Mandibular angle resection was usually performed by internal approach. But internal approach has several complications like asymmetry, subcondyle fracture, overcorrection and undercorrection. These complications maybe result from inaccurate measurement of resection width of mandible angle due to narrow operative field. So accurate measurement of resection width is very important in preventing such complications. Many methods were used for accurate measurement of resection width such as film pattern application, using dental mirror to confirm the cutting site, and metal guiding instrument. But these methods are inaccurate and not convenient to use. 
We designed new mandible angle gauge for accurate measurement of resection width. The resection width from mandible angle could be estimated accurately by using this device. The device consists of body, guide slit, rotating knot, and indicator. The guide slit guided oscillating saw and the first sawing was performed at planned resection width. After the first sawing was established, the device was removed, and remained resection was performed following the initial sawing mark.
From November 1999 to December 2000, madibular angle resection was performed in 5patients by this device. The difference between preoperatively planned resection width and postoperative resected bony segment was evaluated. As a result, the differences was within 2 mm. Accurate resection was performed by using this new device. And there were no complications. The mean operative time was 2 hours and 45minuites. 
In conclusion, this device is very useful in determining the accurate resection width of mandibular angle, especially in case of resection widths of both sides of mandible are different. The beginner in mandible angle resection performed that operation easily by using this device. As results, the operative time, postoperative edema and the rate of complication were decreased.