Analysis of the impact of the facial scanning method on the precision of a virtual facebow record technique: An in vivo study

Positional accuracy of intraoral scan alignment to a facial scan using structured light scanning and trial denture base with occlusal rim markers in patients with complete maxillary edentulism

STATEMENT OF PROBLEM

Creating precise 3D virtual head models for patients with complete maxillary edentulism remains challenging owing to the lack of natural landmarks and limitations of current image-matching technologies.

PURPOSE

The purpose of this study was to evaluate the positional accuracy of intraoral scan alignment to structured light-based facial scans using varying sizes and positions of occlusal rim markers under maxillary edentulous conditions.

MATERIAL AND METHODS

Radiopaque artificial markers of 3 sizes (2, 4, and 6 mm) were made and attached to the maxillary occlusal rim of a completely edentulous patient at different positions (midline-canine [MC], midline [M], canine [C]). Facial scans were obtained of the patient by using a structured light facial scanner under 9 experimental conditions (size-location: 2MC, 2M, 2C, 4 MC, 4M, 4C, 6MC, 6M, and 6C; 5 scans under each condition). Intraoral scans were aligned to the facial scans using stepwise images matching the occlusal rim scan casts. The alignment accuracy was evaluated by comparing the intraoral scan with a reference position established using cone beam computed tomography data. Measured variables included anterior and posterior linear deviations and angular deviation of the arch plane. Statistical analysis was conducted using the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni correction (α=.05).

RESULTS

The 4-mm and 6-mm marker groups exhibited significantly lower deviation in image registration than the groups without markers and those with 2-mm markers (P<.001). Regarding the marker position, the midline-canine group exhibited the lowest deviation value, followed by the midline and canine groups. Markers positioned in the midline exhibited less deformation compared with those in the canine region.

CONCLUSIONS

Occlusal rim markers can be used to align intraoral and facial scans in patients with complete maxillary edentulism when structured light face scanning is included. Markers with a clearly recognizable size in facial scans are less prone to deformation in the facial midline area.

Trueness and precision of a handheld, a desktop and a mobile 3D face scanning system: An in vitro study

OBJECTIVE

This in vitro study investigated the trueness and precision of three different face scanning systems: a handheld, a desktop and a mobile 3D face scanning system.

MATERIAL AND METHODS

Fourteen landmarks were placed on a mannequin head, and sixteen inter-landmark distances were measured using a digital vernier caliper, repeated 20 times over 80 days. Three 3D face scanning systems were evaluated: a handheld (Metismile; Shining 3D Tech Co., Hangzhou, China), a desktop (RAYFace v2.0; Ray Co., Ltd., Gyeonggi-do, Korea), and a mobile application (Heges, Simon Marinek) on a smart device (iPad Pro X, Apple Inc., Cupertino, CA). Sixty facial scans were analyzed using metrology software (Geomagic Control X), and inter-landmark distances were compared to anthropometric measurements. Trueness was determined by absolute linear deviation and analyzed using one-way ANOVA, with Bonferroni and Tamhane tests for significant variance. Precision was compared to anthropometric measurements and analyzed using Kruskall-Wallis test.

RESULTS

3D analysis showed that the handheld scanner had the highest trueness (0.18 ± 0.15 mm) and precision (0.22 ± 0.04 mm). The desktop scanner had a trueness of 0.35 ± 0.26 mm and precision of 0.61 ± 0.18 mm, while the mobile scan application had a trueness of 0.54 ± 0.34 mm and precision of 0.47 ± 0.12 mm. All systems showed the highest trueness for vertical measurements compared to horizontal measurements. In the lower face, the precision was higher than anthropometric measurements for all 3D face scanning systems.

CONCLUSIONS

The handheld scanner demonstrated the highest trueness and its precision surpassed anthropometric measurements. The desktop scanner outperformed the mobile scan application in trueness but not in precision.

