The aim of this randomized clinical trial was to compare the plaque control effectiveness and handling of an interdental brush with a short curved handle and a triangular cross-section of the brush head (IDB) and an interdental brush with a long straight handle in combination with a monotufted brush head (MTB). In a split-mouth design, 110 multibracket patients were randomly assigned to group A using the MTB in the first and third quadrants and the IDB in the second and fourth quadrants or to group B who proceeded the other way around. A crossover was performed after 3 months. The plaque index (PI) was scored every 6 weeks for a period of 24 weeks, and handling was evaluated using visual analogue scales (VAS). Wilcoxon tests were used to determine differences in PI and VAS scores between the two brushes and for PI differences between the different observation periods. Differences concerning personal preference and perceived cleaning efficacy were analysed with chi-square tests. The significance levels used were P < 0.001 and P < 0.01. The PI decreased significantly, but no statistically significant difference was found between the two brushes. Subjects experienced less pain and reported better access behind the archwire with the IDB. The use of an interdental brush reduced the PI irrespective of the design of the brush head. In direct comparison, adolescent patients preferred the IDB. Further trials are required to investigate the effectiveness of the IDB in reducing decalcification during orthodontic treatment.