多济敷对面部磨削创面愈合的临床疗效观察

目的：本研究采用多济敷外用于面部皮损磨削术后创面,观察其对创面愈合时间、皮肤色素沉着等的变化。方法：采用区域神经阻滞或局部浸润麻醉,对不同类型的面部皮损34例进行皮肤磨削治疗,术后创面应用多济敷或凡士林纱布作为底层敷料包扎创面,术后换药一次,保留底层敷料。结果：2001年8月至2003年9月间,通过自身对照,34例面部磨削术后采用多济敷治疗组较凡士林纱布组创面愈合时间缩短(P＜0．05),经过6个月至2年的随访,皮肤色素沉着也有明显改善。结论：多济敷有利于缩短面部磨削术后创面愈合时间,改善面部色素沉着,外观满意。     

The effect of grinding of human dentine examined by X-ray diffraction, infrared spectroscopy, and electron microscopy

Analysis of human dentine by infrared spectrophotometry suggests that ball-grinding may result in damage of the apatite crystallites. The present study includes further assessments of this effect by X-ray diffraction, infrared spectroscopy, and electron microscopy. Each of three coarse-ground dentine samples (Group I) was divided into three portions of 30 mg. One of these portions was ball-ground for approximately 1 min (Group II), the second portion for 6 min (Group III), and the third portion for 23 min (Group IV). The 002 reflection showed line broadening, most marked from Group II to III. Electron microscopy showed a gradual change in crystallite appearance with increased grinding, most pronounced from Group II to III. These observations indicate that by prolonged grinding a limit is approached where no further changes in the crystallites occur. Electron microscopy also indicated that fracture of the crystallites might have occurred. This was probably accompanied by strains in the lattice. The infrared spectra indicated that no breakdown of the apatite structure had occurred during the entire grinding.     

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.     

Hochfrequenzkinematographische Untersuchungen über die Arbeitsweise gebräuchlicher diamantierter Schleifköpfe an Knochen und Knorpel

Summary The mode of operation of grinding faces, rod diamonds and diamond grinding heads which are expecially employed in oto-surgery was investigated in slow motion pictures with the aid of high frequency cinematography. The R.P.M. ranged between 5,000–80,000, the picture frequency was usually 6,000 pictures per second. Full efficiency of the diamond grinding heads (DS) is only guaranteed by adequate flushing. Water stream flushing and drop flushing (drop sequence depending on R.P.M.) must be centered on the grinding head, as increased soiling due to filling of the diamond surface occurs otherwise. Because of the fixed mounting of the spray tube in the direction of the shaft, spray flushing is most useful, although not usable for diamond faces.Due to its very fine-rough surface, the DS produces grinding dust by abrasion from the bone or cartilage which is readily distributed in the airspace over the whole working area. The same does also apply to finely atomized fluid sprays. Cutting is performed tangentially. The percussing DS touches the bone only with a small part of its surface and easily gets soiled. Depending on the R.P.M., the cutting speed was 10,000–80,000 R.P.M. These values also apply for the fluid dropping rate. Contrary to the rose bit or the surgical fraises, the DS got soiled more easily and produced definitely finer cuts.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft     

Green synthesis and antimicrobial evaluation of some new trifluoromethyl-substituted hexahydropyrimidines by grinding

A series of trifluoromethyl-substituted hexahydropyrimidine derivatives were efficiently synthesized in excellent yields via one-pot three-component reaction of aromatic aldehydes, ethyl trifluoroacetoacetate and thiourea(urea) in presence of p-toluenesulfonic acid under solvent-free conditions at room temperature by grinding. The present method does not involve any hazardous organic solvent and has proven to be simple, efficient, environmentally benign and cost-effective compared with the classical synthetic methods.These compounds were screened for their antibacterial activities against Escherichiacoli and Bacillus thuringiensis and found to exhibit remarkably better antibacterial activities than the control drug.     

