The Measurement Analysis Of Differences Between CO And CR Of Class II Division I Malocclusion Patients

Objective 1.To identify the differences between CO and CR by clinical observation of the change of anterior overjet of class II division I malocclusion cases.2.To establish the three dimensional imagings of CO and CR by applying three dimensional reconstruction technology based on spiral CT. 3.To study the positional difference of condyle and glenoid fossa between CO and CR by three dimensional visualization technique.Metheods 1.To apply the sliding gage to measure the change of anterior overjet between CO and CR of 39 patients with class II division I malocclusion without orthodontic treatment in clinic . 2.Choose a typical case to establish a three dimensional imagings of CO and CR by applying the spiral CT. 3.Use the aera method and line-space method to have measurements from sagittal and coronal plane respectively for the two condyles.Results 1.The change of anterior overjet between CO and CR of 39 patients was 0.5mm～2.3mm, the average was 1.1mm. 2. Establish a three dimensional imagings of CO and CR. 3.When condyle was from CO to CR, P/A increased from 0.59 to 0.84 in left condyle and from 0.55 to 0.81 in right condyle, E/I increased from 0.47 to 0.63 in left condyle and from 0.46 to 0.57 in right condyle, X /Hdecreased from 0.54 to 0.52 and from 0.61 to 0.59 in left and right condyle respectively.The change of Y/O was not obvious in left condyle, but decredsed from 0.81 to 0.76 in right condyle.Conclusion There were some differences of anterior overjet between CO and CR of class II division I malocclusion patients,the change was statistical significance .The average difference was 1.1mm.The three dimensional imaging study showed that condyles moved anteriorly and downward from CO to CR by sagittal measurement. The inferior displacement was greater on the left side than that on the right side, while the anterior displacement was smaller on the left side than that on the right side.The coronal measurements indicated that the two condyles moved interiorly from CO to CR ,the displacement was greater on the left side than that on the right side,but the inferior displacement was smaller on the left side than that on the right side.