The fixed all-on-4 prosthesis is the pinnacle for replacing a fully edentulous arch of missing teeth. This concept was introduced to overcome the effect of total tooth loss, limiting the number of implants to 4, with the distalmost implants being tilted up to 45°. The concept was to shorten the posterior cantilever and to allow for forces to be distributed differently than over straight implants. The first clinical case using the all-on-4 protocol was installed in 1998 by Paulo Maló, and many years passed before this concept became accepted as a viable solution to replace an entire arch of teeth.1 A number of widely respected oral implantologists felt this number of implants could not withstand the forces of mastication and panned this concept as flawed and underengineered, considering it an inferior treatment to the mainstream use of 8 (or more) implants distributed over the entire arch.
The Virtual Patient
Three-dimensional analysis with CBCT imaging has yielded the unparalleled capabilities of virtual implant planning with optimal treatment outcomes. A complete study of all maxillofacial anatomy provides the necessary information with which to safely, accurately, and predictably treat challenging edentulous implant cases. The introduction of advanced Simplant software (Dentsply Sirona Implants) in 1991 improved the visual analysis of the maxillofacial anatomy and, combined with CBCT imaging, makes our surgeries today more successful than ever. Real-life, undistorted images of bone architecture, bone volume, vital anatomical structures, and bone densities are revealed without having to expose the patient to exploratory surgery. Strategic clarity is the result of combining the patient’s dentition with the bony anatomy to develop a computer-assisted surgical guide that is customized for each patient’s unique situation.2
|Figure 1. The initial implant plan.|
|Figure 2. The initial presentation.|
This article will review the process employed to return a failing maxillary arch to a fully functioning fixed screw-retained dentition. The treatment for this patient was considered as a reclamation project requiring multiple dental disciplines and making use of the most sophisticated digital imaging of GALILEOS (Dentsply Sirona) and Simplant software to provide state-of-the-art treatment. Simplant software became the foundation for the treatment planning and was used to facilitate the production of the Simplant SAFE Guide (Dentsply Sirona Implants) mucosal surgical guide that would be employed to install 6 implants. The actual placement followed the virtual plan closely, allowing for the conversion of a complete upper denture to a fully fixed screw-retained prosthesis that satisfied all the desires of this patient and resulted in an aesthetic and fully functioning dental arch of teeth in a single visit. The use of a “teeth-in-a-day” protocol in my practice allows for the rehabilitation of an arch in a single visit with outstanding results. In the maxilla, 1 or 2 implants may be added to improve the overall stress distribution when less favorable bone quality and volume are encountered in these cases.
The clinical treatment described in this case report follows an evidence-based plan and employed the knowledge, clinical experience, and judgment gained by the author in the past 34-plus years.
Our patient, who had neglected his oral health for years, initially presented with multiple failing and missing teeth. After performing all conventional diagnostic procedures, I recommended (and the patient agreed to) an enhanced 3-D CBCT scan. The imaging helped us evaluate his maxillofacial anatomy. It was determined that he could be treated conservatively by extracting tooth No. 3, placing 2 implants in the upper-left quadrant, and utilizing his remaining natural teeth and the implants to retain a partial upper denture (Figure 1). With this treatment, he would require periodontal maintenance multiple times per year to retain his natural dentition.
|Figure 3. The processed immediate denture.|
|Figure 4. An edentulous maxilla dual-scan technique for the complete upper denture (CUD).|
|Figure 5. Individual implant sites.|
|Figure 6. A 3-D scan of the skull with a virtual plan. This is where technology and the art and science of dentistry meet.|
|Figure 7. An all-on-6 plan and virtual guide.|
|Figure 8. The axial view and various bone views post site development.|
This initial treatment plan was rejected. He desired a long-term solution as opposed to maintaining his natural dentition with a poor prognosis due to periodontal breakdown and the previous loss of premolars and molars. Psychologically, he could not commit to continual treatment to maintain or modify his maxillary dentition as conditions changed.
A second treatment option was presented that involved full-arch extractions, bone grafting, and the placement of 4 implants to retain a cast-reinforced palate-less overdenture. This is the treatment option that he agreed to as a definitive treatment solution.
