1. Name Date of Presentation
Study Club Name Clinical Implications of Screw Joint Dynamics Abutment Screw Loosening: Causes and Solutions
Name
Date of Presentation
This a “sub module” intended to be included within other presentations

2. Presentation abstract
Abutment screw loosening: Causes and solutions
Occasionally an abutment screw will become loose, causing disruption to the patients schedule and unplanned work for the clinician. Regardless of the implant platform or connection type, abutment screws can loosen over time.
The objective of this presentation is to enhance the patient experience by minimizing or eliminating abutment screw loosening through identification the most common contributors to abutment screw loosening and providing some guidance on how to resolve or (ideally) avoid these issues.
This presentation will review abutment screw loosening in a “problem – solution” format. At the end, a checklist is provided to assist the clinician in identifying potential trouble spots before abutment placement, and to help in discovering why an abutment screw has become loose.

3. Agenda
1. Common causes and solutions
2. Example cases
3. Checklist 6

4. Problem: Abutment screw becomes loose
Solution: Remove the screw and abutment and inspect carefully to determine potential source of the issue
The most common issues that contribute to screw loosening - and solutions - are detailed here
Many issues can be prevented by a quick visual inspection prior to placement Screw loosening is typically the symptom of a problem elsewhere Most common root-causes of screw loosening:
Misfit between components
Lack/change of preload on abutment screws
Occlusal Overload
The process of “root-cause-analysis” often yields a valuable learning experience
Consider use of the checklist provided to discover what may be the source of the problem
Do not simply re-tighten the abutment screw. Remove the abutment and inspect for the cause of loosening.

5. Problem: Occlusal overload
Solutions to these challenges need to be part of initial planning and represent a considerable challenge to resolve or minimize after implants are placed
In particular, be aware of
Bruxer
Poor prosthetic design
Cantilever
Excess angulation of restoration
Cantilever caused by poor implant position
Cantilever example: Single implant framework

6. Problem: Insufficient placement torque
Solution: Ensure screws are tightened to proper torque
Use the proper instrumentation
Not all screws are fastened to the same/proper torque values
Follow the published torque guidelines
Ensure instrumentation is in excellent repair
Replace any instruments that are damaged

7. Problem: Damage of implant/abutment interface during processing (1/2)
Solution: Always protect the implant/abutment interface during processing
Damage / distortion to the interface can be caused:
during handling
by forceps / hemostats
not using protection analog during processing
by contact with polishing wheel or bur
Scratches, dents or gouges
A Protection Analog should be used during all processing steps

8. Problem: Damage of implant/abutment interface during processing (2/2)
Solution: Inspect carefully, under magnification, to ensure no dents or scratches introduced during processing
Gouges
Possible use of hemostats
Excess material (2 places)
Rough surface, rounded edges
Do not attempt to fix these flaws. Start over again

9. Problem: Wrong screw type used
Solution: Verify under magnification proper screw head for the application
Using Ti abutment screw in Zi abutment (or vice-versa)
Screw head is designed for the specific component
Consult with the Product Catalog or IFU1 to confirm
Does not apply for Conical Connection
All conical connections use only the tapered head screws as shown in the rightmost image
Abutment Screw Detail for NobelReplace Tri-Channel
For titanium abutment
For zirconia abutment

10. Problem: Laboratory screw used
NobelReplace Tri-Channel
Clinical and Lab screws for Titanium abutments
Solution: Use only vendor-supplied clinical screw
Laboratory screws are not indicated for clinical use
Laboratory screws do not have the TorqTite coating
Lab Use Only
Clinical Screw with TorqTite coating1
Laboratory Screw
1. Not all Nobel Biocare Clinical Screws have the TorqTite coating.

11. Problem: Screw from another component
Solution: Use only vendor-supplied clinical screw
Screws designed for any other use must not be used (e.g. impression coping screws, guide pins, etc)

12. Problem: Clinical screw used in laboratory
NobelReplace Tri-Channel
Clinical and Lab screws for Titanium abutments
Solution: Use only new vendor-supplied clinical screw
Clinical screws must never be used in the laboratory prior to clinical use
For dentists purchasing abutment directly: the clinical screw should be removed and a laboratory screw substituted before sending the material to the dental technician
Contaminants and constant assembly in the abrasive environment of the laboratory destroys the TorqTite coating
Clinical Use Only
Clinical Screw with TorqTite coating1
Laboratory Screw
1. Not all Nobel Biocare Clinical Screws have the TorqTite coating.

