Sheffield Test – The Passivity Fit Test

Sheffield Test Background

The Sheffield Test, also known as the Sheffield Fit Test or the One Screw Test, is a widely accepted method in dentistry for evaluating the passive fit of implant-supported frameworks. This standardized procedure is employed to assess whether the frameworks fit accurately on their corresponding master casts or in the patient’s mouth. The Sheffield Fit Test is applicable to all screw-retained, one-piece metal frameworks, regardless of composition, fabrication method, or implant system used. While versatile, its effectiveness, like all visual assessments, diminishes as the framework-to-implant-abutment interface becomes less visible for inspection.

The Sheffield Fit Test originated in the early 1990s at the University of Sheffield’s School of Clinical Dentistry (United Kingdom). Initially, it was designed to evaluate the fit of wax/acrylic patterns and cast frameworks on both dental models and in patients’ mouths. This test served to verify the accuracy of dental impressions and other clinical procedures.

Despite advancements in dental technology, the Sheffield test’s enduring relevance is evident in its continued use by researchers, who still refer to it by name in scientific literature. This longevity underscores its effectiveness and importance in the field of implant dentistry.

Part 1: Does a fit discrepancy exist?

Procedure:

Steps	Description
1. Initial assessment	Gently press the framework onto its abutment/implant replicas by hand.
2. Screw tightening	Lightly secure one of the two most distal abutment/implant screws using the appropriate screwdriver. Use only clinical retaining screws, not laboratory or impression coping screws, for accuracy. Avoid using a torque wrench for this test.
3. Visual inspection	Examine the entire framework under magnification (ideally 20x, but any magnification is better than the naked eye) for accurate horizontal and perpendicular fitting.
4. Fit evaluation	If the framework passes this initial test, screw tightening can begin with any screw, as it indicates a passive fit throughout.
5. Secondary check	If a slight vertical discrepancy or ‘shadow’ is observed between the framework and an implant/abutment replica far from the test screw, a second test may be necessary to confirm a satisfactory passive fit. In these cases a satisfactory passive fit may be confirmed by test 2.