Orthodontic traction: Possible consequences for maxillary canines and adjacent teeth Part 1: Root resorption in lateral incisors and premolars

Some professionals are reluctant to indicate orthodontic traction, especially for upper canines. Among the most common reasons for restricting the indication of orthodontic traction are: 1) Root resorption in lateral incisors and premolars. 2) External cervical resorption of the canines under traction. 3) Alveolodental ankylosis of the canine(s) involved in the process. 4) Calcific metamorphosis of the pulp and aseptic pulp necrosis. These conditions do not result primarily and specifically from orthodontic traction, and can be avoided if certain technical precautions are followed. For a better understanding of what these technical precautions are and how they work preventively against the possible consequences of orthodontic traction, we need a biological foundation. This is the goal of this series of studies on orthodontic traction, especially of upper canines, and its possible consequences. Development, structure and functions of the dental follicle The dental follicle occupies the radiolucent space around the crowns of unerupted teeth (Figs 1 and 2). It is firmly attached to the surface of the crown by the reduced epithelium of the enamel organ (Fig 3). This thin and delicate epithelial component is sustained and nourished by a thick layer of connective tissue with a variable density of collagen, sometimes loosely, sometimes even hyalinized. The outer portion of dental follicles binds to the surrounding bone (Figs 2 and 3). In measurements of the pericoronal space in periapical radiographs and orthopantomographs, or panoramic radiographs, the thickness of the dental follicle can reach up to 5.6 mm and still maintain normal structure and organization2,4 (Fig 3). By removing the follicle and detaching it from the surrounding bone a tissue fragment is obtained which is organized like a thin film and is therefore also known as pericoronal membrane. The isolated tissue fragment represented