3D Facial Scanning: Dual-Arch Fixed Prostheses From Diagnosis to Delivery

Traditionally, clinicians have relied on 2-dimensional (2D) photography to design cases. Two-dimensional photography offers a representation of the patient in a static position that is dependent on the angle from which the photograph was captured and does not allow the clinician or laboratory technician to alter the angle or head position.¹ Conversely, a 3-dimensional (3D) scan allows the smile designer to tip, tilt, and change the angle of the scan to visualize the patient from practically any angle. The 3D scan also allows for the merging of multiple scans from media that can be overlayed for visualization of the face, teeth, mouth, lips, hard tissue, and soft tissue virtually. Once the patient is digitized, their image remains virtually on the computer screen allowing comprehensive diagnosis, treatment planning, and design to be carried out without the need for the patient to be physically present.

With 3D facial scanning the patient's face can be replicated 3-dimensionally in multiple lip positions to aid in the diagnosis, design, and fabrication elements of full-arch dentistry.^2,3 Digitally replicating the face allows the clinician and technician to visualize the various possible lip positions, from repose to exaggerated or Duchenne smile,⁴ and any other desired lip positions. The clinician and technician may then plan and design the tooth position and customize the smile design even in the absence of the patient. 3D facial scans can be merged accurately with intraoral scans (IOSs) and cone-beam computed tomography (CBCT) scans to allow for planning of the desired prostheses, implants, provisional prostheses, preparation guides, surgical guides, digital diagnostic wax-ups, and more.^5,6

To illustrate this approach, the following case report was documented utilizing this 3D technology. The case demonstrates the use of the InstaRisa^™ 3.0 3D facial scanner (InstaRisa Digital Dental Technologies, LLC, instarisa.com) to accurately diagnose, treatment plan, design, treat, and deliver dual-arch fixed prostheses.

Clinical Case Overview

A 64-year-old male patient presented for comprehensive evaluation and treatment. His medical history was American Society of Anesthesiologists (ASA) II because of his age and otherwise noncontributory, consisting simply of a history of childhood asthma and no contraindications for dental treatment.

The patient's dental history revealed some restorative dental care and missing teeth resultant from extraction of nonrestorable teeth. His chief concern was that he had "bad teeth" and "lots of cavities," had "lost teeth" and was "unhappy" with his smile (Figure 1). He stated that his previous dental visits were extremely unpleasant and many procedures were performed without any anesthetic, which caused him to avoid seeking further necessary dental care. The patient said he was displeased with the condition and esthetics of his teeth and desired a "new set of teeth."

He was aware of recent changes in his teeth over the previous 5 years, noting that they had worsened significantly and had become shorter due to fractures of what he called "rotten teeth" that were biomechanically compromised. The patient was unaware of any squeezing or clenching to fit his teeth together and had no difficulty eating hard, sticky, or chewy foods. Upon examination, no joint sounds, crepitus, deviations, or discomfort were evident.

Diagnosis and Risk Assessment

Periodontal: Clinical and radiographic examination revealed American Academy of Periodontology (AAP) stage III grade B classification, bleeding on probing and flossing, probing depths of 3 mm to 5 mm, and bone heights generally 4 mm from the cementoenamel junction with no appreciable mobility. Several areas of recession were noted facially with similar relative interproximal bone loss, indicating moderate periodontal disease (Figure 2).

Risk: High

Prognosis: Poor

Biomechanical:The patient had a history of reparative restorations and relative neglect of his dentition resulting in multiple tooth extractions. Generalized moderate erosion was evident with several areas of moderate and severe abrasion. Active caries was evident on several teeth. The overall biomechanical risk was high (Figure 3 and Figure 4). It was determined that the patient would ultimately lose the remaining dentition if left untreated.

Risk: High

Prognosis: Hopeless

Functional: The patient was aware that his teeth had changed in the past 5 years but reported these changes were related to cavitated and subsequently broken teeth. He reported no awareness of squeezing or clenching and had difficulty chewing foods primarily where teeth had been extracted. Joint and muscle examination revealed no joint noises or deviations, a maximum opening of 51 mm, load test negative, and immobilization test negative.

Risk: Low

Prognosis: Good

Dentofacial:The patient presented with moderate lip dynamics, low scallop form, and horizontal asymmetry. He was unhappy with his smile and was interested in a "whole new smile" that he could "be proud of." He stated he was unhappy with the crowding, rotations, and unevenness of his teeth as well as the missing teeth (Figure 5).

