Replication of the Trial Denture

The trial denture is replicated for use as a surgical template in the following manner.

FIGURE 20-2. A radiographic template is tried in the mouth to check fit and comfort. By disoccluding the template in the anterior, 3 mm of cold-cure acrylic can be added to allow the jaw to be in a resting position. Petroleum jelly is placed on the opposing dentition to ensure that the cold-cure acrylic adheres only to the template. The radiographic markers in this template are composed of amalgam and acrylic in a 1:3 ratio.

FIGURE 20-3. A, The Lang denture duplicator. The patient’s dentures (or an acceptable wax try-in) are required to fabricate a duplicate denture. B, First, the denture is seated in alginate in one half of the denture duplicator. The alginate is allowed to set. Then, alginate is placed in the other half of the duplicator, which is fully closed. C, After the alginate has set, the two halves are separated (because alginate does not stick to set alginate, the two halves can be separated easily). An accurate reproduction of the internal surface of the denture is revealed. D, The denture is removed from the set alginate. The reproduced tissue and external surfaces are clearly identified. E, Clear, cold-cure acrylic is overfilled into the concave reproduction of the external side of the denture. F, The duplicator is fully closed and locked into position. Escaping excess acrylic ensures that no voids are present in the template.

FIGURE 20-4. The pressure pot is filled with hot water, and the Lang duplicator is placed in it at 30 psi for 30 minutes to allow the acrylic to set completely.

FIGURE 20-5. A, The clear acrylic duplicate denture after removal from the duplicator. Excess flash is always present. B, Excess flash and rough spots are trimmed with an acrylic bur. C, The finished template should be free of sharp edges and have smooth flanges.

FIGURE 20-6. A, The template is tried in the mouth to ensure comfort and proper occlusion. Final adjustments often are required at this step. B, A temporary fixed prosthesis may be duplicated in a Lang duplicator to form a surgical template and CT scan template.

The clear acrylic denture fulfills its first critical function in presurgical CT scanning. Chapter 4 describes in detail the techniques for embedding a radiopaque medium into premeasured grooves; this process is essential for verifying the locations and dimensions of host sites intraoperatively (see Fig. 20-2). Adding a 3-mm occlusal run to the appliance stabilizes the jaw and provides comfort in the resting position.

After the appliance had been used for CT scanning, it can be used as a surgical template. However, an additional alteration is required. The occlusal incisal edge and lingual acrylic of all potential implant host sites must be cut away (Fig. 20-7). This allows surgical access to the bone while the template occupies its anatomic position. The radiopaque markers allow the surgeon to transfer image findings and dimensions directly to the bony host sites (see Chapter 4).

FIGURE 20-7. The template is relieved to allow access for surgical placement of implants.

Suturing completes the first stage of implant surgery. The original denture now continues its essential role as a stent and wound protector while providing the patient with cosmetic and functional benefits. It requires alteration and relining to satisfy this purpose.

In the second stage of surgery, the clear replica is used to localize the buried implants, especially if it was marked with amalgam-filled bur locator holes in the first stage.

After the healing collars or abutments have been attached, the original denture again can be adapted to serve. After the soft lining has been stripped out, it is altered to fit over the permucosal protrusions or transepithelial abutments (TEAs), where it can function through completion of the reconstruction. As an alternative, it can be trimmed back to its dentoalveolar components by grinding away the palate and flanges and then used with cement or even abutment fixation screws as a transitional prosthesis. The significance and versatility of this appliance and its clones cannot be overemphasized.

Surgical templates are necessary to position implants accurately and predictably. Two different designs of surgical templates are recommended for partially edentulous areas. The first style replicates the provisional denture restoration and is made on the corrected replicated cast. The second style uses an Omnivac template but relies on adjacent teeth and soft tissues for support and positioning. If more than two implants are planned, the surgical template that replicates the provisional prosthesis, rather than the Omnivac template, should be used (Fig. 20-8).

FIGURE 20-8. An example of a template for a partially edentulous patient. In this case, the template was fabricated from an acceptable acrylic partial denture in a manner described for complete templates. As an alternative to this procedure, a template can be fabricated based on a suitable wax-up (see Chapter 4).

A surgical guide for placement of implants can be fabricated either on a cast or using a computer-aided design/computer-aided manufacturing (CAD/CAM) system. The guide is made from the diagnostic wax-ups (model-based method) or from computerized planning of implant placement (computer-based method).

The first steps are the physical and radiologic examinations of the patient (see chapters 3 and 4). The implantologist then decides which planning method to use (model based or computer based). The fabrication company (e.g., SciCat [Sirona], Procera [Nobel Biocare], Navigator system [Biomet-3i]) provides the necessary components to create a customized surgical template. Based on the design of the surgical template, they also supply the implants and the surgical and laboratory instruments required to facilitate the operation.

Before surgery, the surgeon can have a temporary or final prosthesis fabricated that can be attached in the same session as the implant installation.

Definitions

Computer-Based Treatment Planning and Surgery

An impression should be made of both jaws, as well as a bite registration index. A stiff material should be used for the index.

For fully edentulous jaws, the bite registration should be made using the existing optimized prosthesis or, if needed, a newly produced prosthesis (i.e., the radiographic guide).

If the patient has only a few teeth in the opposing jaw and does not wear a partial prosthesis, the surgeon must make sure to fill the area where the teeth are missing with occlusion index material to make contact with the alveolar ridge. This ensures a horizontal, well-balanced bite registration. The radiographic guide is used to simulate the teeth, soft tissue surface, and edentulous space during the CT scan.

Optimal Representation of Position of Restored Teeth

The existing denture (if applicable), if it covers the buccal, lingual, and occlusal aspects and extends over the buccal and lingual soft tissues to the vestibular extension, presents an ideal setup of teeth in terms of occlusion, position, occlusal height, and lip support.

In partial and single cases, inspection windows should be made in a nonopaque material (i.e., acrylic with 25% barium sulfate).

Extend the distal borders of the duplicate denture to the retromolar area and gutta percha can also be inserted as markers.

Correct designing of the radiographic guide is a prerequisite for successful treatment, because the guide determines the final outcome of the rehabilitation.

NOTE

To fabricate a radiographic guide, the surgeon must use acrylic or a material with a similar density. If the jaw is fully edentulous, the existing optimized prosthesis or, if necessary, a new prosthesis should be used. For single and partial cases, the laboratory should be instructed to fabricate an acrylic radiographic guide.

If the prosthetic treatment plan is to place a temporary or final screw-retained or cemented prosthesis at the time of implant placement surgery, the steps of the process are as follows:

Fabrication of the Mapping Guide