My last Spear Digest article focused on the limitations of Locator abutments. Now, let’s examine some of the advantages of four individual Locator abutments supporting a removable mandibular overdenture.

Please reference that article, “Where Is the Line with Locators?” for the essentials of the Locator Implant Attachment System, locator abutments, and techniques for more complex implant cases.

Cleaning

The obvious advantage is the overdenture is removable for regular cleaning. Maintaining a healthy oral environment, particularly the area immediately adjacent to Locator abutments is important for long-term, functional use of the dental implant.

However, removal of the overdenture and cleaning around Locator abutments is dependent on the patient’s ability to remove the prosthesis and clean intraorally.

Multiple indications

Working with the lip, tooth, ridge (LTR) concept, removable overdentures provide an option for tissue support in the lower third of the face. An implant-supported mandibular overdenture can be indicated when opposing an intact or restored maxillary dentition as a restorative treatment option with a relatively low replacement cost following years of functional use.

With three primary areas of mandibular flexure — the neck of the condyle, the gonial angle, and the body of the mandible — a mandibular overdenture provides a “little give” in a scenario where a small residual ridge would be most likely to bend when force is applied.

Individual Locator abutments work best when dental implants are placed to be parallel. A surgical plan for angled implants in the mandibular arch designed to avoid damage to the inferior alveolar nerve would include the space for a connecting bar made with Locator attachments as an option.

In respect to repair potential, modifications can be made following the completion of the definitive prosthesis reducing the time a patient must be without their prosthesis. An acrylic-based overdenture can be repaired in a relatively short amount of time in-office or coordinated with a lab.

A case for a removable mandibular overdenture with four locator abutments

This patient’s periodontist gave her a hopeless prognosis for her lower teeth in 2003 and a 10-year prognosis for her upper teeth.

Since then, she’s been consistent in her periodontal maintenance appointments. Her upper teeth pocket depths range from 2-4 mm with mobility in the upper right premolar (Figure 1). Over time, in following and monitoring her maxillary dentition and lower dental implants and overdenture prosthesis, I’m fascinated by the contrast between the upper and lower.

Maxillary dentition opposing four locator abutments supporting a removable overdenture prosthesis.
Figure 1: Maxillary dentition opposing four locator abutments supporting a removable overdenture prosthesis.

How long does it take her to clean around the upper right first molar? Tooth #3 (1-6) was removed in 2017, and tooth #5 (1-4) was removed in 2020. This patient needs to maintain the remaining natural teeth. How easy must it be to clean the lower arch in comparison to the upper arch?

The maxillary dentition would fit the criteria of terminal dentition because of the generalized horizontal advanced periodontal alveolar bone loss. The lower overdenture was designed to provide a cleansable prosthesis that would work well with the opposing dentition, acceptable maintenance costs, in terms of replacing the nylon Locator attachments over time, and options for repair should the need arise.

What do you notice about the Locator abutments in the lower arch? The periodontist placed the Straumann Standard dental implants in a relatively parallel position within the mandibular arch taking into consideration the pattern of alveolar bone loss expected over time. The periodontist helped to set the stage for a long-term restorative result.

Treatment options for when life happens

While hiking the Grand Canyon, the patient fell and hurt her jaw. A panorex showed (Figure 2) she had fractured the neck of her right mandibular condyle. She was referred to an oral surgeon for evaluation but it was too late for surgery and the fracture had to heal on its own.

Panorex shows the fracture on the right condylar head.
Figure 2: Panorex shows the fracture on the right condylar head.

What are the options at this point? Would the options be different for a metal acrylic dental implant-supported hybrid prosthesis? What might be the scenario for a full arch Zircona fixed-hybrid prosthesis?

Treatment options include equilibration of the lower overdenture prosthesis, reline or rebase the overdenture (Figure 3), or simply construct a new lower prosthesis with a similar or modified design concept. What information is contained in the longtime functioning, lower implant-supported overdenture prosthesis?

Using the existing contours of the previously functional occlusion, the existing overdenture was relined to match the mandibular supporting structures to the opposing maxillary dentition.
Figure 3: Using the existing contours of the previously functional occlusion, the existing overdenture was relined to match the mandibular supporting structures to the opposing maxillary dentition.

The restorative treatment plan involved taking advantage of the ability to modify the existing prosthesis and incorporate the occlusal-designed pattern milled into the overdenture over many years in function.

The existing overdenture was relined to reposition the base over the Locator abutments allowing for the occlusal contacts to match at the desired vertical dimension of occlusion.

The treatment was completed in a relatively short period and at an acceptable cost to the patient. It also allowed the patient to plan a phased approach to achieve the desired outcome.

Douglas G. Benting, D.D.S., M.S., F.A.C.P. is a member of Spear Resident Faculty.


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