The Correlation Analysis Of SNA Angle, SNB Angle, ANB Angle With Other Common Cephalometric Indexes

The importance of X-ray cephalometric in orthodontics clinical work was obvious.In order to analyse, diagnose the malocclusions and establish treatment plans, SNA angle, SNB angle and ANB angle were commonly used to evaluate the sagittal relationship of cranial base, maxilla and mandible.But during the growth of cranial facial, SNA angle, SNB angle and ANB angle would be affected by lots of factors,which made the orthodontics clinical work more difficult.In recent years,many studies showed that there was a definite relationship among cephalometric indexes .To evaluate cephalometric indexes correctly, the comprehensive analysis was needed.Objective: To evaluate the correlation between SNA, SNB or ANB angle and other measurement items such as SNA angle,SNB angle,ANB angle,S-N-ANS angle,S-N-Pr angle,S-N-Po angle,S-N-Id angle,convexity of point A,angle of convexity,the crossing angle of SN plane and FH plane,AB-Npog angle,APDI,saddle angle,the three angle(the sum of saddle angle ,joint angle and mandibular angle) as the indicator of the relationship of cranial base, maxilla and mandible.Method: Lateral cephalograms of 120 persons with skeletal Classâ… ,â…¡orâ…¢malocclusions were traced and measured , and liner regression analysis was applied to determine the correlation between SNA, SNB, ANB angle and other 11 measurement items by SPSS 13.0.Results:1 There was none of the measurement items had differences between boys and girls(P>0.05) in 3 class malocclusions.2 Most items had positive or negative correlation with SNA, SNB or ANB angle.Conclusion: Although SNA, SNB and ANB angle were considered as critical parameters in evaluating the relationship of cranial base, maxilla and mandible, the combining application of SNA, SNB, ANB angle and other items was reliable in diagnosis due to the influence of relative factors.