Crown over Implants
While implants replace teeth, they are artificial and behave differently
from natural teeth. A quick recap will be helpful in explaining why. A
dental implant is a tooth-root replacement, to which an implant crown is
attached. The crown is the only part you see in the mouth. The implant
is placed surgically in the bone of the jaw to which it fuses in a process
called osseo-integration (“osseo” – bone; “integrate” – to join or fuse).
A great deal of thought, research and ingenuity has gone into dental
implant tooth-replacement systems to make them as fail-safe as possible.
Screws facilitate the attachment of the implant crowns to the implants. Implants
must be strategically placed to allow implant crowns to connect to them, so that
the crowns emerge through the gum tissues in exactly the right direction. An
adjoining support structure called an “abutment” is often used to allow for this
transition and connection.
Like Legos, implant components are designed to disassemble. Screw-retained
implant crowns are more easily maintained; they allow for retention — keeping
abutments and implant crowns in place, and retrievability — allowing the implant-
crown components to be more easily removed, repaired or replaced, without
damaging the implant or the restoration. While a successful dental implant can
last a lifetime, most crowns do not. They may need to be replaced or repaired
periodically, and this is much easier to do if they are attached with screws.
Loosening of the screw that attaches the restoration to the implant occasionally
happens. Retightening or replacing the screw when the restoration is screw-
retained is a simple and predictable procedure. This cannot be said for cemented
restorations. Cemented crowns can be difficult to remove and, in the worst
case, a screw access hole may have to be put in to remove the abutment and
crown from the implant. Creating a screw access hole in the back teeth is not
a cosmetic problem but for the front teeth, creating the screw access hole may
affect the crown’s appearance. It is difficult to know where the screw exit is
located and often crowns removed in this fashion have to be remade. A weaker
cement can be used to facilitate removal but this can lead to an insecurely
attached crown falling off the abutment during use.