Viscosity, flow, stickiness, packability, thixotropy and shape stability are important rheological parameters in studying the handling behaviour of dental composite resins. Further important factors are the fluid motions of and the effort needed to deform composite resins.
Rheological parameters can be very different in response to the handling behaviour. In the clinical handling behaviour of composite restoratives, stickiness is a vital rheological parameter. The material should have two characteristics: (1) low stickiness for not sticking on the instrument and (2) high stickiness for staying in the prepared cavity.
There are very few publications on objective scientific methods for measuring these characteristics. The aim of this study is to evaluate the stickiness behaviour of dental composite resins. For this purpose, a new instrument was designed. This "stickiness instrument" contains several measuring and controlling units. The main part consist of a vertical cylindrical stainless steel bolt with a flat circular end and a platform with a cylindrical mold (diameter: 6.1 mm, depth: 2.2 mm) which is filled with the material to be tested. The temperature of the instrument and the speed of the bolt going in and out of the material can be modified. With a force of 350 g, the instrument's plunger moves slowly into the prepared mold which is filled with the unset composite material. The degree of stickiness is deducted from the height (projected height ranges from 0.2 to 1.8 mm) of the "hill" the material forms when the plunger is withdrawn from the mold until the steelhead detaches itself from the composite. The study aims at showing the difference in stickiness between different brands of composite materials. In general, the stickiest among the tested materials is Estelite while Premise is the least sticky material. By benchmarking different products it is possible to discover the adequate material for different problem-areas in dentistry. In addition, the results of this study can provide a good solid basis for studying new dental composite materials with improved application and handling technique.