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First step FE-modelling of internal composite behaviour during curing dental restorations

: Koplin, C.; Jaeger, C.R.


Institut für Biotechnik e.V. -IfB-, Feldafing; TU München:
5th World Congress of Biomechanics 2006. Abstracts : Munich, Germany, 29 July-04 August 2006
München, 2006 (Journal of Biomechanics 39.2006, Supplement 1)
World Congress of Biomechanics <5, 2006, München>
Fraunhofer IWM ()
dental restoration; curing; composite; finite element; local stress; internal stress

Light-curing dental composites have found widespread application in dental restorations due to their tooth-like appearance and easy handling. The development of »adhesive dentistry« (i.e. the use of bonding agents which improve the bond strength between tooth and filling) increased the range application of light curing dental composites e.g. in the area of minimal invasive procedures. Despite intensive research, these composites still introduce internal stresses into the restoration due to the polymerisation shrinkage during curing. These stresses can compromise the marginal integrity and lead to secondary caries, cause initial damage to the material during hardening, and promote chemical and mechanical degradation. The stresses result from a complex interplay between geometry of the cavity, increasing stiffness, decreasing flowability, and changes in the density of the material due to thermal expansion and polymerisation shrinkage. We developed a dedicated mechanical testing set-up which measures stiffness, viscosity, and volume behaviour of the composites during the hardening reaction. The results of the experiments are used in a material model which describes the development of internal stresses for different composite compositions and allows a comparison of the performance of various dental filling materials. The development of heterogeneous distributed stresses and local flow processes close to the filler particles of two different dental composites are investigated as first step but in detail. High filler loads of 60% (vol.) are accomplished in different composites by differing multimodal filler sizes. We compared older but well-known Tetric Ceram with Heliomolar, that are more dislike in filler-structure but more alike in monomer-mixture, by their tendency to handle critical local stresses during curing.