CLINICAL SIGNIFICANCE

The handheld, the desktop and the mobile face scanning system showed clinically acceptable trueness (< 0.6 mm) and could be used for virtual facebow transfer. All 3D face scanning systems in the present study demonstrated superior precision in the lower face compared to anthropometric measurements.

Influence of Head Circumference on the Accuracy of Facial Scanning: An In vitro Study

OBJECTIVES

This study aimed to investigate the impact of head circumference on the accuracy of three-dimensional (3D) facial scans, focusing on trueness and precision across three mannequin heads of different sizes.

MATERIAL AND METHODS

Three 3D-printed mannequin heads with circumferences of 30, 50, and 65 cm were used. Ten facial landmarks were identified to measure seven interlandmark distances and two angles. Direct anthropometric measurement, serving as the reference value, was taken using a digital vernier calliper for linear distance, and angle was calculated using the law of cosines. Each head was scanned six times using two systems: a dual-structured light facial scanner (iTom) and a stereophotogrammetry system (3dMD). Digital measurements were analysed using Meshlab and Blender for distances and angles, respectively. Trueness values were determined by comparing measurements to reference measurements, while precision values were derived from the variability among the six scans. Statistical analysis was performed using the Kruskal-Wallis test due to nonhomogeneous variances, followed by Bonferroni correction for pairwise group comparisons.

RESULTS

For each scanning system, overall deviations in trueness and precision significantly increased with head circumference. Five of the seven distances and one angle showed significant compromises in trueness with larger head circumferences. Most measurements exhibited significant precision decreasing due to head circumference changes, except for N-Pn and Pn-Sn. Additionally, 3dMD displayed higher overall trueness compared to iTom, with five out of seven linear measurements and one angular measurement showing better results.

CONCLUSION

Head circumference significantly affects both trueness and precision of 3D facial scans for both technologies, suggesting that facial imaging should be used with caution for larger faces. Selecting an appropriate scanning system, such as 3dMD, can help mitigate the negative effects of scanning larger objects.

Evolution of Dental Occlusion: Integrating Digital Innovations

The landscape of dental occlusion is undergoing a transformative shift with the integration of digital technologies offering accuracy, efficiency, and improved patient outcomes. This article explores the advancements in digital innovations that have reshaped occlusal analysis and management. By examining tools such as three-dimensional (3D) scanning, virtual articulators, and occlusal diagnostic software, we highlight their impact on treatment planning and clinical workflows. These technologies enable dental professionals to analyse occlusal relationships with a level of detail previously unattainable, paving the way for more accurate and individualised treatment plans. The implementation of digital approaches also enhances patient engagement, as visual data aids in understanding treatment processes. This article also reviews the available research on the reliability of these innovations, providing an evidence-based perspective on their clinical application.

In-vitro accuracy of the virtual patient model with maxillomandibular relationship at centric occlusion using 3D-printed customized transfer key

OBJECTIVE

This study aimed to create a 3D-printed customized transfer key and evaluate the accuracy of the virtual patient model with maxillomandibular relationship at centric occlusion using the transfer key.

METHODS

A 3D-printed transfer key was designed, combining facial and intraoral (IOS) scans. The design included components that recorded the 3D upper and lower arch at centric occlusion. The virtual patient model image was generated in-vitro using a phantom head with soft tissue simulation. Accuracy was assessed by superimposing the 3D scans with reference CBCT images and analyzing trueness and precision using root mean square (RMS) deviations.

RESULTS

The transfer key included an intra-oral part that acts as an anterior deprogrammer to record the relationship of two dental arches at centric occlusion (CO) and an extra-oral with a rotatable cross-shaped design with two arms for locating the facial midline and the two pupils connecting line. Superimposition demonstrated high trueness (RMS: 0.51 mm for the arch regions, 0.69 mm for the whole head region, 0.85 mm in the face region) and precision (RMS: 0.41 mm for the arch regions, 0.52 mm for the entire head, 0.63 mm in the face region) significantly (p < 0.05). Minimal deviations were observed in critical areas, including the tooth and lip position, indicating that the virtual patient model was closely aligned with the CBCT reference. The dental arches achieved the highest accuracy, while slight deviations were noted in the facial regions.

