牙科精密铸钛技术的研究进展

钛制冠桥，可摘义齿支架已应用于临床，但钛的铸造技术尚待改进。本文回顾了国内外对牙科铸钛技术的研究；介绍国外对牙科铸钛机，包埋料，铸造工艺等方面的研究；对各种牙科铸钛机的可铸性能，包埋料的理化性能对钛铸件质量的影响，铸模温度对钛铸伯质量的影响，以及铸道的设计对钛铸件质量的影响等进行了综述。     

蜡模铸道系统的设计与铸件缩孔形成的关系

铸道是指由金属丝或蜡条等制作的连接蜡模与浇注口作为熔融状态金属进入型腔空间的孔道。当铸造完成后,金属填满铸道空间,它与铸件直接相连,直接影响着铸件的完整性、精确性。工作中常遇见很多铸件上有大小不等的缩孔,与铸道设计密切相关,严     

铸钛义齿铸造缺陷的临床分析

目的:评价临床铸钛义齿制作过程中的缺陷,以提高铸造成功率。方法:对328件铸钛义齿进行回顾性总结,并对其发生的铸造缺陷进行统计分析。结果:本文全部铸件中,铸造不全4件,占1.22%,31件有内部气孔,占9.4%,7件存在表面粗糙,占2.13%。在铸钛固定修复中,应用独立分铸道内部气孔发生率明显小于栅栏式铸道(x2=4.65, p<0.05)。结论:铸钛义齿存在一定比例的铸造缺陷,铸道设计是影响铸造缺陷的重要因素之一。     

压差式铸钛机的熔铸条件对纯钛铸件组织结构的影响

目的：分析进口压差式铸钛机铸造的纯钛铸件内部组织结构和缺陷原因，探讨提高纯钛铸造修复体组织结构致密度，减少杂质，避免内部缺陷的方法。方法：应用X－线金属探伤仪定位，数字式金相显微镜分析纯钛铸件内部的组织结构。并应用痕量气体分析仪对气泡内残留成分进行分析，同时对气泡内壁的组织结构进行金相学分析。结果：纯钛铸件内部的气泡主要来自于熔铸室的氩气保护和铸道直径过细，过长所致。结论：短、粗铸道和改进熔铸室的氩气保护方式是减少铸件内部缺陷的关键。     

钛铸造支架制作的几个要点

钛金属以其杰出的生物相容性及生物安全性,良好的物理化学性能,适宜的力学和工艺学性能,成为口腔用金属材料,使钛铸造支架在临床工作中得以推广应用。因钛与常规钴铬金属在理化性质、铸造性能上的差异,使其在铸造技术上有其特殊要求,现将制作要点介绍如下:1钛铸造支架的工艺流程钛铸造支架与常规钴铬支架制作工艺流程无明显差异。基本程序:初始模型-模型-观测-原始模型的填蜡处理-复制耐火模型-蜡型制作-浇注系统形成-包埋-焙烧铸造-喷砂-酸处理-打磨-抛光-完成。2蜡型制作特点钛密度(4.5 g/cm3)低于钴铬合金(8 g/cm3),惯性小,离心作用差,其…     

一种新的带模铸道——螺旋形单铸道

<正> 可摘局部义齿的金属支架,通常采用分级多铸道浇铸。为了求得浇铸完全,可以同时设置贯通排气孔或盲端排气孔。但是分级多铸道的安插并非完美,首先因熔化液态金属互相湍流给铸件造成砂孔、气孔、表面粗糙和浇铸不足等缺陷,影响铸件的质量。其次,多铸道分布散,只要个别铸道位置不够恰当,或者因铸道细,在覆盖包埋料时稍有不慎,易发生折断,都会出现铸件浇注不全的后果。此外,在切割铸道、磨平、抛光等费时耗料。为此,我们设计一种新的带模铸道——螺旋形单铸道。     

高熔合金铸造支架的铸道设计

局部义齿采用钴铬合金等高熔合金铸造支架时,合理地设计高熔合金铸造支架的铸道,不仅能使铸造获得成功,而且能提高铸件的质量和工作效率。近来,我们使用天津医院设备厂制造的高频离心式铸造机,采用单铸道进行浇铸,获得了成功。在制作的50件金属支架中,仅1例失败。     

铸造力对铸钛全冠完整性的影响

本实验的目的是证实铸造力对铸造钛全冠完整性的影响.在树脂牙上进行全冠牙体预备,颊侧边缘为凹型,舌侧边缘为刃状.将18个全冠蜡型分为6组,用专用钛包埋材包埋,用Ohara钛铸造机铸造.1至6组所上的弹簧圈数分别为5、10、15、20、25和30圈,这样便产生逐渐增加的铸造力.第1组只铸出铸道,第2组铸出铸道和部分冠壁;第3、4组的冠大体铸出,但舌侧边缘圆钝并有小的缺损;第5、6组的冠基本完整,边缘锐利,只是舌侧边缘有少数很小的缺损.实验结果表明:①铸造钛金属时要有足够大的铸造力.②如果铸造技术未得到进一步改进,应避免为铸钛修复体设计刃状边缘.     

