In this corner, we have implant crowns that have been cemented to an abutment. In the other corner, we have implant crowns that rely on an abutment screw or prosthetic screw for retention. Okay, I want a good, clean fight. No hits below the belt. Ding!
Porcelain fracture, hygienic maintenance, dentistry on adjacent teeth… there are several reasons why you might want to temporarily remove an implant crown. If you have an access hole to the prosthetic or abutment screw, then retrievability is a piece of cake. Some cements on the market claim to be made specifically for implant restorations and will be retrievable. But if a cement allows a crown to be retrievable, doesn’t that also mean that it’s less retentive and could lead to unwanted exfoliation? I think it’s safe to say that the retrievability of cemented restorations is less predictable than screw-retention. This is especially true as we increase the number of abutments. A multi-unit restoration that is cemented will be even more a challenge to predictably remove.
Round 2: Kindness to peri-implant tissues
A screw-retained crown can be removed periodically for hygiene maintenance. As we’ve already established, a cement-retained crown may be removed, but that can be unreliable. But there’s more! Whenever we cement a crown on an implant, we risk extruding excess cement into the sulcus. This can be very damaging to the peri-implant tissues if it is not completely removed. The literature has shown that subgingival cement around an implant can lead to peri-implant mucositis and peri-implantitis. There are techniques in journals detailing how to reduce sub-gingival cement during cementation, but it’s still a risk.
Round 3: Cost
A cement-retained crown can typically be made using a pre-fabricated abutment that has been prepared, similar to regular crown and bridge procedures. A screw-retained crown, however, typically requires a custom component to be waxed and cast. Not only are the custom components more expensive than their stock counterparts, but more lab work is required which drives up the cost.
Round 4: Ease of use
The chairside and laboratory procedures for making a cement-retained implant restoration are fairly similar to that of regular crown and bridge on natural teeth. Fabricating a screw-retained crown isn’t that much more challenging, but there can be issues with their insertion, as discussed in this article here. The real challenge comes for multiple-unit restorations. While cement-retained restorations on multiple abutments is still fairly similar to routine bridge procedures, we will require extra steps for a screw-retained restorations to ensure that we have passive fit in the framework. For more discussion on passive fit, check out this article here.
Round 5: Ability to handle angled implants
Screw access holes cannot be placed on the facial or incisal contours of implant crowns for esthetic reasons. If the angulation of the implant is off, then we will need an angled, screw-retained abutment and a gold cylinder to cast the crown to the abutment. Unfortunately, this raises the cost of the case. Also, the abutment will also have a few millimeters of height to accommodate both an abutment screw and a prosthetic screw. We may have an ugly metal color peeking up above the gingiva, depending upon the depth of the off-angle implant. If we are relying on cement to retain the crown, then we’re going to have an easier time. Stock angled abutments can correct the problem simply. We could also rely on a custom abutment to cast the component we need, then make a crown to cement to that.
Screw-retained: 2 Cement-retained: 3
Final judgment: Tie, sort of…
My personal preference is to utilize screw-retention whenever possible. Although cement-retention offers some distinct advantages, I personally believe that retrievability and kindness to peri-implant tissues are massive benefits that outweigh the other factors most of the time.
When do I use cement-retention? A single-unit crown that needs an angle correction. I’ll also choose this option for a single-unit crown for a patient who is looking to save money on the case.