Digital Planning for a Maxillary All-on-X Surgery: Considerations for a High Smile Line

Dr. Elaine Bylis
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INTRODUCTION
When planning any maxillary all-on-x case, numerous factors need to be taken into consideration to ensure a successful, aesthetic, and biologically sound outcome. Some of these factors include the height, width, and angulation of the maxillary bone; the position of the maxillary sinus; prosthetic clearance in the posterior of approximately 15.0 mm between the platform of the implant and the occlusal surface of the teeth that the prosthetics will fit within1; and the new incisal edge position of the central incisors. With proper prosthetic-driven implant planning, a clinician can balance these biologic and aesthetic factors to ensure an optimal result.

When planning maxillary all-on-x cases for a patient with a hypermobile lip and excessive gingival display, an additional set of challenges comes into play.

Maxillary all-on-x cases all require that enough crestal bone is reduced to create a resulting tissue height that shows only the prosthetic’s gingival tissue, even when the patient is in a full smile.2 However, for patients with high lip-lines, it is especially crucial that the clinician accurately determines exactly how much crestal bone needs to be reduced. Under-reduction of the crestal bone creates an aesthetic problem because the prosthetic’s resulting tissue height will be too incisally positioned, creating a visible transition between the prosthetic’s gingiva and the patient’s own gingiva.2 Over-reduction of the crestal bone presents a biological challenge because there will be diminished maxillary bone for the implants to engage.3

Figure 1. Preoperative presentation.

This article explores a particularly challenging high lip-line all-on-x case and illustrates methods to balance the resulting biologic and aesthetic considerations. This is accomplished with the use of digital surgical planning to reliably determine the amount of bone reduction needed and subsequently translating this plan into surgical guides in order to precisely execute the procedure. Although these techniques were especially critical for this high smile line case, they can be utilized to ensure the optimal biologic and aesthetic outcome for any all-on-x case.

CASE REPORT
A 68-year-old female presented upon referral from her physician to evaluate her dentition as a potential contributing factor to her elevated white blood cell counts. Her medical history included controlled Type II diabetes and thyroid removal following cancer. After many years since her last dental visit, she presented for a dental evaluation. The oral examination noted numerous abscesses, failing restorations, and missing teeth (Figure 1). The following treatment options were discussed for her maxillary arch: (1) endodontic treatment on multiple teeth, restoring caries, and replacing the missing teeth with long-span bridgework; (2) a full-arch extraction, followed by a locator implant overdenture; or (3) a full-arch, implant-supported, fixed option using a teeth-in-a-day protocol. Upon discussion of the risks and benefits of the 3 treatment options, the patient and her husband elected for the teeth-in-a-day approach for her maxillary arch. The patient’s mandibular teeth would be restored with fillings and crowns.

Surgical Planning
Upon acceptance of the treatment plan, a full diagnostic workup was completed. This included a full photographic series (Nikon [PhotoMed]), an intraoral scan for study models (CEREC [Dentsply Sirona]), and a CBCT scan (RayScan [Genicore]). Those records were imported into surgical planning software (Blue Sky Plan [Blue Sky Bio]) and were sent to the dental laboratory team for denture fabrication (Artifex Lab, Alexandria, Va).

The patient’s upper lip was extremely mobile, ranging from no tooth display at rest (Figure 2a) to showing several millimeters of gingiva on full smile (Figure 2b). This presented a serious challenge for our surgical planning because we needed to predictably plan the correct amount of bone reduction on the day of surgery, but we did not have a method to measure the height that her lip reached. This measurement needs to be extremely accurate because the height of the lip-line determines a significant portion of the prosthetic and surgical planning. The lip-line determines the final height of the patient’s gingiva, which determines the amount of bone reduction needed, which, in turn, impacts the final implant positions. Too little bone reduction would cause a visible transition between the patient’s gingiva and the prosthetic gingiva, but too much bone reduction would compromise the height of bone available to engage our implants; therefore, a more accurate measurement was needed of the patient’s lip-line.

