Implant-assisted Removable Partials: Highlighting the Advantages in 2 Cases

Implant-assisted removable prostheses, specifically for partially edentulous patients, provide an option in the realm of a phased approach to restorative dental treatment. The idea is to identify a clearly defined definitive treatment plan as the desired end-goal in an effort to improve the overall treatment outcome while providing the added benefit of distributing the overall cost of treatment over time.

Three advantages include:

1. Maintaining natural teeth – The idea is helpful to a patient working through the impact of losing their natural teeth, and the thoughts, images and ideas associated with the loss. Keeping teeth is helpful to the patient from a structural point of view by minimizing the effects of residual ridge resorption that accompanies removal of one or more teeth many times in an attempt to minimize the need for alveolar augmentation.
2. Enhanced transitional phase – Abutments (teeth or implant-supported) prove beneficial to the patient to limit movement of the transitional prosthesis when the overall plan includes delayed loading of the implant or perhaps augmentation of the residual alveolar ridge.
3. Pathway to a definitive treatment plan – The position of the dental implant can be planned with intention in terms of location within the arch and the depth of the implant, allowing the potential opportunity to convert to the restoration of choice, whether a fixed or removable restoration, when the time is right.

Case study: Lower removable partial as a phased approach

The first discussion is based on a patient presenting for a restorative evaluation following augmentation and placement of six maxillary implants recently placed by a long-time family friend. You may have experienced a situation where the patient wasn't fully aware of the additional cost for the definitive restoration and was surprised as she was provided the treatment plan with the financial commitment. She had initially come into the office for a second opinion looking for a way to modify the overall cost of treatment. Treatment for the lower arch and how the entire system works together became a component of the discussion where the patient was particularly engaged.

"The treatment sounds great, but there is no way I can do it all now?" Have you heard a patient respond with a version of this statement? The conversation can then move toward a more practical consideration, such as "How can we spread out the cost?

Take a look at Figure 1. A single-unit dental implant-supported restoration remains in the lower left second molar (#18) and natural teeth in the lower right canine (#27) and the lower right second premolar (#29). An upper implant-supported over-denture opposing a lower non-traditional removable partial denture was made and has, at this point, been working for five years.

What are the opportunities available with this treatment approach?

1. We have a chance to conserve and maintain the remaining natural teeth for a little longer in a "nothing to lose" approach. The alternative was to remove the remaining lower teeth. She now refers to the teeth as her "soldiers" and takes pride in maintaining what she has remaining. The commitment to home care and the regular recall maintenance schedule will be of benefit now as well as in the future.
2. The removable partial denture abutments (two teeth and one implant restoration) provide stability and retention for the prosthesis. In contrast, think about the patient's experience with a solid and stable maxillary over-denture opposing a conventional lower denture without abutments to limit the movement of the prosthesis.
3. We have a logical "next step" in the pathway toward a definitive restoration. A dental implant in the lower left canine position (#22) can improve the stability of the removable partial by limiting the rotation around the axis created by a line drawn between the implant crown at #18 and the natural canine #27. The added stability provided by the "stop" in the #22 area (the effect of an indirect retainer) will improve the prognosis of the remaining natural abutment teeth (#27 and #29), provides the opportunity to work with the existing prosthesis, and will set the stage for a dental implant-supported full-arch restoration when the patient is ready. The patient maintains six-month recall, providing the chance to discuss the next phase at a regular interval.
4. The patient has the opportunity to evaluate her experience with the upper dental implant-supported over-denture to help make an informed decision on how she would like to proceed with a definitive restoration for the lower arch. There are advantages in terms of lip support and ease of home care maintenance with a dental implant-supported removable prosthesis and, in contrast, there is the advantage of having a fixed/non-removable restoration, particularly for the lower arch, with less volume required of the prosthesis.

Case study: Maxillary removable partial as a phased approach

How about hiding clasps in the maxillary anterior segment?

