Integration of digital maxillary dental casts with 3D facial images in orthodontic patients

Comparison of the accuracy (trueness and precision) of virtual dentofacial patients digitized by three different methods based on 3D facial and dental images

STATEMENT OF PROBLEM

The accuracy of virtual dentofacial patients has been explored, but the accuracy of virtual patients established by using a straightforward and reliable method and the accuracy of different virtual patients are unclear.

PURPOSE

The purpose of this clinical study was to compare the accuracy of virtual dentofacial patients digitized by using registered-block impression, exposed anterior teeth, and cone beam computed tomography (CBCT) reconstruction methods based on 3-dimensional (3D) facial and dental images.

MATERIAL AND METHODS

From the 15 selected participants who needed CBCT scanning, 3 kinds of virtual dentofacial patients were established by using 3 registration methods based on digital dental casts: 3D facial images, CBCT data, and registered-block impression. Compared with actual measurement, 25 linear distances of all virtual dentofacial patients were selected and measured by using a software program, and 3 separate measurements were calculated by the same person. The 1-way analysis of variance (ANOVA) was used to compare the deviations among 3 kinds of virtual dentofacial patients (trueness) and the deviations within groups (precision). The 1-sample t test was used to compare the difference between the deviation and the ideal error of 0.00 (α=.05).

RESULTS

Compared with the actual measurement, the trueness of the average deviations for registered-block impression (1.02 ±1.24 mm) was better than that of exposed anterior teeth (2.35 ±1.71 mm) and CBCT reconstruction (2.86 ±1.61 mm). The precision of the average deviations for registered-block impression (1.29 ±1.43 mm) was better than that of exposed anterior teeth (2.00 ±1.72 mm) and CBCT reconstruction (2.12 ±1.94 mm). Significant differences in trueness and precision were found among the 3 groups of virtual dentofacial patients (P<.01). Significant differences among the deviations of all linear distances and the ideal error of 0.00 were observed for all groups of virtual dentofacial patients (P<.05).

CONCLUSIONS

The accuracy of registered-block impression was better than that of the exposed anterior teeth and CBCT reconstruction. The accuracy of exposed anterior teeth was lower than that of the other methods but could satisfy the requirements of clinical diagnostics and scientific methods. The accuracy of CBCT reconstruction was poor and could only be used for special situations that permitted low accuracy.

[Soft and hard tissue changes of hyperdivergent class Ⅱ patients before and after orthodontic extraction treatment]

OBJECTIVE

To investigate the hard and soft tissue changing trend and contributing factors of skeletal class Ⅱ hyperdivergent patients before and after orthodontic camouflage treatment by analyzing the cephalogram and the three dimensional (3D) facial scan data.

METHODS

Eighteen skeletal class Ⅱ hyperdivergent adult female patients who finished camouflage orthodontic treatment were selected. Skeletal and dental measurements were carried out with the cephalometric analysis before and after the treatment. 3D facial data before and after orthodontic treatment were acquired and the anatomical landmarks were set after the repositioning and superimposition process. Hard tissue measurement included 17 mea-surement indicators (sella-nasion-subspinale angle, sella-nasion-supramental angle, subspinale-nasion-supramental angle, facial angle, angle of convexity, Frankfort horizontal plane-mandibular plane angle (FH-MP), Y axis angle, sella-nasion plane-mandibular plane angle (MP-SN), pogonion-nasion-supramental distance, upper incisor-nasion-subspinale distance, upper incisor to sella-nasion, lower incisor-nasion-supramental distance, lower incisor-nasion-supramental angle, upper incisor to lower incisor, upper incisor to sella-nasion, lower incisor-mandibular plane angle, and Z angle), and the changes before and after treatment were measured for 11 of them. Twenty soft tissue landmarks (left/right cheekbone, left/right chelion, left/right crista philtra, soft tissue gnathion, left/right gonion, glabella, labrale infe-rius, labrale superius, soft tissue menton, left/right mid-mandibular border, soft tissue pogonion, stomion superius, sublabial, subnasale, and supralabial) and 9 soft tissue indicators (lower lip height, facial convexity, lower vermilion height, mandibular contour, nasolabial angle, philtral length, philtral width, upper lip height, and upper vermilion height) were measured and recorded for treatment changes. Linear-regression analysis and correlation analysis were carried out for analyzing the relationship between hard and soft tissue changes before and after the treatment.

