An Implant-Retained Maxillary Overdenture to Obturate a Patent Oronasal Communication: A Case Report

Many patients with cleft palate have a defect that, even after appropriate surgeries, is left with a communication through the anterior hard palate into the nasal cavity. The incidence of orofacial defects is about 1 per 1000 births, with variations in this rate depending on ethnic group.1 A gene has been identified that causes a 3-fold increased risk for a congenital cleft lip or palate.1 A cleft palate can be identified as early as the 17th gestational week.

While recent surgical techniques advocate early intervention, many older cleft palate patients have not benefited because they were born before these innovations. Such is the situation with the patient treated in this case report. A postsurgical defect has persisted, leaving an oral nasal communication that required prosthetic obturation. There were multiple carious and poor-prognosis remaining teeth that supported ill-fitting partial dentures. Obturating an oral nasal opening for function can be challenging for the clinician. These patients generally have compromised arches and postsurgical scarring of the palate and lips. A maxillary removable denture is typically the only option for these patients.2 In addition, a patient's limited economic status may complicate treatment choices.

Teeth can be lost due to poor oral hygiene; therefore, overdenture prosthetic retainers with a small surface area may place the attachment at less risk for plaque retention. Low-profile retainers were selected for retention in this case to reduce the exposed surface area. The brand selected had an available selection of light retentive retainers.

A 72-year-old retired male factory worker with limited economic means presented for treatment. He had a bilateral congenital anterior palatal defect that had been surgically repaired as a child (Figure 1). There was a persisting 12-mm-diameter oral nasal communication. His medical history was significant for diabetes, which was diet controlled, and high blood pressure controlled with a beta-blocker, metoprolol (Toprol-XL). He was also taking 81 mg of aspirin each day. An asymptomatic distally submerged No. 17 was not removed because of the risk of postoperative fracture.

The patient was rarely wearing his existing bimaxillary partial dentures secured with conventional natural tooth clasps. These were constructed 12 years before and were ill fitting and unsalvageable. The remaining teeth were carious and had periodontally poor prognoses (Figure 2). The patient's oral hygiene was fair to poor. He was subsequently instructed to improve oral hygiene and maintenance.

Clinical, visual, and radiographic examinations were performed, and treatment options were presented. A fixed maxillary prosthesis was deemed inappropriate because of the oral nasal communication. The mandible had suffered moderate to severe atrophy from edentulism. Major osseous grafting would be needed to place implants for fixed prosthetic support in the mandible, and the patient declined this treatment. The treatment plan agreed on included extraction of the remaining maxillary and mandibular teeth, 4 months of healing, implant placement, and construction of bimaxillary removable overdentures.

Immediate implant placement was considered in the maxilla, but very close implant parallelism would be required for easy retainer seating. Multiple parallel implant placements would be difficult after multiple extractions, so a 2-stage–type approach was decided on.

The maxillary teeth, Nos. 2, 3, 4, 12, and 13, were extracted under local anesthesia and grafted with particulate cortico/cancellous allograft (AlloOss, Ace Surgical), calcium sulfate (CapSet), and collagen plugs (Ace Surgical) and sutured with 3–0 chromic gut.

The remaining mandibular teeth, Nos. 26 and 27, were extracted. An immediate 4.1- × 11.5-mm implant (3-I Biomet) was placed into site No. 27. Because of a thin residual ridge, three 2- × 13-mm one-piece implants (IntraLock) were placed at site Nos. 23, 24, and 25. Different brands of implants were used because neither company manufactures the appropriate-diameter implant for the bone contour, width, quality, and volume that was available. Extensive grafting was economically eliminated. A dermal allograft (Alloderm) was placed to increase the soft-tissue base at the anterior mandibular ridge. After healing, a computerized tomogram to evaluate the residual osseous structures was made.

Six implants were flaplessly placed as far apart as the maxillary osseous anatomy would accept at site Nos. 3, 4, 6, 11, 13, and 14. Intraoperative radiographs with gutta percha placed in the osteotomies were made to confirm the appropriate positions.

Press fit sintered surface implants (4 × 7 mm; Endopore, Innova) were used in the right maxillary side site Nos. 3 and 4 because of low bone density and height. Screw-type implants (4 × 10 mm; Biomet, 3-I) were placed in the left side, Nos. 11, 13, and 14, at 35 Ncm (Figures 3 and 4). The bone density encountered was perceived to be Misch type 3.3 

The patient was administered 1000 mg of per oris amoxicillin on the day of surgery and prescribed amoxicillin 875 mg twice daily, chlorhexidine oral rinse, and 7.5 mg of hydrocodone every 6 hours for pain control. A 4-month healing time was observed.

At the third week, the implant at site No. 11 failed to integrate and was removed. Because of remaining bone quality, quantity, and its proximity to the oral nasal communication site and the risk of involvement of the defect, the site was deemed not suitable for another attempt at placement.

Construction of the removable overdentures then began. An obturating protuberance was built into the intaglio of the maxillary denture to block the oral nasal communication (Figure 5).

