Endosseous implants for prosthetic rehabilitation in bone grafted alveolar clefts

The authors report their experience in the surgical and prosthetic rehabilitation of three patients affected by sequelae of cleft lip and palate, with residual alveolar cleft and absence of maxillary anterior teeth. The patients were treated by means of late secondary bone grafting of the alveolar cleft, followed by the insertion of endosseous titanium plasma-sprayed implants (IMZ). After a further healing period (6-12 months) fixed dental prostheses were constructed. Preliminary results from this series have shown how dental prostheses supported by endosseous implants in grafted alveolar clefts are a very reliable possibility in dental rehabilitation of this malformation.     

爆炸喷涂技术的现状和应用

详细地介绍了爆炸喷涂技术的现状，设备特性和技术应用领域，爆炸喷涂涂层与基体的结合强度，涂层的硬度和表观孔隙率都是等离子热喷涂所无法达到的。     

柱状晶对等离子YSZ涂层性能的影响

本文选用微米级YSZ粉末和纳米级YSZ粉末喂料,采用等离子喷涂技术制备了两种YSZ涂层,并通过扫描电镜(SEM)对涂层的微观组织和结构进行了研究。结果表明:微米级YSZ粉末制备涂层内部柱状晶的尺寸较短,长度在1～3μm之间;纳米级YSZ粉末制备涂层内部柱状晶的尺寸较长,长度在8～12μm之间;这种组织结构特征的差异是导致YSZ涂层结合强度和热震性能不同的主要原因。     

微米尺度与纳米尺度陶瓷颗粒等离子喷涂(APS)、超音速火焰喷涂(HVOF)、冷喷涂制备MCrAlY-Al_2O_3复合涂层的微结构与性能对比

陶瓷颗粒增强型金属基复合涂层在诸多工业领域都有需求,其中包括炼钢工业。本文中,MCr Al Y-Al2O3复合粉末通过球磨法制备,并且通过等离子喷涂、超音速火焰喷涂和冷喷涂分别制备了MCr Al Y-Al2O3复合涂层。实验结果显示,可以选用不优先使基体与Al2O3结合的复合粉末控制涂层中的Al2O3含量。涂层粉末的微结构在冷喷涂涂层和超音速火焰喷涂涂层中得到了良好的保留,这是因为喷涂粒子未熔化或部分熔化。然而,对于等离子喷涂的涂层,大多数Al2O3颗粒被隔离在层状界面,在条状界面上形成连续的氧化皮。经退火处理后,由元素扩散引起的条状界面的强化使得超音速火焰喷涂和大气等离子喷涂的涂层硬度增大。此外,冷喷涂涂层由于退火后加工硬化效果的消除,硬度增加不像超音速火焰喷涂和等离子喷涂涂层那样明显。     

Processing and characterization of plasma-sprayed ceramic coatings on steel substrate: Part II. On coating performance

This investigation envisages the performance evaluation of a series of plasma-sprayed coatings from a few inexpensive powders, namely, alumina, plasma dissociated zircon (PDZ), zircon sand, and zircon-20 wt pct calcia. The hardness and adhesion (bond) strength of the coatings have been evaluated. All coatings offer an attractive thermal fatigue property. An added layer of yttria between the top and bond coats improves the thermal fatigue resistance appreciably. The wear performance of these coatings has also been evaluated using a “pin-on-disc” type wear testing setup. The Indian alumina coating offers a superior wear resistance and thermal fatigue property compared to an imported alumina coating. The coatings based on zirconia-silica offer an attractive thermal fatigue resistance along with an acceptable wear resistance. The latter improves considerably upon annealing of the coatings because of the removal of the residual stresses accumulated during deposition. Among these zirconia-silica-based coatings, the zircon-20 wt pct calcia is the most promising. The finishability of these coatings has been studied using a surface grinding setup equipped with a diamond wheel. The cutting forces and the surface roughness of the ground surface have been measured. The coatings have been found to possess a reasonably good grindability.     

Aesthetic considerations for maxillary obturators retained by implants

Maxillary obturators are prostheses used to replace maxillary tissues, missing congenitally or removed by trauma or tumor ablative surgery. These prostheses are used to restore function (speech, swallowing, and mastication) and aesthetics. A considerable number of edentulous patients have difficulty in retaining this type of prosthesis. Utilization of osseointegrated dental implants is a significant adjunct in treating these cases, but it must be undertaken with careful planning to ensure predictable aesthetic results. The learning objective of this article is to discuss the technique of designing aesthetic maxillary prostheses supported by osseointegrated dental implants. The discussion includes indications and contraindications, and a postcarcinoma surgery case is used to illustrate the clinical procedure.     

