The preservation of alveolar ridge architecture remains a critical factor in the long-term success of implant therapy, particularly in the anterior maxilla. Because gingival tissue follows bone levels, severe periodontitis that results in alveolar bone loss can affect soft-tissue stability and ultimately lead to significant esthetic concerns.1 When a tooth is extracted, it removes an essential source of blood supply to the surrounding bone and gingiva, which can lead to ridge collapse and soft-tissue shrinkage.2 To counteract these challenges, partial extraction therapy (PET) has emerged3 as a predictable method for preserving the buccal bone and soft-tissue profile. By maintaining a portion of the tooth's root structure within the socket, PET sustains the existing blood supply,4 prevents excessive ridge resorption, and maintains soft-tissue contours.3 This approach is particularly beneficial in the esthetic zone, where maintaining a natural emergence profile is crucial for a seamless implant-supported restoration.
Case Report
A 41-year-old female patient presented with severely compromised upper anterior teeth that demonstrated mobility, severe root exposure, and esthetic concerns. Clinical and radiographic evaluations were performed (Figure 1 through Figure 3), which revealed that teeth Nos. 7 through 10 demonstrated Grade 2 mobility. Although teeth Nos. 6 and 11 did not demonstrate mobility, their crown-to-root ratios were determined to be unfavorable for long-term prosthetic support. No bleeding on probing was detected, and the patient's dental hygiene was excellent. It should be noted that this patient had undergone periodontic maintenance every 3 months for more than 3 years with the practice's hygiene team.
Discussion of Treatment Options
Possible treatment options were discussed with the patient, during which time she indicated that she did not want a removable prosthesis. Regarding fixed options, the placement of a 6-unit bridge spanning teeth Nos. 6 through 11 was considered, but this was determined to be less than ideal due to the poor crown-to-root ratios of the abutment teeth. An 8-unit bridge spanning teeth Nos. 5 through 12 was also considered, but the patient was worried about the possibility of future bone resorption after the extractions. To avoid the use of unstable abutment teeth and limit unnecessary extractions, placement of a 4-unit implant-supported bridge with implants at the sites of teeth Nos. 7 and 10 was considered but deemed infeasible due to inadequate bone volume at those sites unless guided bone regeneration was performed.
Ultimately, the patient agreed to a treatment plan involving placement of a 6-unit implant-supported bridge spanning from the tooth No. 6 site to the tooth No. 11 site. PET was planned for teeth Nos. 6, 8, 9, and 11, where the implants would be placed, and root banking would be performed on teeth Nos. 7 and 10 in the pontic locations. To achieve optimal esthetics, lithium disilicate veneers would be placed on teeth Nos. 5 and 12. A digital mock-up of the potential results of the proposed treatment was created for evaluation (Figure 4).
Surgical Phase
PET (K0297 PET™ System, Brasseler) was performed and implant placement was accomplished using a surgical guide (Precision Guided Surgery) to preserve the buccal bone and ensure precise, prosthetically driven implant placement.3 At each implant site, the PET2 bur was used to follow the canal path 2 to 3 mm short of the apex, the PET1 bur was used for initial mesiodistal root sectioning, the PET3 bur was used to extend the cut at the interseptal bone without damaging it, and the PET4 bur was used to widen the canal buccally and lingually.
The osteotomies were prepared with the guide; if the palatal piece remained, PET3 was used to remove it. A chisel was tucked between the root and buccal bone, followed by the use of the PET6 bur to trim and the PET7 bur to shape the shield. The buccal shield was refined to under 1-mm thickness and set 0- to 1-mm below the buccal bone.
In total, four PET procedures and two root bankings were completed, followed by the placement of four implants (ET Implant System [ET III and ET IV] Hiossen Implant) with temporary abutments. The total chair time for the entire surgical procedure, including anesthesia, was approximately 2 hours. Cone-beam computed tomography (CBCT) scans were performed after the completion of PET and after implant placement to evaluate the success of treatment (Figure 8).
Temporary Prosthesis Fabrication
A 6-unit flipper, which was designed (DentalCAD, exocad) to hook around the posterior molars to offer excellent retention, was 3D printed with a nanoceramic, biocompatible denture tooth resin (APEX Teeth [shade A1], SprintRay) (Figure 9). It was delivered immediately following implant placement to guide the soft-tissue healing and maintain esthetics (Figure 10 and Figure 11). The patient wore the flipper for a 4-month healing period, even during eating, which gave the implants time to osseointegrate. When compared with Essix-style retainers, flipper-style provisional restorations can offer greater comfort and function.
Later in the healing period, the flipper was converted into a temporary bridge by removing the wings and adapting the teeth to four temporary abutments with a flowable composite (3M™ Filtek™ Supreme Ultra Flowable Restorative [shade A1], Solventum) (Figure 12).
Final Prosthetic Rehabilitation
After completion of the healing period, the ridge and soft tissue were evaluated and determined to be stable (Figure 13). An impression was then acquired to inform the design and fabrication of the final 6-unit zirconia bridge (Cercon®, Dentsply Sirona) and veneers by the laboratory (Protea Dental Studio) (Figure 14 and Figure 15). Prior to delivery of the final bridge, gingival inflammation was observed at the site of tooth No. 7. A periapical radiograph revealed a periapical radiolucency around the root banking site; therefore, the root was surgically removed. As expected, soft tissue shrinkage followed,3 which resulted in reduced volume in the pontic area. Once the final 6-unit zirconia bridge was ready for delivery, it was seated with gold-plated abutments to ensure optimal esthetics for the patient's thin gingival biotype (Figure 16 through Figure 21).
Conclusion
This case demonstrates the benefits of PET in anterior implant placement, particularly in maintaining ridge integrity and soft-tissue esthetics. With digital planning, root banking for the pontic sites, and thoughtful design of the provisional restoration, a functional and esthetically harmonious outcome was achieved.
Michael An, DDS
Michaelangelo
Redmond, Washington
Figures and Images
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