Influence of occlusion on posterior cantilevers

The incorporation of posterior two-unit cantilevers in fixed prosthodontics is generally discouraged because of the assumption that large posterior chewing and biting forces might jeopardize the prosthesis and the abutment teeth. This investigation was performed to study (1) the distribution of chewing and closing forces in dentitions with cross-arch bilateral posterior two-unit cantilever fixed partial dentures and (2) the influence of different occlusal arrangements on the magnitude of these forces along the cantilever segments. Six patients were included in the study. Axially directed closing and chewing forces were measured with miniature transducers bilaterally mounted in pontic units anteriorly and in each of the four cantilever units. In ideal occlusion, occlusal forces decreased considerably along the cantilever segments in the distal direction. Infraoccluding the distal cantilever unit by 80 microns had little influence on the magnitude of the initially small local force in this region, whereas an 80 microns high primary occlusal contact considerably increased the local force over the distal cantilever unit. The clinical implications of the results are discussed.