The Effects Of Activator Treatment On Morphology And Structure Of Mandible And Tmj And Lateral Pterygoid Muscle

In order to evaluate the effects of Activator appliance on growth and displacement of condyle, glenoid fossa and mandible , cephalometric films and MRI images companying with clinical evaluation of TMJ were taken .There are three parts in this study. Part 1. The effects of activator appliance on growth and displacement of condyle, glenoid fossa and mandible : Activator group and control group consisted of 20 Class II, division 1 malocclusion subjects separately. All subjects were chosen randomly according to some certain criterias. A reference grid was defined on before and after cephalometric films. In order to discuss the effects and mechanism of activator appliance, the changes of the stable bone measuring points in horizontal and vertical directions were evaluated which including the condylar growth; glenoid fossa displacement and the growth and rotation of mandible. The correlation factors of promoting the mandible growth were analyzed. The results showed that the directions of condylar growth didn't change after activator treatment, but the amounts of growth increased greatly, especially the amounts of vertical condylar growth. Glenoid fossa was displaced anteriorly and inferiorly after activator treatment. The length of ramus and mandible showed a significant increasement during the functional orthopedic treatment. The vertical growth of condyle played an important role on the changes of ramus and mandible. Part 2. Changes of condylar and disc position in MRI images during Activator treatment and the correlations with clinical symptoms of TMJ: The subjects was the activator group in part1. The objectives of this part were that: 1. to analyze the relationship between the changes resulted from treatment and clinical symptoms. 2. to analyze the correlation between condyle and disc position. 3. to discuss the effect of functional orthopedic treatment on TMJ. The changes in position of condyle and disc during activator treatment were measured in MRI images .The results showed that the positions of condyle and disc didn't change after Activator treatment, the recapture of anterior displaced disc also can not be found. Though Activator treatment can not cause disc anterior displacement of the TMJ with normal position disc, it maybe can cause and aggravate the symptoms of TMJ in those subjects with disc anteriorly displaced. Part 3. Changes of lateral pterygoid muscle in MRI images during Activator treatment and the relationship between changes of LPM and clinical symptoms of TMJ: The subjects were the activator group in part1. The aims of this part were that : 1. to discuss the effect of functional orthopedic treatment on the morphology of lateral pterygoid muscle. 2. to discuss the mechanism of the pathological changes of LPM. The pathological changes of lateral pterygoid muscle were observed in MRI images made in CLPM projection . The relationships among the pathological changes of LPM and condylar mobility and disc position were analyzed. The relationship between images of LPM and clinical symptoms of TMJ were also analyzed . The results showed that the pathological rate of LPM in AngleII1 malocclusion subjects were higher. The rate of pathological changes in the superior belly of LPM are significantly higher than that in the inferior belly of LPM. Hypertrophy changes in inferior belly always companied with various pathological changes of the superior belly . The LPM images displayed no significant changes during Activator treatment. The relationships among the pathological changes of LPM and condylar mobility and disc position showed no significance. Pathological changes of the LPM in MRI were only associated with two clinical symptoms –jaw restricted movement and pain in TMJ. According to above three parts, the conclusions are that Activator treatmentcan prompt the condylar growth and increase the mandible length . It also has no adverse effects on positions of condyle and disc and morphology of LPM. Though Activator treatment can not result in anterior displacement of the disc in TMJs with normal position, this orthopedic treatment maybe lead to and aggravate the symptoms of TMJ in those subjects with disc anterior displacement. So the evaluation of TMJ before functional orthopedic treatment is very important for clinicians.