Technology Upgrades in Re-treating a Hybrid Prosthesis

INTRODUCTION
Technologic advances in full-arch implant reconstruction have made the process streamlined and predictable. Media and Internet searches directly propose improved quality of life and function with dental implants to the public. Although it may appear to be simple, the protocols needed to achieve aesthetics and chewing efficiency with this procedure are relatively complicated. Continued education on the techniques and steps involved will make the general practitioner more proficient and efficient in providing this mode of treatment.

Implant dentistry may be the single most important treatment modality for replacing edentulous spaces today. Patients are now presenting to our practices requesting information on the process and subsequent reconstruction. Edentulous areas are now predictably restored with fixed or implant-retained, detachable prostheses. These will help minimize further bone loss, which physiologically occurs when teeth are extracted and conventional removable appliances are fabricated.¹ Obviously, having fixed teeth is beneficial to the patient’s self-confidence when smiling, kissing, and speaking and provides improved health through better nutrition and chewing efficiency.

Visualizing the final restoration prior to any surgical intervention is certainly an art form in dentistry. There must be a comprehensive appreciation for both surgical and prosthetic applications and a concise understanding of vital anatomy, including the viable nerves and sinus areas. If we consider modern implant dentistry to be prosthetically driven, we need to assume that the implants are not only placed in available hard tissue but that we also take a “tooth up or down” approach to maximize emergence profile and smile design. There are several reasons why many of our colleagues are not currently surgically placing dental implants. These include a lack of competence and confidence due to lack of education and fear of complications that could occur due to damage to vital anatomy. However, our patients are presenting to our practices requesting information on the procedures.

Computer tomography diagnosing is a progressive method of idealizing implant position and prosthetic construction. We can now use software to virtually place our implants and determine the final tooth position prior to any surgical intervention.^2,3 Precise surgical guides are fabricated, which, when accurately created, can ensure a positive placement. Since the dental implants are idealized, the final reconstruction is made more accurate and predictable with an improved long-term prognosis. The 3-D approach provides the practitioner with much information on the anatomy required for proper integration of our dental implants. CBCT analysis is an excellent diagnostic tool that allows for a determination if implants are possible or if the case is beyond the experience of the general practitioner. In the latter case, the patient could be referred. Bone and tissue are evaluated, and the type, length, width, and position of the implants are determined. Two-dimensional, conventional periapical and panoramic dental radiographs do give us some important information as to vertical bone availability, but the ability to see the sagittal, cross-sectional view of the facial-lingual/palatal hard tissue is paramount. The coDiagonstiX CBCT implant planning software (3D Diagnostix [3DDX]) helps in determining the position of the final tooth restoration. CT scans generate volume images from digitized information that result in a cross-sectional or sagittal view, an axial view, and a panoramic view. There is no distortion of the images, so precise measurements of bone availability can be made.4 With a consultation from 3D Diagnostix, a surgical guide was created. This process allows for reduction in the surgical time involved and provides the dentist with confidence in implant positioning. The coDiagnostiX planning software gives me a high level of confidence in placement. Our patient was impressed by the idea of virtual placement of the implants. With the help of the stable surgical guide, stabilized by the 3 remaining previously placed implants with healing abutments and stabilizing pins, the implants were placed to the desired depth and angulation.⁵

The clinical case presented herein demonstrates an invasive surgical procedure that was restoratively driven in that the final aesthetic design had been determined prior to surgery.

CASE REPORT
A 65-year-old male patient who presented to our office was on Eliquis for blood clots following an automobile accident. His cardiac condition was controlled, and he was otherwise in general good health. Figure 1 illustrates the maxillary implant-retained hybrid appliance fabricated 8 years ago for this edentulous patient. At that time, eliminating his conventional maxillary complete denture and replacing it with a fixed implant-retained prosthesis was important to him. The design was rather complicated, with a zirconia infrastructure milled and threaded directly into his dental implants. Because the access holes would have penetrated through the facial aspect of the prosthesis, individual crowns were cemented onto the screw-retained infrastructure. Unfortunately, the severe automobile accident debilitated him for an extended period of time. There was also significant facial trauma, which resulted in an eventual loss of several of the abutment implants and the maxillary prosthesis (Figure 2).

Proper bone sites needed to be created prior to considering implant placement. To expedite healing of the dehisced sites that required grafting, venous blood was drawn and used to fabricate a platelet-rich fibrin (PRF) clot.⁶ This clot would be used as a protective membrane over the grafted socket sites (Figure 3). The implants were removed, and the sockets were aggressively curetted. A demineralized allograft material (Newport Biologics) was used to repair the bone defects created by implant removal. The PRF membrane was positioned to protect the graft from invagination of the epithelium during the 4-month healing phase (Figure 4).⁷ The 3 remaining Replace Select Tapered (Nobel Biocare) implants were maintained since they were well integrated. Some physiologic bone loss had occurred over the previous 8 years, but it was not significant enough to warrant the removal of the implants (Figure 5). Figure 6 illustrates the suturing (Vicryl [Implant Direct]) of the attached gingiva over the grafted site. Because the patient had been converted back to a conventional maxillary complete denture during the extensive integration time that was required of the grafted material following implant removal, a reline material (Mucopren [Kettenbach LP]) was used as a long-term liner during the healing phase (Figure 7). The postoperative CBCT analysis (Vatech America) indicated remodeling of the bone (Figure 8).

Following the integration of the allograft material, Figure 9 illustrates the virtual planning that was completed to visualize implant position prior to any surgical intervention (coDiagostiX) planning software). To create a proper surgical guide, CBCT DICOM files were electronically sent to 3DDX through 3DDX Connect (a HIPAA-compliant online portal), along with models of the edentulous ridge and a bite-relations record.4 From this information and CBCT analysis, a 3-D reconstruction of the patient’s CT scan was done.

