[The biomechanical research on the different stress distributions between complete and defective dentition]

To evaluate the stress distribution of crowns under mastication from the biomechanical respect, and observe the physical effects on different teeth through the interproximal contacts.

A healthy adult skull with both maxilla and mandible was selected, which had normal overbite and overjet, standard occlusal relationship, and tightly contacting with interproximal teeth. After preparation, a 1mm x 1mm strain foil was bonded on every crown. In centric occlusion, 20 kg vertical load was applied on it. The stress value of crown(GPa) was detected by the YJD-17strain gauge. There were three groups: group 1 with complete dentition, group 2 with the first molar missing, and group 3 with missing of right mandibular first molar, lateral incisor and central incisor.

The stress value in complete dentition was 3.4641 in second molar, 0.5132 in second premolar, 1.0264 in canine, and 0 in others. In group 2, the stress value was 5.003 in second molar, 1.4113 in second premolar, the values of other teeth equal to that of group 1. In group 3, the stress value was 5.2603 in second molar,1.6679 in second premolar,3.2075 in canine, 0 in first premolar, respectively.

In complete dentition, the occlusal strength is distributed through the contact area between interproximal teeth, therefore, the stress value of crown is low. However, in the area near the defective dentition, it will be obviously high.