3D Extraoral Facial Scanning for Facially Generated Treatment Planning and Design

A digital revolution is occurring that is rapidly changing the world of dentistry for dentists, laboratories/digital technicians, smile designers, and patients. Major advancements in digital technology have significantly improved the dentist's and the dental technician's ability to create esthetic and functional results for the patients whom they are treating. In many ways, digital dentistry has brought the future to the present.

The use of CAD/CAM technology has allowed for more predictability in fabricating full-mouth implant-supported restorations. Guided implant surgery has become mainstream with the aid of CBCT. Digital intraoral impression scanning and laboratory scanning have revolutionized the impression taking process.¹ With the assistance of computer-aided framework and prosthesis design and high-precision computer-guided milling and 3D printing, the field of prosthodontics has been altered forever.² CAD/CAM technologies have been successfully applied to treat dentate, partially edentulous, and fully edentulous patients with a myriad of prostheses, including implant-assisted and implant-supported prostheses.^3,4,5

Much of the focus of these technological advances has been on the development of full-arch prosthodontics, and now with the emergence of 3D extraoral facial scanning, these procedures can be further enhanced. Dentists and technicians also have been able to capitalize on these advancements for all dental prosthetics.

3D extraoral facial scanning brings the missing link of treatment planning and design into the arena. Digitization of the patient via CBCT, intraoral scanning, and extraoral scanning allows for all of the data needed for evaluation, design, and treatment planning to be precisely aligned and merged together for a completely digital representation of the patient.⁶ This workflow places the digital patient on the computer screen, allowing the dentist, designer, and technician to evaluate, manipulate, and treatment plan in a way that was heretofore not possible with analog and two-dimensional workflows (Figure 1).^7,8

The face has been a critical missing link in digital dentistry because it is essential to the predictability and efficiency of developing an esthetic and functional result.⁹ Digitizing the teeth and the bony architecture are important, but without the face and the facial data to reference, it proves to be a bit like working on a dentoform.

Furthermore, technological developments in 3D facial scanning have allowed for the realization of economic, compact, portable, in-office systems that integrate with software platforms that are geared toward prosthetic dentistry.^10,11,12 Coupled with the aforementioned CAD/CAM systems, 3D facial scanning has made it more viable to virtually design and fabricate full-arch prostheses, single-tooth restorations, and all dentistry in between using a completely digital approach.^5,13

3D Facial Scanning

An increasing number of 3D scanners on the market have been designed for purposes such as robotic mapping, industrial design, reverse engineering, prototyping, and quality control. Several companies have recently adapted these commercially available scanners to be utilized for medical and dental applications. Newer software has been developed to adapt some of these scanners to create precise and accurate 3D representations of the face and teeth¹⁴ (Figure 2). The adaptation of these scanners and their related software can produce enough precision, accuracy, and trueness to be utilized in dentistry to design and fabricate simple and complex prostheses, and well-fitted and well-adapted restorations that seat with the appropriate passivity to be predictable and long-lasting.^15,16,17

Facially Generated Treatment

The face and facial data become the missing link in treatment planning and smile design once the patient has left the operatory.¹⁸ Two-dimensional photographs can assist the dentist and technician in representing this information to the designer, but many limitations remain. Unlike a photograph, the 3D scan allows the designer to manipulate the image. A photograph, if taken off-angle, cannot be uprighted. The midline of the face, occlusal cant, profile representation, inferior and superior views of the teeth, and lip positions cannot be viewed simultaneously without clicking between photos. Consequently, combining them is left to the artistic interpretation of the designer.

Natural head position (NHP) and natural head orientation (NHO) also have proven difficult to obtain and reproduce with two-dimensional techniques.^19,20 Multiple techniques and devices have been developed to attempt to communicate this information to the technician, but they are often laborious and lack predictable accuracy. Once the models have been fabricated and articulated, the bench top often becomes the "horizon."  Without an accurate reference, an occlusal cant is often created, reproduced, and/or enhanced.²¹

With the utilization of 3D extraoral facial scans, the face is reintroduced into the design protocols. The midline of the face is easily discernible and able to be viewed from different angles, as the patient's head can be rotated and tilted to any angle, showing the designer the complete facial anatomy preoperatively, during the design phase, and in the post-design (Figure 3 and Figure 4). The occlusal cants can be verified and altered to the NHP with grid lines on the computer to ensure the proper position of the teeth in the face, in real-time (Figure 5). The profile, as well as the inferior and superior views, can be referenced simply by turning and tilting the patient's head on the screen, giving the designer complete control for a facially generated smile design (Figure 6).

