INTRODUCTION
The advancements in full-arch dental implantology have provided dentists and their patients with tremendous advantages in restoring proper function and aesthetics when natural dentitions fail. Full-arch implant prosthetics have been classified by McGarry1 based on their aesthetic and functional demands into FP1, FP2, and FP3 restorations. The FP1 classification encompasses implant-supported prostheses that aim to exactly replicate the appearance and function of natural teeth with exceptional detail and precision. These restorations typically involve crowns or bridges supported by dental implants that only replace the crowns of the teeth and do not have any artificial gingiva. Instead, the goal when creating an FP1 restoration is to create prosthetic teeth that have a “socket fit” appearance where the prosthetic teeth are emerging out of the natural gingiva (Figure 1).
The FP1 implant restoration (Figure 2) represents the pinnacle in function and aesthetics in implant dentistry and most closely mimics the patient’s natural dentition, making it the preferred choice for patients seeking the highest level of dental implant care. To be sure, not every patient is a candidate for an FP1 prosthesis, and every treatment plan must be individually tailored to each one’s particular condition. However, it is concerning how many cases are being completed with a one-size-fits-all approach using excessive bone reduction to accommodate an FP3 prosthesis without ever considering FP1 as an option. This may result in serious long-term consequences for patients because if/when cases fail and require revision, the question will be, “What do you have left to work with?” The younger the patient undergoing treatment, the more this question should be at the forefront of our minds. To paraphrase G.V. Black, our goal as dentists is to make things fail as slowly as possible. By preserving as much bone as possible utilizing an FP1 approach, we are also preserving options for our patients down the road.
While most dentists generally agree upon this, the fact remains that FP1 restorations make up only a small percentage of full-arch implant prosthetics that are made today. There are several reasons why this is the case. The first reason is that not every patient is a candidate for an FP1 prosthesis. It is often the case, especially in patients who have been edentulous for some time, that patients will already have significant loss of bone and soft-tissue volume. In such cases, an FP1 is not an option because restoring these patients to the proper VDO would require replacement of the missing bone and soft-tissue volume in addition to the crowns of the teeth. This is a perfectly valid reason why an FP1 may not be the restoration of choice in some patients.
Another reason that FP1 prosthetics are often not used is that they can be extremely difficult to execute correctly from both a surgical and a prosthetic perspective. The fact that an FP1 is only replacing the crowns of teeth means that there is far less prosthetic space in both the vertical and horizontal components. Whereas an FP3 restoration may provide plenty of prosthetic space to use angled multi-unit abutments to correct less-than-ideal implant positions, the FP1 is much less forgiving and requires that the position of the implants be in the exact right spot. This requires meticulous preoperative planning of where the ideal teeth need to be for each patient and then precise placement of the implants within the arch to support those teeth.
Finally, the need to re-create a natural gingival architecture around the prosthesis can be very challenging. With an FP2 or FP3 restoration, there is usually a flat plane of bone reduction, and successful soft-tissue management is defined as having adequate keratinized gingiva around all the implants and cleansable contours around the restoration. The FP1 approach is far more demanding from a soft-tissue management perspective. Gingival architecture will follow the bony architecture, so re-creating a natural gingival profile necessitates that the bone is contoured in a scalloped profile, that the ideal prosthetic teeth are an exact distance from the bone, and that the prosthesis is perfectly contoured to train the tissue to have the correct gingival margins and interproximal peaks.
Given these substantial difficulties, it is not surprising that many clinicians opt for bone reduction and an FP2 or FP3 prosthesis, even when an FP1 approach may be a more ideal approach. It is the goal of this article to explain the digital approach to treatment planning, surgery, and prosthetics that the authors have used to achieve consistent and ideal results in FP1 full-arch implant cases.
This is my general process for full-arch guided surgery:
- Gather data: CBCT scans, IOS scans, facial scans, charting, patient desires, and photos.
- Determine where the ideal teeth should be using dual scans, smile simulations, digital wax-ups, and intraoral mockups.
- Decide what restoration can/should be done (overdenture, hybrid, FP1) based on available bone, prosthetic space requirements, and finances.
- Plan implant positions based on the ideal tooth positions.
- Design the appropriate surgical guides.
- Perform surgery.
CASE REPORT
A young male adult presented with a failing maxillary dentition (Figures 3 and 4). The presenting factors and challenges with this case (Figure 5) included:
- A high smile-line
- A gummy smile
- Apical incisal edge position
- Gingival asymmetry
- Maxillary excess
Upon collecting all the data, the planning stage begins. It is the authors’ opinion that figuring out where the ideal teeth should be is the most critical step in any complex case. The pictures of the patient’s face (Figure 6) are imported into PowerPoint, and lines are overlaid on the interpupillary line, the facial midline, and the interalar width, and, finally, a golden proportions ruler is scaled to fit the interalar width. This facial analysis clearly shows any existing deficiencies in the smile, such as midline shifts, occlusal cants, and height/width discrepancies.
