated in a supervised and progressive 55-min class once per week for 12-weeks. CRF was measured using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Cancer Related Fatigue 12 and lower limb strength was assessed with the sit and stand test.ResultsNo adverse events were reported during the training period and all participants completed the exercise protocol. There was a significant increase (p = 0.01) in lower limb functional strength (pre: 19.60 (SD = 2.19) vs post: 24.60(SD = 2.19)) with an effect size of d = 2.28 and a decrease in CRF (p = 0.245) (pre: 29.36 ± 24.42; post: 17.85 ± 14.23) with a trivial effect size (d < 0.5).ConclusionsThese preliminary findings indicate that a supervised once per week multimodal program that includes hypopressive exercises for postmenopausal cancer survivors increased lower limb functional strength without exacerbating their CRF. These findings support further randomized trials of hypopressive training programs on patients with cancer.     

表面处理对双固化黏结剂Panavia F黏接强度的影响

目的评价表面处理对双固化黏结剂Panavia F与不同界面黏接强度的影响。方法测定Panavia F与牙本质使用和不使用牙本质处理剂ED primer时的剪切强度,以及Panavia F与钴铬合金、镍铬合金、纯钛、银金钯合金使用和不使用金属表面处理剂Alloy primer时的剪切强度,数据作统计学检验,分析其黏接机制。结果使用ED primer处理后,Panavia F与牙本质的剪切强度从9.1MPa提高到17.6MPa;使用Alloy primer处理后,Panavia F与纯钛的剪切强度从29.0MPa提高到35.9MPa,而与处理后的银金钯合金的剪切强度从21.6MPa提高到30.2MPa。结论Panavia F通过采用ED primer对牙本质的表面处理显著提高对牙本质的黏结强度;Alloy primer可以显著提高纯钛和贵金属与黏结剂的黏结强度,而对钴铬合金和镍铬合金则不明显。     

The effect of isometric quadriceps strength training in mid-range for osteoarthritis of the knee

This case report describes the effect of strengthening the quadriceps of an effused osteoarthritic knee joint of a 53-year-old man isometrically in mid-range. The instruments included an isokinetic dynamometer, a knee scoring inventory, and a visual analog scale. The outcomemeasures of isometric quadriceps torque and work, clinical status, and pain were recorded before andafter the exercise intervention. The exercises were carried out three times per week for a 6-week period with the subject seated on an exercise chair. Following training, quadriceps torque increased, clinical status improved, and pain with walking decreased. Subject to further investigation, isometric training of the quadriceps in mid-range could prove useful for improving the function of persons with painful or effused knees who might otherwise experience muscle inhibition by exercising in the more traditional inner ranges of knee extension.     

添加不同类型、比例的显影剂后骨水泥性能的变化

目的探讨添加不同类型、比例的显影剂后骨水泥(聚甲基丙烯酸甲酯,PMMA)聚合过程的变化,X线密度和抗压强度等生物力学的差异。方法用非离子碘造影剂和纯硫酸钡粉作显影剂分别加入PMMA,按粉∶液∶钡粉比例分别为15∶10∶3,15∶10∶1.5和粉∶液∶非离子碘造影剂分别为15∶10∶5,15∶10∶3组成4个实验组,用粉∶液比例为15∶10为对照组,每组8份,在体外测试其聚合过程;并制成相同大小的PMMA圆柱体40节,每组8份。结果添加硫酸钡粉后PMMA的聚合时间延长60～120s,15∶10∶3组平均延长约120s,添加非离子碘造影剂的2组则聚合过程无明显影响。添加硫酸钡粉或非离子碘造影剂后PMMA的最高聚合温度均有显著性差异;与对照组相比,4个实验组的X线密度有显著性差异,以15∶10∶3添加纯钡粉的PMMA组显影最强;加入非离子碘造影剂后PMMA最大抗压强度降低25%～31%(P<0.05),而加入纯钡粉的PMMA的最大抗压强度无显著变化。结论PMMA中加入一定比例的纯硫酸钡粉可延长聚合时间,而加入一定比例的非离子碘造影剂对聚合时间无明显影响;添加这两种显影剂后均可提高PMMA的X线显影能力,而以15∶10∶3添加纯钡粉的PMMA组显影最强;加入一定比例纯钡粉对PMMA的最大抗压强度无显著影响。     

剪切波弹性成像技术量化评估健康人斜方肌弹性模量的应用

目的 探讨剪切波弹性成像技术(SWE)量化评估颈椎屈曲不同角度斜方肌弹性模量的应用价值.方法 2018年10月至2019年1月于河南省洛阳正骨医院招募20名健康成年男性实习医师作为试验对象.在受试者颈椎屈曲0°和30°时,测试人员A和B分别使用SWE量化评估斜方肌上束剪切模量,5 d后测试者A进行重复评估.记录颈椎屈曲...     

低层流切应力对内皮细胞表面B族Ⅰ型清道夫受体表达的影响

目的 研究低层流切应力作用下,血管内皮细胞表面保护性脂蛋白高密度脂蛋白的特异性受体B族Ⅰ型清道夫受体的表达水平,探讨切应力对内皮细胞表面B族Ⅰ型清道夫受体表达的影响在动脉粥样硬化发生中的可能作用.方法 无菌条件下取健康产妇剖宫产分娩的胎儿新鲜脐带培养人脐静脉内皮细胞,选择2～4代的细胞用于实验,将内皮细胞种植于载玻片上培养,待细胞长满汇合后放入流室系统中.实验分为实验组和对照组,选择静态条件下未施加切应力组为对照组,实验组为低切应力组(4.2 dyne/cm~2).切应力加载时间为1 h、2 h、4 h和8 h.作用完成后行半定量RT-PCR测定B族Ⅰ型清道夫受体的表达.结果 在层流低切应力(4.2 dyne/cm~2)刺激后,B族Ⅰ型清道夫受体表达随时间延长明显减弱,在8 h达低谷,在电泳图上几乎不显现.结论 高密度脂蛋白的特异性受体B族Ⅰ型清道夫受体在低切应力(4.2 dyne/cm~2)作用下表达减弱;低切应力可能通过下调B族Ⅰ型清道夫受体的表达,降低胆固醇的逆转运,促进血管动脉粥样硬化的发生.     

In vitro shear stress modulates antithrombogenic potentials of human endothelial progenitor cells

Background Recent study suggested that endothelial progenitor cells (EPCs), a novel therapeutic approach for endothelial dysfunction, present limited antithrombogenic potentials. However, few attempts have been done to improve the antithrombogenic potentials of EPCs. Our previous study proved that in vitro shear stress contributes to the increase in t-PA production by human EPCs. Here, we further investigated whether in vitro shear stress contributes to the secretion of antithrombogenic substances including plasminogen activator inhibitor-1 (PAI-1) and prostaglandin I₂ (PGI₂) by human EPCs. Methods The peripheral blood mononuclear cells of healthy subjects were induced into EPCs. Then the human EPCs were treated with four levels of shear stress including stationary condition low media and high flow shear stress. The production of PAI-1 and 6-keto-prostaglandin F1_1α(6-Keto-PGF_1α) by human EPCs with shear stress treatment were measured. Results In vitro medium and high flow shear stress inhibited PAI-1 secretion by human EPCs, but low flow shear stress had no effect on PAI-1 secretion by human EPCs. All levels of shear stress significantly increased 6-Keto-PGF_1α production by human EPCs in a dose-dependent manner. Conclusions The present study demonstrates that in vitro shear stress can promote PGI₂ secretion and inhibit PAI-1 secretion by human EPCs, which improves the antithrombogenic potentials of human EPCs.