Abstract: Abstract： Objective To establish 3-D finite element mode of mandibular fixed denture with loose tooth as abutment and discuss its rationality in order to provide further clinical basis and guidance. Methods By SCT scanning technology in combination with PHOTOSHOP CS2 and ANSYS11.0 software, establish composite mandibular fixed bridge model. Results While the looseness was I°, the stress of abutment teeth obviously increased, and stress concentration was observed through stress clouds; While the looseness was or , the stress also increased to different degrees but no sudden increase of stress was observed. Conclusion When the abutment teeth at the two ends of composite fixed bridge are loose, especially when single rooted teeth are loose, the range of stress is extraordinary big, and they alone are not suitable to be abutment. Multi-rooted teeth have small effect on stress distribution, so they alone can be abutment. When the abutment teeth in the middle of composite fixed bridge were loose, no matter the looseness was I° orⅡ° , they can not cause visible stress centralization, so they can be abutment.