The Establishment And Clinical Application Of Measuring Method Based On Spiral CT To The Normal Occlusion Models For Han Nationality Teenagers In Lanzhou

First part:Objective To verify the reliability, repeatability and precision of 128-slice spiral computed tomography system by comparing the measurements of 20 normal occlusion models by 128-slice spiral computed tomography (CT) with traditional manual measurements so as to provide rapid and suitable the normal occlusion models smeasurements with favorable stability, reliability and precision for clinical orthodontics. Methods:The workstation software supported by 128-slice spiral CT machine (SOMATOM Definition AS+,3D, Dental, Inspace) was used to conduct the volume scanning and data acquisition to the nonnal occlusion models and reconstruct the function to obtain the images (0.6mm) and then it was transferred to the workstation 3D Dental, Inspace (4D persistent real-time interactive 3D imaging technology) et.al software. The axial images, MPR (maximum density projection reconstruction), CPR (contour reconstruction) and VR (surface and volume reconstruction) were used to measure the maxillodental and mandibular dental width, arch length and related indicators of normal occlusion models; meanwhile, vernier caliper was used to measure the maxillodental and mandibular dental width, arch length and related indicators of normal occlusion models; all measurements received statistical analysis. Results:The same models were treated by 128-slice spiral CT system. For the same models with the measurements at different time and different models with their measurement, r>0.75 and p<0.05,, suggesting that these two methods had similar parallel validity. The error in CT system was-0.02～0.02mm with high precision.Conclusions:There is no significant difference between the measurements by Siemens 128-slice spiral CT and manual measurements. The 128-slice spiral CT is a rapid and suitable measurement for normal occlusion models with favorable stability, reliability and precision and can assist to conduct clinical orthodontics.Second part:Objective:This study was to establish the normal values of the width and height of crown, the width anlength of the dental arch,the height of the palate on normal occlusion in Lanzhou teenagers, The normal occlusion based on the measurements of 128-slice spiral computed tomography (CT) to 80 for Han nationality teenagers aging from 13 to 16 in Lanzhou and to provide the referencefor diagnoses in orthodontics.Methods:80 standard dental casts (40 female casts and 40 male casts) aging from 13 to 16 in Lanzhou were selected as the subjects and Siemens 64-row 128-slice spiral CT system was used to measure the width and height of crown,the width and length of the dental arch,and the height of the palate were measured with a vernier. The measurements were analysed with statistic methods and compared the relevant document.Results:The width and height of crown the width and length of the dental arch, and the height of the palate in Male were larger than those female in female. (P<0.05), the width of maxillary dental crown was 6> 7> 1> 3> 4> 5> 2 in order; the width of mandibular dental crown was 6> 7> 4> 5> 3> 2> 1 in order. The height of maxillary dental crown was 1> 3> 2> 4> 5> 6> 7 in order; the height of mandibular dental crown was 3> 2> 1> 4> 5> 6> 7 in order. The measurements were different comparing with national and international reference data. Conclusions:The width and height of crown the width and length of the dental arch, and the height of the palate in Male were larger than those female in female. (P<0.05) Normal values f teeth, dental arch and basal bone are established to provide the reference for clinical orthodontics in the teenagers of Lanzhou. The crown and dental arch of human were different according to different area race and sex. We shoud use our own norms in orthodontics.