Risk: Moderate

Prognosis: Fair

Digitizing the Patient

Although 2D photographs are helpful in making assessments of esthetics, such as lip position and tooth display, these images are limited in their ability to aid in the design of the proposed restorative options that will be offered to the patient. For instance, it is difficult to determine the length of the teeth relative to the lips in repose when there is no tooth display in the repose position, such as in this case (Figure 6).

Conversely, 3D scans that are overlayed upon each other allow the clinician to visualize the tooth position relative to the lip in any position regardless of whether or not the teeth are displayed in that lip position. This information affords the clinician the ability to diagnose, plan, and design the desired restorations for delivery of the optimum esthetic and functional outcome while eliminating laborious, time-consuming try-ins and verification appointments (Figure 7). Further, the clinician is able to visualize the hard and soft tissues relative to the lip position, which enables predictable placement of an appropriately hidden finish line.

Upon completion of 3D facial scanning, intraoral scanning, and CBCT scanning, the patient can be virtually digitized to allow for treatment planning, design, implant planning, and guide and prosthesis fabrication without the need for the patient to be present.

Treatment Options

The primary risk factor for this patient centered around the remaining hopeless dentition and his desire to have a more esthetic smile. One of the treatment options discussed involved periodontal therapy and restorative treatment to maintain as many of the patient's natural teeth as possible. The patient was aware that he would still have some level of risk of future problems and tooth loss, similar to what he had been experiencing, if he were to maintain and restore his teeth. Although his risk might be reduced upon completion of this proposed treatment, he was unwilling to accept the risk of continued complications similar to what had plagued him much of his adult life. He also understood that to replace his posterior dentition and improve his chewing function, the use of a removable appliance and/or dental implant therapy would be required.

The only remaining options to eliminate the possibility of any future carious lesions involved removal of the remaining dentition. Thus, the patient elected to undertake the necessary procedures to have his remaining dentition extracted and dental implants placed to facilitate a fixed, implant-supported restoration, FP3 (fixed-prosthesis-3) appliance.⁷ Several options related to implant-retained and implant-supported prostheses were discussed, as were maxillary and mandibular complete dentures.

Planning

Extraoral 3D facial scans were taken with the InstaRisa 3.0 3D facial scanner in multiple lip positions. The scans acquired for this particular patient included a repose position, a Duchenne smile or exaggerated smile, a "natural" smile, and a retracted bite scan. A CBCT scan was acquired to assess bone quantity and quality and provide a comprehensive visualization of the patient's presenting anatomy. An IOS of the existing dentition also was acquired with the use of an intraoral scanner (TRIOS 3 Basic, 3Shape, 3shape.com). All of the acquired files were uploaded into a dental software program (exocad, exocad.com).

Once uploaded into the exocad software, the files are able to be overlayed and aligned and the case planned and designed with a facially generated design. The designer can see, in three dimensions, lips, teeth, and prosthetic positions. This facilitates the development of incisal edge position, occlusal plane, and midline without the need for the patient's physical presence (Figure 8). In the authors' experience, this process allows for a high level of esthetic design accuracy and potentially eliminates the need for multiple try-ins and esthetic preview appointments.

Design Treatment

Once the design of the prostheses was finalized, the implants were planned within the available bone and in the appropriate position to facilitate the prosthetic design (Figure 9). Depending on the clinician's preference, the clinician may choose to order or fabricate surgical guides to assist in the precise placement of the implants into the preoperative planned positions, or, as was done in this case, opt to place the implants freehand, without a guide, but choose to fabricate a surgical template. A freehanded surgical template can be milled or 3D printed with a window created within the acceptable position for screw-access holes. In this case, the template was 3D printed (Asiga Max UV, Asiga, asiga.com) (Figure 10). Utilizing this template, after the teeth have been extracted the surgeon can visualize the most desirable place for the screw-access openings and place the implants and multi-unit abutments in positions that will allow the access opening to be created within that window. Although not as precise as a surgical guide, this protocol allows the surgeon to place the implants into the best available bone, in a freehanded fashion, allowing for any changes that may occur during the extraction process while maintaining control over the prosthetic design driving the implant component.