CONCLUSIONS

The 3D-printed customized transfer key effectively enhanced the virtual patient model's accuracy, surpassing traditional trueness and precision methods. This novel approach offers a streamlined, patient-friendly solution for digital dental workflows.

The Orientation in Space of the Maxillary Arch: New and Old Devices in the Prosthetic Digital Workflow

OBJECTIVE

In extensive prosthetic rehabilitations and in those involving the anterior area, a correct 3D spatial position is of fundamental importance for effective communication between the clinician and the dental technician. The aim of this article is to analyze the different methods used to position in space and/or in an articulator the maxillary arch in analog workflows highlighting shortcomings and difficulties in order to understand how to overcome them when employing digital workflows.

OVERVIEW

Traditional mechanical devices, such as anatomical, kinematic, esthetic and postural facebows, have clear indications, but also limitations, especially in cases of skeletal asymmetries. Modern digital tools, including photography, CBCT, facial scanners and jaw recording devices, are here critically analyzed to illustrate the advantages of working in a virtual space.

CONCLUSIONS

The adoption of digital tools in the prosthetic workflow represents a significant improvement compared to traditional techniques, as it reduces errors and artifacts of registration and transfer of the position of the maxillary arch in the articulator space. This contributes to more predictable esthetic and functional results, with a positive impact for clinicians and technicians, improving clinical-laboratory communication, operational efficiency and overall quality of work.

CLINICAL SIGNIFICANCE

The integration of digital tools into prosthetic workflows represents an important advancement in clinical practice since they reduce human error and facilitate communication between the clinician and the laboratory. When carrying out rehabilitations involving changes in esthetics or occlusal plane orientation, the proper and accurate positioning of the upper arch in space is particularly relevant.

An overview of the different digital facebow methods for transferring the maxillary cast into the virtual articulator

OBJECTIVES

The purposes of this study were to classify the described digital facebow techniques for transferring the maxillary cast into the semi-adjustable virtual articulator based on the digital data acquisition technology used and to review the reported accuracy values of the different digital facebow methods described.

OVERVIEW

Digital data acquisition technologies, including digital photographs, facial scanners, cone beam computed tomography (CBCT) imaging, and jaw tracking systems, can be used to transfer the maxillary cast into the virtual articulator. The reported techniques are reviewed, as well as the reported accuracy values of the different digital facebow methods.

CONCLUSIONS

Digital photographs can be used to transfer the maxillary cast into the virtual articulator using the true horizontal reference plane, but limited studies have assessed the accuracy of this method. Facial scanning and CBCT techniques can be used to transfer the maxillary cast into the virtual articulator, in which the most frequently selected references planes are the Frankfort horizontal, axis orbital, and true horizontal planes. Studies analyzing the accuracy of the maxillary cast transfer by using facial scanning and CBCT techniques are restricted. Lastly, optical jaw trackers can be selected for transferring the maxillary cast into the virtual articulator by using the axis orbital or true horizontal planes, yet the accuracy of these systems is unknown.

CLINICAL IMPLICATIONS

Digital data acquisition technologies, including digital photographs, facial scanning methods, CBCTs, and optical jaw tracking systems, can be used to transfer the maxillary cast into the virtual articulator. Studies are needed to assess the accuracy of these digital data acquisition technologies for transferring the maxillary cast into the virtual articulator.

An overview of artificial intelligence based applications for assisting digital data acquisition and implant planning procedures

OBJECTIVES

To provide an overview of the current artificial intelligence (AI) based applications for assisting digital data acquisition and implant planning procedures.

OVERVIEW

A review of the main AI-based applications integrated into digital data acquisitions technologies (facial scanners (FS), intraoral scanners (IOSs), cone beam computed tomography (CBCT) devices, and jaw trackers) and computer-aided static implant planning programs are provided.

