抄録
The purpose of this paper is to clarify biomechanical characteristics of lingual orthodontics. Orthodontic treatment of patients with lingual appliances necessitates modification of the conventional mechanotherapy used with labial appliances because of the very unique type of tooth movement in lingual orthodontics, which is obviously caused by the different bracket position. The unique bracket position, morphology of the lingual tooth surface, anatomical difference of the cortical bone, and reduced arch circumference and interbracket distance result in very different characteristics of tooth movement.
In my estimate, approximately double orthodontic force should be applied in lingual orthodontics to produce the same magnitude of toque on incisors as in labial orthodontics.
It must be understood that lingual orthodontics belongs to an entirely different world of orthodontics.
For example, it is naturally tempting to apply the straight wire concept to lingual orthodontics.
To realize this with a lingual straight wire appliance, however, anterior brackets would be located too far lingually. (Fig. 3) The moment of force created with lingual brackets is opposite in direction to that with labial brackets. In addition the further lingually the brackets are positioned, the greater the moment of force will be, increasing anterior crown lingual torque significantly. (Fig. 2)
The treatment of open bite and so-called gummy smile cases with lingual orthodontics requires special consideration to its biomechanics, which is distinct from that of conventional orthodontics.
