The Effects Of Intermaxillary Class â…¢ Orthopedic Magnetic Force On Temporomandibular Joint: An Experimental Study On Rhesus Monkeys

Angle's Class â…¢ malocclusion, which can severely degrade the aesthetic characteristics of facial contour, oral function and mental health , takes a high proportion in all kinds of dentofacial deformities. Although class â…¢ orthopedic appliances(chin cap and face mask) are frequently applied in the treatment of early functional or skeletal Angle's class â…¢ malocclusion, its mechanisms have not been elucidated completely and the biologic safety and curative effects remain controversial. Meanwhile the literatures reporting on the mechanisms of intermaxillary class â…¢ functional orthopedic system are limited. So, it is necessary to carry out more improved basic research.In this research, the rhesus monkeys were selected and treated as the animal model for class â…¢ orthopedic force; the twin-block magnetic appliance (TMA) was modified by using casting technique With TMA the animal model of introral class â…¢ orthopedic force established successifully. To investigate the morphologic histological and molecular biologic effects of intermaxillary class â…¢ orthopedic force on condylar cartilage, photograph , cephmetry and CT were employed in this study, theexpression and distribution of multiplication nucleolus antigen expression(PCNA) and apoptosis and its regulatory gene Bcl-2, Bax gene in TMJ were observed under the Class â…¢ orthopedic force and the mechanism of Class â…¢ orthopedic force were discussed to provide reference for future clinical treatment. Results:(1): The magnitude and the direction of the force produced by twin-block magnetic appliance were competent to be applied as the class â…¢ functional orthopedic force and the ideal animal model for the study on the class â…¢ functional orthopedic treatment could be established through the application of TMA on the rhesus monkeys. (2) The molar relationship was changed significantly following intermaxillary Class â…¢ orthopedic force and it was caused by maxilla growing forward and the change of the growth direction and position of mandible; TMJ joint space was changed: the anterior space increased, the posterior space decreased and the change of three month group was more obvious than that of the one and half month. group (3) Significant remodeling was taken place in the condylar cartilage in the monkeys treated with intermaxillary class â…¢ orthopedic force, the growth of posterior portion of cartilage was inhibited, the multiplicative and the prehypertrophic zones thinned significantly ; while the anterior portion presented a hyperplastic reaction mainly caused by the increase in the thickness of the multiplicative zone. (4). apoptosis is programmed cell death, it is regulated by Bcl-2 and Bax.The balancing result of the two protein determine whether the cell will exist or die out. Class â…¢ orthopedic force had no obvious effect on the cell apoptosis;while it could improve the expression of PCNA,BCL-2 on anterior portion, and inhibited the expression of Bax, hyperplasia appear on anterior portion, on the contrary it could improve the expression of Bax and inhibit the expression of PCNA,Bd-2, and the growth of posterior portion was inhibited to some degree.Based on these fin digs , we can draw the followingconlusion : 1 )maxilla move forward and the growth direction of mandible was changed; TMJ joint space was changed: the anterior space increased, the posterior space decreased. 2)Significant remodeling was taken place in the TMJ, the growth of anterior portion was promot , while the growth of posterior portion was inhibited. 3)class â…¢ orthopedic treatment had no obvious effect on the apoptosis of cartilage. 4)Bcl-2 and Bax played a role in the remodeling of condyle cartilage.