Bench Mastery: Kahng on an ideal implant bridge [VIDEO]

August 13, 2014

Our case study patient involves a 50-year-old woman whose case required screw-retained implants to create the most functional and esthetically pleasing implant bridge. Often clinicians will ask about procedure for a case of this nature because they would like to better understand protocol.

Our case study patient involves a 50-year-old woman whose case required screw-retained implants to create the most functional and esthetically pleasing implant bridge. Often clinicians will ask about procedure for a case of this nature because they would like to better understand protocol.

In my experience, an open tray impression is preferred from the laboratory’s side as the results are much more accurate. After the lab receives the open tray impression, they will pour up the impression and fabricate a bite block to get a correct bite record.

After the lab receives the bite block and set the teeth, they will then put in the temporary abutment with jig then light cure it by engaging Primotec gel. The case is then sent back to the clinician.

Laboratory Procedure

Check out this video with figures from the case study ...

01 Fig. 1 shows the placement of the five implants in the patient’s mouth prior to taking the impression with open tray (fig. 2).

02 In the mouth, the jig was tried in to check for rocking (Fig. 3). During the tooth set-up, the denture teeth were tried in with the bite block (Fig 4). At this time, it was noted that the No. 11 access hole was too far out facially, so it was trimmed down and another created. Because it was canted, the correction was made to the left. Central No. 9 had a good incisal edge but No. 8 was longer than the temporary. The size, horizontal and vertical lines, color and pink color were all checked and matched. This was good information to keep in mind for the final restorations.

03 During the wax try-in stage, the temporary was scanned to set the access holes for the five implants (Fig. 5). The entire design was finalized during this scanning with the Amann Girrbach Map 400 scanner (Fig. 6).

04 The denture teeth were tried-in the patient’s mouth to check for her opinion. She was happy with the results, so the scan was copied with a white zirconia block (Fig. 7).

05 It was mirrored exactly and then taken out and ground with a carbide burr 1 mm down. The restorations were fully contoured and the facial trimmed. The porcelain created esthetic and natural-looking restorations. The molars were sized correctly and only needed staining.

06 Next, I completely ground the upper restorations in this mirrored image before sintering. Proper grinding is more difficult to accomplish before sintering (Fig. 8).  

07 The image we see here was taken from an upside down angle-flipped over 180° (Fig 9). This angle shows the access hole underneath the restoration. The zirconia I used is pre-shaded but I added liquid in A1 color.

Related technique: How to efficiently match color

08 Tooth No. 10 was a titanium-based restoration that I cut back with scissors to make sure the zirconia abutment would fit the patient’s mouth properly.

09 After cutting, I placed the restoration back on the titanium-based implant site (Fig 10). In Figures 11 and 12 the titanium base was fit to the zirconia frame base and screwed down to the model.

10 Before firing (Fig. 13), I internally stained the restorations to create a life-like appearance. Restoration No. 11’s zirconia coping was created with two pieces to cover the access hole for esthetic purposes. The color-base used was A1 with enamel applied, and the build-up porcelain used was GC Initial GU pink with overlay enamel color (Fig. 14).

11 The second time bake was then activated at 810°C with a two-minute cooling cycle (Fig. 15). The next image demonstrates the after-firing stage, before cool down (Fig. 16).

12 Covering the access hole is another zirconia coping-made up of two pieces-for No.11, with build-up for tooth No. 11 as a continued process (Fig. 17). Next is a mirrored arch view shown before the zirconium base was placed (Fig. 18). The next mirrored image shows the finished access hole for No. 11, with a porcelain crown to be cemented in the patient’s mouth to show the two-piece image (Fig. 19). Next we see the mirrored, final image (Fig. 20).

Conclusion
This case was created using the All-on-4 technique. A denture was fabricated, with zirconia fused to porcelain. The All-on-4 Hybrid bridge used all zirconia, but there are many available options for a technician to choose from. The decision depends on the implant company and the patient’s particular situation. From the lab’s standpoint, technicians must have knowledge and feel good about the results they think they will achieve with material choice. Bone density and overall health also have to be considered when we are discussing and planning for five implants. 

This article originally appeared in the January 2014 issue of Dental Lab Products. To learn more about great products, click here to subscribe to DLP's newsletter.