Due to the nature of the fixed orthodontic appliances system, side effects can happen during and after treatment due to interaction between the patient, doctor, and the orthodontic technique. The most common side effect is a white-spot lesion, followed by periodontal disorder and external apical root resorption. They usually can be found affecting patients' esthetic, oral hygiene, and function. If an orthodontist left it untreated, the mentioned side effect can cause more serious problems for the patient in the long run. The objective of this literature review is to address each side-effect of orthodontic treatment, its effect on patients during and after treatment. In addition, orthodontic treatment methods and materials are recommended to minimize or prevent these side effects from happening.