A new technique using standardized test facings was designed to evaluate interdental plaque accumulation on different restoration materials. In 10 volunteers, a total of 40 samples, including enamel, two different ceramics and a bonding composite, were inserted one by one into a precision attachment in an experimental inlay bordering on either the lower second premolar or the lower first molar. Bacterial accumulation on each approximal specimen was allowed to mature for 3 d. Following microbiological processing of the plaque samples, total bacterial counts, colony forming units and the bacterial vitality were determined. The results revealed different accumulation rate patterns. Both ceramics accumulated less plaque with a reduced vitality compared to enamel, while the bonding composite showed no significant differences compared to the natural tooth substance. No significant differences were detected when comparing the two examined ceramics.