脊柱手术机器人研究进展

脊柱手术机器人具有定位精准、操作稳定、减少辐射暴露等优势,具有极大的临床应用价值,近年来已成为机器人研究和应用的热点领域。论文根据不同应用场景将脊柱手术机器人按引导式和主动操作式两种进行分类,并对应介绍国内外研究机构和公司研发的脊柱机器人及最新成果,同时结合研究和应用现状,对脊柱机器人应用的关键技术和未来机器人发展趋势进行简要阐述和总结。     

Characterization of the grinding behaviour in a single particle impact device: Studies on pharmaceutical powders

The grinding behaviour of different materials can be described by the two material parameters f_Mat and W_m,min [Vogel, L., Peukert, W., 2003. Breakage behaviour of different materials—construction of a mastercurve for the breakage probability. Powder Technol. 129, 101–110]. f_Mat describes the resistance of particulate material against fracture in impact comminution, W_m,min characterizes the specific energy which a particle can take up without comminution. The material parameters are determined experimentally by single particle impact tests. This concept is also applicable to pharmaceutical powders, as will be shown in this work. A device is presented for the characterization of particles with sizes down to a few 10 μm. Particles are dispersed and accelerated in an air stream which is flowing against an impact plate. The impact velocity is controlled by the air flow. An LDA system enables the measurement of particle velocities. The results obtained with this jet mill are in accordance to those obtained from another single particle impact device used by Vogel and Peukert, in which the influence of fluid flow is completely avoided. Since the new device is especially designed for finer powders, it will allow a more detailed analysis of the material parameters at smaller particle sizes. Additionally, a new analysis method has been developed in order to determine the breakage probability not from sieve analysis but from laser light diffraction (LLD) data by using a population balance.     

An Efficient,Robust, and Inexpensive Grinding Device for Herbal Samples like Cinchona Bark

An effective, robust, and inexpensive grinding device for the grinding of herb samples like bark and roots was developed by rebuilding a commercially available coffee grinder. The grinder was constructed to be able to provide various particle sizes, to be easy to clean, and to have a minimum of dead volume. The recovery of the sample when grinding as little as 50 mg of crude Cinchona bark was about 60%.Grinding is performed in seconds with no rise in temperature, and the grinder is easily disassembled to be cleaned. The influence of the particle size of the obtained powders on the recovery of analytes in extracts of Cinchona bark was investigated using HPLC.     

The adverse effects of tungsten carbide grinding on the strength of dental zirconia

ObjectivesThis study investigated the effects of tungsten-carbide grinding on the surface characteristics and mechanical strength of dental 3 mol% yttria-stabilized zirconia (3Y-TZP).MethodsTwo types of tungsten-carbide burs (TC), 6-blade (TC₁) and 8-blade (TC₂) were used to grind 3Y-TZP, in a dental air-turbine handpiece with water-cooling and were also subjected to air-particle abrasion (APA): TC₁ + APA and TC₂ + APA; and rubber polishing (RP): TC₁ + RP and TC₂ + RP; one group received only rubber-polishing RP. The control group received no treatment. Surface characterization was examined by surface roughness (R_a) and atomic force microscopy. Specimens were also observed with scanning electron microscopy (SEM) and X-ray-diffraction (XRD) for microstructure and crystalline phases. A piston-on-three-balls biaxial-flexural strength (BFS) test was performed with 15 samples-per-group and the broken specimen were observed under SEM to investigate the fracture origin pattern. One-way ANOVA, Kruskal–Wallis test and Weibull analysis were performed at α = 0.05.ResultsGroups TC₁ and TC₂ had the lowest mean BFS (p < 0.05) with up to 74 % reduction in strength. APA and RP both significantly increased the mean BFS after tungsten-carbide grinding but was still less than the control (p < 0.05). Compared to the control, the mean BFS was significantly reduced for all groups except for the RP group (p < 0.05). APA and rubber-polishing following TC₂ grinding had significant higher mean BFS than those following TC₁ grinding respectively (p < 0.05). SEM revealed distinct micro-cracks after tungsten-carbide grinding.SignificanceTungsten-carbide burs (6- and 8-blade) are not recommended for zirconia grinding due to the significant reduction of biaxial-flexural strength and observed micro-structural surface and subsurface damage.