RESULTS

Significant differences were noticed for 18 out of the 20 cephalometric measurements and facial measurements before and after the treatment (P < 0.05), which mainly represented the sagittal retraction of lip area after the treatment. Significant vertical displacements were revealed for soft tissue menton after treatment [(1.88±2.61) mm, P < 0.05]. Significant sagittal displacements were revealed for left/right cheilion [(-2.95±1.9) mm, (-2.90±1.92) mm], labrale inferius[(-4.94±1.95) mm], labrale superius[(-3.25±1.44) mm], sublabial [(-3.10±3.5) mm], and subnasale [(-1.23±1.06) mm] after treatment (P < 0.05). An average of 4.10°±2.57° increasement was noticed for Z angle after treatment. High correlation (r>0.7) was noticed for the displacement of menton after treatment with FH-MP, with the rate of -0.183 :1, and MP-SN, with the rate of -0.157 :1. Moderate correlations (0.7≥r>0.4) were noticed for the other measurements with correlations (P < 0.05).

CONCLUSION

A certain extent of facial improvements could be achieved with orthodontic camouflage treatment for skeletal class Ⅱ hyperdivergent patients, which were mostly represented by the improvement of sagittal relationship of nose, lips, and chin. Certain correlations were noticed for the hard and soft tissue changes.

[Current Status and Analysis of the Clinical Application of Digital Technology in Oral Medicine]

With the increasing maturity and popularization of digital technology in oral medicine, its application has now expanded to various clinical subspecialties of oral medicine. Digitalization has become one of the important development directions of oral medicine. What is the current development status of digital technology in oral medicine? In what ways is digital technology applied across various clinical specialties of oral medicine? Dentists are particularly concerned about these issues in their clinical work and research. In this paper, all the digital technologies applied in oral medicine are organized and categorized from a technical perspective. In this paper, we focused on presenting three-dimensional data acquisition technology, dental computer-aided design technology, dental computer-aided processing technology, and oral surgery implementation technology. Their technical principles, technical characteristics, applications in oral medicine, a secondary discipline of medicine, and the development status of domestically-developed technology are described and reviewed in detail. The other technologies such as oral digital materials, oral virtual simulation teaching, and oral multi-source data management are briefly discussed. We intend to provide references for dentists to apply digital technology in clinical practice and research.

Perceptual difference of smile aesthetics between 2-dimensional photographs and 3-dimensional dentofacial images: a cross-sectional study

BACKGROUND

The aim of this study was to compare the perceptual difference of smile aesthetics between 2D photographs and 3D dentofacial images as perceived by orthodontists and graduate students.

METHODS

Forty-eight subjects finished orthodontic treatment were recruited with 2D photographs of frontal, oblique and lateral views as well as 3D dentofacial images. Twelve senior orthodontists and 13 postgraduate students were asked to rate the 2D and 3D smile simulations based on visual analog scale (VAS) and to vote for smile features that affect the attractiveness of smile. At the end, they completed a questionnaire about their views on different smile simulations. Wilcoxon signed-rank, Bland-Altman analysis, and multiple linear regression were used to compare the ratings and votes of smile perception between raters and between records.

RESULTS

Orthodontists and postgraduate students rated smile consistently with 2D photographs, while orthodontists tended to give a higher rate for unattractive smiles and a lower rate for attractive smiles with 3D dentofacial images. The 3D dentofacial images were rated significantly lower than 2D photographs and the voting of most of the smile features showed significant negative main effect on VAS scores, while the effect of demographic characteristics of raters, voting on visible width of upper dentition and buccal corridor was not significant. In addition, a significant negative main effect of commissure and facial profile was found on the rating discrepancy between 2D and 3D images.

CONCLUSIONS

Senior orthodontists tend to perceived 3D images more conservatively in smile evaluation. 3D dentofacial images were rated lower than 2D photographs and most of the smile features affect the aesthetic perception of smile. The perceptual difference of commissure and facial profile contributed to the lower ratings in 3D dentofacial images.

Integration accuracy of craniofacial cone-beam computed tomography images with three-dimensional facial scans according to different registration areas

OBJECTIVES

To evaluate the integration accuracy of cone-beam computed tomography (CBCT) images with three-dimensional (3D) facial scans according to different registration areas.

