A Preliminary Study On The Correlation Between SN Plane And FH Plane In The Lateral Position Of Han Nationality Population

Correlation Studies on SN Plane and FH Plane of Permanent Teeth Occlusion Skull Positioning Lateral Projection among the Han Population in QingdaoObjective: to reduce the X-ray measurement error brought by inaccurate positioning of FH plane by verifying the relationship between SN plane and FH plane of orthodontic X-ray skull positioning lateral projection among the Han population in Qingdao, and replacing the FH plane that is difficult to locate and unstable with relatively stable SN plane.Methods: 23 cases of Han people patients in Qingdao with individual normal occlusion type I aged 12~40, who received treatment in the Orthodontics Department of Qingdao University Affiliated Hospital from October 2013 to October 2015 were selected and divided into four groups, including 12 cases of men, and 11 cases of women, 8 cases of permanent teeth early treatment and 15 cases of permanent teeth treatment. 23 cases of patients took X-ray skull lateral projection with natural head position and CBCT. The X-ray with the variation of SN plane was eliminated. The average value of the included angle between SN plane and FH plane was obtained through cephalometrics software of Qingdao University and CBCT images positioning. Next, 5 pieces of skull lateral projection were randomly extracted from the different genders to test. By taking N of SN plane as the origin, clockwise rotation for 6°, 7°, 8°, 9° and 10° were used to replace the imaginary FH plane; the 6 line distance and angles associated with FH plane were measured under the 5 rotation angles. Through computer software system positioning and manual depicting measurement, the measured values were entered computer system. Statistical analysis was conducted on the data with software SPSS17.0. Besides, the data were tested through method of group t test and single factor variance analysis.Results: for the Han population in Qingdao with the permanent teeth early period and permanent teeth period normal individual occlusion, the differences between FH plane and SN plane were not significant, while the differences for different genders are statistically significant. After clockwise rotation 8° for men and clockwise rotation10° for women with N of SN plane as the origin, the differences between the measured data and the really-measured FH plane angle has no statistical significance.Conclusions: for Han population in Qingdao with individual normal occlusion group, FH plane can be replaced with clockwise rotation 9.75° for women and rotation 8.26° for men with N point as the origin of SN plane.