Verification Index Fabrication
Inaccuracies can be introduced during the making of the impression, attachment of the analogs to the impression copings, and pouring of the cast. These inaccuracies cause misfit and lead to non-passive castings.26 Passively fitting implant prosthesis can only be generated on a cast with verified implant positions.27-29 It is recommended to use a verification index for verifying the implant positions on the cast.30-32 A verification of the master cast prior to the framework fabrication minimizes the possibility of having to remake the framework. Verification of the master cast is a critical step in prosthesis fabrication and it aids in decreasing stress, dissatisfaction, and treatment costs.
Fabricating an all-resin verification index may give the clinician a false-positive result owing to the flexibility of the resin material. A rigid material and non-engaging copings (false-positive results may be achieved with engaging copings) should be used for the fabrication of the verification index. Verification indices may be fabricated using a thick metal wire (as thick as a coat hanger wire) and minimal auto polymerizing resin material (DuraLay, Reliance) (with minimum polymerization shrinkage) to join the wire segments.26 The verification index is first tested on the cast with one screw test (Sheffield test).
The maxillary healing abutments and the mandibular healing caps are removed and placed in labeled containers. The verification index is tested in the mouth with the one screw test (Figure 9). A single screw is tightened, and the seating of all the other copings is noted. This process is repeated for all the implants. A panoramic/periapical radiograph is taken to verify complete seating of the verification index with one screw test when the junction of the coping and the implant platform is subgingival. When the verification index does not seat on the other implants with one screw tightened, it indicates that the cast is inaccurate. When the cast is inaccurate, the impression needs to be remade and the cast would need to be reverified.
Fabrication of Trial Denture Base and Wax Occlusal Rims and Registering the Jaw Relation Records
Trial denture base (Triad, Dentsply Prosthetics) and wax occlusal rim are fabricated for the mandibular abutment level cast. The healing abutments attached to the maxillary implants in the mouth are removed and are attached to the implant analogs on the maxillary cast and the trial denture base is fabricated over the healing abutments. This helps in achieving improved stability of the maxillary trial denture base while registering the interocclusal records.
The healing abutments (retrieved from the laboratory) are reattached to the maxillary implants in the mouth. Using standard complete denture clinical methods for assessing esthetics, phonetics, and biomechanical dictates of appropriate denture tooth position, the maxillary wax occlusion rim is appropriately adjusted clinically. The adjusted wax occlusal rim served as a guide for setting the prosthetic teeth accurately. Maxillary anterior teeth are set chairside and evaluated for esthetics and phonetics at the same appointment.33-38 This procedure is time-consuming, however, it precludes the need for redoing the wax try-in procedures associated with the improper setting of anterior maxillary teeth. Preview shell teeth (Nobilium) may be waxed to the maxillary occlusal rim and utilized for evaluating esthetics and phonetics.
The mandibular wax occlusal rim is adjusted to establish the optimal occlusal vertical dimension (OVD). The centric relation record is registered at the established OVD with a VPS bite registration paste (Regisil, Dentsply Caulk) (Figure 10). Next, a face bow record and a protrusive record (to set the articulator’s condylar elements, to achieve balanced occlusion) are registered. The casts, trail denture bases, and the interocclusal records are sent to the laboratory for mounting of the casts in the articulator and setting the prosthetic teeth.