Full-Mouth Rehabilitation With Fixed, Implant-Supported Prostheses

A 35-year-old female patient presented to the practice with a noncontributory medical history and stated that her chief complaint was that her dentist placed implants but couldn't give her teeth. She was told by her previous dentist that a removable prosthesis was the only remaining option to replace her missing teeth. Although the patient had undergone placement of three maxillary tissue-level implants, which were connected by an overdenture bar, she couldn't receive the planned implant-supported prosthesis because of the implants' malposition and angulation as well as the supraeruption of her mandibular anterior teeth (Figure 1 and Figure 2). A radiographic examination confirmed the malposition of the three, bar-connected maxillary implants and revealed that the supraerupted mandibular anterior teeth had been endodontically treated and then restored with crowns (Figure 3).

Impressions and Records

After the maxillary overdenture bar was removed, and the implants were covered with healing abutments, preliminary impressions were made in stock plastic trays with alginate (Jeltrate^®, Dentsply Sirona). Models were poured with type 3 dental stone (Microstone, Whip Mix), and then a light-cure acrylic resin tray material (Triad^® TruTray^™, Dentsply Sirona) was used to fabricate record bases with occlusion rims.

Intraorally, the incisal edge position was determined, and the vertical dimension of occlusion was established. Dental bite and impression wax (Aluwax^™, Benco Dental) was used to record the centric relation position, and an earpiece-style facebow (Hanau^™ Springbow, Whip Mix) was used for a facebow transfer. To verify the esthetics, phonetics, vertical dimension of occlusion, and centric relation, a wax try-in was performed. During the evaluation, the amount of available restorative space was found to be insufficient for an implant-supported restoration. The wax trial dentures were then placed on their respective articulator-mounted casts, and silicone matrices were fabricated. Next, immediate dentures, radiographic templates, and surgical guides were fabricated, and a cone-beam computed tomography (CBCT) scan was acquired to assist with placement of the proposed implants.

Surgery

The existing maxillary implants required removal due to their surgical malposition. This was followed by osseous crestal reduction to provide adequate restorative space for the new prostheses. To accommodate the planned implant positions, a bilateral internal sinus lift was performed, and then seven root form implants (Straumann^® Bone Level Implant [3.3 mm x 12 mm], Straumann) were placed throughout the arch.

Regarding the mandible, the remaining anterior teeth were extracted, an alveoloplasty was performed, and six implants (Straumann^® Bone Level Implant [3.3 mm x 12 mm], Straumann) were placed with the terminal ones angulated distally to increase the anterior-posterior spread (Figure 4). The immediate dentures were lined using a resilient relining material (COE-SOFT^™, GC America) and delivered, and the patient was dismissed to heal.

Provisionalization

Following a 3-month healing period, the patient returned, and the implants were uncovered and evaluated. The immediate dentures were modified and transitioned into screw-retained fixed provisional prostheses.

An implant-level impression was then made, which was used to fabricate a preliminary cast. Open tray impression copings were attached to the implant analogs embedded in the preliminary cast, and a verification jig was fabricated by linking these impression copings together with dental floss and acrylic resin (Pattern Resin^™ LS, GC America). The verification jig and the undercuts on the cast were blocked out with wax, then the light-cure acrylic resin tray material was used to fabricate a custom tray. After a thin disc was used to section the copings of the verification jig, they were placed on the implants and then rejoined intraorally using the acrylic resin. An open tray impression was made using a medium-body polyether impression material (Impregum^™, 3M), and the verification jig was picked up in the impression. To reproduce the soft tissue around the implants, a silicone-based gingival mask material (GI-MASK^®, Coltene) was used, and then the master casts were poured.

The esthetic parameters, phonetics, occlusal plane, vertical dimension of occlusion, and centric relation position were all verified using the provisional prostheses. A centric relation record was created, and the definitive casts with the screw-retained provisional prostheses were mounted on the articulator. To serve as a guide for fabrication of the definitive prostheses, silicone indices of the provisional prostheses were then made.

