Guidelines for Problem Solving and Trouble Shooting
In working with implant-supported prostheses since 1982, many difficult and unusual problems have been encountered. The techniques that we have developed through our long-term experience can save time, experimentation, and frustration.
Even the most thorough planning and meticulous fabrication techniques can sometimes go awry. The creative technician can further develop and modify existing components and procedures to fit demanding situations. Metal frameworks can fracture or be ill-fitting. Special soldering techniques are used to correct the alignment and integrity of fit between gold cylinders and titanium abutments.
Many times extreme masticatory forces are present in patients with implants. 1 (pp. 271-2) Since proprioception is lost, it is difficult for the patient to determine their biting forces. 1 (pp. 89-97) The result is prosthetic teeth being forced away from their position on the fixed denture bridge. The maxillary anterior lingual bite plate was developed for some patients as a solution to this problem.
The inability to remove laboratory guide pins from the processed denture bridge is another problem area. A heating implement is held on the threaded part of the embedded guide pin. As heat is transmitted, the acrylic in the immediate area of the guide pin wi11 soften slightly and the guide pin can be forced through and removed (Fig. 10-19).
Pink porcelain can be used to esthetically enhance the restoration or to hide an unsightly gold cylinder. An impression can be taken at the fixture level and the diagnostic cast used to determine the correct abutment. This technique can save chairside time, laboratory procedures and the cost of incorrect abutments.
Post Soldering A Ceramo-Metal Tissue- Integrated Prosthesis
The tissue-integrated prosthesis shown does not fit after the porcelain is baked to the framework and sectioned into two pieces.
Both sections are screwed into place and a plaster matrix is taken.
Brass replicas are fastened to the gold cylinders with guide pins. The porcelain is blocked out with wax to elimin'ate contamination.
This cross-section reveals the rela-tionship of the matrix, bridge, wax block-out and brass replicas.
The yellow stone cast is used to verify the accuracy of the soldering procedure.
Four Branemark System titanium implants are used to stabilize the bridge in the investment. Special solderitrg replicas are now available.
After attaching the implants to the bridge, the matrix is used to check the fit.
After two sections are luted together, the porcelain is blocked out with wax.
High heat soldering investment (Whip Mix Corp.) is mixed according to the manufacturer's ratio and poured to form a firm base. Note how the porcelain is clean and free of any stone or investment. The model is placed in a cold burn-out oven and heated to 1,OOOoP. It is then placed in a porcelain oven and heated to 1,450oP. A high gold solder (Jelenko 615, lelenko Co.) with a melting point of 1 ,365°F is then fluxed lightly and flowed into the joint. The model is then removed from the oven and bench cooled.
After careful divesting, the solder joint is inspected. The metal is carefully polished using the protective replicas for the cylinders.
This intraoral view illustrates excellent esthetics and fit.
The maxillary anterior lingual biteplate is used when a balanced occlusion cannot be attained. The lower teeth strike the gold framework instead of the pink acrylic and/or the prosthetic teeth. This greatly reduces the possibility of acrylic fractures and the "popping off" of teeth. This gold substructure maxillary frame with lingual biteplate is ready for tooth wax-up.
This is the finished prosthesis with anterior teeth securely luted to the frame.
Because of the vertical opening, it is sometimes necessary to add pink porcelain to the prosthesis. Mixtures of different porcelain powders and modifiers are needed to attain the correct patient tissue color. 2 This gold substructure has pink opaque added to the tissue flanged area.
The finished prosthesis ready for insertion. Note the fine detail at the cemento-_namel junction.
Pink porcelain is added interprox-imally to mask the underlymg cylinders.
Sometimes small portions of pink porcelain are added to enhance the restoration esthetically.
Because overdentures are hollowed out internally, their strength diminishing, it is sometimes necessary to cast a metal backbone to prevent breakage. This lingual view shows a finished maxillary overdenture with a metal backbone incorporated, in acrylic. The underside of the frame has loops and beads to secure it to the acrylic. The tissue side of the prosthesis is all acrylic to enable the clinician to reline it as needed.
A heating implement heats the gold screw and softens the surrounding acrylic for easy removal.