Orthodontic therapy, like any other medical intervention, in addition to its benefits carries the risk of potential complications and is associated with adverse effects-including periodontal problems, external root resorptions, pulpal changes, enamel damages (demineralization, discoloration, attrition), temporomandibular disorders, infective endocarditis, soft tissue damages, discomfort, pain and the risk of either aspiration or indigestion of medical instruments and appliances. Usually these effects are multifactorial in origin- most often a result of interactions between the patient, the dental practitioner and the technical aspects of the appliances or techniques. With preventive measurements and care, most of these complications can be either limited or completely avoided. Therefore, every dental practitioner must be fully aware of these effects and associated risk factors in order to maximize the treatment outcome. The present review aims to summarize these effects of orthodontic therapies, and provide a detailed description of factors and preventive measures, in order to minimize these damages.