Written by Robert A. Lowe, DDS; Charles Maragos, CDT; and Pete Hemstock Thursday, 14 February 2013 09:45
A Review of Part 1: Delivery and Recovery
In November of 2010, “A Team Approach to Implant Reconstruction” was published in Dentistry Today. In this article, a fixed/removable implant reconstruction case was highlighted, discussing the preclinical condition, treatment planning, and execution of treatment for a 76-year-old partially edentulous patient. All of the remaining maxillary teeth were given a poor to hopeless periodontal prognosis. Of the remaining mandibular teeth, only the canines were sufficiently healthy to consider retention. The treatment plan—decided upon after consultations among the periodontal specialist; the implant specialist, Mr. Pete Hemstock (Valley Dental Arts); and me (Dr. Robert Lowe)—was to have all remaining teeth extracted except teeth Nos. 22 and 27. The maxillary arch was to be restored using an implant-supported bar-retained full denture. The mandibular arch would be reconstructed using a conventional fixed bridge replacing teeth Nos. 22 to 27, and 2 independent implant-supported fixed bridges extending from teeth Nos. 19 to 21 and Nos. 28 to 30. Potential complications existed with the positions of the maxillary sinuses bilaterally, being too close to the ridge to allow for implant placement posterior to the first premolar position. In addition, the patient’s skeletal Class II jaw relationship precluded the prostheses from having incisor to incisor contact in centric relation position.
The clinical steps from both the dentist and dental laboratory team perspectives are described in detail in the November 2010 article. After failing to gain an adequately retentive result with the original maxillary overdenture prosthesis, the process of converting the original attachments to locator attachments, fabrication of an interim prosthesis for the patient to wear during the lab steps required for the conversion, and delivery of the prosthesis with the redesigned bar and attachment assembly, was discussed.
The rebuilt prosthesis performed very well clinically for a little more than one year.
Then, part 2 of the restorative saga for this patient began with the discovery that one of the implants which supported the maxillary bar had lost bony integration and failed! In this article, we will describe the clinical steps and decisions on both sides of the restorative team that were used to recover from the failure of this implant. The saying that “We learn more from our failures than from our successes” was never more true as we see in the description that follows.
Step 1: Sectioning the Maxillary Bar and Replacement of the Failed Implant
After discussion with the periodontist, the first step was to isolate the failed implant from the rest of the bar. Figure 1 shows the maxillary bar/locator assembly at the time it was originally delivered to the patient. The implant that had failed was in the tooth No. 5/6 position.
After talking with Mr. Hemstock at Valley Dental Arts, it was decided to section the bar anterior to the failed implant (Figure 2). We felt that the remaining bar/locator assembly would adequately retain the maxillary prosthesis while the patient had the failed implant recovered by the surgeon, the site bone grafted, and eventually would have a new implant(s) placed in the same area. This process would take several months. When the new implant(s) were sufficiently integrated, the plan was to take a pick-up impression with the remaining bar/locator assembly and fixture level impression copings on the new implant(s). This would be done so that a new section could be fabricated, laser-welded (LaserStar [Bego]), and soldered to close the seam of the bar in the laboratory; and the new locator(s) would be cold-cured into the denture base.
The intaglio of the denture in the bar area was hollowed out to accommodate the bar and attachment assembly (Figure 3). Figure 4 shows the sectioned bar/locator assembly in place inside the intaglio of the maxillary full denture. The remaining portion of the bar was then screwed to placed and torqued to 22 Ncm (Figure 5). The locator attachments were then placed on the bar and then picked up in the prosthesis with a cold-cure acrylic material (Quick Up [VOCO America]). Figure 6 shows the attachments cured into the denture base.
During the healing of the bone graft and subsequent placement of 2 implants, one mesial and one distal to the original failed implant site, the patient functioned well with the partial bar assembly and his original maxillary full overdenture prosthesis (Figures 7 and 8).
|Figure 1. An occlusal view of the locator/bar assembly on the master model, prior to delivery.||Figure 2. The locator/bar assembly was sectioned to remove the portion that was over the failed implant site.|
|Figure 3. The maxillary denture was hollowed out in the area of the bar to accommodate the bar/attachment assembly.||Figure 4. The sectioned bar was trial-fit into the denture to make sure sufficient space had been made.|
|Figure 5. The locator/bar assembly is shown from the occlusal view after placement.||Figure 6. Locator attachments were “cold-cured” into the denture using acrylic resin (Quick Up [VOCO America]).|
|Figure 7. A retracted view of the maxillary overdenture in place.||Figure 8. A full-smile view of the maxillary prosthesis.|
|Figure 9. An occlusal view of impression copings in place after replacement implants on the maxillary right side integrated. The implant in the tooth No. 12/13 position was not included because of the broken screw.||Figure 10. An occlusal view of the master impression and denture/bar assembly.|
When the new implants in tooth No. 5/6 position were sufficiently integrated, the plan was to take a new fixture level impression (including the new implant positions), so that a master model could be made in the dental laboratory, and the bar/locator assembly could be laser-welded back together and soldered to close the seams. Then, the new locator abutments would be cold-cured into the denture base in the manner previously described.
Step 2: A Broken Screw!
Unfortunately, it was discovered (at the impression appointment to reattach the remaining bar to the fabricated piece that attached to the new implants in the tooth No. 5/6 position) that the screw in the implant in the tooth No. 12/13 position had broken at the thread-head interface.
The patient was sent to the periodontist in an attempt to retrieve the broken screw, but he was not able to do so. At this point, a new fixture level impression was taken. It included the new implants in order to reattach the right side of the bar and to place locators on the new implants in the tooth No. 5/6 position (Figures 9 and 10). With 2 implants in that position, Mr. Hemstock and I felt there would be sufficient retention and support to use the original prosthesis while the implant in the tooth No. 11/12 position was recovered and replaced.