Final Delivery

Screw-retained maxillary and mandibular cast metal frameworks for porcelain-fused-to-metal prostheses were fabricated and tried in. The maxillary prosthesis was constructed in two segments to facilitate a passive fit, which was confirmed intraorally.

After veneering porcelain was applied to the metal frameworks, the esthetics, vertical dimension of occlusion, and centric relation were again verified. Occlusal adjustments were performed to develop a group function occlusal scheme that would more evenly distribute the forces of mastication over the implants. To correct any angulation discrepancies, angled transmucosal abutments were utilized.

The prostheses were polished (Figure 5) then delivered and torqued to the value recommended by the manufacturer. To verify complete seating, a postoperative radiograph was taken (Figure 6). The screw access holes were blocked with PTFE tape and restored with a flowable composite (Filtek^™ Supreme Flowable Restorative, 3M). Following fabrication and delivery of a maxillary occlusal guard, the patient was provided with maintenance instructions and appointed for 1-week and 1-month follow-up visits. She expressed that she was highly satisfied with the treatment provided, which addressed her chief complaint as well as her esthetic and functional desires (Figure 7 and Figure 8).

A lack of preoperative treatment planning regarding final prosthetic outcomes may lead to increased treatment costs and times, failed treatments, and dissatisfied patients. In this case, proper diagnosis and treatment planning started with the appropriate design of the proposed prosthodontic restorations based on function and esthetics,^9-12 followed by assessment of the available restorative space. The residual bone volume and potential implant sites were visualized using the CBCT scan, and the development of an appropriate treatment plan was accomplished using implant planning software (SICAT Implant 2.0, Dentsply Sirona).^6,13,14

Due to the improper positions and angulations of the previously placed maxillary implants, their removal was necessary to achieve a predictable outcome and provide the patient with a satisfactory prosthesis.¹⁵ In addition, osseous reduction was completed to provide adequate restorative space and to conceal the tissue junction of the maxillary prosthesis below the patient's high smile line.^9,16

Extraction of the remaining mandibular teeth and ostectomy corrected the supraeruption and created a proper occlusal plane with adequate restorative space.¹⁷ The terminal mandibular implants were angled distally to maximize the anterior-posterior spread and minimize the distal cantilever length.^18,19 This distal angulation of the posterior implants was corrected with angled transmucosal abutments, and one-screw and screw resistance tests were used to verify the fit of the frameworks.^20,21

To provide the patient with optimum esthetics, metal-ceramic fixed prostheses were fabricated, and pink porcelain was used to maintain proper tooth proportions and restore the gingival contours.^22,23 The nonporous nature of this restorative material results in an excellent tissue response from the supporting soft tissue when compared with a prosthesis fabricated from resin. Furthermore, the occlusal surfaces of the prostheses will exhibit little-to-no wear, and the framework design provided for an even thickness of the veneering porcelain, which will minimize the risk of chipping.^24-27 Although the patient did not report any parafunctional habits, a maxillary occlusal guard was fabricated and delivered to provide additional protection from any excessive occlusal forces that might be generated during sleep.^28-30

As this case demonstrates, improper diagnosis and treatment planning can lead to the failure of treatments and devastating results for patients. Assessment of the availability of adequate restorative space during the diagnostic phase, prior to implant placement, is crucial to the treatment planning, execution, and long-term success of edentulous rehabilitations using implant-supported prostheses because it allows clinicians to begin with the end in mind. 

Abdulmohsin Alhashim, BDS, MSD
Fellow
American College of Prosthodontists
Assistant Professor
Dental College of Georgia
Augusta University
Augusta, Georgia

Ronald L. Harris, DDS
Assistant Professor
Dental College of Georgia
Augusta University
Augusta, Georgia

Ahmed Zaher, BDS, MSD
Fellow
American College of Prosthodontists
Assistant Professor
Dental College of Georgia
Augusta University
Augusta, Georgia

Barry D. Hammond, DMD
Professor
Dental College of Georgia
Augusta University
Augusta, Georgia