Inheriting an Implant Case: A Cautionary Tale

Marvin A. Fier, DDS
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The TV show Strange Inheritance (Fox Business Channel) deals with stories about unusual inheritances and how the beneficiaries handle the bequests. This article is about an implant-supported denture case that I inherited from another dental office where a patient had previously sought care. It had many challenges and did not work out the way that we had hoped it would. I am sharing this experience with Dentistry Today readers so that other clinicians can be aware of, and avoid, the pitfalls that I encountered. 

CASE REPORT
The periodontist who initially treated the patient called and asked if I would take this case over. The plan was to make the patient a full overdenture, supported by 4 implants. The denture was supposed to have an open palate, which the patient was very happy about. The patient’s general dentist made a full upper immediate denture for her to wear during the healing phase. At some point, the dentist told the periodontist to find someone to take over the case because it was too complicated for him. I agreed to see the patient and requested additional information from the periodontist.

Notes from the Periodontist
The patient presented with 7 remaining teeth in her maxillary arch, all with a fair-to-poor prognosis. The alveolar ridge was significantly atrophied and labially flared. An i-CAT scan (Imaging Sciences International) using SimPlant Pro Crystal software (Materialise Dental) was done. Less than 1.0 mm of bone beyond the premolar region remained below the maxillary sinuses bilaterally. Several treatment plan options were discussed with the patient. A full removable overdenture using 4 implants for support with ball attachments was the final plan. All remaining teeth were to be extracted.

Sinus and onlay bone grafting using extra- and intraoral donor sites was presented to the patient as necessary in order to obtain ideal implant positions and allow the use of larger (stronger) implants. These ideas were rejected by the patient due to the high complication rates, costs, and discomfort. Instead, bone grafting using granular material and collagen membranes was employed. The limitations of this technique were made clear to the patient. She was informed that the prognosis for the implants was less than ideal due to the existing bone morphology, along with the unpredictable results of granular bone grafting. Implants were still considered to be worth attempting, if for no other reason than to help maintain support by acting as a scaffold. Without implants, it was feared that the ridge would atrophy faster, leaving less retention for the denture.

At the appropriate time, bone grafting was done with a 50/50 enCore OD Cortical & Cancellous allograft (Osteogenics Biomedical) and Bio-Oss large particle 1.0 to 2.0mm (Geistlich). When the ridge was deemed ready, a combination of Replace Select (Nobel Biocare) and NobelActive (Nobel Biocare) implants were placed. The sizes used were two 3.5- x 10-mm implants, one 3.5- x 13-mm implant, and one 3.0- x 13-mm implant.

Diagnosis and Treatment Planning: First Visit in Our Office
At our initial intake interview, I asked the patient about her recent dental experiences and what her expectations were. A comprehensive examination was done, including visual and digital oral cancer screenings (extraoral and intraoral) followed by a sub-surface VELscope (LED Dental) exam. The patient’s lower teeth and periodontium were evaluated and her medical history reviewed. Multiple photos were taken (Canon G 10 Powershot [PhotoMed International]), and impressions for study models were made using an alginate substitute material (Silginat [Kettenbach LP]) in COE Spacer Disposable Trays (GC America).

Upon examination of the immediate denture, an opening to accommodate one of the implant healing caps was present (Figure 1). The patient’s vertical dimension of occlusion (VDO) appeared to be closed (Figure 2). After adding approximately 2.0 mm to the inside of her immediate denture with a resilient denture liner (COE-SOFT [GC America]) (Figure 3), her orofacial muscles assumed more physiologic positions (Figure 4).

Figure 1. The immediate denture, showing an opening for a healing cap. Figure 2. The vertical dimension of occlusion (VDO) appears to be closed.
Figure 3. A soft liner (COE-SOFT [GC America]) was added to the immediate denture.

I took a stone model (Figure 5), showing the healing caps in place, and the patient’s implant information with me to visit Bob Renza, MDT, the laboratory technician who would be doing the case with me. At our treatment planning consultation (TPC), we discussed the options and considered several possible designs for a new prosthesis. An implant-supported bar would provide good stability and take more space. We also considered a LOCATOR (Zest Anchors) attachment-retained overdenture. The LOCATOR attachment is a self-paralleling, low-profile, resilient, stud overdenture attachment. These seemed to be better options than the ball attachments that were mentioned by the periodontist. We agreed that we would make a final decision after seeing a model showing the positions and insertion angles of the implants.