Identification and characterization of a new splicing variant of vascular endothelial growth factor: VEGF183

The purpose of this study was to determine implant survival rates by means of life table analyses for a cohort of patients not part of a prospective efficacy trial and treated by practitioners at varying experience levels. Prognostic variables associated with implant failure were identified by means of proportional hazards models and advanced statistical methods that account for patient effects. Ninety-nine consecutive patients treated from 1987 to 1991 with follow-up to 1994 were included in this retrospective study. A total of 384 dental implants (79.7% Br?nemark, 19.3% IMZ plasma-sprayed, 1% IMZ hydroxyapatite-coated) were placed and subsequently supported 108 prostheses. Survival and proportional hazards modeling were used to generate Kaplan-Meier survival curves and to identify variables associated with implant failure. Survey data analysis was used to adjust for any patient effects for variables identified as significant through the proportional hazards models. Thirty-four implants failed over the follow-up period (median follow-up time 3.6 years), resulting in an overall failure rate of 8.9%. Seventeen of 99 patients experienced an implant failure. When prosthesis type was excluded from the modeling process, survey data analysis identified posterior location and an implant width of less than 4.0 mm as being associated with implant failure (all P < .05).     

Structural changes in friction surfaces of plasma-sprayed coatings

The features surface morphology are considered for plasma-sprayed coatings used with various counterbodies under conditions of boundary friction. The tribotechnical characteristics of the coatings are examined in relation to the structure. There is found to be a substantial effect from the porosity on the formation of the secondary structures, the changes in topography, and the changes in elemental composition of the friction surface. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 92–97, January–February, 1999.     

等离子喷涂Y-PSZ复合陶瓷涂层的应用

描述了空气等离子喷涂的Ｙ－ ＰＳＺ 复合陶瓷涂层,并采用光学显微镜、电子探针、Ｘ—线衍射仪对涂层进行了分析,研究了Ｙ－ ＰＳＺ涂层高温时效相态的变化,并采用该涂层制备了连续退火炉炉辊,取得了良好的效果     

Adhesive Strength of Material Joints for Orthopaedic Stomatology

Wetting, adhesion, and adhesive strength of a stainless steel substrate with SINMA plastic and MK porcelain are studied. It is shown that clean and plasma-sprayed substrates are readily wetted with plastic at temperatures less than 800 K and with porcelain at 1450 K. It is established that plasma-sprayed dentures with a plastic facing have an adhesive strength greater by a factor of three to five compared with conventional dentures.     

Primary insertion of osseointegrated dental implants into fibula osteoseptocutaneous free flap for mandible reconstruction

Twelve patients with segmental mandibular defects were reconstructed with fibula osteoseptocutaneous flaps and simultaneous placement of osseointegrated implants. Decision to perform this procedure was based on the facts that all patients had benign diseases, did not require postoperative radiotherapy, were in good general and oral conditions, and were psychologically motivated. A total of 34 fixtures was inserted in the first stage. Eight patients underwent second stage surgery, which consisted of connection of the implant abutments to the fixtures and the use of palatal mucosal grafts around the implants. Final dental prostheses were fixed 1 month later in seven patients, at this time. All flaps survived after surgery, and no implant failure was observed after a mean follow-up period of 25 months. Only one fixture was not used during the subsequent stage and was left as a sleeper. Fixed dental prostheses were used in five patients and removable overlay prostheses in the other two. Chewing function was recovered between 4 and 6 weeks after the start using the definitive dental prosthesis. In contrast to previous results, we conclude that excellent results can be achieved when this combined procedure is used in carefully selected patients. In addition, it is confirmed that the fibula osteoseptocutaneous flap is a versatile, reliable composite tissue that facilitates primary placement of osseointegrated dental implants during mandible reconstruction, thus allowing full oral rehabilitation in a shorter period of time.     

Amplitude dependence of the internal friction of plasma-sprayed coatings

Conclusions An internal friction study of plasma-sprayed coatings has shown that the application of such coatings substantially changes the ADIF parameters (decreases _cr and increases tan ) of a clad specimen. The effects of the dislocation structure of a basis on the physicomechanical properties of a plasma-sprayed coating applied to it have been established.Translated from Poroshkovaya Metallurgiya, No. 2(206), pp. 30–32, February, 1980.     

Metals used to fabricate removable partial denture frameworks

This article will help the dental technician choose from among the many alloys available for fabricating dental prostheses. It will explain terminology and compare and explain inherent properties and characteristics of alloys. Although all of the materials discussed produce a clinically acceptable removable partial denture framework, the predominantly base alloys dominate the market because of the low cost of the metal, case of casting, high yield strength and modulus of elasticity.     

微/纳米结构含锌硅酸钙基涂层成骨性能研究

骨科植入物涂层的表面形貌和化学组成对炎症反应的进程和骨形成的发生都发挥着重要调节作用。为综合利用微/纳米仿生结构和生物活性元素的优势,将含锌(Zn)的纳米结构物质引入到经水热处理后的等离子喷涂硅酸钙(calcium silicate, CS)涂层表面,对所制备涂层的物相组成、表面和截面形貌、比表面积、Zeta电位和生理环境下离子溶出等物理化学性能进行了表征。相比于常规CS涂层,具有微/纳米复合结构的CS和含锌CS涂层拥有更高比表面积和孔容,可吸附更多血清蛋白和纤维连接蛋白,通过刺激细胞内整合素以及下游vinculin和FAK基因表达,提高了骨髓间充质干细胞(BMSCs)铺展能力。涂层中锌的引入进一步提高了其表面BMSCs的增殖能力和与成骨细胞分化相关的基因表达。具有微/纳米复合结构的涂层明显上调了RAW264.7巨噬细胞中M2表型因子(CD206和ARG)基因表达,而涂层中溶出的Zn²⁺显著提高了RAW264.7细胞中抑炎症因子(IL-1ra和IL-10)基因表达,促使其向抑炎症表型转化。骨科植入物涂层表面锌元素和纳米结构的引入有利于创建良好的骨免疫微环境,促进骨...     

