Competition will usually develop between the opposing walls as the restorative resin shrinks during polymerization. Magnitude of this phenomenon may be depended upon cavity configuration and volume.

The purpose of this sturdy was to evaluate the effect of cavity configuration and volume on microleakage of composite resin restoration that has margins on the enamel site only.

The labial enamel of forty bovine teeth was ground using a model trimmer to expose a flat enamel surface. Four groups with cylindrical cavities were defined, according to volume and configuration factor (Depth × Diameter / C-factor) - Group I: 1.5 mm × 2.0 mm / 4.0, Group II: 1.5 mm × 6.0 mm / 2.0, Group III: 2.0 mm × 1.72 mm / 5.62, Group IV: 2.0 mm × 5.23 mm / 2.54.

After treating with fifth-generation one-bottle adhesive - BC Plus™ (Vericom, AnYang, Korea), cavities were bulk filled with microhybrid composite resin - Denfill™ (Vericom). Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Specimens were thermocycled 500 times between 5℃ and 55℃ for 30 second at each temperature.

Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (µA) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level.

The results were as follows:

1. Small cavity volume showed lower microleakage score than large one, however, there was no statistically significant difference.

2. There was no relationship between cavity configuration and microleakage.

Factors of cavity configuration and volume did not affect on microleakage of resin restorations with enamel margins only.