<p>Maintaining good oral hygiene is a major challenge during orthodontic treatment. Various appliances—whether fixed or removable—create new niches for plaque and bacteria, and make it difficult to clean teeth. This can lead to carious lesions, gingivitis, gingival hyperplasia, or peri-implant inflammation. Adolescents with fixed appliances in particular often fail to implement hygienic measures despite being informed. Removable systems such as aligners or functional orthodontic appliances allow for easier cleaning, but require a high level of compliance. The success of orthodontic treatment depends to a large extent on sufficient oral hygiene. Structured hygiene instructions, individual patient motivation and regular dental check-ups are therefore essential not only to prevent oral disease, but to also ensure treatment success. </p>