While the prosthetic design is facially driven, the surgical planning is prosthetically driven. During the design phase, it is often necessary to plan some degree of alveoloplasty to aid in the proper positioning of the prosthetic design. A bone reduction guide can be fabricated preoperatively and computer-assisted manufacturing (CAM) milled or 3D printed to allow for a precise removal of alveolar bone. In this case, the aforementioned surgical template was fabricated to function as a bone reduction guide as well. A landmark may be maintained to enable the accurate alignment, seating, and delivery of a guide or template that is utilized and to facilitate the scanning process to digitally capture the implant positions. Often, as in this case, a tooth that will not interfere with the desired implant placement is used as the landmark (Figure 11). Once the implants are placed, the appropriate multi-unit abutments are placed; it must be verified that the angulation will allow the screw access to be placed within the window of the template and ultimately the final prosthesis. Prior to suturing, scan bodies are placed on to the multi-unit abutments, and the implant position is captured using the previously used IOS scanner.

Some reports have stated that intraoral scanning with a commercially available intraoral scanner is not reliable to predictably provide an accurate and well-fitting full-arch restoration on multiple implants, particularly when the scan is captured at the time of implant surgery in a field containing blood and saliva.⁸ Trueness values have been shown to be widely variable, with variability increasing as the inter-cylinder distance and cross-arch dimension both increase.^9,10 Stereophotogrammetry recently has been used to capture implant positions and overcome the variability issues of direct intraoral scanning, particularly for full-arch scans, divergent implants, and long-span inter-cylinder distances.^11,12 The use of photogrammetry, however, necessitates more equipment and components and consequently higher capital costs than intraoral scanning. In this case, a proprietary, patent-pending technique was utilized, similar to the continuous scan strategy, to accurately capture the implant positions and avert the inherent difficulties related to direct intraoral scanning.¹³

Once the digital impressions are captured, healing abutments are placed onto the multi-unit abutments and the surgical wound is sutured. All the digital files, including the final IOS of the implants, are uploaded and combined with the previously created design files. Once all of these files are aligned, the provisional prosthesis can be fabricated-either 3D printed or CAM milled to the exact dimensions of the preoperative, facially generated design. In this case, the maxillary provisional prosthesis was printed with a 3D printer (Asiga Max UV) while the surgeon performed surgery on the opposing arch. Once the surgeon completed the surgery, captured the implant position of the opposing arch, and sutured the wound, the maxillary provisional prosthesis was complete and able to be delivered. At this time, the files for the mandibular arch were uploaded and aligned, and the mandibular provisional prosthesis was fabricated using the same method.

Delivery

After surgery was completed on both arches, the maxillary provisional prosthesis was delivered. The abutment screws were screwed to the multi-unit abutments with a passive fit, verified with the Sheffield test, and torqued to the manufacturer's recommendation.¹⁴ An immediate postoperative set of bitewing radiographs was captured to evaluate the passivity and fit of the restoration (Figure 12). Due to time constraints of the patient, he elected to return the following day for delivery of the mandibular provisional prosthesis, which was done in the same manner as described for the maxillary provisional prosthesis (Figure 13 and Figure 14). The treating clinician's common practice is to deliver the prostheses the day after the surgical appointment to make efficient use of the clinical appointments and the laboratory protocol. The patient did not require anesthesia for the delivery appointment. Because both prostheses were fabricated using the preoperative 3D data captured with the 3D facial scanner and were created to the exact dimensions of the digital design, the delivery appointment, including occlusal adjustment, was completed in 12 minutes with very minor occlusal adjustments to ensure equal, bilateral, simultaneous contacts and to alleviate any contacts on inclines associated with the chewing envelope (Figure 15 and Figure 16).

Conclusion

Utilizing a 3D facial scanner, the treating clinician was able to capture 3-dimensional data to aid in a facially generated smile design, fully edentulate the patient's failing dentition, place the appropriate implants, and deliver a set of dual full-arch provisional prostheses in 3 consecutive days. With the additional data captured 3-dimensionally, including the retracted "bite scan," the clinician and technician were able to create an extremely esthetic and functional set of prostheses that required minimal adjustment. All of the facial data was digitized 3-dimensionally so that the technician could visualize the patient virtually, during the design phase, in any desired lip position. The use of the proprietary 3D facial scanner scan capture protocol allowed for a true and accurate fit of the prostheses without the additional equipment and costs associated with other techniques. This approach allows delivery of precise design and placement of incisal edge positions, planes of occlusion, and straight midlines, for exceptional esthetics with efficient use of chairtime, lab time, and patient appointments.

The authors thank Fernando Polanco, DDT, for computer and laboratory support in this case.

Dr. Bynum is Chief Clinical Director and Dr. Mirelez is Chief Executive Officer of InstaRisa Digital Dental Technologies, LLC.

Jeff H. Bynum, DDS

Private Practice

J. Art Mirelez, DDS

Private Practice, Clovis, California; Fellow, International Congress of Oral Implantologists; Fellow, Academy of General Dentistry