Orthodontic Correction of Traumatic Luxations, Disadvantages of Continuous Arch Techniques: A Clinical Protocol

The orthodontic management of traumatic vertical tooth dislocations requires to correct apply biomechanical principles. In fact, the choice between continuous or segmented arch technique is of great importance to avoid side effects on the dental elements adjacent to the traumatized ones. The purpose of the present work is to analyse the biomechanical advantages related to the correct application of mechanical classes according to Burstone. In the management of these situations, a fixed orthodontic appliance is usually used, with a continuous or segmented technique. Two types of techniques were compared: the continuous arch technique and the segmented arch technique, evaluating for each the vectors of single forces and the moments generated by pairs of forces acting on the bracket of the affected element and the anchorage unit. In Author’s opinion, the best choice is segmented mechanic because it allows to avoid a Burstone Class I interaction between the adjacent teeth. A class I mechanic may cause disadvantages: 1) opposite vertical movement of the unaffected tooth 2) less intrusion of the affected tooth 3) uprighting of both affected and unaffected tooth 4) the amount of the force may be inaccurate. These side effects do not exist in a segmented arch technique, because a single precise force passing through the center of resistance of the affected tooth is created, while the anchorage unit is only located on molars.