[The effect of occlusal force on the formation of experimental cervical wedge-shaped defects on human teeth]

Nine pairs of premolar from 7 patients were divided into three groups according to different occlusal forces. Every tooth was tested with pH5 or pH7 water bath by an electric toothbrushing machine and an electric occlusal force fatigue machine alternatively. Only the buccal surface of every tooth suffered from brushing test. There were 600 000 strokes of occlusal force fatigue test and/or 800 000 cycles of cross-brushing test for every tooth throughout the experiment with 4 intervals. During every interval, the depth at the profile of the cervical defect on each replica of tested tooth was measured and the shape of every defect was recorded with a computerized Seescan image analysis system. The findings suggested that the occlusal force played an important role in the formation of experimental cervical wedge-shaped defects. Occlusal force alone could produce cervical tooth defect in very slow rate. When the occlusal force associated with acid erosion and tooth-brushing abrasion, the depth of cervical defect increased significantly and the wedge-shaped defects were formed.