It develops a frame into which the ideal teeth should fit based on the patient’s face.
This information is used to create a smile simulation (Figure 7) of the patient in PowerPoint to visually assess what the patient’s smile could look like. In this example, an attractive-looking smile was chosen from a library and positioned so that the incisal edges of Nos. 8 and 9 were at the wet/dry line of the lower lip (Figure 8). The library smile was then scaled so the anterior 6 teeth fit between the interalar lines and the individual teeth followed the golden proportions. Additionally, the smile is warped so that the maxillary teeth follow the general curvature of the lower lip. Given that this patient had excessive maxillary gingival display, the vertical height of the teeth were scaled up to find out where his gingival margins should be. Once an ideal simulation is achieved, it can be shown to the patient for approval and modified as needed. One very important step is to take the final simulated smile and reduce its opacity by 50% in order to visualize where the existing teeth are relative to where they should be. This is an incredibly valuable tool that can now be used to aid in creating a 3D, digital wax-up that mimics the 2D simulation (Figure 9).
The patient’s cone-beam scan was then imported into Blue Sky Plan (Blue Sky Bio) along with the intraoral scans (i500 [Medit]) and a 3D facial scan (MetiSmile [SHINING 3D]) representing a fully digitized patient. The same lines that were placed in the PowerPoint facial analysis can be imported into Blue Sky Plan as 3D facial planes, creating a similar grid that tells us where to position the teeth in the digital wax-up. By utilizing this facially generated grid and constantly referencing the image of the transparent simulated smile overlaying his actual teeth, it was possible to precisely design a digital wax-up that we knew would achieve an ideal aesthetic outcome (Figure 10).
Additionally, by utilizing the automatic bone segmentation feature in Blue Sky Plan, an accurate model of the maxilla and sockets was created. This is utilized to ensure that the new prosthetic teeth are designed to be emerging out of the pre-existing sockets. It should be noted that when there are major discrepancies between existing sockets—positions relative to where the ideal tooth should emerge (ie, major midline shifts)—the clinician should proceed with extreme caution to avoid re-creating the problems of the patient’s existing smile into his new prosthesis (Figure 11).
It should be noted that very little consideration is given to implant planning until this ideal digital wax-up (Figure 12) is completed because it is impossible to know where the implants belong until we know where the teeth belong. The implants are positioned (Figure 13) so that they emerge lingual to the incisal edges of the anterior teeth, through occlusal surfaces of the posterior teeth, and at a depth within the bone that will allow for a natural emergence out of the gingiva. Only at this stage can we be certain that an FP1 prosthesis is even possible to achieve. In this case, the ideal gingival margin location was significantly apical to his existing gingival margins. Visualizing the required implant depth to achieve these new gingival margins compared to his existing bone levels and gingival margins made it evident that strategic bone reduction would be required. In scenarios in which very precise reduction of bone and very precise implant positions and depth are required, guided surgery should be utilized (Figure 14).
The most posterior implants on each side did not require any bone reduction and lent themselves to a simple, tooth-supported guide that was designed in Blue Sky Plan. Not only was this simple to fabricate and use, but it was also desirable to place these 2 implants first for a different reason. When approaching such cases digitally, consideration must always be given to how the postoperative data scans and implant positions will be related back to the pre-op planning. Suppose all the teeth are removed and the implants are placed and scanned. In that case, the only common data that can be used to stitch the post-op to the pre-op is the palatal anatomy, which will be distorted from surgical trauma and injection of anesthetic.
By placing 2 implants first before removing the other teeth, an intermediate scan of the arch could be captured, which contained the first 2 implants placed as well as the existing teeth. This allowed it to be easily stitched back to the pre-op data by referencing the existing teeth. However, once all the teeth were removed and the last 4 implants were placed, the final scan was also easily stitched to the pre-op data using the common landmarks of the 2 implants that were placed initially. In this way, there was a continuous bridge of data that allowed exact stitching of all the post-op data to the pre-op data (Figure 15).
For the 4 remaining anterior implants, it was decided to create a thin, milled titanium scalloping guide to show exactly where bone needed to be reduced to accommodate the ideal tooth positions established in the digital wax-up. This was achieved by initially creating a solid 1.5-mm guide that sat directly on the maxilla. It is only possible to create ideal gingival contours if you create ideal underlying bone contours, and it was determined that 2 mm of space was needed between the prosthetic teeth and the bone, which would be occupied by soft tissue. To achieve this, each prosthetic wax-up tooth used the Boolean Subtract from the initial solid guide with an additional 2 mm of offset beyond the tooth. The resulting guide would be scalloped, showing exactly where bone needed to be contoured (Figure 16).
Following bone reduction, the remaining 4 implants would need to be placed, so a stackable, magnetic drill guide was 3D printed for guided implant placement (Figure 17).