Preparation for his accepted treatment option began by extracting tooth No. 3 (his chief complaint was pain in this area) and then teeth Nos. 2 and 5. An immediate complete upper denture was fabricated and inserted after extracting and bone grafting 5 remaining teeth (Figures 2 to 4). Additional labial grafting in the area of teeth Nos. 11 to 13 was also accomplished during this visit.3,4 Healing was uneventful, but the anatomical limitations that existed in the edentulous maxilla precluded retention and stability, thus reducing function for this patient. A palatal torus that was present in the posterior palatal seal area, multiple frenum pulls throughout the arch, and a narrow and shallow flat palate with little vestibular depth all resulted in a non-retentive foundation for adequate function. This condition led this patient to upgrade his treatment plan from a removable overdenture over 4 implants to the all-on-6 fixed prosthesis. Inadequate retention and function could be completely reversed with the “teeth-in-a-day” approach5 (Figure 5).
The Digital Treatment Plan and Surgical Guide
A virtual patient plan was created with a digital workflow using the Simplant software. The dual-scan technique was employed to fabricate a well-distributed “all-on-6 implant” plan. This required scanning the patient’s existing complete upper denture with eight 2.3-mm markers distributed across the labial and palatal acrylic denture base and flanges. This radiographic scan appliance must be scanned in the same orientation as the prosthesis was inserted during the patient scan. These 2 scans are merged and become the blueprint for the virtual implant positions, which results in the digitally produced Simplant mucosal SAFE Guide surgical guide.
Our treatment plan called for the installation of 6 implants through a flapless guided implant surgical approach. The sizes and positions of each NobelActive (Nobel Biocare) implant were carefully planned so that the angulation and depth would be precisely observed during the surgical phase of the visit. Knowing the maxillary anatomy allowed us to plan and place our implants while considering the available bone volume and avoid penetrating the maxillary sinus and incisive canal. The screw access holes within the prosthesis will be directed to exit through the occlusal fossa, in the anterior cingulum areas or more palatal, and avoid coming out the labial portion of any crown. The result of the digital plan is the production of a sophisticated, well-fitting surgical guide that can be affixed to the maxilla through the use of fixation pins. The process of developing a treatment plan to eliminate mistakes with vision, otherwise known as “the art of seeing the invisible,” leads to a reduction in surgical time by as much as 50% and the installation of well-positioned, strategically placed implants that are placed within submillimetric precision to the planned positions. This type of accuracy allows for a minimally invasive surgery when conditions allow and, consequently, faster healing, as the tissue punch and flapless approach preserves the vascular structure through transmucosal drilling. These cases are usually handled with local anesthesia, and bleeding is minimized and sutures are unnecessary. The common cascade of events that follow conventional flap surgery, ie, edema, swelling, pain, and possible suture openings, are avoided during flapless guided implant surgery.6-8
|Figure 9. The surgical guide (Simplant [Dentsply Sirona Implants]) with fixation pins.||Figure 10. A Simplant SAFE Guide (Dentsply Implants) (mucosa-supported), prepared for the surgical phase.|
|Figure 11. Guided implant surgery.|
|Figure 12. Immediately after removing the surgical guide.||Figure 13. Multiunit abutments.|
|Figure 14. A CUD was seated over temporary cylinders and trial material.|
|Figure 15. The prosthesis is connected to the cylinders.|
Much of the case workload was accomplished prior to the surgical visit. The immediate complete upper denture became the conversion prosthesis that was going to be altered to become a fixed, screw-retained, teeth-in-a-day solution for our patient. Although the denture lacked the stability and retention for function, it was aesthetically pleasing and maintained the proper vertical dimension for its transition to a fully fixed prosthesis. The smile curve was natural and had the proper amount of tooth display. This denture was actually the basis for the mucosal guide that would be used the day of surgery. The 3-D plan in Simplant was transferred to the digitally produced surgical guide, which, in turn, would be used to regain what was lost when this patient became edentulous: his ability to speak, smile, and chew normally (Figures 6 to 12).
