Crown/Prosthesis Forum & Type of Abutment

It is important for a single crown or the units of a fixed partial denture to emerge from the peri-implant mucosa with a form that replicates that of the missing natural tooth/teeth and also provides an environment for optimization of the soft tissue form. When the implant is located below the margins of the peri-implant mucosa, the crowns can be shaped so they emerge from the soft tissue with the desired diameter and circumferential form. The peri-implant mucosa will mold itself to the form created by the crown or fixed partial denture unit. If the interproximal bone is of sufficient height (5 mm apical to the proximal contact when there is thick soft tissue present and 4 mm apical to the contact when the soft tissue is thin), the soft tissue will also fill the cervical embrasure space.

When the peri-implant mucosa will not fill the cervical embrasure space, the cervical crown contours may have to be increased (greater lateral flaring of the crown) to reduce the dark cervical embrasure space. The use of gingival-colored ceramics may also be needed to close the cervical embrasure space and simulate the missing soft tissue.

When the implant is only slightly below the soft tissue margin and the tissue height is therefore minimal, the transition of the restoration from the round diameter of the implant to the form of a natural tooth is more challenging and must occur over a shorter distance, requiring a greater transitional angle (greater lateral flaring) to be developed in the cervical aspect of the crown. Another challenge related to an implant being located close to the soft tissue crest is the potential for visibility of any cervical metal present in the crown where it attaches to the implant.

In the anterior maxilla, it is often necessary to fabricate custom abutments to create an angular transition between the long axis alignment of the implant and that desired for the crown. When this need is present, it is important that the implant(s) be positioned incisocervically so a custom metal abutment can be used and it will be not visible. Alternately, ceramic abutments may be needed to provide an acceptable soft tissue color when a metal abutment would be visible through the mucosa.

The base of implant overdentures and the cervical aspect of fixed complete dentures must have forms that support the facial soft tissues and yet permit access for oral hygiene procedures.