Wear Resistance of Plasma-Sprayed Coatings in Intensive Abrasive Wear Conditions

The abrasive wear resistance of plasma-sprayed oxide ceramic (Al2O3 and Cr2O3) and clad cermet ((Ti–Cr–C)–30% Ni and (TiC)–30% Ni) coatings was studied. The wear characteristics of the coatings such as wear rates, friction forces, friction coefficients, and wear groove depth determined with two methods were compared. The wear test methods included simulation of the friction process using loose abrasive particles and reciprocal ball-on-disk friction using a diamond indenter. The plasma-sprayed TiC-based coatings showed the lowest wear rate and can be applied to protect equipment parts subjected to intensive abrasive wear. The wear loss of the (Ti–Cr–C)–30% Ni and (TiC)–30% Ni coatings determined by friction against loose abrasive particles was 10–17 μm, while the wear loss of the oxide ceramic coatings was 20–42 μm, being 2–2.5 times higher on average.     

Pulsed laser treatment of plasma sprayed coatings

A pulsed CO₂-TEA laser was used to melt the surface of plasma-sprayed coatings. An analysis of the laser parameters on the heat transfer is made: the melt depth and the surface temperature were calculated for different laser inputs. It was found that the pulse length must be in the range of 20 to 40 μs in order to fill up the pores of the coating and to keep the surface temperature below the boiling range. Experimental results on surface modification are explained in terms of power density.     

Mechanical-indentation analysis of the microstructure and properties of plasma-sprayed ZrO2-based coatings

The relationship between the mechanical properties of plasma-sprayed thermal-barrier coatings and the properties of feedstock powders is studied. These powders have the same chemical composition and are obtained by hydroxide coprecipitation followed by air-drying and by a cryochemical method. Information on TBC failure mechanisms is used to pose and solve the problem of increasing the plasticity and, consequently, the stress relaxation coefficient of the ceramic coating. The finer structure of the cryochemical powder sprayed coating also improves its crack-resistance. The minor reduction in the hardness of the cryopowder-sprayed coating should not deteriorate the performance of the thermal-barrier coating.     

A comparative evaluation of the antifriction properties of plasma- and weld-deposited steel coatings

Conclusions The basic antifriction properties — running-in ability, minimum pressure to seizure, and the coefficient of friction of plasma-sprayed steel coatings are comparable to those of weld-deposited coatings and nodular iron. However, the wear resistance of such coatings is twice that of the former and three times that of the latter. The optimum plasma-deposition-process parameters, imparting high antifriction properties to coatings, are as follows: current intensity 425 A, voltage 30 V, rate of flow of plasma-forming gas 18 liters/min, rate of feed of wire 1.26 m/min, spraying range 50 mm, forced cooling.Translated from Poroshkovaya Metallurgiya, No. 9 (129), pp. 87–90, September, 1973.     

等离子喷涂氧化铝涂层连通孔的准分子激光表面处理改性

等离子喷涂氧化铝陶瓷涂层由于内部存在孔隙、层迭及层间裂纹等缺陷而呈现出复杂的微观结构。这些典型的微结构特点显著影响着涂层的力学性能。本研究开发了一种等离子喷涂氧化铝涂层的准分子激光表面处理技术以优化石油工业缆绳工具的部件性能。相比于CO2或YAG激光器的液相处理技术,准分子激光工艺采用短波激光,这对陶瓷材料来说就意味着能量主要被表面区所吸收。首先,采用SEM研究了涂层的表面和截面微观结构,并表征了激光处理后表面粗糙度和消融状态。然后采用X射线微观断层成像技术获取了涂层的三维微结构以研究激光处理后涂层的3D孔隙率。最后,借助纳米压痕和电化学阻抗谱方法分别表征了改性后涂层微结构的力学和电学性能。结果表明,准分子激光表面处理技术是一种控制等离子喷涂氧化铝涂层绝缘性能的创新工艺。     

Wettability, surface tension, and reactivity of the molten manganese/zirconia-yttria ceramic system

A basic research study for improvement of plasma-sprayed zirconia coatings has been conducted. The contact angle and surface tension of the molten manganese/zirconia-yttria ceramic system were measured at 1573 K by the sessile drop method, suggesting that molten manganese would spontaneously infiltrate open pores in zirconia coatings. Structure and elementary composition development of zirconia ceramics caused by reaction with manganese were examined by using scanning electron microscopy (SEM), an electron probe microanalyzer (EPMA), and an X-ray diffractometer (XRD). Manganese not only stabilized cubic zirconia but also contributed to the growth and volume increase of zirconia particles. In this article, the mechanism of making zirconia coatings dense with manganese is discussed based on the results of experiments.