Following the recommendations of Dr. Elias Rivera (University of Maryland Prosthodontics) and Dr. Paul Bylis (Innovative Dental Design, Glen Burnie, Md), the patient was brought back to take one additional record. This new record would objectively determine her lip-line when she displayed the fullest smile. This would form an accurate and repeatable landmark of where the lip extends on full smile rather than have our full surgical plan relying on an estimate from a photo. The premise of this record was the following: create a putty matrix in the patient’s mouth that represents the exact level of her lip on full smile, and then transfer that lip-line record into the digital planning software. To accomplish this, we created a putty matrix (Panasil Putty Soft [Kettenbach LP]) on her study model in preparation for the appointment. At the appointment, we seated the matrix in her mouth, had her make her “biggest smile ever,” and then used a pen to mark her lip-line on the putty. The stent was cut along that line and placed back into her mouth, and then small modifications were made to the stent based on observing her talk and smile. Photos of the patient wearing this stent were then taken (Figure 3a).

After this appointment, the matrix was placed onto her study model, and a No. 8 round bur (Brasseler USA) was utilized to indent the flange of the matrix (representing the patient’s lip-line) onto her cast. This cast was digitally scanned, imported into the implant planning software, and then aligned with her other models/CT scans (Figure 3b). The digital plan now had a defined plane of the patient’s exact lip-line, aligned with her CT scans/other models, which represents the maximum height that her lip extends and, therefore, the coronal-most position of the gingiva.

This was a critical piece of information, which allowed for the virtual design and planning of the other aspects of the case. The bone level was digitally cut to 3.0 mm apical to the height of the gingiva. Then the implants were placed to the height of the bone, and the prosthetic clearance was made to be 15.0 mm from the platform of the implants to the occlusal surface of the prosthetic. All implants and surgical guide stabilization pins were digitally placed based on the prosthetic plan and anatomical boundaries (Figure 4).

The surgical plan called for the fabrication of 3 guides: a pin guide, a bone reduction guide, and an implant guide. All 3 guides’ placements were triangulated based on 3 stabilization pinholes. This is unlike a typical single-tooth implant, which uses a tooth-borne guide and seats on the adjacent teeth for orientation.

The first guide is the pin guide, which is used to determine the 3 pinholes. The purpose of these pinholes is to orient the subsequent 2 guides, which are fixated and stabilized by 3 pins. For this case, the pin guide was made to be placed following extraction of the teeth and to be seated over the patient’s edentulated arch. Since there was not an actual model of how the patient’s bone would present after the teeth were extracted, a model was generated by modifying the segmented maxillary model to virtually extract the teeth (Meshmixer [Autodesk]). Next, this edentulous bone model was imported into the planning software, and a vacuum-formed guide was fabricated with 3 pinholes. Surgically, the pin guide is placed following the extractions, the 3 holes are drilled, and then the guide is set aside.

The next guide is the bone reduction guide: a thin guide in which the coronal portion represents the new level of the bone; all bone coronal to the bone guide should be reduced to that level. The final guide is the implant guide, which also engages the 3 pinholes and was used with our fully guided implant kit (TAG Dental [Genicore]) to predictably place all 8 planned implants. All 3 guides were 3-D printed (Digi3DWorks) in preparation for the day of surgery.

Surgery Day
On the day of surgery, local anesthetic was administered, and a full-thickness mucoperiosteal flap was laid. Then the patient was atraumatically and fully edentulated on the maxillary arch (Figure 5), and all infected tissue was curetted until solid bone was reached. Due to the large amount of bone reduction required for this procedure, a large flap had to be laid to allow the guides to seat apically enough. Following edentulation, the pin guide was seated on the bone, and the 3 pinholes were created (Figure 6). Next, the bone reduction guide was placed, engaging the 3 pin holes and showing exactly how much bone needed to be reduced (Figure 7a). A large bone-cutting bur (Global Dental Products) was used with copious irrigation to reduce the bone to the level of the bone reduction guide (Figure 7b). The bone reduction guide was then removed, and the implant guide was placed, engaging the same 3 pinholes (Figure 8). Implants (TAG Dental implants [Genicore]) were placed using fully guided protocols, bone (MinerOss [BioHorizons]) and MIS Implants Technologies’ collagen membranes (Genicore) were placed, the flap was approximated using simple interrupted sutures, and a final CBCT scan was taken to confirm the placement of the implants.