钴铬合金铸造性能的探讨

我国 5 0年代运用 18- 8不锈钢合金材料用于局部托牙支架和金属全冠、半冠、嵌体、桩冠等修复体。 70年代开始钴铬合金材料替代 18- 8不锈钢材料使用至今。修复体的制作经过取模、设计、蜡型制作、包埋、熔蜡、铸造及打磨抛光等工艺。每一道工艺的正确制作 ,材料性能的优劣 ,是修复体成功与否的关键。材料的性能如弹性模数、抗拉强度、断面收缩率、布氏硬度等对修复体的质量起了较大的影响。为此本人作如下探讨。1　蜡与包埋材料 :　蜡有蜡条、蜡网及薄蜡片等。蜡必须选择优质铸造蜡。应用合理的蜡型制作技术制作蜡型。接插铸道以圆形为主。…     

铸道设计、铸造机和热源对铸件多孔性的影响

本研究调查了各种铸道的设计,铸造机及热源(五种常用铸道方法,四种常用铸造机和热源)对铸件多孔性的影响。材料和方法:制作60件颊(牙合)面用烤瓷覆盖的铸件,分为三类:前磨牙全冠、磨牙全冠、前磨牙桥体。制作上颌第一前磨牙和第一磨牙金属烤瓷修复体的帽状冠蜡型,并各复制20个,分为四组,按照设计的五种铸道方式安插铸道。用磷酸镁包埋材料包埋,放置一小时后,置于炉内预热到600℉,持续30分钟,再转入烤炉预热到1200℉,持续一小时。用新的烤     

Full-Arch Implant Framework Casting Accuracy: Preliminary In Vitro Observation for In Vivo Testing

Purpose Conventional techniques for implant metal framework fabrication produce error of a magnitude that is inconsistent with the passive-fit requirement for osseointegrated implants. To understand the correlation between prosthesis fit and the implant-tissue response, evaluation of the interface tissue reactions to customary levels of fit is required. The purpose of this study is to determine the accuracy of torch casting full arch frameworks using a high palladium alloy and a ringless phosphate-bonded investment technique. Materials and Methods Three different variables were considered relative to casting accuracy effect. The first variable, completeness of mold-fill, compared cast specimens where the entire sprue system was filled as part of the casting and cast specimens without the sprue system filled. The second variable, phosphate-bonded investment special liquid concentrations, compared groups of castings produced from 0%, 12%, 25%, and 50% special liquid. The third variable, investment mold shape, compared casting produced from a conventional ringless mold shape with a modified ringless mold shape where the investment in the same horizontal plane as the pattern was equal in thickness at the internal and external surfaces. Horizontal and vertical distances on the wax pattern and resulting framework were measured using a machinists microscope to determine casting error. Combined vertical and horizontal error was used for comparison between groups (one-way analysis of variance). Results No significant differences existed among the three groups compared (P > 0.05). The mean error comparison between the complete and incomplete mold-fill groups showed no statistical difference, while the incomplete fill group was found to be more porous. The mean error of all groups (0.130 mm) exceeded the recommended level of fit needed to satisfy the passive fit requirement by more than 10-fold. Conclusions These results verify clinical observation and suggest that the use of conventional lost wax casting technique to cast one-piece full arch implant frameworks is both imprecise and inaccurate as judged against the passive fit requirement. The consequences of screw-fastening misfitting prostheses to osseointegrated implants is currently under investigation.     

Effect of sprue design on the castability and internal porosity in pure titanium castings.

