Implant Occlusion — ORE Part 1 MCQ
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Correct answer: E — Central loading through the implant axis to minimise off-axis forces
Abutment screw loosening is driven by cyclic fluctuation of screw preload under occlusal loading. Off-axis (non-axial) forces generate bending moments on the abutment-screw junction, causing greater preload loss than purely axial loading. Evidence from in-vitro studies shows that reducing the angle of screw loading (i.e., more axial/central loading) significantly reduces loosening risk. Option E directly addresses this principle: central axial loading minimises off-axis forces and their destabilising moment effects. Option C concentrates dynamic force on the implant, amplifying preload fluctuation. Option D (canine guidance) is contraindicated—lateral forces are inherently off-axis on an implant and increase screw loosening. Option B (group function with equal contacts on the implant) still includes off-axis loading during lateral movements. Option A is impractical and biologically unfavourable. The answer reflects established implant biomechanics: axial load distribution is protective; off-axis loading is harmful.
Reference: Hotinski E, et al. Abutment screw loosening in angulation-correcting implants: An in vitro study. J Prosthet Dent. 2019;121(1):151–155. https://pubmed.ncbi.nlm.nih.gov/30006224/