Take a look at Figure 2, where the patient was interested in an option where he could maintain his upper natural teeth #9 and #11. The overall goal was to identify a clearly defined definitive treatment plan in order to influence the transitional restoration.

Think about this patient's situation where the concern relates to the missing posterior teeth. Certainly, the supporting alveolar bone and periodontal ligament allow for movement of the natural teeth over time. Dental implant-supported restorations, in contrast, are rigidly connected to the supporting alveolar bone and rigidly connected to the corresponding abutment. How would this information influence your discussion with the patient regarding treatment options?

Specifically, would there be any concern with a dental implant-supported three-unit fixed bridge canine to central (#6-#8) and a tooth-supported three-unit fixed bridge central to canine (#9-#11) made to support a removable partial to for the missing posterior teeth bilaterally? This is frankly one of those questions that falls in the gray zone where the goal is to provide information to help the patient make a decision. Take a look at the Spear TALK post on a similar topic of discussion focused on tooth-supported restorations and a structural failure of an anterior dental implant-supported restoration in the anterior.

The treatment provided for the patient included dental implants in the #6 and #8 positions that are incorporated in a removable partial denture prosthesis to include the natural teeth #9 and #11 as abutments. The most popular of the available attachment systems designed for dental implants can be described as resilient in nature. The goal is to work in a non-rigid system that includes the supporting structures of the natural teeth #9 and #11 as well as the posterior edentulous segments bilaterally.

A few important considerations:

• Implant position that will correspond to future needs should the patient complete transition from partially edentulous to fully edentulous state. Planning for the vertical height of the attachment sets the stage for a dental implant-supported prosthesis should the patient decide to proceed in the future.
• The ability to repair a removable prosthesis should the need arise during the maintenance period of the transitional phase of restorative dental treatment could present with a different financial commitment than would be expected for a structural failure of a dental implant-supported fixed-bridge prosthesis.
• The long-axis of the dental implant should be parallel to the guide planes of the abutment teeth along the path of insertion. Certainly, there are limits to the abutment options related to angle correction where many require increased space as a result of the vertical height of the abutment.

The dental implants were placed with precision to be aligned parallel to the path of insertion for the removable partial denture with the goal being to place attachments that are connected directly to the dental implant. Ball-O-Ring attachments allow for a slight angle correction through positioning of the attachment at various locations of the spherical interface. This attachment system requires more vertical space than the low profile locator attachments that also provide a range of angle correction, particularly with the more recent R-Tx abutments. ERA attachments allow for angle correction in the form of a cemented abutment should the need arise.

What's next for this patient?

The addition of dental implants has improved the retention and stability of the removable partial denture. Teeth #9, #11 and #14 are preserving the supporting alveolar bone to provide options for future treatment and, while it may include augmentation, maintenance of the native bone provides options in critical areas. The area of concern relates to the posterior right edentulous space with an expanded, pneumatized sinus. The transitional prosthesis in the form of a removable partial denture allows for modification while working through the process of arriving at the finish line for the definitive restorative treatment plan.

Phasing the treatment while including the patient in the process provides the opportunity to evaluate and customize the definitive treatment to meet the patient's specific needs and expectations.

Think about the conversation you would have with the patient (Figure 3) regarding treatment options in terms of how to plan for the future move forward toward a restorative treatment plan that they can plan for and be excited about.

Certainly, there is a difference in the patient's experience between a denture, a two-implant-assisted over-denture, four implants for an implant-supported prosthesis and the potential for a fixed hybrid. Imagine if we had the opportunity to add just one dental implant in the distal extension area in the lower right posterior. The experience becomes different – the patient is now engaged in the process, the restorative treatment can be planned and the terminal dentition conversation has now been altered.

(Click this link for more dentistry articles by Dr. Doug Benting.)

Douglas G. Benting, D.D.S., M.S., F.A.C.P., Spear Visiting Faculty and Contributing Author - www.drbenting.com