Although casting is currently the first choice to produce metallic frame work selective laser melting (SLM) has established. Based on a CAD/CAM system the digital data of the frame work are transferred to the production machine. The three dimensional data set of the transferred in to numerous quasi 2-dimensional data. Each of these data sets represents a single slice, which is then produced. Due to the production process complex geometries and outstanding mechanical and chemical properites can be realized. Advantageously is also the large number of simultaneously fabricated parts, which makes this method very economic.
TopIntroduction And Present Status
In dentistry destroyed enamel and/or dentine has to be replaced by artificial materials. If the defects are too big also complete teeth have to be replaced. Therefore materials for fillings (e. g. composites, amalgams, alloys or ceramics) and for crown and bridges (acrylics, ceramics, metals) have to be distinguished. The present article will focus on metallic materials for the production of frameworks.
The most common way to fabricate metallic frameworks is casting. In this process the dental technician transfers the impression made by the dentist into a model (most made of gypsum). Than the framework is mold with wax. After this he invests the wax modelations and sprueings in special investment materials. In special furnaces the wax is burned out. In those hollow spaces the alloy is than cast. After embedding the framework is polished or veneered with ceramics or composites.
Several different hundred metals are available for frameworks. They may be classified due to their usage (e. g. inlays/onlays, crown and bridges or for partial dentures), their fabrication (e. g. casting, sintering) or their composition (Table 1).
Table 1. Overview of dental alloys classified according to their main component
| Precious alloys | Non precious alloys |
Gold-based
Pure gold (galvano technique)
High gold content
Gold reduced
Palladium-based
Palladium-copper
Palladium-silver
Silver-based
Silver-Palladium
Silver-gold | Cobalt-based
For partial dentures
With ceramics venerable
Nickel-based
Nickel-chromium alloys
High chromium content
Low chromium content
Nickel-titanium alloys
Iron-based
Titanium
Pure Titanium
Titanium alloys |
In the present the price of the restorations is getting more and more important. The US and the European markets have great difficulties to compete with the Asian laboratories because of the low labor costs there. One possible way to over come this is to automate the production process. This is one of the reasons CAD/CAM systems are entering the market in Europe successfully.
In general on have to divide the automated production process in to two parts. The first part is the CAD step (CAD: computer aided design). In this step the geometry of the parts which should be produced is defined. Than the second step, the CAM (CAM: computer aided manufacturing), follows. Here the information for the production is merged. Mostly the control of the production machines is made here.
Figure 1.
Production machine for SLM technique
CAD/CAM in dentistry is discussed since over 20 years (Strietzel & Lahl, 2007). One of the pioneers is the French Duret who published basic ideas for 20 years (Duret, 1992, 1993; Duret, Blouin, & Duret, 1988; Duret & Preston, 1991). Another important (among others) is the working group of Rekow (D. Rekow, 1987; E. D. Rekow, 1991; E. D. Rekow & Erdmann, 1985; E. D. Rekow, Erdmann, & Speidel, 1985).