BACKGROUND:It is very important to appreciate the Sagittal discrepancy during the diagnosis and therapy in orthodontics patients.At present,ANB angle,AXB angle,Beta angle and APDI value were often used to evaluate the mandible and maxilla relationships in orthodontic clinic.Correlation and variance degree among these parameters were analyzed to judge the reliability.OBJECTIVE:To compare the reliability of ANB angle,AXB angle,Beta angle and APDI value in assessing sagittal discrepancy between mandible and maxilla in transitional dentition cases with Angle's class Ⅲ malocclusion.METHODS:Totally 56 patients of Angle's class Ⅲ malocclusion in transitional dentition at the Department of Orthodontics,First Affiliated Hospital of Xinjiang Medical University,between January 2004 and June 2009,were selected.ANB angle,AXB angle,Beta angle and APDI value of Angle's class Ⅲ malocclusion in transitional dentition were measured on the cephalometric radiographs.The radiographs were scanned by Microtek Phantom 9800 XL scanner at proportion of 1:1 with 300 dpi pixels,and saved as JPG format.The JPG pictures were fixed-point using Photoshop 8.0 to measure ANB angle,AXB angle,Beta angle and APDI value,the mean value was obtained after 3 times measurement.The correlation and variance degree among these parameters were analyzed.RESULTS AND CONCLUSION:Significant correlation was found among ANB angle,AXB angle,Beta angle and APDI value (P＜0.05).The coefficients of variation for the 4 indexes were 1.35,0.75,0.07 and 0.04,respectively.The results demonstrated that,it is accurate to use ANB angle,AXB angle,Beta angle and APDI value as cephalometric norm to evaluate sagittal discrepancy of maxmandibul in transitional dentition cases with Angle's class Ⅲ malocclusion.However,the APDI value is more reliable as cephalometric norm.

BACKGROUND:Beta angle,as a new index for the assessment of sagittal jaw relationship,has been widely used by clinical doctors.However,hand-made measurement but not academic software is still adopted in some hospital.OBJECTIVE:To study the beta angle of different skeletal patterns in Urumqi city for the clinical use of the method to assess the sagittal jaw relationship,and verify the possibility of Photoshop software to measurement of beta angle.DESIGN,TIME AND SETTING:An observational experiment and measurement design was performed at Department of Orthodontics,the First Affiliated Hospital of Xinjiang Medical University from July 2006 to May 2009.PARTICIPANTS:A total of 262 malocclusion cases including 94 males and 168 females were lived in Urumqi City.They were divided into three groups based on type of facies ossea,including type Ⅰ group (n=119),type Ⅱ group (n=74),and type Ⅲ group (n=69).METHODS:Lateral position of skull was photographed using X-ray,and beta angle was measured using Photoshop 8.0 software.Sex and type of facies ossea were compared using one-way analysis of variance and t test.MAIN OUTCOME MEASURE:Beta angle of male and female;beta angle of the types Ⅰ,Ⅱ,and Ⅲ.RESULT:There was no significant difference in beta angle between males and females (P>0.05).Beta angle of type Ⅰ was (34.15±3.88)°,that of type Ⅱ was (26.42±2.65)°,and that of type Ⅲ was 42.41°±1.88°.There was significant difference in beta angle among three types of facies ossea (P<0.01).CONCLUSION:Beta angle is an index for the assessment of sagittal jaw relationship.The reference range of the beta angle is 30°-38°.Photoshop 8.0 software is a novel tool to measure cephalometry.