Measurement of tooth movement

Abstract

1. Tooth movement relative to the alveolar bone can be precisely described only by superimposing on fixed points in the bone. Implants are the best known way today. Over short-term studies laminagraphy and the use of bony trabeculations are also useful. Remodeling occurs extensively on bony surfaces, making them too labile for use as stable landmarks. To project small amounts of tooth movement based on the use of such methods is so questionable as to represent little better than a guess or a clinical impression. 2. Growth can be separated into vertical and anteroposterior vectors with respect to the dentition. Since the occlusion is the concern, orientation of vertical and anteroposterior vectors to the occlusal plane is a reasonable baseline. The vertical and anteroposterior dental changes may not show a linear relationship in the anterior and posterior parts of the mouth when jaw rotations are occurring. 3. Growth can be disproportionate in either the vertical and/or the anteroposteroir plane of space. If the vertical increments of the anterior face differ from the vertical increments at the posterior face, mandibular rotations occur. This growth is accompanied by dental compensations that tend to mask the rotation. Therefore, open bite and deep bite are frequently skeletal growth problems. 4. Disproportional forward growth of the maxilla or mandible in an anteroposterior direction can lead to Class II or III relations. The growth that leads to Class II or Class III is accompanied by dental migrations that tend to mask this disproportionate growth. Orthodontic treatment of growth disproportionalities usually represents attempts to make the teeth further compensate. If surgical options are elected, the dental compensations should be removed prior to surgery in order to achieve a full surgical correction. 5. The teeth tend to move and grow in the opposite direction of the growth disproportionality. The teeth tend to mask the disproportionality. Thus, in an open bite, the incisors tend to move vertically further than in deep bites. Vertical imbalances may be more difficult to mask. Backward rotation of the mandible requires more vertical movement at the incisor than at the molar just to maintain vertical incisor relationships.