CHAPTER 21 Provisional Prostheses
In the cascade of therapeutic events surrounding implant placement, the patient requires a provisional or interim prosthesis at two stages: during the integration period after first-stage surgery and after placement of the healing collars and abutments.
Several significant factors must be considered with regard to a provisional prosthesis. Acceptable and believable esthetics are required at every stage in oral reconstruction. In addition, sound prosthetic principles must be observed. Well-balanced occlusion and correct centric occlusion and vertical dimension are necessary, as is built-in protection for implant areas during the healing period. If natural teeth are to be part of the final restoration, they should be used for a temporary fixed prosthesis, which spares the gingival tissues overlying the implants. If a fixed prosthesis cannot be made, a tissue-borne, removable prosthesis must be constructed that is broad based enough to distribute forces evenly. Sound measures incorporate soft relining material (e.g., Coe-Soft, Viscogel, PermaSoft), which is frequently changed; careful examination of the tissues overlying the operative sites to detect early signs of pressure; and in maxillae, full palatal coverage, even though many patients do not care for this feature.
The patient usually has a complete denture that has been used for the jaw requiring treatment. Chapter 20 describes the preparation of a new denture and a replicated clear template, which subsequently serve as radiographic indicators for computed tomography (CT) scans, a surgical template, and an interim prosthesis. These prostheses must be made with unfailing attentiveness to classic prosthetic principles. Vertical dimension, centric occlusion, incisal length, free-way space, tooth position and angulation, and patient-approved cosmetics must be satisfied. Except for retention, the final implant-borne prosthesis can never be better than the initial one, the characteristics of which govern implant locations and emergence angles.
After implant surgery has been completed and hemostasis has been ensured, a large, round, acrylic bur is used to aggressively ream out the tissue-borne surface of the denture to approximate the implant sites. The flange linings, as well as the ridge crest, are managed in this fashion so that when the denture is seated postoperatively, no rocking or instability exists. Relief of the acrylic must take into consideration the possible added bulk of bone created by expansion techniques or graft materials, the protrusion of healing screw heads (especially for external hex implants), the increased dimension caused by a bulky suture line (i.e., mattress closures), and edema. Use of the duplicate, clear, diagnostic, plastic base plate is beneficial for this critical step if it is ground until no surgical site mucosal blanching is noted. The correction experience then is simplified while the grinding in the interim denture is replicated.
Sufficient overcorrection is made to allow for a several-millimeter thickness of soft lining material. The dental surgeon then dries, lines, and seats the denture and closes the patient’s mouth into centric position. Gentle muscle molding is performed, and the excess soft material is trimmed with a Bard-Parker (BP) No. 11 blade in a scalpel handle. Sharp shears are used to round the borders carefully to eliminate irritating irregularities.
If vascular oozing continues, hemostasis can be facilitated by adding a 50/50 mix of denture adhesive and ferric chloride powders; the mix is sprinkled onto the moistened lining with a salt shaker reserved for this use. Additional retention accompanies the rapid coagulation.
Its progenitor, the surgical template (which should have been retained), is brought to the host area. With the assistance of the radiopaque markers and carefully made mapping notes, each implant, although not visible through the mucosa, can be located (see Chapter 9).
After the healing collars or abutments have been placed, the surgeon turns to the acrylic routing burs, this time to make deeper but more discreet modifications designed to accommodate the transepithelial abutments (TEAs) in a trauma-sparing environment.
The exact locations in contact can be revealed by touching the dried occlusal surfaces of the abutments or collars with pressure indicator paste (PIP) and placing the denture, now relieved of its soft lining, against them (Fig. 21-1). Concentration on eliminating these areas leads to a prosthesis that is totally relieved of directing pressure to the implants. Again, a soft lining of choice is placed. Definitive prosthetic measures are completed while this removable interim denture serves in its classically versatile manner.
FIGURE 21-1. A, The first step in adapting a transitional denture to accommodate newly placed healing collars is to outline the collars with a Thompson marking stick or indelible pencil. B, After the denture has been seated and removed, the markings outlining each implant are transferred to its tissue-borne surface. C, After the denture base material has been reamed aggressively at the marking sites, the denture is relined with Coe-Comfort or TruSoft.
At second-stage surgery, the dentist and patient may want to substitute a fixed interim prosthesis for the removable one. This decision is based on the same principles that govern the design of fixed prostheses (see Chapter 24). The following section presents advice on preparing such devices and may be followed with essentially no modifications.
Implant-borne restorations range from single tooth (see Chapter 23) to more sophisticated, complex implant/tooth designs. The provisional prostheses may be removable or fixed, but they always must respect the recently submerged implants.
If a fixed provisional prosthesis is urgently needed, even when few or no potential abutments are available, the surgeon may plan to add some strategically placed implants at the time of first-stage surgery, in addition to those inserted for therapeutic use. Regions such as the tuberosities, pterygoid plates, or interimplant spaces may be suitable for placement of regular implants or mini-implants (see chapters 9 and 19). Although no significant expectations should be held for their long-range prognosis, some mini-implants succeed at osseointegration and may be kept for incorporation into the final prosthesis. Those that do not, because of mobility or bone loss or because they are not required for final superstructure stabilization because of location or angulation, can be shaved level to the gingivae or must be removed. Periodic radiographic and clinical observation of these interim implants is important, because peri-implant disease, if present, can affect adjacent teeth and implants. In such cases, immediate removal and repair are indicated (see Chapter 24).
The patient may have recently lost an incisor (or another esthetically critical tooth) as a result of trauma. Gingival tissues and bone may be intact or virtually so. In such cases, a temporary prosthesis should be supplied immediately. The following are possible surgical alternatives.
As a simple alternative, the fractured crown of the tooth can be bonded, as long as the fracture is below the level of the cementoenamel junction (CEJ), or an esthetically acceptable acrylic denture tooth can be bonded to the adjacent proximal enamel surfaces. If occlusal forces appear threatening, an easily fabricated, all-acrylic, Maryland-type bridge may be prepared chair side (strengthene/>