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Automatic system for the production of ceramic dentures

Objective


TASK 1 Development of measuring system
The objective was the development of the measurement system with scanning device, sensor, controlling unit, PC and scan-software.
As a result of the work CeraDent realised a working digitising system for fast and accurate three-dimensional digitisation of small objects and especially dental models which fits the needs regarding accuracy and measurement time. Optimisations lead to an remaining measurement uncertainty of about 10 µm which includes the uncertainty of the sensor as well.
Further refinements leading to a market ready product will have to be carried out mainly with regard to the mechanical construction and the user interface which both were aimed at research purposes.

TASK 1 Development of CAD/CAM software-modules

The realisation of a software-system for the generation of the complete tooth shape and NC data with a user interface and all CAD/CAM functions necessary is achieved.
A modular software architecture allows to control the data transfer with the scanner, the creation of occlusal surfaces, the generation of lateral surfaces to form a closed tooth contour and to generate NC data for automatic denture processing.

TASK 3 Development of ceramic materials

The CeraDent consortium originally intended to develop a new, easily machinable ceramic material that also complies with the requirements of the dentistry sector with regard to stability and bio-compatibility.
The project partners initially gave preference to two ceramics: ZrSiO4 and ZrO2. Two more ceramics were discussed.
Since 1998 the dental ceramic IPS Empress 2 is available on the market by an external producer in various compositions and forms. The CeraDent partners were able to test this material in an early stage. The results show that IPS Empress 2 material is suitable for the proposed use as a raw material for dental restoration. Therefore it was decided to choose IPS Empress 2 as CeraDent ceramics material.
The development of a new ceramic material was thus completed, since it has emerged that a ceramics which is ideally suited to the requirements of the CeraDent project, is freely available on the market.
A lot of investigations on the material IPS Empress 2 evaluating the mechanical and physical properties as well as the biocompatibility was carried out however.

TASK 4 Development of process technologies for cutting of ceramics

The aim of this task is to optimise the production process and clamping system as well as the machining parameters and tools in such a way that the workpiece can be machined economically and without any damages.
Investigations on different ceramic materials like IPS Empress 2 were examined regarding their cutting property. The parameters feed speed and feed for the assigned tools and the material used in each case were systematically examined. For the cutting speed into preliminary tests a value of vc = 4.2 m/s was intended. A further increase of this parameter does not make a sense due to the small tool diameters, since it comes to an increase of the single grain load, which causes a premature wear of the tool. With higher cutting speeds the thermal influence of the tool increases.

TASK 5 Integration of the components in the system and
TASK 6 Optimisation of the completed system

The objective of the development work is to assemble a prototype of the system from the different task-results that can be used to manufacture ceramic dentures. At the end of the project, the entire system was comprehensively tested and the quality of the components, software and process within the system optimised.
The complete CeraDent process chain consisting of measuring device (scanner), CAD denture modelling software, CAD machining software, milling machine, machine equipment and tools was brought together, tested and optimised at the project co-ordinator. Several ceramic dentures were manufactured and tested by the partners. The interface to the CAD system was set up and tested. The continuous data transfer between measuring device - CAD/CAM - machining could be ensured.

The data transfer works stable and reliable. On the base of optimal machine parameters an economical
and time-optimal production of ceramic dentures is possible.
Objectives and content

The conventional manufacturing of dentures is based upon single-piece production involving various cost-intensive manual stages. The fitting accuracy of dentures less than 50 pm, which is required by the dentists and substantially influencing their durability, is at the time not reproducible. Because of the processes used, the conventional production is moreover limited to materials that are not optimal from a dental point of view.
The industry as well as the research made great effort to develop a process for the automatised production of individual, high-grade dentures. Despite technical progress made in the past years the systems developed up to now are not satisfying. This is due to their poor accuracy, the properties of the materials used, the complex operation and the resulting high costs.
The objective of the project is the development of an innovative, high-precision system for the production of ceramic dentures with an accuracy of less than 20 pm consisting of the following components:

- high-precision, non-contact measuring system for the digitalisation of small objects (up to 100 mm edge length) with complex free-form surface areas - user-friendly CAD/CAM system for the production of dentures involving data acquisition, automatic NC data generation and machining of complex tooth geometry
- ceramic materials optimised regarding machinability and medical properties - machining processes, tools and equipment for machining (especially milling) of dentures made from the ceramics developed

This project will provide the technological basis for a more inexpensive, more precise and higher quality production of individual dentures made from advanced ceramic materials. With regard to the continuously rising costs in public health, this system can effectively contribute to cost cutting. Compared to other dental materials, ceramics are age resistant, aesthetic and very bio-compatible and therefore constitute a high-quality, cost-effective and not health-injurious alternative to amalgam.

11 partners from 6 different European countries are working on this research project. The necessary overall approach to solve the complex difficulties mentioned above, is reflected in the interdisciplinarity of the project. The consortium is composed of partners coming from different backgrounds as measurement techniques, machine tools, material development, precision engineering, CAD/CAM system development, dental techniques and dentistry, and combines the scientific competence of various European Research Institutions with the practice-oriented, technical know-how of the industry.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Hacker Feinmechanik GmbH
Address
2,Im Polder 2
94560 Offenberg
Germany

Participants (10)

Dendia-Werk GmbH
Austria
Address
21,Jochen Rindl Strasse 21
1230 Wien
Ducera Dental GmbH
Germany
Address
7,Rodheimer Strasse 7
61191 Rosbach
FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG E.V.
Germany
Address
Steinbachstrasse 17
52074 Aachen
Fundación INASMET Asociación de Investigation Metalúrgica del País Vasco
Spain
Address
12,Camino De Portuetxe 12
20009 San Sebastián
Isper SpA
Italy
Address
Piazza Milano 12
24040 Ciserano-zingonia
Johann-Wolfgang-Goethe Universität Frankfurt
Germany
Address
7,Theodor-stern-kai 7
60590 Frankfurt-am-main
Raytec Systems AG
Switzerland
Address
22,Commercialstrasse 22
7007 Chur
Rheinisch-Westfälische Technische Hochschule Aachen
Germany
Address
53B,steinbachstrasse
52056 Aachen
Technoset Ltd.
United Kingdom
Address
Unit 3A, Glebe Farm Industrial Estate
CV21 1DB Rugby
Unigraphics Solutions Handelsgesellschaft m.b.H.
Austria
Address
Wiener Strasse 482
4030 Linz