The object of this study was to compare the microleakage between various composite resin systems of multistep, one-bottle, and self-etching systems using electrical conductivity.

After making class V cavities (4×3×1.5 mm around CEJ), they were bulk filled with three kinds of resins of A3. Teeth were storaged in a saline solution for one day, after then, they were finished and polished using Sof-Lex system. Another stress of thermocycling was made for 500 times from 5° to 55℃ with each dwelling time of 10 seconds. Electrical conductivity (microamphere, µA) was checked four times: before and after cavity preparation, after filling, after thermocycling.

One-way ANOVA and 95% Scheffe Post Hoc test was used for checking any statistical difference among groups. Another 95% Paired Samples T-test was also used for estimating any significant difference within group after cavity filling or thermocycling.

The results were as follows:

Every specimen showed various range of microleakage after filling.

There was, however, no difference between composite resin systems.

Within the limits of this study, it was concluded that much more consideration should be needed when using thermally unstable one-bottle and self-etching systems that have multi-advantages from simplified step. More studies will be needed to solve these kinds of problems.