The purpose of this study was to investigate if there were a significant difference between cephalometric measurements of mandibular position derived from a centric occlusion tracing compared to those of a converted centric relation tracing in
the
Class
III malocclusion.
The sample consisted of 25 Class III malocclusion and 25 normal occlusion persons who had no orthodontic treatment. The records included an lateral cephalometrics in centric occlusion, centric relation and centric occlusion bite registration and
diagnostic casts mounted on the SAM II articulator in CR. The amount of CR-CO discrepancy of condyle was recorded using a MPI (Mandibular Position Indicator, MPI 200(r). Great Lakes Orthodontics. USA). The conversion of the CO cephalogram to CR
using
the MPI readings was performed on the Conversion work sheet.
Measures of mandibular position were chosen for the purpose of this study. The comparison of the difference between CO and CR cephalometric measurements in the normal occlusion and Class III malocclusion group were studied.
@ES The results were as follows:
@EN 1. In the features of CR-CO discrepancy of the condyle, the condyle was displaced posterior and inferior when the teeth were in centric occlusion. The horizontal component(ΔX) in Class III malocclusion group was greater than the vertical
component(ΔX) and also greater than the horizontal component(ΔX) in normal occlusion group. There was no statistically significant correlation between MRI measurements and the groups of normal occlusion and Class III malocclusion group.
2. In the comparison of the cephalometric measurements in each group, Normal occlusion group showed significant difference in measurements such as ANB, Facial angel, Facial convexity and ODI. Class III malocclusion group showed significant
difference
in measurements such as ANB, Facial angle, Facial convexity, ODI, SNB, APDI, L1-FP and it had more significace than the normal occlusion group.
3. The Value of cephalometric measurements was significantly different between CO and CR abut three were on differences between the groups of normal occlusion and Class III malocclusion.
The results of this study suggest that if the discrepancies are greater than the amount of normal displacement from clinically captured centric relation, centric relation should be considered as the starting point for proper diagnosis and
treatment
planning.
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