Screwless Fixed Detachable Partial Overdenture Treatment for Atrophic Partial Edentulism of the Anterior Maxilla

Osseointegrated implant-supported prostheses have been advocated as an excellent treatment option for both edentulous jaws.1 Fixed or removable implant-retained and -supported overdentures are highly successful prosthodontic treatments options and can a have a predictable prognosis even for the combination syndrome patient.2^,3 Residual edentulous alveolar ridge width and height may decrease with time, and replacement of this lost tissue may present a treatment problem. However, acrylic-based prostheses have been used in the past to correct the alveolar bone loss and provide patients with lip support and function.4 In addition, pink-colored porcelain can also be used to simulate a lost gingival ridge for appearance and function.5 

Tissue-borne prostheses can cause osseous resorption from chronic occlusal forces over time. Implant-supported prosthodontic treatment changes the occlusal force distribution and may attenuate or cease further bone resorption.

A 47-year-old woman of Japanese descent with an insignificant medical history presented for treatment. The patient adamantly desired to keep as many natural teeth as possible and declined any type of removable treatment. She had been wearing an all-acrylic provisional appliance, a flipper, for many years and had made a decision to be rid of it. Implant therapy was initially discussed and provisionally accepted by the patient. Visual and radiographic examinations were done including full-mouth series and a computerized tomograph. Mounted study casts were made (Figures 1–4).

The patient had an Angle class II occlusal/osseous relation. The maxillary anterior teeth No. 7 to 10, 4, 13, and 14 and all of the posterior mandibular teeth were missing (Tables 1 and 2). The patient was wearing a tissue-borne maxillary prosthesis to replace teeth No. 7 to 10. This situation resulted in severe atrophic bone loss in the anterior maxilla from either osseous pressure atrophy or from bone that was removed during the extraction procedure. In addition, there was moderate to severe loss in the posterior mandible, thus mimicking combination syndrome. A review of her condition was discussed with the patient. Some options offered to the patient included no treatment, extraction of all maxillary teeth, and construction of a full arch implant-supported maxillary dentition and implant-supported bilateral fixed mandibular partial dentures. Another treatment option was to extract guarded, poor, and hopeless teeth and construct bimaxillary removable partial dentures.

Bone grafting was offered but declined by the patient. Vertical extracortical bone grafting may not be predictable to the height needed for an esthetic outcome in this case. Her lip line was low, and she was accommodated to an acrylic-based appliance. She finally opted for fixed prosthetic treatment including the edentulous span of No. 7 to 10. The atrophic anterior segment required lip support and a correction of function problems. This span was deemed too long for a conventional fixed partial denture, and the maxillary lip needed support. A maxillary treatment plan, including an implant-supported screwless fixed-detachable prosthesis, was conceived. This prosthesis would replace No. 7 to 10 and be supported by endosseous small-diameter implants with overdenture-type retainers. To restore the lost component and restore lip support, a unique appliance design was instituted. Because there was a large vertical component to the site, support at the level of the occlusal plane was also designed to prevent facial and lingual leverage, with the implants being the fulcrum. Thus, the remaining maxillary teeth would be crowned, and the cuspids would be fitted with mesial female interlock attachments to accept male attachments placed at the distal of No. 7 and 10 on the acrylic-based prosthesis that would be seated onto implant retainers (Figures 5 to 9). The prosthesis would not be easily removed by the patient, so in her mind it would be fixed but could be removed by a clinician for maintenance. Because the occlusal forces in the anterior maxilla are less and the prosthesis would be implant retained as well, it was deemed that endodontically treated teeth No. 6 and 11 would withstand the occlusal functional demands. The patient approved this design concept. Implant-supported bilateral fixed partial dentures were discussed for the mandible and also affirmed by the patient.

Mounted study casts were made and wax try-ins were done to visualize the treatment outcome and to gain acceptance by the patient. The appropriate vertical dimension was to be restored for the patient and place most occlusal stress on the posterior segments.