Low-profile retainers were planned. Locator overdenture retainers were selected (Figure 6). This patient could not master the highest levels of oral hygiene, and the low-profile attachments present a small surface area for plaque accumulation. The lowest retention retainers were used to minimize difficult removal and placement (Figure 7).

A flat, 0° occlusal scheme was implemented to minimize lateral occlusal forces delivered to the retaining implants. The overdentures were delivered, and the patient was instructed with regard to hygiene and maintenance (Figures 8–10).

The patient has been in function for more than 1 year and has returned for maintenance appointments. He is functioning well and has slightly improved his oral hygiene care (Figure 11).

Treatment of oral nasal communications can be a challenge, but prosthetic design options are available. Generally, removable prostheses are the only option for prosthetic obturation of persisting oral nasal defects.

Construction of an implant-supported bar for retention and support distributes occlusal forces among the supporting implants; however, a bar increases the surface area for plaque retention, treatment cost, and treatment time.

This case was treated with implant-retained, soft-tissue–supported overdentures to minimize maintenance and reduce treatment costs. However, there would be an increment of occlusal support borne by the implants as well.

There is limited evidence published as to the successful treatment of implant-retained maxillary removable overdentures. However, there has been a set of implied parameters published4 (the Table). Parameters that may be important for these types of maxillary cases are rough-surface implants, parallel implant placement, more dense bone sites (Misch type 1–3), diameter of 3.7 mm or larger, length longer than 9 mm, spread-out implant positioning, a flat or a lingualized occlusal scheme, use of a minimum of 4 implants and low-profile attachments such as Locators or SternGold ERA attachments, light attachment retention, and full or partial palatal coverage that provides some lateral resistance.

The Locator female retainers (pink and green), used in this case, have the lightest retention and are removed with 2000 and 2500 g of force, respectively (Figure 6). This force is below the approximate 200 Newtons of force that may be required to luxate a newly placed implant 150 μm when directed laterally.5,^–10 

While this theoretical 150-μm micro-movement limit applies to newly placed implants, although not proven, the dimension may also apply to integrated implants. Preventing detrimental off-axial forces is important for prosthetic longevity. Light retention may prevent off-axial forces from being chronically applied to the implants. The flexible and compressible retainers tend to distribute forces to all the implants and the soft tissue when a lateral force is applied. As a single elastic retainer is compressed by the moving denture, the others will also be engaged and the elastic component compressed as well, thus damping the denture movement and transferring the force to all of the implants and the soft tissue. In addition, the light retention allows the patient to remove the denture for cleaning and maintenance. A more rigidly retained denture may transfer all, or a larger amount, of off-axial forces directly to the retaining implants and may transmit off-axial forces.

A flat occlusal scheme may also reduce lateral forces delivered to the denture and implants by allowing the jaws to move freely without encountering tooth cusps that may induce a transfer of lateral force to the implants. The flat occlusion did not allow anterior contact in protrusive movement. It also restricts the occlusal forces in the posterior area to prevent dislodging of the maxillary denture.4 Low-profile retainers may also reduce the leveraged force applied by occlusal forces.

The loss of the No. 11 implant was probably due to the site's poor bone quality and volume and proximity to the defect and possible impaired postsurgical vascular supply. One less supporting implant places more of a burden on the remaining 5 implants. However, the 5 surviving implants are more than the recommended 4 implants. A cusped group function or anterior guidance occlusal scheme may apply occlusal force against one lateral side of supporting implants.

The prosthesis intaglio seats against the palate and gingival ridge tissues and slightly resists lateral movements. The palatal coverage and facial denture flanges can also slightly resist lateral occlusal forces.4 

The implied parameters for this treatment modality are all directed to reduce and minimize lateral and off-axial forces delivered to the retaining implants. Each of the parameters contribute incrementally to minimize forces to the implants to ensure that no single implant is overstressed and thus allow the denture to function without detriment to the integration of the implants.4 

It may be that this case would not have been successful if all the parameters were not instituted.

In this case, a patient with a persisting oral nasal defect was rendered edentulous, and successful removable maxillary and mandibular implant-retained overdentures were constructed. This case report demonstrates that by observing all of the parameters implied by the successful outcome of this and previously reported cases, it is possible to treat selected patients with removable implant–supported maxillary and mandibular overdentures. The maxillary prosthetic design enhanced esthetics and phonetics and reduced treatment complexity, difficulty, maintenance, and costs.

This and other cases reported imply a set of parameters for successful implant-retained maxillary overdenture treatment: denture flanges, light retention retainers, a flat or lingualized occlusal scheme, maximum implant positional spread, and a minimum of 4 parallel, rough-surfaced, long, wide implants placed in denser-type bone sites.

Only a small number of cases treated in this manner have been reported. Therefore, clinicians should not use these case reports as a sole basis for treatment. If this design and technique prove to be appropriate and successful, then patient costs may be reduced and clinical outcomes and patient satisfaction improved.