OBJECTIVE: The aim of the study was to evaluate the pure titanium castability and internal porosity with 3 different sprue designs. METHOD AND MATERIALS: The sprue designs selected were the conventional cylindrical, funnel-shaped, and sheet-form sprue formers. To evaluate the castability, the mesh monitor was chosen. Eight mesh patterns (14 3 14 mm) of 49 squares were attached to each type of sprue design. They were invested in titanium investment material and cast in a semiautomatic titanium casting machine. The titanium castings were evaluated by 2 methods. One was the visual observation of the castings for completeness, and the second was the radiographic qualitative analysis for the location of the internal porosities. RESULTS: Data were analyzed with analysis of variance and Student t test for paired comparison among different sprue designs. According to analysis of variance, all sprue designs revealed a statistically significant difference at the 5% level of confidence (P <.05, F = 3.50). Mesh patterns attached to funnel-shaped sprue designs showed better percentage castability values. CONCLUSION: For titanium, casting using a funnel-shaped sprue design displayed better castability values and less internal porosities in the castings.     

The effect of sprue design on the marginal accuracy of titanium castings

The purpose of this study was to measure the effects of sprue number and position on cast titanium crown margins. Twenty‐four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30° bevel finish line. Twelve wax patterns were sprued with one 8‐gauge wax sprue and the remaining 12‐gauge double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting machine following the manufacturer's instructions and using commercially pure titanium (> 99·5%) ingots. The castings were than carefully cleansed and the margins were examined with indirect impression technique. Data were analysed with an ANOVA and the Student's t ‐test with confidence level at 95%. The results revealed that the marginal discrepancy for the double sprueing group (32·1 ± 12·8 μm) has significantly less discrepancy ( P < 0·001) than the single sprueing group (49·8 ± 16·4 μm). There was no statistically significant differences in marginal discrepancy between locations within the sprueing techniques ( P > 0·05). An improvement in the degree of casting accuracy of titanium crown was indicated by the double sprue design used in this investigation.     

Investigation of the effect of three sprue designs on the porosity and the completeness of titanium cast removable partial denture frameworks.

STATEMENT OF PROBLEM: Although titanium has been used to cast removable partial denture frameworks, the casting process is arduous and requires specialized equipment. PURPOSE: This study evaluated the ability of 3 sprue designs (tree, ball, and circular) to produce complete, void-free castings of removable partial denture frameworks made from commercially pure titanium. METHODS AND MATERIAL: A cast with a Kennedy class III, modification 1, partially edentulous arch was used. The blocked-out cast was modified to facilitate assessment of the completeness of the casting of the clasp arms. Thirty refractory casts were made, and 10 wax patterns for each sprue design were fabricated and invested with ethyl silicate investment. Castings were made with an arc-type automatic casting machine in an argon atmosphere. Castings were examined with radiographic equipment to detect the presence of voids in the castings, and the completeness to each casting was visually verified. Data on porosities were tabulated and statistically analyzed with 1-way ANOVA followed by Student Newman-Keuls test. Chi-square analysis was used to identify statistically significant differences in casting defects among the 3 sprue designs. RESULTS: No statistically significant differences in the total number of porosities were found between the 3 sprue designs (P =.51). Results of completeness of castings evaluated by using chi-square test revealed a statistically significant deference among the 3 sprue designs (P =.008). CONCLUSION: The ball-sprue design produced the most complete castings for the removable partial denture titanium frameworks.     

ZrP99铸钛包埋材料的铸模温度对铸造精度的影响

目的：研究ZrP99铸钛包埋材料的铸模温度对铸造精度的影响。方法：利用代型模具，制作30个超硬石膏全冠预备体代型．并制作相应的全冠蜡型，随机分为5组，每组6个样本，其中4组为实验组，采用ZrP99铸钛包埋材料进行包埋，分别在铸模温度为600℃、450℃、300℃、150℃条件下进行铸造；另外一组为对照组，采用Titavest—CB包埋材料进行包埋．在铸模温度为600℃条件下进行铸造。利用显微图像分析技术．在实体显微镜下分别测量蜡型及相应的铸件边缘与代型肩台之间在标志点处的间隙，两者差值即代表铸造精度。采用t检验及单因素方差分析进行统计学处理。结果：Titavest—CB包埋材料组的铸造精度显著优于在不同铸模温度下ZrP99包埋材料组：当ZrP99包埋材料的铸模温度低于450℃时，随着温度升高，铸造精度显著提高。结论：ZrP99铸钛包埋材料的铸模温度必须高于300℃．才有可能满足临床精度要求。     

Internal porosity of cast titanium removable partial dentures: Influence of sprue direction on porosity in circumferential clasps of a clinical framework design