13. Problem: Reusing a damaged screw
Solution: Use only new vendor-supplied clinical screw
Inspect the Clinical Screw under magnification
If any defect is noticed, replace with a new, unused Clinical Screw

14. Problem: Screw from a 3rd party vendor
Solution: Use only vendor-supplied clinical screw
“Other” vendors screw:
May not fit perfectly – likely not designed to proper tolerances and parameters
Likely not be quality tested to the same levels as Nobel Biocare components

15. Precision of fit evaluated on a high quality optical comparator
Problem: 3rd party restorative components with ‘sloppy’ tolerances (1/2)
Solution: Use only vendor-supplied abutments
Nobel Biocare Multi-unit Abutment with a “compatible” impression coping by 3rd party major implant manufacturer
Precision of fit evaluated on a high quality optical comparator

16. Optical comparator display
Problem: 3rd party restorative components with ‘sloppy’ tolerances (2/2)
Solution: Use only vendor-supplied abutments
Image detail showing 50 micron gap between Multi-unit Abutment (top) and 3rd party impression coping (bottom)
Optical comparator display

17. Damage to the underside of the lobe
Problem: Misaligned abutment (1/2) Abutment not fully seated into mating aspect of implant
Solution: Use a post placement radiograph to confirm abutment and impression coping are fully seated
When the screw was tightened, the tri-lobes rested on top of implant – not into mating channels in the implant
This misfit was likely caused by the impression coping misfitting exactly the same way
Damage to the underside of the lobe

18. Problem: Misaligned abutment (2/2) Abutment not fully seated into mating aspect of implant
Solution: Use a post placement radiograph to confirm abutment and impression coping are fully seated
It is not always easy to “feel” the abutment or impression coping drop into the implant
A gentle ‘back-and-forth’ rotation is often all that is required to resolve the problem shown
Misaligned NobelActive abutment
Properly aligned NobelActive abutment

19. Problem: Foreign material processed onto surface
Solution: Visual inspection under magnification of the abutment interface
Interface should be clean-and-smooth
Re-make the restoration – never attempt to fix by grinding or scraping
Porcelain processed onto implant/bridge interface
Porcelain processed onto implant/abutment interface

20. Problem: Grit blasting abutment/implant interface
Solution: Never grit blast, grind or polish the implant/abutment interface
Chemically Divested Notice the crisp edges and smooth surfaces
Grit Blasted
Crisp lines and smooth surfaces are destroyed

21. Fit of chemically divested GoldAdapt
Results in a machined surface which fits perfectly into the implant.
Fit 20X magnification
Fit 500X magnification
This connection is stable

22. Fit of grit blasted GoldAdapt
During normal functioning, this has a large potential to become loose.
Fit 20X magnification
Fit 500X magnification
This connection is not stable

23. This connection is stable
The importance of an unmolested implant/abutment interface surface is universal across all implants
Example: Machined Titanium Abutments, External Hex
Abutment
Implant
Implant/abutment interface, external hex Titanium Abutment
Magnified cross-section showing excellent fit of the abutment to the implant (red arrow)
This connection is stable

24. This connection is not stable
Example of an external hex abutment interface after grit blasting during processing
All critical geometry and surfaces are destroyed
Abutment
Implant
Implant/abutment interface, external hex grit blasted during processing.
Magnified cross-section showing unacceptable fit of the abutment to the implant (red arrow)
This connection is not stable

25. Agenda
1. Common causes and solutions
2. Example cases
3. Checklist 31

26. Example: Impact of a large amount of rocking when this abutment is placed onto an implant
Gouges
Possible use of hemostats
Excess material (2 places)
Rough surface, rounded edges

27. Seemingly minor damage to the cone created two primary points of contact
These defects prevented conical seal and allowed rocking 1 2
Surface damage to the cone consisting of a dimple surrounded by a raised surface. This raised surface prevents the cone from seating perfectly inside the implant cone.
Contact point 180º opposite location 1. Primary points of contact of the GoldAdapt to the implant are location 1 and 2. 1 2
Note: This abutment was also grit blasted .

28. Raised surface surrounding dimple on cone1 1
This close up shows the raised ring around the dimple. Note the raised surface is highly burnished.

29. Burnished surface 180º opposite dimple2 2
Highly burnished surface at location 2, 180º opposite location 1 and at the bottom of the cone.

30. Agenda
1. Common causes and solutions
2. Example cases
3. Checklist 37

31. Screw loosening diagnostic checklist
Clinical Screw Inspection (magnification)
Proper screw for the implant and the abutment/bar type
Screw sourced from implant vendor
Threads clean and undamaged
Screw is new and never used in dental laboratory
Restoration
Occlusal overload (e.g. bruxer or malocclusion)
Design - excess cantilever or angulation
Abutment Placement
Properly and fully engaged/seated into implant (confirm with post placement radiograph)
Placed with indicated torque
Placed with proper and undamaged instrumentation
3rd Party Components
3rd party abutment or impression components
3rd party clinical screw
Implant-abutment interface inspection (magnification)
No scratches or gouges
No excess/foreign materials
No grit blasting - Edges still 'crisp and sharp‘
No attempt was made to ‘fix’ any of the 3 problems listed above
Do not attempt to fix these implant/abutment interface flaws. Start over again

32. Thank you very much for your attention!
© 2009 Nobel Biocare Holding AG
Thank you very much for your attention!