Heraeus hosts satellite symposium at CED congress 2009

Modern composites reduce shrinkage stress

Hanau, Germany, November, 2009 – The development of modern composites must aim at reducing shrinkage stress. On this point all experts agreed at Heraeus’ satellite symposium “Facts behind shrinkage” during the CED congress 2009 in Munich. Shrinkage stress is after all one of the most important factors for the durability of a dental filling.

At the 44th congress of the CED (Continental European Division) of IADR (International Association for Dental Research) in September, 700 scientists used the opportunity for international exchange. With around 140 participants Heraeus’ satellite symposium on composites also attracted wide interest there. “Low shrinkage composites are the latest trend,” the chair of the symposium, Professor David Watts from the University of Manchester, UK, stated in his introduction. Professor Claus-Peter Ernst, Dr Christof Koplin and Dr Andreas Utterodt gave an overview over the requirements of modern composites and the latest trends in research and development. As a researching company Heraeus traditionally attaches great importance to a tight and long-term cooperation with international scientists and to the feedback of experts and practitioners.

Demands on composites yesterday, today and tomorrow
Professor Claus-Peter Ernst from the University of Mainz, Germany, outlined the past, present and future requirements of dental composites from the practitioner’s perspective. For a long time, dentists’ main concern was shrinkage. “By now, we know that it is rather shrinkage stress that determines the durability of the filling”, Ernst explained. Here, modern composites differ widely as a study presented by Ernst shows: With a shrinkage stress of 2.5 MPa Venus Diamond ranks far ahead its main competitors. However Ernst demanded to focus not just on shrinkage and shrinkage stress. In his opinion the physical properties of the filling material are just as important, as studies have shown that filling fractures are the main reason for failure of composite restorations. Venus Diamond is strong in this regard, due to its unique combination of low shrinkage stress coupled with high flexural strength. In Ernst’s opinion this makes it possible to extend the indication range of composite fillings regarding replacement of several cusps or restoration of endodontically treated teeth. Initial clinical cases he showed on that allow for an optimistic look into the future.

Shrinkage stress scrutinised
Dr Christof Koplin from the Fraunhofer Institute for Mechanics of Materials in Freiburg, Germany, introduced a simulation of the polymerisation process. This makes it possible to calculate the development of internal stresses during polymerisation and to ensure low polymerisation stress for the composite, already during material development. The advantage of this simulation compared to conventional measurement of shrinkage stress is the visual representation, which shows exactly what stress is produced, in which area of the cavity and at which time. Apart from the cavity geometry, the thickness of the adhesive layer and the layering technique, the properties of the composite are decisive parameters for the magnitude of shrinkage stress: viscosity, stiffness and volume changes from polymerisation shrinkage and thermal expansion. In this simulation, Koplin found that Venus Diamond had a low tendency to internal stress combined with good material properties, supporting the findings of Ernst.

New monomer minimises shrinkage stress
“Based on the previous resin matrix, further improvements in shrinkage stress were hardly possible,” Dr Andreas Utterodt, head of R&D fillings at Heraeus, reported in his lecture on the evolution of resin molecules used in composites. Since the discovery of the cross-linker monomer Bis-GMA, for the last 40 years it’s mainly the filler system from glass or ceramic particles that had been improved. Now, Heraeus has developed a customised cross-linker molecule for the new generation of Venus Diamond composites. The new Tricyclodecane (TCD) monomer with its rigid backbone structure at the core, together with a densely packed filler system with nano-particles, now enables to combine in an unprecedented manner very low shrinkage with high strength, natural aesthetics and superb handling properties.

The symposium was a complete success, which was demonstrated by the lively discussions following the presentations.

The company:
Heraeus, the precious metals and technology group headquartered in Hanau, Germany, is a global, private company with over 155 years of tradition. Our businesses include precious metals, sensors, dental products and biomaterials, quartz glass, and specialty lighting sources. With product revenues approaching € 3 billion and precious metal trading revenues of € 13 billion, as well as nearly 13,000 employees in more than 110 companies worldwide, Heraeus holds a leading position in its global markets.

Heraeus Dental is a global supplier of dental products headquartered in Hanau, Germany, with subsidiaries in the US, Europe, and Asia. Being one of the world’s leading manufacturers of dental products, specialist for dental alloys and single-source provider of systems for the conservation and restoration of natural teeth, Heraeus Dental offers an extensive product portfolio for dentists and dental laboratories.

Contact:
Dr. Marianne Gräfin Schmettow
Heraeus Kulzer GmbH
Public Relations Dentistry
Gruener Weg 11
D-63450 Hanau

Tel.: +49 (0) 6181/35 3814
Fax: +49 (0) 6181/35 3572
marianne.schmettow@heraeus.com