Restorative Phases: Prosthetic Design, Occlusion, and Biomechanics
Framework
Restorative questions center on prosthetic design decisions: screw-retained vs cement-retained, emergence profile, platform switching, abutment selection, impression techniques (open vs closed tray, digital scanning), and provisionalization. Understand when angulated screw channels are useful and the trade-offs of cement (retrievability, excess cement risk) versus screw retention (passive fit, access hole position).
Occlusion and biomechanics
Know occlusal scheme principles for single crowns, fixed partial dentures, and full-arch prostheses: light centric contacts, freedom in excursive movements, avoiding cantilevers where possible, and considering implant-protective occlusion (reduced occlusal contact, narrower occlusal tables). Cantilever length, crown-to-implant ratio, and parafunction are key risk factors for mechanical complications (screw loosening, fracture, porcelain chipping).
Traps
Frequent traps: assuming cement-retained restorations are always easier to clean (residual cement is a peri-implantitis risk); ignoring the effect of angulation on screw access; or attributing prosthetic failure to material when occlusion or parafunction is the driver. Another common error is confusing impression accuracy issues with fit problems caused by misfit at the implant-abutment interface.
Rule of thumb
Design the occlusion before choosing the material. If a cantilever is unavoidable, keep it short and reduce contacts. Example: a single posterior implant crown in a bruxer - use a screw-retained, monolithic design with light centric contacts and no working-side interference to reduce mechanical risk.
Key concepts
Screw vs cement retention, emergence profile, impression techniques, occlusal scheme, cantilever and crown-to-implant ratio, mechanical complication risk.