This lower edentulous jaw was prepared for a bar over denture with 4 NobelBiocare MkII implants (15by3,75 mm). This picture was taken following the placement of 4 Standard Abutments.
The plastic cover screws are removed with the hex screwdriver. The tapered impression copings (single slot) are tighten by hand. The impression (with Impregum) follows. After removal of the impression tray, remove the impression coping. Replace the cover screws. Do not pour the impression. Send the impression coping to the lab along with the impression.
Great precision is not required in the first impression. The laboratory technician will fabricate a gold bar according to denture teeth position (determined by normal denture fabrication techniques). The gold bar should be segmented in sections to be indexed in the mouth.
The indexing material uses cyanoacrylate glue. It is helpful to apply vaseline on the abutments, surrounding gingiva, and mucosa. Patient and operators must wear protective glasses.
The 4 pieces are mounted in the mouth using a slotted screwdriver.
The pieces should not be in contact. To validate, insert a mylar film between each piece. If the mylar is scratched, replace the portion in a slightly different position. Retest.
Use Zapit gel. It comes as a base and an accelerator. You can either squeeze the gel out of the bottle and plastic needle dispenser or pour some gel in a Dappen dish. You can then carry the gel with an explorer. We also recommend that you place the accelerator in a Dappen dish and use a cotton pliers as a liquid carrier.
Each section is 1) dried, 2) filled with a small amount of gel.
Carry a drop of accelerator on top of the gel using the cotton pliers technique. Keep gel and accelerator off of the screw heads.
The bar is gently removed, facilitated by the vaseline application.
Four abutment analogs are screwed in place. Hold the analog instead of the bar, when you are tightening the screw .
Use die stone. The thick mix is poured into a plastic box.
The analogs are placed on the stone. Do not push the bar/analogs into stone but tap the box gently on the table top (will have a similar effect as a vibrator). The analogs will penetrate gently into the plaster . Leave 3 mm of the analogs exposed outside of the plaster. The plaster should set before being transported to the lab. This is now your master cast.
The lab will deliver the finished bar on the master cast.
The bar is tested for passive fit. We recommend that you try to tighten one screw at the time. Check for rocking movement of the bar. The final test consists of tightening all the screws together (the screws should engage freely in the threads until a sudden stop, opposed to a progressive stop with friction). Failure of this test necessitate sectioning of the bar (Step 5). We recommend that you take an intraoral picture of each abutment/bar margin if you own with an fiberoptic camera.
Bar is delivered.
Three removable plastic clips retain and support the denture
Denture inserted
General Dentist: Dr Gery Ganz,
Long Beach.
Laboratory technician: Jim Wehrman,
Nordent Lab, Long Beach.
Surgeon: Dr Bernard Gantes