The treatment team for this case included 2 surgical assistants, a photographic assistant, a dental laboratory technician, and me. I performed the implant surgery and prosthetic treatments that this teeth-in-a-day, implant-supported process required. The team prepared the surgical operatory in advance of our patient’s appointment. Our patient was pre-medicated with Amoxicillin (500 mg) and would continue with this antibiotic for 7 days. A dose pack of 4-mg Medrol was prescribed to aid in the reduction of postoperative swelling. Local anesthesia was delivered to anesthetize the entire maxilla, and 6 tissue punches were drilled through the guide once the 1.5-mm fixation pins secured the guide into the alveolar bone through the labial flange as previously planned. The guide was removed to clear the tissue and expose the underlying bone using a sharp surgical curette and rongeurs. The first implant site was drilled in the area of tooth No. 13 to become an additional fixation area for the guide when the implant would later be inserted and secured with a guided fixture mount. One by one, each osteotomy was prepared under copious irrigation with sterile saline, and then each site was irrigated to remove any surgical debris. A total of 6 NobelActive implants were placed through the Simplant SAFE Guide as anticipated and without incidence. As the fixation pins were removed and fixture mounts unscrewed, we would quickly discover that the surgery was accomplished in a minimally invasive manner and there was little to no bleeding in the surgical field. A Resonance Frequency Analyzer (RFA) (Osstell) was used to determine if the bone-to-implant contact was sufficient to allow for an immediate load of the implants installed.9 An Osstell peg was hand tightened into each of the 6 implants and produced readings of 64 to 70 ISQ. This objective measurement gave us the confidence to provide our patient with a fixed prosthesis, knowing that the initial mechanical stability of the implants is adequate to handle the masticatory load that will be introduced when this patient begins chewing again. Over time, this mechanical stability will be replaced by a biological stability that will lead to the completion of osseointegration during the bone-remodeling phase of this process. (Figures 13 to 14).
Prosthetic Phase of Treatment
After all 6 implants were evaluated using the Osstell RFA device, we proceeded to insert multiunit abutments to change the platform level and to redirect the implant angulations so that the screw access holes would exit through a central fossa (or more palatally). This avoids the access being through a labial surface, hindering the aesthetics of the prosthesis. I filled up the intaglio surface of the denture with a bite material and seated the maxillary denture so that the lab technician could begin preparing openings through the denture. These openings are where the temporary cylinders would peak through for fixation during the conversion process. The openings needed to be large enough for the denture to be fully seated at its desired vertical dimension. This took a while to complete, as we moved around the arch and opened individual sites until all 6 temporary cylinders exited through the openings without interference. I hand tightened each prosthetic screw into its implant and covered the access holes with Teflon tape and light-body impression material. When it became possible to seat the denture completely, the lab tech filled the openings with a triad acrylic, and the denture was inserted and removed without curing the triad base material. This material doesn’t flow and keeps its shape inside the opening and over the cylinder. What followed was the most important part of the conversion: A dried surface is absolutely necessary to gain a connection between the cylinder and the acrylic. Dual-cure acrylic was syringed around each temporary cylinder, and then the denture was inserted until fully seated. My assistants cured the acrylic for approximately 4 minutes. This prosthesis was now fixed, and, once the acrylic was fully cured, I removed the light-body impression material and Teflon tape covering each cylinder so that I could unscrew the prosthetic screws and remove the fixed prosthesis. Periapical radiographs were taken to verify the full seating of each multiunit abutment over its respective implant10-13 (Figures 15 to 17).
|Figure 16. A postoperative, panoramic radiograph.|
|Figure 17. Post-op cross-section views of 4 implants.|
Laboratory Work and Delivery of the Fixed Prosthesis
The dental laboratory technician at Innovation Dental in Jersey City took over from this point and my patient and I took a needed respite. This began the conversion of the complete denture to a fixed, screw-retained, interim hybrid prosthesis. The lab process took about 75 minutes to complete. We used the downtime to obtain a post-op CBCT scan. The 3-D analysis validated the guided surgery that was accomplished without any unexpected interruptions. The implant placement distribution looked good, with full expectations that they would function well after loading under controlled occlusion. The palate and flanges were removed, and a highly polished, hybrid-designed acrylic prosthesis was produced. The resultant prosthesis was finished with emergence profiles that were contoured to support the patient’s lip without overlapping the gingival tissue. The laboratory technician took great care to finish the gingival surfaces with a glaze-like polish, and the prosthesis was modified to allow implant floss threaders to pass underneath to properly maintain the undersurface.
|Figure 18. The converted hybrid prosthesis.||Figure 19. The prosthesis was secured on 6 abutments.|
|Figure 20. The fixed interim all-acrylic prosthesis was inserted. The patient was delighted with the outcome.|
Our day’s work culminated with the placement of a fixed dentition that reclaimed the patient’s ability to smile, speak, chew, and function as he should. We knew the prosthesis would seat properly because we allowed the conversion process to completely finish undisturbed over the implants. The all-on-6 hybrid was tried in and evaluated for any movement. The prosthesis was checked with the Sheffield screw test, and it passed, showing no rocking on the 6 implants. The occlusion was handled by creating even contacts in centric occlusion across the arch, canine guidance, and freedom in lateral excursions. A follow-up regimen was prescribed, and the patient was dismissed (Figures 18 to 20).
