Screw retained or cement retained crowns?
We know that the restorative abutments in implant dentistry attach the crown, bridge, or over-denture to the implant, but how is the attachment made? A crown or bridge may be cemented onto an abutment or it may be screwed on. But why the difference and which is better?
An abutment which has had to be angled, and therefore does not have its axis coincident with that of the implant, cannot be screw retained if the screw hole is to pass through the occlusal surface of posterior teeth or lingual/palatal to the incisal edge of anterior teeth.
In these cases the crown would have to be cemented onto the abutment. The advantages of this procedure include:
• Complete integrity of the porcelain of the crown
• No compromise of aesthetics of the crown
• Anteriorly the crown can be made less bulky.
If a single implant retained crown is to be screw retained, the screw must pass through the occlusal surface of the crown in posterior teeth and just palatal or lingual to the incisal edge of anterior teeth. This is possible if the abutment axis and the implant axis are coincident.
Advantages of this method include:
• The crown may be easily removed from the abutment
• There is no cement lute to retrieve sub gingivally
• The accuracy of fit of crown to abutment is greater.