It has been my experience that many implant surgeons who place implants favor screw-retained prostheses because they can be retrieved when maintaining implants, screws and prostheses. Occlusion usually is affected by the screw access hole until the screw hole on the occlusal surface is restored.
When you retrieve an implant prosthesis, you should be able to remove the screw access hole restoration without damaging the retaining screw or the implant prosthesis itself. Restoring the implant prosthesis’ occlusal surface, however, demands a durable restoration surface, marginal integrity and an adequate marginal seal. Therefore, you need to restore the screw-retained implant screw access hole with a durable, functional and esthetic occlusal restoration that can be removed easily to retrieve the prosthesis. In this article, I present a technique for restoring screw-retained prostheses.
The opaque resin blocks the color of the metal, which would decrease the value of the translucent composite resin by making it look gray.
THE TECHNIQUE
Once you determine that the prosthesis is acceptable, the screw access hole should be restored. To facilitate retrieval of the prosthesis easily in the future, ensure that the restoration is soft enough to be removed from around the head of the screw without damaging it. Inject polyvinylsiloxane, or PVS, impression material or occlusal registration material into the access hole around the screw head and into the hex. (You can remove excess material with an end-cutting fissure bur after the material has set.) You should push on the occlusal surface of the PVS or occlusal registration material with a condenser to ensure that no air is trapped between the material and the screw. The material can be removed easily from the head of the screw and the hex.
The next step is to air-abrade the walls of the screw access hole or sandblast it with 25 to 50 micrometers of aluminum oxide for two to four seconds. The microetching creates micromechanical retention, removes surface contamination and increases the wettability of the surface. Next, apply an opaque resin to the floor and walls of the access hole and bond it, using an appropriate bonding agent. The opaque resin blocks the color of the metal, which would decrease the value of the translucent composite resin by making it look gray. Instead, the composite resin is bright and esthetically pleasing. Another benefit of using an opaque resin is that if it needs to be removed, the brighter opaque resin will alert you to where the outer border of the composite resin is and to the impending proximity of the prosthesis’ metal wall.
Finally, place a hybrid composite into the access hole and contour it with a plastic instrument that has one end for contouring and another end for condensing. Remove the excess material with an egg-shaped, 12-fluted finishing bur until the patient’s occlusion is appropriately adjusted and the occlusal anatomy is properly developed. Then polish the surface of the composite resin with the appropriate polishing points (Figure
).
