The aim of this study was to evaluate the effect of two polishing methods and chemical conditioning on the surface of hybrid composites.

Ninety cylindrical specimens (diameter: 8 mm, depth: 2 mm) were made with three hybrid composites - Filtek Z250, Tetric Ceram, DenFil. Specimens for each composite were randomly divided into three treatment subgroups - ① Mylar strip (no treatment), ② Sof-Lex XT system, ③ PoGo system. Average surface roughness(Ra) was taken using a surface profilometer at the time of setting and after immersion into 0.02N lactic acid for 1 week and 1 month. Representative specimens were examined by scanning electron microscopy. The data were analyzed using ANOVA and Scheffe's tests at 0.05% significance level.

The results were as follows:

Mylar strip resulted in smoother surface than PoGo and Sof-Lex system(p<0.001). Sof-Lex system gave the worst results.

The PoGo system gave a superior polish than Sof-Lex system for the three composites. However, the correlation to clinical practice may be limited, since there are several processes, such as abrasive, fatigue, and corrosive mechanisms. Thus, further studies are needed for polishing technique under in vivo conditions.

Several ways of curing are being tried to improve material’s properties and reduce marginal gap. However, all are considering about the pattern of light intensity. It was noted from the preliminary study the change of light wavelength from filter changing may give an impact on material’s property and microleakage.

The object of this study was to verify the effect of filters with various wavelength width on the microhardness and microleakage of composite resin; hybrid type of DenFil and submicron hybrid type of Esthet X. Composite resins were cured using 3 kinds of filter; narrow-banded(465-475 nm), mid-banded(430-470 nm), wide-banded(400-500 nm). After the estimation of microhardness, degree of dye penetration and the maximum gap from SEM evaluation were done between 4 groups that showed no difference in microhardness value of the lower surface.

The results were as follows:

Adequate microhardness could not be gained with a narrow-banded filter irrespective of curing time. At the upper surface, DenFil should be polymerized with middle or wide-banded filter for 20 seconds at least, while Esthet X be cured with middle or wide-banded filter for 30 seconds at least to get similar hardness value to control group.

From these results, it could be concluded that curing with wide-width filter would be better than the other techniques, even though the curing technique using mid-width filter seems to have its own unique advantage.