Casting Metals in Dentistry: Past - Present - Future

Abstract

This article deals mainly with the development of dental casting techniques and formulation of the different groups of alloys used in the fabrication of ceramo-metal restorations. It is recognized that in order for the quality of dental cast restorations to be improved, having alloys with the proper composition is not enough. Biocompatibility, good mechanical and physical properties, longevity of the restoration, compatibility with porcelain, and a simple manipulative technique are as important. Researchers have contributed to different aspects of dental castings and have made cast restorations what they are today. Unfortunately, much of the original basic research has been overlooked by present investigators, who have duplicated studies conducted in the past without realizing that the study had already been performed and the research had been published. The main reason for this is that abstracts of articles published prior to 1975 are not available through a library computer-search system. To obtain copies of articles published prior to 1975, one has to search the literature to know where they were published. This article provides references for much of the past work in this area. Also, dental libraries do not carry copies of U.S. patents. This places the majority of researchers located at dental schools at a disadvantage. They are not familiar with what the patents claim, what is taught, and why certain elements are added or eliminated from alloys and investment materials. This article also provides the numbers of many U.S. patents. By having the patent number, one can obtain the text of the patent from the U.S. Patent Office in Washington, DC. Since esthetics plays an important role in today's society, emphasis will be given only to alloys designed for fabrication of ceramo-metal restorations. Many ceramo-metal alloys are available today, and they are classified differently by different individuals. In this article, classification will be based on the major components of these alloys, as well as on a chronological introduction of one group leading to the development of the next group. Based on this, one can classify these alloys into six major groups. Chemical composition, properties, and the developers of these alloys, along with their U.S. patents, are given. Recently, two types of all-ceramic restorations have been introduced. The main advantage of the all-ceramic restoration is its superior esthetic quality compared with that of ceramo-metal restorations. Their main disadvantages are low strength and ductility. Their strength, however, is sufficient for single-unit restorations, but not for bridgework. The use of titanium for dental restorations has also been studied, and it has been found to be suitable. Future Studies - Future work should be devoted to the following: (1) the development of stronger and more ductile ceramic materials: (2) further study of the promising palladium alloys from the noble metal group and titanium alloys from the base metal group; (3) the development of easier and less-time-consuming techniques for the fabrication of dental appliances; (4) the development of a powder technique rather than a cast technique for future fabrication methods; and (5) the development of new laboratory equipment, e.g., a single sintering oven capable of sintering both ceramic and metallic particles, which would be accepted if the powder technique is developed.

Corrosion resistance assessment of Co-Cr alloy frameworks fabricated by CAD/CAM milling, laser sintering, and casting methods

“…Several studies have previously investigated corrosion and electrochemical characteristics of cast Co-Cr alloys. 8,26,[28][29][30][31][32][33][34][35] However, only a few studies evaluating corrosion resistance and electrochemical properties of the alloys produced by conventional casting, milling, and laser sintering methods have been reported. 36,37 The purpose of the present study was to evaluate electrochemical corrosion resistance of Co-Cr specimens produced by casting, CAD/CAM milling, and DMLS methods in a medium simulating the oral environment.…”

A Comparison of Retention Characteristics in Prefabricated and Custom‐Cast Dental Attachments

“…Moreover, the choice of casting alloys may also affect the accuracy of the attachments. The choice of casting alloy is governed by a number of factors, including cost, biocompatibility, mechanical properties, and the ease of casting 6 . Many studies have compared the mechanical properties and accuracy of various dental alloys after the casting process 7–9 .…”

Adaptación de cofias metálicas confeccionadas con dos técnicas: cera pérdida colada por centrifugación convencional y fresado de bloque blando en CAD/CAM

“…Esta aleación se puede utilizar con los sistemas convencionales de colado o mediante sistemas digitalizados CAD/CAM para fresado y láser (21)(22)(23)(24)(25)(26)(27)(28). Para la obtención de cofi as metálicas se puede utilizar la técnica de cera perdida colada por centrifugación (CPC), que consiste en encerar un patrón de cera, posteriormente la cera es evaporada por calor en un horno, mediante un soplete se funde el metal y por último se impulsa el metal fundido por medio de una fuerza centrí-fuga en el molde a través de un canal denominado bebedero (29)(30)(31)(32). Dentro de los sistemas CAD/CAM existe la técnica aditiva y la sustractiva, en la técni-ca sustractiva se puede utilizar el fresado de bloques duros sinterizados o se puede utilizar la soft milling block o fresado de bloque blando (SMB) que utiliza bloques presinterizados.…”