Maxillary Incisor Replacement for a Patient With High Esthetic Demands
Partial extraction therapy maintains gingival architecture for immediate implant placement
Rick Ferguson, DMD
The use of dental implants to replace missing teeth has become the norm in many instances; however, challenges still remain, particularly in the esthetic zone. Research into partial extraction therapy has added a useful tool to clinicians' armamentaria to overcome problems associated with resorption of the buccal aspect of the ridge following extraction and implant placement. Partial extraction therapy for immediate implant placement involves sectioning the crown from the roots, sectioning the roots mesiodistally, and then extracting the palatal portion, leaving a thin shell of the buccal root intact and attached to the bone and periodontal tissues to help preserve the ridge. The following case demonstrates the benefits of partial extraction therapy for a patient with high esthetic demands.
Case Report
A 59-year-old female patient presented to the practice for a second opinion regarding a draining fistula on the palatal aspect of the gingiva associated with tooth No. 8. Previously, she had been advised by another dentist that because there was most likely a root fracture, the tooth should be extracted and replaced with an implant. A cone-beam computed tomography (CBCT) scan (CS 8100, Carestream Dental) was performed, which revealed the presence of a long post that extended palatally to the edge of the root (Figure 1). The post space appeared to have been prepared outside of the root canal space, leaving a thin area on the palatal portion of the root with the possibility of a palatal root perforation.
A weakened area like this is prone to stress fracture from any lateral forces on the post transmitted through the crown, so the previous dentist's impression that root fracture was the cause of the fistula appeared to be correct.
Treatment Planning
The patient was very concerned about the esthetic result, and she indicated that she wanted the implant-supported crown to look identical to the existing one and the shape of the gingiva to remain unaffected. Due to the hard- and soft-tissue changes that occur after tooth extraction, even with immediate implant placement, this type of high-demand case requires proper treatment planning and attention to detail to achieve the desired result.1 Partial extraction therapy was suggested to meet this patient's demands because it can help to retain the dimensions of the existing gingival architecture with no detrimental effect on the osseointegration of an implant placed into the remaining socket if a proper protocol is followed.2 If initial implant stability is not ideal, support of the soft-tissue structures with a temporary crown or customized healing abutment can help to prevent tissue collapse as well.
The risks were explained to the patient, and she elected to proceed with the treatment plan, which involved the use of a guided surgical protocol (Guided Surgery Kit, BioHorizons) to facilitate immediate implant placement, followed by a temporization period for healing. Using the CBCT data and an intraoral scan (CS 3600, Carestream Dental), a digital design was created in planning software (Blue Sky Plan®, Blue Sky Bio) (Figure 2) and used to fabricate a surgical guide on an in-office 3D printer (Form 2, Formlabs). Research has shown that surgical guides produced by in-office 3D printers are similar in accuracy to those produced by laboratories.3
Surgical Phase
Once profound anesthesia was achieved, the preexisting crown was sectioned and removed from tooth No. 8 to potentially be used as part of the new temporary restoration (Figure 3). A partial extraction therapy kit (P.E.T. Partial Extraction Therapy Bur Kit, Salvin Dental Specialties) was then used to section the root of the tooth to the apex, facilitating removal of the palatal portion but leaving a "shield" that remained attached to the buccal plate (Figure 4 and Figure 5). In addition to maintaining this portion of the root's attachment to the buccal bone, it has been suggested that it be thinned into a concave shape.4
Following partial extraction therapy, the 3D printed surgical guide was inserted into the mouth and used to create the osteotomy for the implant. The implant's position was digitally designed so that there would be a space of at least 1 mm between the implant and the shield after placement to allow for full bony integration. To achieve the highest level of precision, the implant was placed through the surgical guide (Figure 6). Resonance frequency analysis was then performed (Osstell® ISQ, Osstell), which revealed that the implant's implant stability quotient (ISQ) was 64 (Figure 7). Because it is recommended to avoid fully loading an implant with an ISQ below 70, the decision was made to place a custom healing abutment instead. The custom healing abutment was fabricated by reducing a stock temporary abutment (Easy Ti Temp Abutment, BioHorizons) and adding a flowable composite to establish the desired emergence profile (Figure 8). After a bone allograft blend (MinerOss® Cortical & Cancellous, BioHorizons) was packed between the implant and the root shield (Figure 9), the custom healing abutment was placed with a membrane of concentrated growth factors using Sohn's poncho technique5 to create a biologic tissue seal (Figure 10 and Figure 11). A postoperative CBCT scan was acquired, and the patient was temporized with a removeable Essix appliance. Overlaying the postoperative CBCT image with the digital plan demonstrates the accuracy of the actual final implant position that was achieved with the 3D printed surgical guide (Figure 12). The root shield as well as the grafted space between it and the implant can be appreciated in this image as well.
Restoration
After 5 months of unloaded healing, the custom healing abutment was removed, and a new screw-retained temporary crown was fabricated and delivered (Figure 13). This would help to finely develop the tissue contours to the patient's satisfaction. To provide the laboratory with the necessary data to fabricate a custom zirconia abutment with a titanium base that matched the subgingival contours of the screw-retained temporary restoration, the intraoral scanner was used to scan the temporary restoration extraorally Once the custom abutment was delivered to the practice, it was placed and scanned intraorally (Figure 14). This scan was used for the in-office design and milling (CS 3100 Milling System, Carestream Dental) of the final lithium disilicate crown (IPS e.max®, Ivoclar Vivadent), which was customized with staining and glazing to match the adjacent central incisor and bonded with a universal resin cement (Maxcem Elite™, Kerr Corporation). Following cementation, a radiograph was acquired to verify the seating (Figure 15).
Conclusion
The challenges presented by patients with high esthetic demands can necessitate knowledge and skills that transcend normal everyday dentistry. Surgical partial extraction therapy requires training, experience, and patience to accomplish successfully. If the root shield is dislodged in any way, it must be removed, leaving the site to be treated using traditional hard- and soft-tissue grafting techniques with potentially increased esthetic risks. When successful, partial extraction therapy to shield sockets for implant placement can reduce treatment times and increase the long-term esthetic success of cases in the esthetic zone, and research has demonstrated that it results in implant survival rates similar to those achieved by conventional immediate and delayed placement approaches.6 Placing a single anterior implant-supported crown requires attention to detail and good communication with the dental laboratory. Although this can be simplified through in-office fabrication and customization, that requires more time and effort on the part of the dentist and his or her staff. In this case, the effort paid off because the patient was pleased with the final result, which exhibited gingival architecture that for all intents and purposes looked identical to what it looked like preoperatively (Figure 16).
About the Author
Rick Ferguson, DMD
Diplomate
American Board of Oral Implantology/ Implant Dentistry
Director
Implant Educators Academy
Private Practice
Davie, Florida
References
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