CONCLUSIONS

The main AI-based application integrated in some FS's programs involves the automatic alignment of facial and intraoral scans for virtual patient integration. The AI-based applications integrated into IOSs programs include scan cleaning, assist scanning, and automatic alignment between the implant scan body with its corresponding CAD object while scanning. The more frequently AI-based applications integrated into the programs of CBCT units involve positioning assistant, noise and artifacts reduction, structures identification and segmentation, airway analysis, and alignment of facial, intraoral, and CBCT scans. Some computer-aided static implant planning programs include patient's digital files, identification, labeling, and segmentation of anatomical structures, mandibular nerve tracing, automatic implant placement, and surgical implant guide design.

True horizontal or gravity plane registration for transferring the maxillary scan into the virtual articulator by using a facial scanner without the need for an additional device

Different reference planes can be used to transfer the maxillary cast into the analog articulator, including the true horizontal or gravity reference plane. Different techniques have been described to record the gravity reference plane for transferring the maxillary scan into the virtual articulator by using facial scanning techniques. However, these digital facebow procedures require the use of an extraoral scan body system, printed reference device, or orientation reference board. This manuscript describes a technique for recording the gravity reference plane by using a facial scanner without the use of an additional device. This technique aims to reduce the clinical time needed to capture a patient's digital data and minimize the laboratory time needed to integrate the virtual patient and transfer the maxillary scan into the virtual articulator.

True horizontal or gravity plane for transferring the maxillary cast into the virtual articulator by using an optical jaw tracking system

Different techniques of transferring the maxillary cast into the analog semi-adjustable articulator by using the true horizontal or gravity reference plane have been reported. However, procedures are required for recording this reference plane and transferring the maxillary cast into the virtual semi-adjustable articulator. In the present manuscript, a technique is described for registering the true horizontal or gravity plane in relationship to the natural head position of the patient by using an optical jaw tracking system. Additionally, the recorded true horizontal plane is used to transfer the maxillary cast into the virtual semi-adjustable articulator by using a dental computer-aided design program. This technique facilitates the maxillary cast transfer into the virtual articulator by using the true horizontal plane recorded with an optical jaw tracking system, maximizing the functionality of the optical jaw tracking device.

Facial scanning technologies in the era of digital workflow: A systematic review and network meta-analysis

PURPOSE

The aim of this network meta-analysis is to evaluate the accuracy of various face-scanning technologies in the market, with respect to the different dimensions of space (x, y, and z axes). Furthermore, attention will be paid to the type of technologies currently used and to the best practices for high-quality scan acquisition.

MATERIAL AND METHODS

The review was conducted following the PRISMA guidelines and its updates. A thorough search was performed using the digital databases MEDLINE, PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials by entering research lines or various combinations of free words. The main keywords used during the search process were "photogrammetry", "laser scanner", "optical scanner", "3D", and "face".

RESULTS

None of the included technologies significantly deviated from direct anthropometry. The obtained mean differences in the distances between the considered landmarks range from 1.10 to -1.74 mm.

CONCLUSIONS

Limiting the movements of the patient and scanner allows for more accurate facial scans with all the technologies involved. Active technologies such as laser scanners (LS), structured light (SL), and infrared structured light (ISL) have accuracy comparable to that of static stereophotogrammetry while being more cost-effective and less time-consuming.

A complete digital approach for facially generated full arch diagnostic wax up, guided surgery, and implant-supported interim prosthesis by integrating 3D facial scanning, intraoral scan and CBCT

Continuous innovation in digital dental technology offers new prospects for creating a complete virtual environment. The technique described adds a facial approach to the conventional digital workflow by incorporating 3D face scans to cone beam computed tomography and intraoral scans. Using this workflow, clinicians can obtain a complete virtual patient for facially generated diagnostic wax up and plan and implement a predictable implant placement and interim prosthesis. This technique provides a full digital workflow for restoratively-driven computer-aided implant planning, guided surgery, and 3D printing of an interim complete-arch fixed implant-supported prosthesis.