Hopeless teeth, No. 2 and 13, were extracted. The maxillary teeth, No. 3, 5, 6, 11, and 12, were treated with endodontic therapy and full crowns (Table 1). The maxillary cuspids were fitted with mesial female interlock attachments to accept the acrylic-based anterior prosthesis. The mandibular implants were placed, and the maxillary crowns and mandibular fixed splinted prosthetics were constructed and cemented with zinc phosphate (Flecks). A cuspid-premolar–guided occlusal scheme was used. The maxillary anterior prosthesis was premade so that it could be immediately installed after the placement of the implants. Small-diameter mini implants were placed in the anterior maxilla and immediately functionally loaded with a pick up–type acrylic technique (Figures 5 to 9). The acrylic base was constructed scalloping the implant attachment housings with point contact on edentulous areas for appropriate oral hygiene. For seating, the acrylic-based prosthesis first engages the cuspid attachments and then is moved superiorly to engage the implant male attachments until fully seated.

The patient is not able to remove the denture, but the denture can be removed by a clinician at maintenance appointments for servicing. The patient has been successfully functioning for 2 years. Appropriate lip support has been obtained (Figure 10).

The mandible was restored with implant-supported splinted fixed partial dentures at No. 19 to 21 and No. 28 to 30 (Figures 11 and 12).

Future treatment includes crowns for No. 22 through 27 and extraction of the remaining maxillary right third molar.

This patient was successfully treated with a removable partial overdenture that could be removed only by a clinician. The prosthesis provided lip support and incising capability. Full arch implant-supported acrylic-based prostheses have been used to treat patients who require lip support.4 Pink-colored porcelain fused to metal has been used for other types of atrophic sites.5 

The treatment of the partially edentulous maxilla and mandible presented here has similar presenting conditions as the maxillary edentulous combination syndrome. However, in this case, the osseous anterior maxillary deficit may have been caused by traumatic extraction of the maxillary anterior teeth and/or pressure atrophy from long-term use of a tissue-borne prosthesis.

Treatment options deemed unsuitable by the patient included removable partial dentures, long-span fixed conventional full denture involving all the maxillary teeth for support, complete maxillary extractions and complete denture construction, implant-supported fixed complete denture, the optimal treatment, and, of course, no treatment.

The anterior residual bone volume and width was insufficient for standard-sized implants. In addition, standard-diameter (3.7–4.1 mm) implants may not allow adequate hygiene access at the base of the prosthesis because of the volume of acrylic required to retain the retainer housings.

The maxillary lip required support for appropriate physiologic function and appearance. A removable mini implant and tooth-supported acrylic-based partial denture treatment was elected. Small-diameter mini implants were used. Thus, the prosthetic support was obtained by the implants and the interlock attachments at the mesial of the maxillary cuspids. The removable partial overdenture denture was supported at its base by 4 small-diameter mini implants with rubber/metal cup retainers in the gingival base and at the coronal by 2 interlock attachments located on each mesial of the maxillary cuspids. The male attachments are located on the denture at the distal of No. 7 and 10. The prosthesis has excellent retention and cannot be removed by the patient but can be removed by a treating clinician for maintenance. The design of the prosthesis allows appropriate oral hygiene. The base is scalloped around the implant's retentive housings with no ledges. All of the surfaces of the prosthesis are accessible for cleansing.

Natural teeth intrude under load, but implants do not. The resilient implant attachments used here allow some movement and stress relief for the endodontically treated cuspids. The cuspid attachments prevent facial or lingual movement. This design, however, may not be appropriate for a more posterior-located site, where the forces of occlusion are much greater and endodontically treated teeth may not fare as well.

Patients present with myriad combinations of anatomical conditions: many are atrophic. The treating clinician can use multiple modalities for appropriate treatment outcome. This case was treated successfully with a screwless fixed-detachable maxillary anterior overdenture prosthesis to provide anterior maxillary teeth, with interlock attachments on the remaining maxillary cuspids and an acrylic base for physiologic lip support. This design allows for oral hygiene access.

The author acknowledges the kind and gentle redactions of Ralph Bozza, DMD.