Improved Access Hole Position With The Modified Core-Vent Screw Post Attachment
This maxillary cast shows six Core-Vent implant replicas. The long axis angulation of these implants presents a difficult situation in which to create the desired esthetic result.
An acrylic baseplate is fabricated using two plastic sleeves (Core-Vent #PSO) and Titanium fixation screws (Core-Vent #TSF). All undercuts are blocked out prior to the application of the clear acrylic (Orthocryl Caulk, Dentsply).
With soft bite wax added to the acrylic base, the occlusal vertical dimension is established. The screw-retained bite rim offers added stability and increased accuracy to this procedure.
The selected prosthetic teeth (Bioblend lPN, Dentsply) are set up in a Class I occlusal scheme. A duplicate clear acrylic baseplate is fabricated and used as a base for the wax setup. The setup is tried intra orally and checked for esthetics and occlusion.
An alginate impression is taken of the approved wax setup mounted to the master cast. A stone model is poured and prepared. A clear acetate vacuum-formed matrix is made. The matrix is refitted to the master cast using the palette as a guide. The diagnostic information provided by the clear matrix is crucial in determining the ultimate positions of the screw access holes.
The castable PCZ at right is short-ened to the desired height, then hol-lowed out to accommodate the screw housing (Core-Vent #TSFH). The clear matrix will show the position of the angulated screw in relationship to the available lingual anatomy.
A cross-sectional view reveals the internal screw threads, the female portion of the TSFH, and the modified PCZ. This pattern is sprued up and invested using a high heat phosphorus material (Cermagold II, Whip Mix Corp). After the recommended burnout procedure, the ring is cast in (Palliag-M, Degussa Corp.) following the manufacturer's specifications. A special casting screw is provided for use during the casting procedures to preserve the integrity of the female screw heads.
The pattern is carefully devested and the casting screw removed. Maintaining the detail and condition of the post portion of this attachment is critical in the anti-rotational design of the implant component. All areas exposed to the oral cavity are highly polished.
This is the maxillary master cast with six finished screw posts and titanium fixation screws.
The screw posts are tried in and verified for fit. Note the comparison of the soft tissue surrounding the implants with the stone reproduction in Figure 9-44.
The full intraoral view shows good screw angulation made possible by the modified screw post attachment.
A framework is designed using six castable plastic sleeves (CoreVent #PSO) and six titanium fixation screws (Core-Vent TSF). This design is to accommodate a processed acrylic resin base with acrylic resin teeth (see Chapter 3). The frame pattern is checked with the matrix, sprued up, invested, and cast in (Palliag-M, Degussa Corp.) in the recommended manner. The castability of the Core-Vent sleeves permits the use of virtually any suitable metaL The casting is devested, cleaned, and all metal finishing completed. The accuracy of fit between the framework and the master cast must be completely passive.
The metal frame is tried in the mouth and checked for proper fit.
The teeth are set in wax on the metal framework and verified again for esthetics. Setup is approved and the prosthesis is processed in Lucitone 199. Esthetics are preserved with access holes lingual to all denture teeth through the use of the modified screw post attachment.
With a thorough knowledge of available components and their use, it is possible to create an esthetic and functional prosthesis where misaligned implants are present.