Abstract
Orthodontic appliances may profoundly influence the morphology and structure of the craniofacial complex. This paper identifies the various regions under these influences and reviews some investigations on the effect of appliances on the teeth, periodontal membrane, alveolar bone, craniofacial bones and the orofacial musculature. The complexity of reactions resulting from the interaction of these factors is highlighted. The understanding of these basic tissue reactions, the planning of simple mechanics and the monitoring of these treatment-induced changes using suitable progress record systems, is stressed as necessary if controlled treatment is to follow.