The patient wore the immediate denture for several weeks, and I relined it as needed to confirm the new VDO. In the interim between her last visit to soft reline and final impression visit, I researched the literature to see if there was a case to be made for one attachment system over another. I also explained to the patient that, given the small implant sizes, type of bone grafts she had, and potential angulations of the implants, I would not use an open-palate design. Further, I told her that since I had not been involved with preplanning her treatment, I’d do the best I could with what I was inheriting, and the prognosis was guarded at best. She understood everything and did not like the idea of burying the implants and wearing a conventional full denture, which I included as an option. She said she was willing to try if I was willing.

Figure 4. The VDO after addition of the COE-SOFT liner. Figure 5. The stone model was taken to the laboratory for a treatment planning consultation (TPC) with the dental technician.
Figure 6. The custom tray for the final impression. Figure 7. Note the divergence anteroposteriorly and mesiodistally.
Figure 8. The final working model. Figure 9. The case was mounted on a Panadent articulator.

In an article by Cakarer et al,1 the authors concluded that the LOCATOR system showed superior clinical results compared to the ball and bar attachments, with regard to the rate of prosthodontic complications and the maintenance of the oral function. Considering that we were dealing with small implants in less-than-ideal bone, I also considered the findings from additional research. In an in vitro study,2 greater angulation of the abutments was found to influence the retention capacity of the attachments and the fatigue test simulating 5 years of denture insertion. A third study found that, in comparing the structure of Magfit and the LOCATOR attachment, the contact of the Magfit attachment was rigid, while the LOCATOR was resilient. The LOCATOR attachment could improve stability of the denture dramatically. It had a stronger effect on defending horizontal movement of the denture.3 A fourth study confirmed what I thought would be best in this case: LOCATOR attachments showed better retentive properties than ball attachments after 500 insertion/separation cycles.4

Clinical Protocol
A custom tray was made (Figure 6) for an open-tray technique. After coating the tray with an adhesive (Identium Adhesive [Kettenbach LP]), a final impression was taken using the appropriate impression copings and Identium Medium (Kettenbach LP) mixed in a Pentamix 2 (3M). As seen in Figure 7, the directions of the implants became apparent with the impression copings in place. The final impression was sent to the laboratory team and poured up, and the working model was sent back to me (Figure 8).

Figure 10. The LOCATOR (Zest Anchors) females in place (with one implant not being used). Figure 11. The overdenture, showing housings, processing males, and the Vitallium frame (Dentsply Sirona).
Figure 12. Custom-designed LOCATOR females in offset supports. Figure 13. A Photo of the patient taken in June 2017.

When my laboratory technician and I met again, we agreed on the LOCATOR option. This was because Zest Anchors now offers extended-range males that would allow us to restore nonparallel implants with up to 20° of angulation on either side, calculating to 40° of divergence between 2 implants. It seemed like this would work. However, we were dealing with 4 implants, not 2, and therein was the problem. With 2 implants, the divergence would be in one plane between the implants. However, with 4 implants, all bets were off. We were now dealing with divergences in multiple planes. Imagine a game of chess on a conventional board and call it 2-dimensional. Now try to imagine a 3-D chess game with pieces coming from any and all directions. Dealing with these implants was like 3-D chess.

We proceeded to do the case using the LOCATOR attachments that corresponded to the implants. The case was mounted on a Panadent 1650 ARlMagnetic Model PCF Articulator (Panadent) (Figure 9) using the Kois Dento-Facial Analyzer System (Panadent) to locate the hinge axis. We did not use one implant (Figure 10) because the angulation of the implant in the position of the upper right canine-lateral area was so severely out of position that we could not use it with the final prosthesis.

A metal Vitallium frame (Dentsply Sirona) was fabricated to hold the male attachment housings and reinforce the full denture (Figure 11). Trubyte Bioblend IPN teeth (Dentsply Sirona) and Lucitone 199 Denture Base Resin (Dentsply Sirona) were used for the denture base. The male attachments were inserted into the housings chairside, and the denture was inserted, leaving the nonretentive processing males in place while the patient adjusted to her new prosthesis. At a subsequent visit, the processing males were exchanged for retentive males and an attempt was made to insert the denture. What should have been easy was not! With the retentive males, the denture was not clicking into place. I left the processing males in place and set up a visit for Renza to see the patient with me. We concluded that the divergence of the implants in multiple planes would not allow us to seat the denture even though we had used the extended-range males.

