When restoring an edentulous arch with a fixed implant prosthesis, the tissue, or intaglio, surface is an important but often overlooked aspect of prosthetic design. The contours of this surface can affect patient comfort, ease of cleaning, support for the facial structures, and the esthetics of the restoration. By understanding the characteristics of each surface type and their clinical applications, along with the overall advantages of a convex intaglio surface, clinicians can treatment plan and restore full-arch implant cases in a manner that will produce the best result possible. Although every case is unique and should be treated accordingly, here are some general concepts of intaglio surface design.
The intaglio surface of a prosthesis is based on the individual patient’s anatomy and can have areas described as convex or concave. These design characteristics are not mutually exclusive, as many generally convex surfaces will contain concavities and vice versa. Clinical circumstances such as the shape of the edentulous ridge, the positioning of the implants, and the esthetic demands of the case must be considered when determining the optimal intaglio surface design of the full-arch restoration. In order to achieve the best contours possible, the clinician should also consider altering the patient’s soft-tissue anatomy.
A convex intaglio surface design is ideal, as it minimizes recesses where plaque, food, calculus and debris can accumulate, simplifying the patient’s hygiene (Fig. 1). Further, a convex interior structure facilitates a narrow facial-lingual width for the full-arch restoration, which offers esthetic advantages while creating space for oral structures. This also allows for a smaller contact area between the intaglio surface and the soft tissue, and results in a prosthetic design that minimizes flanges. Intaglio surfaces with convex and ovate designs create a naturally cleansing prosthesis and minimize plaque and debris retention.
Intaglio surfaces with convex and ovate designs create a naturally cleansing prosthesis.
While a convex intaglio surface has many advantages, practitioners will encounter situations in which patient anatomy requires a concave structure. In some cases, flanges must be incorporated into the prosthesis design in order to establish proper lip support or replace lost bone and soft tissue. This can at times be avoided by depending on the prosthetic teeth for lip support; but when the patient is missing a substantial amount of bone, it can be difficult or impossible to avoid extending the flanges, resulting in a concave design. In these situations, it is still important to minimize the occurrence of food traps by ensuring the intaglio surface abuts the soft tissue properly. With this design, it should also be noted that the patient’s awareness of oral hygiene must be at a high level and the dentist’s responsibility for follow-up treatment is considerable.
For the reasons stated above, and barring patient anatomy that dictates otherwise, a convex intaglio surface is the default design for the BruxZir® Full-Arch Implant Prosthesis.
The contours of the edentulous arch must be evaluated to determine the proper intaglio surface design. When the ridge and tissue surface are relatively flat, a convex design can be established with relative ease (Figs. 2a–2d). When the ridge structure is more rounded, it can be difficult to achieve a convex intaglio surface. In some situations, the shape of the arch allows for a convex interior intaglio surface, but with a concave design at the outer edges in order to create a proper transition between the prosthesis and soft tissue (Figs. 3a–3d).
To optimize intaglio surface design, it should be included as part of the restorative-driven treatment plan. For cases in which an immediate fixed denture is being delivered, ovate pontics can be added to the intaglio surface of the temporary appliance, which contours the soft tissue in preparation for the final implant prosthesis. This helps create concavities in the soft tissue during the healing phase, making it easier to establish a convex intaglio surface in the final restoration. When converting a complete denture into a fixed provisional restoration, self-curing acrylic or composite can be added to the intaglio surface of the immediate fixed denture, checked for a proper fit, and adjusted as needed (Fig. 4).
Whether the implants are being immediately loaded or a delayed protocol is being followed, the intaglio surface should be considered when the restorative phase of treatment begins. For example, when completing the prescription for the full-arch implant restoration, instructions can be provided to apically extend the intaglio surface 0.5 mm into the soft-tissue surface represented on the master cast. This design slightly compresses the soft tissue and creates a seal, preventing gaps where bacteria, food particles and debris can be trapped under the restoration (Figs. 5a–5d).
The intaglio surface should be closely evaluated during the wax setup try-in. One advantage of the BruxZir Full-Arch Implant Prosthesis is that the final restoration is an exact replica of the doctor-approved design (Figs. 6a–6e). This provides the opportunity to build out the intaglio surface at the try-in appointment. The intaglio surface design is then verified with the milled provisional prosthesis, which is worn for a trial period, allowing the patient to confirm comfort, esthetics and ease of cleaning. This provisional prosthesis can also be adjusted to help contour the patient’s existing anatomy to receive a properly contoured final prosthesis. The confirmed design is ultimately copy-milled in the form of the monolithic zirconia restoration.
In order to create a seal and avoid food traps, there should be contact between the gingival and intaglio surfaces.
After trying in the wax setup or milled provisional prosthesis to ensure it seats completely, the entire intaglio surface should be inspected to determine whether it is touching the soft tissue. In order to create a seal and avoid food traps, there should be contact between the gingival and intaglio surfaces. Mild tissue blanching is acceptable at the discretion of the clinician. Material should be added to any gaps between the intaglio surface and soft tissue, and removed from areas that impinge on the soft tissue. The clinician and the patient should be able to thread and pass floss underneath the prosthesis and clean between the intaglio surface and the soft tissue.