Temporomandibular joint growth adaptation and articular disc positional changes in functional orthopedic treatment: Magnetic resonance imaging investigation
Functional orthopedic appliances have been proposed for the correction of Class II malocclusion due to a retrognathic mandible. The aim of using this appliance is to stimulate mandibular growth by forward positioning of the mandible in order to achieve normal jaw relationship. However, the modes of action using this appliance are still inconclusive. Also the effects of this therapy on the temporomandibular joint (TMJ) are still subject to doubts and discussion. Magnetic resonance imaging (MRI), the gold standard for assessing the soft tissue and position of the TMJ articular disc, therefore, was used to help clarify the effect of this appliance on the TMJ. The aims of this article are to provide a literature review of the methods that are used to assess changes in the TMJ, as seen on MRIs, from functional orthopedic appliances which include condylar and glenoid fossa remodeling assessment, condyle-fossa relationship assessment and articular disc assessment and to review clinical studies using MRI to investigate the effects of functional orthopedic treatment on the TMJ.
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ABSTRACT: Introduction: Magnetic resonance imaging (MRI) is considered the examination of choice for the diagnosis of abnormalities in the TMJ. Considering the difficulty in defining and standardizing the diagnostic criteria, and the need for more accurate and reliable diagnosis of conditions in the TMJ, the aim of the present study was to compare three different MRI parameters: T1-weighted, T2-weighted and proton density–weighted in the diagnosis of changes in the temporomandibular joint.
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ABSTRACT: This study aimed to define the effects of asymmetric force on rat temporomandibular joints (TMJs). A total of 232 10-week-old rats were used in the experiment. Their left TMJs were kept forward and upward with 40g or 120g. The histological and osteogenic changes, as well as the expression of type I, II and III collagens were observed. Our results showed that the curve of the cartilage thickness changes in the anterior part of the treated side in the heavy force group (HS) decreased first and increased later during the strength and the recovery periods, while the reverse changes were shown in the middle and posterior parts. The cartilage thickness change on the other side in the heavy force group (HO) was the opposite. Additionally, the cartilage thickness change on the treated side and the other side of the light force group (LS and LO) were similar to but not as significantly changed as HS and HO. There were significant differences among the experimental groups. The subchondral bone trabecula also decreased after the pressure loading and removing, then recovered, without significant differences among these groups. Furthermore, more pathological changes such as fractures, bone cysts, the degradation of type II collagen and the increased expression of type III collagen were observed on the treated sides following the application of heavy force. In contrast, more osteogenesis and more active changes were found in the light force group. In conclusion, our study demonstrated that asymmetric force exerted different effects on the cartilage, subchondral bone and collagens of TMJs. Greater changes occurred in the heavy force group, and light force provided more benefits for TMJs remodelling.
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