Abstract:

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.