STATEMENT OF PROBLEM: Although internal porosity is a potential risk factor for clasp fracture, little is known about its frequency in the clasps of titanium removable partial dentures. PURPOSE: This study investigated the influence of the direction of auxiliary sprues on porosity in the circumferential clasps of a pressure-cast titanium removable partial denture. MATERIAL AND METHODS: Wax patterns of a removable partial denture framework were made on 10 identical refractory casts of a Kennedy class II, modification 1, mandibular partially edentulous arch. For the auxiliary sprues directed to the circumferential clasps, 2 designs were used: straight and curved. Casting was performed in a 1-chamber pressure casting machine. Pore number and size were assessed on radiographs of the castings. The data were analyzed with the 2-tailed Student t test (P <.05). Randomly selected specimens were sectioned for morphologic observation of the internal surface of the pores. RESULTS: The number of pores >or=0.5 mm diameter and the total number of pores were significantly lower in the molar lingual arms of the curved sprue group than in the corresponding clasp arms of the straight sprue group (P =.03 and P =.009, respectively). No significant differences between the 2 groups were found for pores of any size in other locations. The pores had smooth internal surfaces. CONCLUSION: Within the limitations of this study, the curved sprue design produced significantly less porosity in the circumferential clasp arms of a cast titanium removable partial denture than the conventional straight design. The results suggest that internal porosity in titanium castings can be controlled through sprue design.     

钛铸件内包埋材主要元素扩散情况分析

目的分析采用不同配比含锆磷酸盐包埋材铸造的钛铸件中包埋材主要元素的扩散情况,探讨此类包埋材应用的可行性。方法采用二层集合体法和成刃器制作30°简化刃状边缘蜡型,分别采用含30%、40%、50%ZrO2的磷酸盐包埋材包埋后进行铸造。用EPM-810Q电子探针微分析仪对铸件中包埋材主要元素的扩散情况进行分析。结果 3组试件中均可见Si和P元素的扩散是同步的,但Si元素的扩散(反应层厚度)深,30%组约37μm,40%组约28μm,50%组约25μm。结论 3种不同配比含锆磷酸盐包埋材钛铸件中Si元素的扩散深度(反应层厚度)均小于40μm,均可达到临床要求。     

铸模温度对铸钛机械性能及表面反应层结构的影响

钛在高温状态下化学性能活泼，易氧化且与包埋料发生化学反应。我们采用拉伸试验及现代表面分析技术，研究了不同铸模温度对铸钛机械性能及表面反应层结构的影响。结果表明，随着铸模温度升高，铸钛件的抗拉强度、屈服强度增加而延伸率下降，同时，铸钛表面硬化层增厚。用室温铸模铸造时钛铸件表面硬化层厚５０μｍ，用８５０℃铸模铸造时钛铸件表面硬化层厚１２５μｍ。ＳＸｍａｃｒｏ电子探针微区成分分析显示，锆、铝二元素在钛铸件表面扩散深度不随铸模温度增高而加深，但硅元素的扩散则随铸模温度升高而加深。室温铸造时硅元素的扩散深度为３０μｍ，８５０℃铸造时已达９０μｍ。研究结果提示，临床制作铸钛修复体时，必须考虑铸模温度对铸件质量的影响。     

Titanium casting: the surface reaction layer of castings obtained using ultra-low-temperature molds

To examine whether the surface reaction layer of titanium castings can be reduced by lowering the mold temperature during casting, we cast titanium at three mold temperatures, including an ultra-low temperature produced by cooling the mold with liquid nitrogen, then measured the tensile strength and elongation of the castings. The titanium was cast using a centrifugal casting machine, and the molds were incinerated according to the manufacturers' instructions. Castings were then made with the molds at 200 degrees C, 600 degrees C, and an ultra-low temperature (-196 degrees C). The castability of titanium cast in the mold at the ultra-low temperature was good. The Vickers hardness near the surface layer of castings decreased as the mold temperature decreased.     

三种铸钛包埋材料对铸型尺寸的影响

目的研究三种体系的铸钛包埋材料对铸型尺寸的影响。方法蜡型分别包埋在氧化硅系、氧化钒系和氧化镁系铸钛包埋料巾，经900℃烧结后柃测铸型的内外径、高度和厚度的尺寸变化。结果氧化铝系包埋材料引起的铸型尺寸变化最小，氧化硅系包埋材料收缩最大，氧化镁系包埋材料的铸型变化在心者之间。结论氧化铝系铸钛包埋材料的铸型尺寸变化最小，是一种较理想的铸钛包埋材料。