Being the master technician that he is, Renza designed custom LOCATOR abutments that could be made parallel in the laboratory. We hoped they would eliminate the challenges brought about by the multiplane divergences. (I do not know if we used the now available LOCATOR R-Tx Retention Insert [Zest Anchors]). It would have made a difference in this case, as the new retention inserts have 60° convergence/divergence between 2 implants, which is a major step forward.

Three custom abutments were designed to be parallel to the implant that appeared to be the most ideally placed. We included a custom abutment for the severely malpositioned implant, hoping we would be able to use it (Figure 12). A new overdenture was made, and the metal housings were incorporated into it at the chair. We tried, without success, to include the severely angled implant. With the new overdenture seated, I placed the retentive males a week after the trial insertion. The patient then wore her new denture for many months, and all seemed well for several recall visits.

About 8 months later, the patient called and said she had bitten down on an almond and that her denture did not feel right. She took it out and tried to reseat it, but it would not go into place. She tried again the next day and still could not seat her denture. When she arrived at our office for an exam, it was clear the upper left terminal implant had loosened. I took the male housing out of the overdenture and referred her to the periodontist who placed the implants. He saw her and then called to tell me that he had to remove the implant, which is what I expected to hear.

Six more months passed, and another implant loosened and had to be removed. At this point, I again discussed with the patient all that we had talked about at the onset of our relationship. She was disappointed at what was happening, but she clearly understood why she had these problems (ie, poor bone quality and volume; small implants). I added denture reline material where we no longer had functioning LOCATOR attachments and basically converted the overdenture to a conventional full denture.

CLOSING COMMENTS
After several conversations with the periodontist who placed the implants, we agreed that this case needed a block bone graft (sometimes called an onlay graft) rather than a particulate graft, similar to the type used for periodontal pockets and socket preservation. With the severely atrophied ridge, and the need for a large amount of bone, a block graft that was left to heal for 4 to 6 months would have been a better way to build up the patient’s ridge. This would have given us more bone volume and better bone quality for the predictable placement of larger implants.

I tried to help this lovely woman, and the outcome simply didn’t work out the way we hoped it would. This brings me to my final points: Predictability of an outcome is something I seek in all involved cases. This case was clearly unpredictable. Management of the patient’s expectations was handled successfully, even though we had failed to get the clinical result that we desired. We started out with undesirable circumstances. I told her she could not have an open palate and that, at best, the final outcome was a gamble in view of what I inherited. With full knowledge of the challenges, she took a chance, and so did I.

At the time of writing this article, 8 months have passed, and the patient has been wearing her denture successfully (Figure 13). I see her regularly, and our relationship is strong. She is a wonderful patient, and she has referred other patients to the practice.


Acknowledgment
The author wishes to acknowledge and thank Mr. Bob Renza, MDT, and his team at Renza Dental Studio in New City, NY, for their input and support in this hugely challenging case.


References

  1. Cakarer S, Can T, Yaltirik M, et al. Complications associated with the ball, bar and locator attachments for implant-supported overdentures. Med Oral Patol Oral Cir Bucal. 2011;16:e953-e959.
  2. roso C, Silva AS, Ustrell R, et al. Effect of abutment angulation in the retention and durability of three overdenture attachment systems: an in vitro study. J Adv Prosthodont. 2016;8:21-29.
  3. Yang X, Rong QG, Yang YD. Influence of attachment type on stress distribution of implant-supported removable partial dentures [in Chinese]. Beijing Da Xue Xue Bao. 2015;47:72-77.
  4. Türk PE, Geckili O, Türk Y, et al. In vitro comparison of the retentive properties of ball and locator attachments for implant overdentures. Int J Oral Maxillofac Implants. 2014;29:1106-1113.

Dr. Fier maintains a full-time private practice. He is the executive vice president and a Fellow of the American Society for Dental Aesthetics. He is also a Diplomate of the American Board of Aesthetic Dentistry. He was honored with Fellowships in the American College of Dentists, the International College of Dentists, the Academy of Dental-Facial Esthetics, and the Academy of Dentistry International. Dr. Fier is a contributing editor for REALITY and is on the dental advisory board of Dentistry Today. He lectures internationally on aesthetic and restorative dentistry and, since 1997, has been listed in Dentistry Today’s annual Leaders in Continuing Education directory. He can be reached at (845) 354-4300 or via email at docmarv@optonline.net.

Disclosure: Dr. Fier reports receiving material, lecture, or workshop support from companies mentioned in this article.

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