Hi everyone and welcome back to another blog post. Today we will be discussing cement versus screw retention, a hot topic that has gone back and forth in implant dentistry.
In my practice, I prefer to use screw retention in most cases of single units and use a custom abutment to control the emergence profile that we have created or customized as seen in our previous blog posts (LINK HERE)
Although ti-bases can be commonly used instead of a custom abutment, I believe that in the posterior zone of the mouth, they are often too small to withstand the occlusion and stress of the area. Cost factors often limit the use of custom abutments for many practitioners although I do believe that custom abutments are better in the long term.
The picture below shows a classic fracture of ti-bases , although the crowns are screw retained, the short height of ti-bases and unsupported zirconia can shear off.
So should you cement or screw retain your cases? well i think it DEPENDS ! for more than a single unit, the passivity of case can be more difficult to achieve. This is where I believe the use of custom abutments shines. Implants have an internal connection that allows for what we call an anti-rotation feature of the crown, this also takes the pressure off the screw only to hold the crown in the right alignment.
By using a combination of custom abutments and cement retention we can get the best of both worlds. In essence, custom abutments are placed on to the implants. The bridge is then placed over top with screw channels if we ever wish to access the screw channels later. The cement space ensures passivity of bridge over the custom abutments.
In the photo above, you can see that one custom abutment is pre-bonded. This custom abutment can be either hexed or non hexed, the other abutment will be placed intraorally and splinted restoration to go over top. Please ensure that you are relieving the area of excess cement by making a duplicate of the crown interior with PVS to pump excess cement extra-orally prior to intra-oral cementation (see this LINK for explanation) The use of the custom abutment will also ensure that your cement does not get subgingivally into the implant connection which is another reason why I prefer them over a small ti-base.
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