Key points

Facial scanners and their role in the creation of a virtual dental patient

The recognition of the facial morphology is necessary for the preoperative, postoperative evaluation, and symmetry assessment. It has significant applications in dentistry. Facial morphology and analysis are very critical in various disciplines of dentistry such as craniofacial surgery, maxillofacial surgery, orthodontics, craniofacial orthodontics, prosthodontics, and forensics. Facial scan analysis is presently a new highlight area of research. Conventional strategies for assessing facial morphology were based entirely on 2-dimensional (2D) methods. ^, In the past, using 2D imaging and photographs, mathematical instruments were used to obtain the facial analysis data.

With the improvement of optical scanning technology, the study of facial morphology using 3-dimensional (3D) face scanners has gained traction and reached to a new level from 2D to 3D. ^, One such example is shown in Fig. 1 , where a facial scan is displayed via a design software(InLab by Dentsply-Sirona).

Facial scan displayed via design software.

A facial scanner is a noninvasive measuring tool that can acquire 3D facial models in an open data format with real skin texture color and a scanning process that is typically very short. The literature increasingly reported that 3D facial scanners could be used in the dental clinics, with the 3D facial samples acquired by scanners being used for 3D quantitative diagnostics and treatment assessment.

With the advancements in technology, the volumetric data obtained from the CBCT scans, intraoral scans may be superimposed to create a 3D virtual patient. This virtual patient can help in preoperative procedures, treatment planning, and patient outcomes. The data points such as facial landmarks can be obtained using the 3D face scanning using the scanner.

The advancements in technology have not only improved the speed and accuracy of the treatment but also has enhanced outcomes in the facial esthetics, facial profile and in creating the digital smile design. Greater accuracy improves the quality of the data recorded from the face scanner, which ultimately improves the outcome.

There are 2 fundamental types of facial scanners: laser scanners and white light scanners. Although the equipment is different, both types of scanning systems use the principle of triangulation to produce a 3D image of the face. Laser scanners project multiple dots or lines on the patient’s face, forming a triangle between the laser (typically 200 FPS infrared class I Laser compliant), light sensor (usually a camera), and the patient. The laser pattern moves over the face to scan the surface area and create a 3D image. The distance of the different surface levels on the patient’s face is determined by triangulation. In contrast, white light scanners project light patterns onto the face, forming a triangle between the projector, light sensor (ie, camera), and the patient. In addition, there are different types of scanning systems including fixed and moveable systems. Fixed scanners, such as the OBI Scanner (Viale Lombardia 6, 20133 Milano, Italy) are supported by a tripod placed directly in front of the seated patient. The patient is prompted to make specific head movements (ie, right, left, upward, downward) by the software. Moveable scanners, such as the Artec Evan Scan, are portable and moved around the face to acquire a 3D scan.

Three-dimensional scans are easily obtained using a smartphone with a dedicated application and the corresponding software. Face scans use fast, noncontact scanning and are generally well-tolerated by the patient. Laser stripe is safe for the human eye and unperceived by the patient except when it passes directly over the pupils. However, some face scanners flash a series of bright lights to capture the 3D image, which could cause slight discomfort for some patients. To ensure a constant state of facial expression, the patient is directed to close his or her eyes during the light flashes. Each scanning system has a different range that the patient must stay within for the duration of the scanning process. To ensure that the patient’s head is still and in its natural position, support of the head and neck can be used. In addition, hair should be secured away from the face to decrease noise data and facial expressions should be kept unchanged during the scanning process. Moreover, controlled indoor lighting is preferred to avoid image distortion owing to the sensitivity of the light sensors. Some interferences may be seen owing to the reflective surfaces of teeth. However, this could be corrected after image capture.

To obtain a holistic and more accurate 3D image, multiple scans can be taken in different facial positions (rest position, smiling position, and cheek retracted position). The scans are then aligned using the forehead to obtain more information on the patient’s smile line, tooth display, and soft tissue. Integrating 3D facial scans with intraoral and extraoral scans provides valuable information for treatment planning. If the operator wishes to scan the teeth separately, facial scanning software allows for the implementation of virtual facebow transfer technique. To use the virtual facebow technique, markers (round opaque stickers) are attached to the margin of the left or right eye orbit and the Beyron points on both sides.

After scanning is complete, the files are saved and imported into the software, which allows for size and lighting adjustments, display from various angles, and merging of 3D images. If the accuracy of the scan is perceived as less than optimal, the scanning software is used for postcapture manipulation including: smoothing skin, improving mesh quality, and filling holes in scan. After the completion of the necessary edits, the 3D scanned image is used for various treatment plans, such as orthodontic treatment and the fabrication of dental prostheses.

Role of intraoral scanners in the creation of a virtual patient

Different technologies are used to obtain a digital impression of teeth and surrounding intraoral tissues. These technologies are constantly updated and refined, so are the actual scanners to make them more user and patient friendly as well as easy to navigate and handle in the oral cavity. A strategic scanning technique that subsequently captures all areas and angles has to be used and become routine for maximum scanning efficiency and quality outcomes. Current intraoral scanners do not require the once-necessary antireflective powder and have to ability to scan. Besides eliminating all the uncomfortable aspects of a conventional impression, one of the great advantages of intraoral scanning is that select areas, which may not have been adequately captured, can simply be rescanned without having to retake the entire impression.

Intraoral scanners function by projecting structured light (white, red, or blue), which is recorded as individual images or video and compiled by the software after recognition of specific points of interest. A 3D model is then generated by matching the points of interest taken under different angles. Extreme points can also be eliminated statistically to decrease noise.

The time needed for taking a digital impression is less than that for a conventional impression. In addition, patients clearly prefer the digital scan. Digital full-arch impressions taken with an intraoral scanner seem to have slight deviations in respect to cross-arch accuracy. Other researchers have found similar accuracy levels between scanners. A recent literature review concluded that, currently, the literature does not support the use of intraoral scanners for long-span restorations on teeth or implants and there remain areas in respect to digital impressions of dental implants that need further investigation. However, new intraoral scanning technologies such as photogrammetric imaging allow for high accuracy even for full-arch implant restorations.

Scanning technique and sequence also play a major role. When properly applied, the digital impression technique seems to be more accurate than a conventional impression. ^, A surgical guide in preparation in a proprietary design software is shown in Fig. 2 (CoDiagnostix, Dental Wings GmbH, Düsseldorfer, Germany).

Surgical guide in preparation in a proprietary design software.

Traditionally, intraoral scanners were connected to mobile carts as a complete unit with the computer and monitor. More recent versions of scanners are connected wirelessly to laptop computers. Companies that produce scanners as well as dental chairs offer the option of incorporating the scanner into the dental chair.

Cone beam computed tomography: the creation of virtual skeletal data

CBCT volume acquisition enables the dentist to be able to see the maxillofacial structures 3-dimensionally for not only diagnosis of dentoalveolar pathology, but also to plan the dental treatment including the restorations and prosthodontic care. Since the introduction of root form implants in dentistry, placement of dental implants are enabled by an accurate depiction of the mandibular and maxillary anatomy. The quality of the image depicted depends on the pixel resolution, which can be controlled to a certain extent by the operator. This would be contingent upon the type of CBCT machine and the manufacturer-set pixel resolutions based on the fields of view (FOV) chosen for the patient.

Essentially, there are 3 distinct broad categories that affect the final outcome of the CBCT volume and its diagnostic quality.