Surgical execution of implant placement is faster, more proficient, and less stressful once the guide is fully seated. Prior to extracting all the teeth, we placed pterygoid implants in the posterior maxilla using the tooth-borne surgical guide. We placed a palatal fiducial used as a cross-reference marker for designing the prosthetics for the entire upper arch.
An IOS scan of the upper arch with 2 pterygoid implants was performed, incorporating the natural teeth and palatal reference marker. Once completed, we were able to remove all teeth and place our surgical guide. The metal “base” guide is used to support the fully guided surgical guide. Once AnyRidge (Mega’Gen) implants were torqued (>45 Ncm) into place, we could then remove bone scalloped profile based on the surgical guide contours (Figures 18 and 19).
Post-op intraoral scans were taken to capture the final implant positions and tissue, as well as an Imetric photogrammetry scan, which was used to correct any potential accuracy errors from the intraoral scan (Figure 20). The tissue was very loosely approximated with sutures, and the patient was released. The post-op scans were sent to the lab (Louisiana Dental Implant Lab), and all the data was stitched back to the pre-op planning data in exocad. The lab then indicated the final implant positions. They converted the digital wax-up that was done pre-op into a full-arch, screw-retained, FP1 prosthesis that screwed directly to the multi-unit abutment platform using the Vortex Screw (Louisiana Dental Implant Lab). This prosthesis was then printed in OnX Tough Resin at 50-µm resolution on the Pro 55 S 3D printer (SprintRay).
The following morning, the patient returned, the healing abutments were removed, and the immediate load FP1 prosthesis was delivered directly to AnyRidge MUAs. No anesthesia was required since the tissue was only loosely approximated. Furthermore, by leaving the flaps loosely approximated, the tissue was forced to heal by secondary intention, resulting in significant gains in keratinized gingiva. Additionally, the tissue conformed itself to the shape of the pontic forms of the ideal temporary, and there was no concern about developing black triangles since the bone had been precisely contoured to sit 2 mm below the prosthesis. The result was an FP1 prosthesis (Figures 21 to 24) that is difficult to distinguish from the natural dentition it replaced.
CONCLUSION
It is the author’s opinion, after completing many similar cases, that the digital workflow demonstrated in this article provides a paradigm shift in the way FP1 cases are approached. Such cases are incredibly complex and fraught with ways in which even small mistakes can derail the case, resulting in less-than-ideal outcomes. However, by leveraging the digital protocols shown, it is possible to remove many of these barriers to success.
The FP1 restoration, when executed well, is the closest thing to a natural dentition that we can offer to a patient. It is not the easiest or the most expedient option. It may not be the most affordable option. However, it is the option that virtually every dentist would want in his or her own mouth, and thus, it should be considered the gold standard of full-arch implantology and the treatment modality of choice whenever possible.
REFERENCES
1. McGarry TJ, Nimmo A, Skiba JF, et al. Classification system for partial edentulism. J Prosthodont. 2002;11(3):181-193.
ABOUT THE AUTHORS
Dr. Glenn graduated from the University of Tennessee (UT) Health Science Center College of Dentistry. Following graduation, he went on to complete the Lutheran Medical Center’s advanced education in general dentistry residency at the UT Memphis branch. He is a graduate of the Georgia Maxi Course in Implant Dentistry and the American Orthodontic Society’s Comprehensive Ortho Program and is credentialed as an Associate Fellow in the American Academy of Implant Dentistry. He lives in Winchester, Tenn, with his wife and 3 daughters. In 2015, he was diagnosed with APL leukemia, and while he did achieve full remission, he was unable to return to clinical practice due to ongoing back problems following treatment. Now, he focuses entirely on teaching and technology development in the field of digital dentistry. Additionally, he now serves as the director of clinical technology for Blue Sky Bio, a dental implant and software company. He can be reached at ncoryglenndds@gmail.com.
Dr. Domingue graduated from the Louisiana State University School of Dentistry and obtained his DDS degree in 2007. After dental school, he completed a 3-year advanced training at Brookdale University Hospital and Medical Center in New York City, where he served as chief resident of the dental and oral surgery department. Dr. Domingue is a member of the ADA; a former president of the Acadiana District Dental Association, American Academy of General Dentistry; and is the founder and president of the Acadiana Southern Society. Dr. Domingue currently resides in Lafayette, La, where he and his partner, Dr. Jerome Smith, work in an implant referral practice: Acadiana Dentistry. Dr. Domingue can be reached at danny@jeromesmithdds.com.
Disclosure: Dr. Glenn is director of clinical technlogy at Blue Sky Bio. Dr. Domingue is the owner of Acadiana Dentistry and owner of Louisiana Dental Lab.
UPCOMING FREE CE WEBINAR
Drs. N. Cory Glenn and Daniel Domingue will present a FREE CE WEBINAR expanding on the topic of this article on April 30 at 4 PM (EDT).
