The clinical implication of the biologic width is that there is typically more initial bone loss around submerged implants than around non-submerged implants. It appears that bone levels are equally stable in both implant types. There is usually a greater distance from the implant to the gingival margin with submerged implants than with non-submerged implants, so it is easier to create the desired emergence profile for the final restoration. A subsidiary, there is a greater risk in the aesthetic zone that a non-submerged implant will become visible if there is any supporting tissue loss after implant placement.
The latest change of the implant assembly has been favored to protect the initial crestal bone loss that is seen at the implant–abutment interface when the implant is placed at or below the bone crest. By placing an abutment of smaller diameter onto the implant platform, the dental implant–abutment interface is moved inward from the implant shoulder. Hence, the microgap-induced inflammation, described above under “Biologic width,” is further away from the crestal bone. For instance platform switching is shown radiographically. This so-called platform switching may better maintain bone and soft tissue levels around the implant. Platform switching may be particularly beneficial in the aesthetic zone where soft tissue preservation is critical.
Comparison of cement and screws as retainers for prosthese
Both cement-retained and screw-retained prostheses have been approved in clinical studies, and each type of retention has particular pros and cons. Historically, screw-retained prostheses were widely used on dental implants because the restorations could be retrieved for judgment of the underlying implants and repair of any possible complications. Cemented restorations are now widely used as they allow a more aesthetic restoration to be created. While they are not as readily retrieved as a screw-retained prosthesis, cementing restorations with provisional cement allows a degree of retrievability. There is some evidence that cement-retained fixed prostheses have fewer prosthodontic complications after delivery. It is generally simpler to control a misaligned dental implant with a cemented restoration. In the case of screw-retained restorations, if the implant is misaligned, the screw access hole may be in a variety of locations. A misaligned access hole may perforate the labial surface of the restoration or create an abnormally shaped cingulum area. This may lead to aesthetic or phonetic problems. Similarly, on a posterior tooth, the access hole may obliterate much of the occlusal anatomy. With a screw-retained prosthesis, once the retaining screw has been tightened, the access hole is filled with a resin material. During function, this material wears and stains, and periodically needs replacement. The screw access hole may represent 50% or more of the occlusal surface of a posterior tooth, so the correct occlusal contacts must be built into the resin restoration chairside.