The Advantages of Implant-Assisted Removable Partial Dentures (RPDs)

For many decades, osseointegrated implants have been considered the “standard of care” solution for patients who present with partial or full edentulism, and surgical techniques and implant designs continue to evolve, allowing clinicians to graft and install implants even in clinical conditions were severely resorbed bilateral maxillary and mandibular posterior edentulous ridges exist. In this article, I will discuss why implant-assisted removeable partial dentures may sometimes be the preferred treatment choice.

Let’s start with an example.

A Second Opinion, Another Option

A 35-year-old female patient (Fig. 1) came to see us in search of a second opinion. She was treatment-planned elsewhere for extraction of the remaining mandibular teeth, placement of four implants and a fixed hybrid restoration (a treatment modality that is becoming increasingly common).

In a previous Digest article, we discussed a treatment planning algorithm that provides a matrix for helping the treating team decide if the condition of the remaining teeth calls for extraction, or if it makes sense to preserve teeth and place the implants only in those edentulous sites. With that matrix in mind, we chose to offer her a fixed implant-supported solution to address her posterior edentulism without extracting the anterior teeth (Fig 2).

It seems hard to argue against the notion that there is a global pattern of overtreatment in many such cases, where too many teeth are being extracted to fit the fixed hybrid treatment modality mold, and too many patients are offered a “cookie cutter” approach. Patients are being offered this type of solution as a panacea when, in fact, dental scientific literature has extensively reported that patients may experience extremely common complications down the road.

An Academic Case for Implant-Assisted RPDs

Twenty years ago, I participated in publishing a retrospective study¹ evaluating the performance of implant-assisted removable partial dentures. During the late 90’s, I was a graduate student at the University of Washington’s Advanced Prosthodontics program, and this concept was brought to our attention by our mentor, Dr. James Brudvik, a world expert on removable prosthodontics who was a staunch believer in this implant therapy model.

Dr. Brudvik recently passed away, which is one of the reasons I wanted to write this article. I wanted to honor his memory by sharing this concept, which—20-plus years later—is even more relevant, as dental practitioners are humbly becoming more aware, when we monitor our patients long enough, of the inexorable complications that occur because of implant therapy.

There is no doubt in my mind that we should challenge the idea of “implants and implant-supported restorations are meant to be forever.” And embracing the concept of implant-assisted removable partial dentures as a “transitional solution” may help clinical teams and our patients to buy some time—either for the eventual loss of the remaining teeth (at which point we would design a full arch implant-supported solution), or, in those instances where the patient cannot afford multiple implants, before replacing the posterior missing teeth with a fixed solution.

Conceptually, the relevance of an implant-assisted RPD design became compelling, as there are historic common complaints associated with the bilateral distal free-end (Kennedy Class I) and unilateral distal free-end removable partial denture (Kennedy Class II)—complaints such as lack of stability, minimal retention, and unesthetic retentive clasping.

Therefore, patients in the study were treated with osseointegrated implants to improve stability and/or retention of the removable prostheses, eliminating the need for clasps when possible. A periodic follow-up clinical evaluation, consisting of evaluation of patient satisfaction, radiographic examination, and soft tissue health was performed.

Resilient types of attachment were used, which allowed for a small divergence from the path of insertion. Results indicated consistent increased satisfaction in all patients. (However, the need for sporadically replacing the resilient component of the attachments was a common finding).

All the examined patients exhibited stable peri-implant soft tissues, with no radiographic evidence of excessive bone loss.

Another Clinical Example

A middle-aged female presented to our clinic with some of the concerns I just described:

1. Discomfort utilizing RPDs because of lack of retention and stability, making the previous attempts to utilize removable partial dentures functionally inadequate.
2. Dissatisfaction due to the unesthetic nature of the clasps of previously inserted RPDs.
3. Lack of financial means to afford multiple implants bilaterally to fabricate fixed restorations.

After a thorough discussion with the patient and the rest of the treating team, the patient was presented with a treatment plan that consisted of providing an implant-assisted removable partial denture. Nonetheless, a contingency plan was built in, to entertain the possibility of an eventual upgrade for a fixed solution, in which the implant could be re-purposed.

This entailed placing one implant bilaterally at the level of the mandibular first molar, which was prosthetically guided during surgery. Care was taken to ensure that the implant was surgically installed following three-dimensional guidelines: mesio-distal center, buccal lingual center, 3 mm apical to the gingival margin, as well as properly angulated.

Once time was allotted for conventional osseointegration process, the prosthetic design consisted of:

1.  Placing a resilient attachment (“OSO” rings), allowing the prosthetic design of the RPD to improve the retentive challenge.
2.  Fabricating porcelain fused-to-metal surveyed crowns with adequate guide planes and rests, permitting the RPD to rest in the lingual aspect of the crowns—thereby avoiding the need for those unesthetic clasps in the facial aspect of the crown and providing the patient with a more esthetic solution.

A Solution Worth Exploring

As contemporary clinical teams, we should be equipped with a diverse range of solutions in our “bag of tricks” to satisfy the needs and differing financial capabilities of our partially edentulous patients.

All too often the treatment offering pendulum swings—from the high-end grafting /fixed solution to the extraction and fixed hybrid solution, to the dreaded RPD solution, which is hardly even taught in many dental schools. (I specifically say “dreaded,” because they are known for their lack of retention and unesthetic clasping.)

An “upgraded” implant-assisted removable partial denture may fit the patient’s current financial needs and expectations—as well as keep treatment within a minimally invasive realm. Moreover, when adequately treatment planned and when their surgical placement is prosthetically guided, implants that initially may serve as a retentive mechanism for the RPD could eventually be easily incorporated and converted into an implant-supported fixed solution, making it a versatile feature for contingency-driven treatment plans.

Ricardo Mitrani, D.D.S., M.S.D., is a member of Spear Resident Faculty.

References

1. Mitrani, R., Brudvik, J. S., & Phillips, K. M. (2003). Posterior implants for distal extension removable prostheses: a retrospective study. International Journal of Periodontics & Restorative Dentistry, 23(4).
2. Wismeijer, D., Tawse‐Smith, A., & Payne, A. G. (2013). Multicentre prospective evaluation of implant–assisted mandibular bilateral distal extension removable partial dentures: Patient satisfaction. Clinical oral implants research, 24(1), 20-27.