A research of periodontal stress distribution and pain threshold of the right sec-ond premolar on lower mandible

The periodontal stress distribution and pain threshold of the right second prernolar on lower mandible were studied.The results showed:（1）When the maximal vertical and lateral forces are loaded,the periodontal stress isn’t evenly distributed and the maximal value of σ1（maximum principle stress）is 4.99 × 10^-3 MPa and 4.35×10^-3 MPa. The pain threshold of the periodontium in this model is 4.35×10^-3 MPa;（2）It is very important for protection of the pulp vessle and nerve because the value of σ1 over the periappical area is very small;and（3）The rnaximal vertical bite force measured by dynamometer doesn’t represent the poten-tiality of periodontium.