Upon confirmation of successful implant placement, multi-unit abutments and cylinders (TAG Dental products [Genicore]) were placed on the implants, the maxillary denture was seated over the cylinders and was picked up with acrylic (Lang Dental), the prosthetic was adjusted/polished, and the palate of the denture was removed. The finalized temporary was inserted (Figure 9), engaging 7 of the 8 implants, and occlusion was checked. The eighth implant was not engaged due to insufficient insertion torque and, instead, was buried with a bone healing cap. The screw access holes were sealed with light-body putty (Kettenbach LP). Photos at the one-day followup revealed that the patient was healing well (Figure 10).

Modification of the Temporary Prosthesis
Although the temporary maxillary hybrid was a major cosmetic improvement from the patient’s original presentation, the lengths of the teeth were too short and not ideal. This was largely due to the removal of such a large amount of bone that it was difficult to exactly predict where the final teeth positions would be. The fixed orthotic allows the patient and practitioner to “test drive” the aesthetics that were planned, allowing for any required modifications to be made to the final prosthesis. To improve the cosmetic appearance, it was decided to lengthen the teeth on the hybrid. This modification was beneficial because the enhanced cosmetics would be pleasing to the patient. In addition, because the temporary reflects the final vision, it would enhance communication with the lab team when designing the final zirconia prosthetic.

To modify the acrylic temporary hybrid, study models and a photo series were taken to complete a diagnostic wax-up. In this wax-up, approximately 2.0 mm of length was added to Nos. 8 and 9 (blended to the other teeth) to create an incisal edge display at rest. This was then transferred to the patient’s mouth using a clear putty matrix of the wax-up (Futar D [Kettenbach LP]) that was fabricated prior to the appointment. On the day of the wax transfer, the acrylic hybrid was prepared by roughening the surface in the patient’s mouth. The clear matrix was loaded with a dual-cure core build-up material (CosmeCore [Cosmedent]), the matrix was seated in the patient’s mouth, and the material was light cured through the clear matrix. Upon curing, the matrix was removed, and the prosthesis was polished where the composite had been added. The new smile line was now the appropriate length and in harmony with the patient’s lips at both the rest position and full smile (Figure 11). When it was time to process the case for the final zirconia hybrid, the laboratory technician would simply copy the temporary hybrid that was now in harmony with the smile that had been approved by the patient (Figure 12).

CLOSING COMMENTS
The case presented herein demonstrates several techniques that should be considered for treatment planning all-on-x cases. To ensure success, these cases require thorough and comprehensive treatment planning, which includes the consideration of both biological and prosthetic factors along with their limitations. Digital planning and manufacturing of surgical guides allow the surgeon to place implants in difficult clinical situations with more precision than previously possible. Even with successful surgical planning, the aesthetic landmarks of these cases are often estimated and may require some modification. This can be done by waxing and transferring the new shapes to achieve a harmonious cosmetic result. In conclusion, careful planning is paramount to success, and the techniques presented herein can be incorporated into any all-on-x case to achieve large improvements in aesthetic and functional outcomes.


References

  1. Misch CE. Contemporary Implant Dentistry. 3rd ed. Mosby Elsevier; 2008:99-100.
  2. Bidra AS. Technique for systematic bone reduction for fixed implant-supported prosthesis in the edentulous maxilla. J Prosthet Dent. 2015;113:520-523.
  3. Tonellini G, Saez Vigo R, Novelli G. Double guided surgery in All-on-4 concept: when ostectomy is needed. Int J Dent. 2018;2018:2672549.

Dr. Bylis practices at Innovative Dental Design by Dr. Paul Bylis in Glen Burnie, Md. A 2017 graduate of the University of Maryland School of Dentistry, she can be reached at dr.e.bylis@bylisdental.com or at (410) 969-2177.

Disclosure: Dr. Bylis reports no disclosures.

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