A Study Of The Influence Of Unilateral Mastication To The Movement Of The Orthodontic Tooth

Objective: To study the influence of unilateral mastication to the movement of the orthodontic teeth and the effect of the different bite force on morphology of orthodontic tooth periodontal tissues.Methods: Animal models were induced by extracting the right mandibular molars; then the left maxillary molars served as increased bite force modals while the right maxillary molars served as decreased. The untreated (non-extracting teeth) used as the control. An initial force of 50g drawn the maxillary first molar mesially. Tooth movements were measured at 0, 3, 7, 10, 14days. Then dissected the tissue including the maxillary first molar and its periodontal tissues, HE stained and observed the dynamic changes of the periodontal tissue.Results: (1)The tooth on the side of increased bite force moved more slowly than the control but the tooth on the decreased side moved faster. It meant that unilateral mastication had an effort on the rate of the orthodontic tooth movement. (2)The dynamic changes of the periodontal tissue on the increased bite force side was similar as the normal bite force but ligament width was significantly wider than the normal. The periodontal tissue on the decreased bite force side became degenerative. (3)The study showed that under the three situations of normal, increased and decreased bite forces, the movement tracks of orthodontic tooth all expressed these three stages including instantaneous-moving stage, slow-moving stage and rapid-moving stage which according with the common rule of orthodontic tooth movement.Conclusion: The animal experiment showed that unilateral mastication influences the velocity of orthodontic tooth movement. Under the same orthodontic force, bite force is an important effective factor to the velocity of tooth movement. But no matter how fast it moved, the movement showed the same rule, including three stages of instantaneous-moving stage, slow-moving stage and rapid-moving stage. In morphology, the dynamic changes of the periodontal tissue on the increased bite force side was similar as the normal bite force but the decreased bite force side became degenerative.