Measuring Three-dimensional Displacement of Tooth-supported Rigid Fixed Bridge under Oblique Concentrated Loading using Digital Laser Speckle Photography

Objective To measure three-dimensional displacements of rigid fixed bridge under oblique concentrated loading and to analyze the effect of displacement on the stability of abutment teeth. Methods Right mandible of Beagle dog was used to establish the tooth-supported rigid fixed bridge. Digital laser speckle photography was employed to measure the three-dimensional displacements of the prosthesis under oblique concentrated loading ranging from 200 g to 3000 g. Results The displacements of prosthesis increased as the load increased. When the load was on the abutment, the buccolingual displacement of the abutment under loading was the biggest but no more than 100 μm. This was followed by mesiodistal and occlusallingual displacements. With slighter loadings, the buccolingual displacements of non-loaded abutment were greater than the mesiodistal displacements. However, as the loading increased greater mesiodistal displacements on non-loaded abutment were found compared to buccolingual displacements. When the bridge was loaded, the biggest displacements of the prosthesis were always shown on the buccolingual direction, followed by the mesiodistal direction and the occlusallingual direction. The displacements with loaded bridge were smaller than those when the load was applied on abutment. Conclusion The displacements of rigid fixed bridge change with different loading positions. This has implications on the design of prosthesis. Lateral force should be minimized and early occlusion contact should be avoided, especially on the feeble abutment. This study has developed a new method for measuring bit shift of teeth.