Mesial drift as a function of growth

ABSTRACT

Migration of teeth in apparent mesial directions through maxillary and mandibular alveolar bone is a well known process. Such drifting of teeth has been presumed to function in maintenance of firm contact between teeth in order to compensate for wear on contact surfaces. Histological changes associated with this process involve differential deposition and resorption of bone on selective surfaces of alveolar walls. Although this functional interpretation of mesial drift is sound in principle, other equally important factors also appear to be involved. As the maxilla and mandible grow in size, a continuous remodelling process takes place that involves successive relocations of all areas into new positions within the entire bone. The purpose of such relocation is to maintain the constant shape, proportions, and relationship of the bone as a whole. The process involves localized additions and removal of bone in order to adjust the shape and size of each area as it is relocated into successive new positions. For example, a molar area at a given growth level is actually occupied by a premolar region at a later stage of growth. The remodelling movements of all such areas within the whole bone also requires corresponding movements of teeth inorder to maintain the constant positions of each tooth relative to its location in the growing bone. Since bone is a hard, calcified tissue, such tooth movements involve deposition and resorption of bone on selective surfaces of the alveolar wall, thereby resulting in the histological picture characteristic of mesial drift. It is suggested that these growth and remodelling movements represent the actual basis for drift, and that the maintenance of functional contact between teeth is a secondary but nevertheless important function of the same process (AU)