Virtual planning revealed all the vital anatomy and eventual positioning of the implants to accommodate emergence of an aesthetic bridge. A bone-level surgical guide was created over the previously placed and integrated dental implants (Figure 10). Using the Hahn Tapered Implant Surgical Kit (Glidewell Laboratories), the dental implants were precisely positioned through the surgical guide in the posterior maxilla. The Hahn Tapered Implant was selected because of its pronounced threads that help establish initial implant stability. The machined collar helps prevent bone loss around the necks of the implants and also provides a cleansable surface. The prosthetic connection has a built-in platform-switching design that helps minimize physiologic bone resorption.⁸

The osteotomies were created through the surgical guide, and the implants were also torqued to 35 Ncm through the guide (Figure 11). The post-op panoramic radiograph in Figure 12 illustrates the position of the newly placed dental implants. The implants were allowed to integrate for an additional 4 months, after which impression copings were threaded to place to allow for fabrication of a master cast at the dental laboratory (Glidewell Laboratories) (Figure 13).

The prosthetic process began with screw-retained stable record bases, followed by a denture tooth wax setup to establish the desired aesthetics and occlusion (Figure 14). In this case, the dental laboratory team milled custom titanium abutments with margins just slightly subgingival. This would help maintain periodontal health and make hygiene maintenance by the patient easier (Figure 15)^9,10 Once the wax set-up try-ins were deemed acceptable by the patient, the lab team created a polymethyl methacrylate (PMMA) transitional appliance to, once again, verify form and function (Figure 16). The PMMA illustrated in Figure 17 was then returned to the dental laboratory for the fabrication of the final cementable solid zirconia (BruxZir [Glidewell Laboratories]) implant-retained prosthesis. This implant-retained bridge was cemented with a transitional implant cement (IMPROV [Salvin Dental Specialties]). Figure 18 shows the final CBCT analysis of the final implant-retained prosthesis.

DISCUSSION
The advantages of CAD/CAM technology in the creation of our dental prosthetics includes ease of milling, fabrication precision, and reduction in human error. The zirconia materials used in this case are strong and fracture-resistant. Because our patient had experienced the advantages of a fixed maxillary prosthesis for more than 8 years, there was a desire to replicate the form and function of that previously designed screw-retained zirconia hybrid appliance. To meet the patient’s expectations, additional implants needed to be placed in healthy bone structure.¹¹ The process was challenging, but with the use of high-quality allograft material and surgical techniques using PRF membranes to protect the graft from epithelial invagination and the eventual placement of implants that provided initial stability and integration, an acceptable replacement was provided to the patient.

CLOSING COMMENTS
Diagnosing and planning are most critical in any complex prosthetic reconstruction. The advances in materials used and technologic tools, like CBCT and planning software, provide a means of establishing acceptable tooth replacement. The fixed implant-retained prosthesis was certainly a viable option for this edentulous patient. Aesthetics, function, stability, increased chewing efficiency, better speech, and excellent wear resistance are a few of the advantages of this modern dentistry.

References

1. Kern JS, Kern T, Wolfart S, et al. A systematic review and meta-analysis of removable and fixed implant-supported prostheses in edentulous jaws: post-loading implant loss. Clin Oral Implants Res. 2016;27:174-195.
2. Ganeles J, Mandelaris GA, Rosenfeld AL. Image guidance for implants. Inside Dentistry. 2013;9:96-100.
3. Kosinski T. Technology makes a complicated implant restoration simple. Dent Today. 2011;30:128-135.
4. Jacobs R, Salmon B, Codari M, et al. Cone beam computed tomography in implant dentistry: recommendations for clinical use. BMC Oral Health. 2018;18:88.
5. Tischler M. A maxillary fixed bridge supported by dental implants: treatment sequence and soft tissue considerations. Compend Contin Educ Dent. 2012;33:340-344.
6. Magalhães VS, Ribeiro RA, Leite do Amaral JMB, et al. The use of platelet rich fibrin in dental implants: a literature review. Trends in Transplantation. 2018;11:1-3.
7. Misch CM. Maxillary autogenous bone grafting. Dent Clin North Am. 2011;55:697-713.
8. Kosinski TF. Placing implants in sites lacking keratinized tissue. Inside Dentistry. 2017;13:42-50.
9. Javed F, Ahmed HB, Crespi R, et al. Role of primary stability for successful osseointegration of dental implants: factors of influence and evaluation. Interv Med Appl Sci. 2013;5:162-167.
10. Carames J, Tovar Suinaga L, Yu YC, et al. Clinical advantages and limitations of monolithic zirconia restorations full arch implant supported reconstruction: case series. Int J Dent. 2015;2015:392496.
11. Limmer, B, Sanders AE, Reside G, et al. Complications and patient-centered outcomes with an implant-supported monolithic zirconia fixed dental prosthesis: 1 year results. J Prosthodont. 2014;23:267-275.

Dr. Kosinski is an affiliated adjunct clinical professor at the University of Detroit Mercy School of Dentistry (Detroit Mercy Dental) and is the associate editor of the AGD journals. He is a past president of the Michigan Academy of General Dentistry. Dr. Kosinski received his DDS degree from Detroit Mercy Dental and his mastership in biochemistry from the Wayne State University School of Medicine. He is a Diplomate of the American Board of Oral Implantology/Implant Dentistry, the International Congress of Oral Implantologists, and the American Society of Osseointegration. He is a Fellow of the American Academy of Implant Dentistry and received his mastership in the AGD. Dr. Koskinski is the Implants Editor of Dentistry Today. He can be reached at drkosin@aol.com or via the website smilecreator.net.

Disclosure: Dr. Kosinski reports no disclosures.

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