Screw or cement retention- Which is best?
Well it depends who is asking.
With enough experience and care both give exceptional results as such it comes down to personal preference which has been developed over time to play to the strengths of a particular implant system. For the less experienced, dogmatic teaching can give the impression that one is always better than the other - not the case!
"Retrievability is king", and easy to achieve with screw retention, as the whole abutment and crown whether one or two piece can be unscrewed and removed. To achieve retrievability with cement retention has been achieved with the use of tempbond - as a long term cement.
[IMAGE RIGHT] - The screw access hole can be filled so that it is imperceptible
One abutment - One time
We aspire to place an abutment once and then leave it alone. Soft tissue hemi-desmosome attachment is weak and easily broken (hence the caution to use a prob with care) But once an abutment is torqued in place it makes sense to leave it alone if the restoring protocol allows.
Early cement retained protocols carried the challenge of cement management. Tempbond allowed relatively easy retrievability as crowns collared with a siqveland matrix could be tapped off for access to the abutment beneath. Excess cement is the enemy and can have hideous consequences including implant failure or aesthetic disasters.
[IMAGE LEFT] A small amount of tempbond - used as a long term cement - allowing retrievability if necessary.
With milled abutments the better support and retention afforded make crowns cemented with tempbond more difficult to remove predictably - and is sometimes impossible!
Milled crowns mean that a replacement crown is a click away so damaging the original crown is less of a problem. So, permanent cement can be used in the knowledge that if access is required a replacement can be milled. It also provides support for softer ceramic crowns with the inherent aesthetic benefits they offer.
The aesthetic zone favours cement retention as intra-bony implant placement can be achieved without having to accommodate discreet screw access. Angle correction is now straightforward for most systems.
So, if you have lots of experience - follow your preference - both pathways are valid and challenges in approach easily managed.
[IMAGE RIGHT] The final cemented restoration with the improved aesthetics of cement retention.
A model free workflow where optical impressions and CAD/CAM production can deliver excellent cement retained restorations is less suitable for screw retained restorations where I find marginal adaptation is improved and occlusion easier to verify with a printed model.
If you have little experience and are perhaps limiting your involvement to restoring straightforward cases, I suggest that screw retention is a simpler protocol. It is what I recommend for restoring partners.
[IMAGE LEFT]- A digital impression with fixture level scan flags in place -CAD-CAM straight to fit (model free) is possible with a cement retained bridge.