Abstract Background: Orthodontic treatment is associated with various risks, such as enamel discoloration, erosion, demineralization, and caries. The presence of microleakage between the enamel and adhesive and between the adhesive and the base of the orthodontic bracket allows penetration of the bacteria, molecules, and liquids into the enamel. The aim of this in vitro study was to evaluate microleakage in five adhesive systems commonly used in orthodontic practise for bonding brackets.