Effects of Fabrication, Finishing, and Polishing Procedures on Preload in Prostheses Using Conventional 'Gold' and Plastic Cylinders

This study reviews fundamental concepts related to the use of screws and presents data describing the effect of fabrication, finishing, and polishing procedures on as-received preload for implant cylinders. Specifically, this study measured and compared preload produced when using as-received gold cylinders (the reference or gold standard), and cast cylinders produced from premade gold and plastic cylinders in the as-cast condition and following postcast finishing and polishing manipulations. The results reveal that preload in the gold screw-gold cylinder-abutment joint can be affected by the casting process, and that the choice of cylinder type, casting alloy, investment, and finishing/polishing technique may affect the resultant preload as compared to as-received joint conditions. The data from this study indicate that when plastic patterns are used as part of the framework, finishing and polishing of implant cylinder components should provide an increased preload compared to no such manipulations. Also, if maximum preload is desired, the use of premade metal cylinders offers an advantage over plastic patterns in both preload magnitude and precision. Keywords: friction, preload, screw joints, torque