Patient Acceptance and Co-Diagnosis

A key element of restorative dentistry and prosthodontics is gaining patient acceptance of treatment plans, and the technologies utilized for diagnostics can help in this regard. Many patients favor optical impressions, which have minimized the need for conventional analog impressions with trays and materials such as alginate, polyvinylsiloxane, and poly-ether. The majority of patients have never received a facial scan at the dentist and perceive a "wow" factor with this level of treatment. The significant other and/or caregiver or companion are able to remain in the room during the scans and experience the same level of interest and excitement as the patient. The scans also can be used as a patient education tool to explain findings and create engagement.

Digitizing the patient's face and teeth and displaying these scans on a large monitor in the office allows the patient to see their teeth and their smile in a new way (Figure 7). Seeing their teeth magnified, the patient can express their desires; they can point out aspects that they are pleased with and what they would like to see altered, assisting the clinician with a co-diagnosis (Figure 8). The patient can "own their condition." Treatment options and planning can then be proposed and all involved parties can have the opportunity to plan any restorations to meet the patient's needs and desires while minimizing any disappointments that may occur with the delivery of the definitive treatment. This allows the clinician to customize the treatment, design, and end results to more confidently meet patient expectations.²²

The need for multiple impressions and various forms of try-ins and verifications are virtually eliminated. The patient is able to view their smile and the proposed smile design virtually in their face, allowing them to request changes that can be addressed digitally, prior to any addition or subtraction to their actual dentition. Once the design is completed, the patient can approve the design and have confidence in the result because they can see it virtually in their face, eliminating the "guess-work" by the clinician (Figure 9).²²

Alignment and Merging of Scan Data

The virtual models from 3D facial scans allow technicians to create dental prostheses that rival and potentially surpass the accuracy of many analog techniques.^23,24,25,26

Utilizing commercially available design software—such as exocad, 3Shape Dental System, and Blue Sky Bio Plan—STL, PLY, and OBJ files can be imported and aligned, integrating each of the individual scans together to create a digital representation of the patient in a one-to-one format and allowing the digital technician to design the smile directly in the virtual version of the patient's face²⁷ (Figure 10). Multiple scans can be imported and merged to display multiple lip positions⁶ (Figure 11).  The digital design can then be carried out utilizing a Duchenne (exaggerated) smile, natural smile, repose lip position, or any other lip position to accurately place the incisal edge position of the maxillary and mandibular arches, as well as to visualize the occlusal plane of the posterior teeth (Figure 12). Once the files are precisely aligned, the designer can utilize the intraoral and extraoral scans to design the smile to the most esthetic and functional position from a facially generated approach, merge the CBCT data, and design surgical guides to facilitate precise prosthetically generated implant positions, along with a multitude of other prosthetic and functional appliances^13,18(Figure 13).

Laboratory Applications

In a traditional analog and two-dimensional workflow, the laboratory technician has minimal ability to manipulate images. Models, mock-ups, provisional prostheses, and verification appliances are often fabricated to give the clinician and the patient an idea of what is possible. With full-arch treatment, the laboratory technician traditionally attends the appointment to assist with the conversion and/or alteration of the prosthesis.

Once the patient is digitized and placed virtually on the screen, the technician can complete all of this work at the laboratory with the same level of accuracy, saving valuable time and expenses. During the design phase, the technician can view the scans and immediately give feedback to the clinician.

Discussion

CAD/CAM technology is no longer a novelty, and 3D extraoral scanning is allowing the dentist, the patient, and the technician to have all of the data readily available not only to display and educate, but to connect, discuss, plan, and develop the ideal customized treatment.

Utilization of digital dentistry creates a higher level of efficiency for all involved, capitalizing on the advantages of the CAD/CAM procedures. These include the elimination of multiple clinical evaluation visits and procedures, thereby reducing chair-time and treatment costs while allowing better communication with the dental laboratory regarding prosthesis design and increased ability to realize an individualized tooth arrangement.

With any technology, there is an initial outlay of capital expenditure. With an increase in efficiency, accuracy, and precision afforded by 3D facial scanning, the savings in time and remake percentages can quickly make the investment a worthwhile expense.

The nearly unlimited nonrestorative uses of digital technology are redefining how intraoral and extraoral scanners are being used without compromising the level of treatment being provided.

About the Authors

Jeff Bynum, DDS
Clinical Instructor/Course Facilitator
Kois Center

Fernando Polanco
CAD/CAM Digital Dental Technologist

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