Our team approach is synchronized with a common goal in mind: to provide patients with life-changing implant treatment outcomes in the most efficient and effective ways. This patient’s demand for a fixed case necessitated careful evaluation of the regenerated bone volume. Evaluating the images using Simplant software has advanced patient care by marrying the art and science of dentistry, as the software was used to streamline and innovate the rehabilitation of the patient’s edentulous condition.14 The visual analysis and conversation with the patient was made clearer during case presentation due to the creation of the digital virtual patient. Three-dimensional imaging was used to uncover and avoid potential pitfalls that the clinician may encounter during maxillofacial surgery. The reduction in post-op complications is a common occurrence, along with our patients requiring fewer post-op medications and little to no interruption to their daily routines. I attribute this to the use of 3-D imaging and flapless guided implant placement.
Our patient was given the confidence and ability to smile, chew, and function normally again after being debilitated by his loss of teeth. At a follow-up visit, he commented, “I felt as if nothing had been done.” He was overjoyed with the results.
The clinical results of the digital workflow validate the use of 3-D imaging and guided implant placement, and the patient testimonials reinforce the success of this protocol.
The author would like to thank the laboratory team at Innovation Dental in Jersey City for the work performed in this case.
- Maló P, de Araújo Nobre M, Lopes A, et al. “All-on-4” immediate-function concept for completely edentulous maxillae: a clinical report on the medium (3 years) and long-term (5 years) outcomes. Clin Implant Dent Relat Res. 2012;14(suppl 1):e139-e150.
- Ganz SD. Conventional CT and cone beam CT for improved dental diagnostics and implant planning. Dent Implantol Update. 2005;16:89-95.
- Garg AK. Bone Biology, Harvesting, & Grafting for Dental Implants: Rationale and Clinical Applications. Chicago, IL: Quintessence Publishing; 2004:97-110.
- Buser D. 20 Years of Guided Bone Regeneration in Implant Dentistry. 2nd ed. Chicago, IL: Quintessence Publishing; 2009:47, 50, 82.
- Christensen GJ. Recommending the best treatment for patients. J Am Dent Assoc. 2013;144:426-428.
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- Osstell. The technique behind Osstell and how ISQ correlates to torque. www.osstell.com/clinical-guidelines. Accessed February 11, 2018.
- Moy PK, Palacci P, Ericsson I, eds. Immediate Function & Esthetics in Implant Dentistry. Chicago, IL: Quintessence Publishing; 2009:58-60, 96-98.
- Babbush CA, Kutsko GT, Brokloff J. The All-on-Four immediate function treatment concept with NobelActive implants: a retrospective study. J Oral Implantol. 2011;37:431-445.
- Orentlicher G, Horowitz A, Goldsmith D, et al. Cumulative survival rate of implants placed “fully guided” using CT-guided surgery: a 7-year retrospective study. Compend Contin Educ Dent. 2014;35:590-600.
- Orentlicher G, Goldsmith D, Horowitz A. The power of 3-D computer-generated implant planning and surgery. Selected Readings in Oral and Maxillofacial Surgery. 2009;17:1-32.
- Tardieu PB, Rosenfeld AL. The Art of Computer-Guided Implantology. Chicago, IL: Quintessence Publishing; 2009:74-83, 200-207.
Dr. Ramirez earned his DDS degree from the New York University College of Dentistry. He is a Master of the AGD and a Diplomate of the International Congress of Oral Implantology. He maintains a private practice in Brooklyn, NY, focusing on cosmetic smile design and implantology. He utilizes 3-D CBCT imaging and CEREC CAD/CAM technologies to promote a fully integrated digital dental practice to improve the quality of life for his patients. He can be reached at (718) 748-3003 or via email at firstname.lastname@example.org.
Disclosure: Dr. Ramirez is a key opinion leader for Dentsply Sirona, a CEREC Doctors mentor, and a CEREC trainer.