There are many interdental cleaning aids available for patient use, including toothpicks, dental floss and interdental brushes (IDBs). Most are available in various shapes and sizes. The aim of this laboratory study was to evaluate and compare the cleaning efficacy of waist-shaped interdental brushes to those of cylindrical shape. Four groups of IDBs, ranging in diameter from 2 mm to 9 mm, were tested. To reduce production and material bias, all brushes tested were from the same manufacturer. Cleaning efficacy was tested on two different devices: 1) a geometrical model, using opposing rectangular blocks at separation distances of 1 mm to 4 mm and 2) an anatomical model, displaying a standardized maxillary segment from canine to 3rd molar. The surfaces in both devices were coated with a titanium oxide slurry, then cleaned under standardized conditions and planimetrically evaluated. The measurements took place after 1, 5 and 10 cleaning strokes, respectively. Both models showed significant superiority in the cleaning efficacy of the waistshaped brush (p < 0.001), at 1, 5 and 10 strokes. Based on the present results, it can be concluded that interdental brushes with a waistshaped form showed cleaning potential superior to their cylindrical-shaped counterparts, under standardized laboratory conditions.