The effects of antagonist size and shape on occlusal contact forces

Abstract

Background: Occlusion is a biomechanical phenomenon wherein teeth experience loads (forces and moments) in three dimensions. These load profiles are complex and are often simplified in laboratory experiments and numerical models with the use of, for example, a spherical antagonist. Objective: The purpose of this study was to examine the effects of antagonist shape (denture tooth vs. steel spherical balls) and sphere size (2.9 vs. 5.9 mm diameter) on occlusal contact forces in paired 1st molar/1st molar and 1st molar/sphere systems. Methods: The occlusal forces experienced by in-vitro occluding two-element (tooth/tooth and tooth/spherical indenter) systems were measured. The occlusal relationship was altered by 0.05 mm incremental shifts of the lower member into 21 positions. Results: The data indicate that the peak magnitudes and/or directions of the in-occlusal plane force components acting on the tooth were significantly different (p values from <0.001 to 0.03) with the 3 loading protocols. Conclusion: Spherical indenters cannot replicate the mechanical environment produced by natural molar crowns. Thus, spheres should not be used in studies related to the loading of the tooth support structures (periodontal ligament, root and bone), and implant bodies and attachments.