Mustafa Borga Dönmez

Screw-retained prostheses are preferred over cement-retained restorations; however, ideal placement of an implant may not be possible in some clinical situations. To avoid cement-retained crowns or screw-retained crowns with buccal screw access channel, angled screw channel abutments were introduced. These abutments allow the redirection of the screw access channel to a more ideal location and eliminates the need for intermediary abutments and cement-retained crowns to rehabilitate implants placed in unsatisfactory positions. Nevertheless, regardless of the retention type, screw loosening is a commonly encountered problem with implant-supported crowns, which might lead to mechanical and biological complications. The tightening of the screw generates a clamping force between the implant fixture and the abutment that is known as preload and when the external force exceeds the preload, mechanical complications such as instability, micro-movement, screw loosening, and screw fracture occurs. Implant-abutment connection is an essential factor that affects screw stability and internal conical implant-abutment connections are generally preferred in daily practice considering their high abutment micromovement resistance under axial and oblique forces. However, each implant-abutment connection is unique like a finger print. Currently available internal conical implant-abutment connections differ in design. This presentation elaborates the possible reasons behind the effect of implant-abutment connection on screw stability by focusing on a study on the long-term screw stability of a newly introduced implant-abutment connection (TorcFit; Straumann AG) restored with straight or angled screw channel titanium-base abutments by comparing it with the conventional implant-abutment connection of the same brand (CrossFit), in which stable removal torque values were demonstrated.

Mustafa Borga Dönmez is currently working as an Associate Professor at the Department of Prosthodontics Faculty of Dentistry at Istinye University, Turkey. He obtained his undergraduate dental degree from Hacettepe University in Turkey. He received his postgraduate degree from Selcuk University. He has been working as a Visiting Researcher at the Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine of the University of Bern, Switzerland (ZMK Bern), since 2021.