POROSITY IN COMPOSITE RESINS

Porosity in the pastes of composite resins before and after polymeriza tion has been measured. The influence of the diameter of the extrusion orifices and the spatulation of the chemically-activated pastes has b een evaluated. Considering that thin layers of these materials are tra nsparent, the investigation has been carried out mainly by analysis of similar to 300 mu m or lower thickness layers, that are still transpa rent under the microscope. Generally, there was a significant dependen ce of the porosity on the orifice diameter. However, this rule showed some exceptions. As far as the chemically-activated pastes were concer ned, in all examined cases the number of small size (10-40 mu m) poros ities increased after spatulation.