The effect of placement technique upon the compressive strength and porosity of a composite resin.

This paper examines the effect of two placement techniques upon the compressive strength and level of porosity of specimens of a composite resin. Those specimens prepared by a condensation technique had a significantly lower mean compressive strength (P less than 0.05) and value of Weibull modulus (P less than 0.05) than specimens prepared using a smearing technique. No significant differences in the overall mean percentage area occupied by porosity and mean number of pores were demonstrated (P greater than 0.05) between the two placement techniques. Specimens prepared using the smearing technique, however, had significantly smaller mean maximum pore diameters (P less than 0.05) than those prepared using the condensation technique. It is therefore desirable when placing composite resins to reduce to a minimum handling procedures that are likely to influence the levels of porosity within the material.