In order to have an interim prosthesis for the patient to wear, we used his original transitional maxillary denture and relined it with a soft denture material (Ufi-Gel [VOCO America]) (Figures 11 and 12). The patient wore the maxillary full denture with a soft liner for another several months as a new implant was placed and integrated into the alveolar bone in the tooth No. 11/12 position.
|Figure 11. A soft liner (Ufi-Gel [VOCO America]) was placed in the interim maxillary full denture to be used as a temporary appliance during replacement of the implant in the tooth No. 12/13 position.||Figure 12. A retracted view of the interim maxillary denture in place.|
|Figure 13. An occlusal view of the healing caps of the implants, after integration of the new implant in the tooth No. 12/13 position. Note the placement was mesial and palatal to the original implant position.||Figure 14. Placing the original locator/bar assembly shows that the second placement of the implant mesial and palatal to the original site did not line up with the existing bar assembly.|
|Figure 15. A new fixture level impression was taken to correct the bar assembly.||Figure 16. Removal of the impression coping screws for the anterior implants that were open tray.|
|Figure 17. The completed remade master impression.||Figure 18. The new locator/bar assembly, shown on the master model.|
|Figure 19. The locator/bar was tried-in, but did not fit passively on the implants.||Figure 20. The locator/bar assembly was sectioned and luted with pattern resin (GC America) to be corrected in the dental laboratory.|
Step 3: A New Bar/Locator Assembly
Figure 13 shows the new implant site several weeks after second stage surgery and placement of the healing abutment. The new implant had to be placed in a palatal position to the previous implant site to engage sufficient bone for support. The position of this site in relation to the original bar can be seen in Figure 14. At this point, Mr. Hemstock and I decided it would be best not to try to piece the old bar back together; a new fixture level impression was made, including all of the existing implants. The 3 replacement implants (Straumann) had closed-tray impression copings. The 2 original implants in the tooth No. 8/9 position, were micro mini implants (Biomet 3i), requiring open tray impression copings (Figure 15). Figure 16 shows removal of the screws from the section of the impression that had the open-tray impression copings. The completed master impression is seen in Figure 17. As the patient continued to wear the interim maxillary full denture with the soft liner, Mr. Hemstock (in the laboratory) constructed a new bar/locator assembly that would be retrofit into the original overdenture prosthesis (Figure 18).
Unfortunately, at the try-in appointment for the new bar assembly, it was discovered that there was yet another problem. There must have been an error in the fixture level impression. Perhaps an inaccuracy in the transfer of the closed-tray impression copings on the patient’s right side (tooth No. 5/6 position). The bar did not fit passively on all of the implants, so it had to be sectioned in the mouth (Figure 19), indexed with pattern resin (GC America) (Figure 20), and sent back to the laboratory to be laser-welded together. Figure 21 shows the laser-welded maxillary bar/locator assembly, which then fit passively on all the implants. With the number of locator attachments to retrofit back into the original prosthesis, it was decided that we would use impression copings on the locator attachments rather than attempt to cold cure them into place and risk luting the denture to the bar. The locator attachments were then processed into the maxillary overdenture using the master model in the laboratory (Figures 22 and 23) and the prosthesis was finally ready to deliver to the patient.
|Figure 21. The locator/bar assembly was laser-welded, and then fit passively on the implants.||Figure 22. The locator attachments were then processed into the denture in the laboratory using the master model.|
|Figure 23. The intaglio of the denture shows the locator attachments in place.||Figure 24. The completed maxillary overdenture.|
|Figure 25. A retracted intraoral view of the completed maxillary overdenture.||Figure 26. An occlusal view of the mandibular ceramic reconstruction 2 years postdelivery.|
|Figure 27. A “smile” view of the completed maxillary overdenture.|
Figures 24 to 27 show the completed prosthesis, opposing fixed reconstruction, and the patient’s smile. The patient was glad the whole process was finally completed! From the time of the discovery of the failure of the implant in the tooth No. 5/6 position, to the final recovery and delivery of the case, about 18 months had lapsed.
It has now been about 2 years since the completion of the case and everything is going well. Hopefully, there will not be a “Part 3” to this case!
“All’s Well That Ends Well!”
On this one case, the clinical and laboratory team experienced and dealt with many of the typical types of failures that can sometimes happen with implant-supported reconstruction cases. Any long-term success depends on the supporting elements, namely the implants. Why did that first implant fail after only one year? If the patient would have allowed the surgeon to perform bilateral sinus lifts, thus giving us the ability to place more implants in a more posterior position, would this have changed the force distribution and prevented the de-integration of the implant in the tooth No. 5/6 position, or the breaking of the screw in the tooth No. 11/12 position, that started this “roller coaster” of events happening? What about the mandibular fixed implant-supported, tooth-supported reconstruction? Would an overdenture on the mandibular arch have exerted less force on the maxillary bar than the fixed case, and have prevented an implant failure? These are some of the questions that have been asked when looking at this case in retrospect.
The experience with this case may thus alter treatment decisions for similar cases in the future, or at least allow the reconstruction team to better predict pitfalls and come up with other creative ways to avoid similar circumstances. When unexpected issues cause failure of a case, it is extremely helpful to be able to tap into the valuable resources found in a creative and knowledgeable clinical and dental laboratory team. Together, the restorative team can help identify the problems faced and to find the solutions required to succeed.
Disclosure: Dr. Lowe reports no disclosures.
Disclosure: Mr. Maragos reports no disclosures.
Disclosure: Mr. Hemstock reports no disclosures.
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