MATERIALS AND METHODS

Twenty-five patients (14 males and 11 females), with a mean age of 19.0 ± 11.3 years, were included in this study. Each patient underwent CBCT and facial scans on the same day in an upright position. The facial scans were integrated with the corresponding soft-tissue images of CBCT scans. Three methods were used to integrate the two imaging modalities based on the facial regions scanned: R1, only the forehead and nasal bridge area were included; R2, the right and left malar area were included; and R3, the forehead, nasal bridge, and malar areas were included. The integration accuracy between the facial scans and CBCT images was evaluated by color-mapping methods and average surface distances, calculated by measuring the 3D distances between the surface points on the two superimposed images.

RESULTS

The average surface differences between facial scans and CBCT images were less than 1.0 mm in all three methods. The R3 method showed fewer differences between the facial scans and CBCT images than the other methods did.

CONCLUSIONS

Facial scans obtained using a low-cost facial scanner showed clinically acceptable performance. The integration accuracy of facial and CBCT scans can be increased by including the forehead, nasal bridge, and malar areas as registration areas.

The accuracy of a three-dimensional face model reconstructing method based on conventional clinical two-dimensional photos

Background

This study aims to investigate the accuracy of a three-dimensional (3D) face reconstruction method based on conventional clinical two-dimensional (2D) photos.

Methods

Twenty-three patients were included, and Character Creator v3.2 software with the Headshot v1.0 plugin was used for 3D face model reconstruction. Various facial landmarks were finely adjusted manually to refine the models. After preprocessing and repositioning, 3D deviation analysis was performed. The accuracy of the landmarks in different dimensions was determined, and twelve facial soft tissue measurements were compared to validate the clinical potential of the method.

Result

The reconstructed 3D face models showed good facial morphology with fine texture. The average root mean square errors between face scan models and reconstructed models at perioral area (1.26 ± 0.24 mm, 95%CI: 1.15–1.37 mm) were significantly smaller than the entire facial area (1.77 ± 0.23 mm, 95%CI:1.67–1.88 mm), P < 0.01. The deviation of menton of soft tissue was significantly larger than pronasale (P < 0.01). The deviations of all landmarks in the Y-direction were significantly larger than those in the other 2 dimensions (Y > Z > X, P < 0.01). A significant difference (P < 0.05) of approximately 1.5 mm was found for facial height. Significant differences (P < 0.05) were also identified in the remaining 6 soft tissue measurements, with average deviations no greater than 0.5 mm (linear measurement) or 1.2° (angular measurements).

Conclusion

A 3D face modeling method based on 2D face photos was revealed and validated. The reconstruction accuracy of this method is clinically acceptable for orthodontic measurement purposes, but narrow clinical indications and labor-intensive operations remain problems.

Integrating maxillary dentition and 3D facial photo using a modified CAD/CAM facebow

Background

Accurate integration of the dentitions with the face is essential in dental clinical practice. Here we introduce a noninvasive and efficient protocol to integrate the digitized maxillary dentition with the three-dimensional (3D) facial photo using a prefabricated modified computer-aided design/computer-aided manufacture (CAD/CAM) facebow.

Methods

To integrate the maxillary dentition with the 3D facial photo, the CAD/CAM facebow protocol was applied to 20 patients by taking a series of 3D facial photos in the clinic and integrating them in the laboratory. The integration accuracy of this protocol was compared with that of a valid 3D computed tomography (CT)-aided protocol concerning translational deviations of the landmarks representing maxillary incisors and maxillary first molars as well as the rotational deviation of the maxillary dentition. The intra- and inter-observer reproducibility was assessed, and the time of clinical operation and laboratory integration was recorded.

Results

This facebow-aided protocol generated 3D fused images with colored faces and high-resolution dentitions, and showed high reproducibility. Compared with the well-established CT-aided protocol, the translational deviations ranged from 0 to 1.196 mm, with mean values ranging from 0.134 to 0.444 mm, and a relatively high integration error was found in the vertical dimension (Z) with a mean ± standard deviation (SD) of 0.379 ± 0.282 mm. Meanwhile, the rotational deviations ranged from 0.020 to 0.930°, with mean values less than 1°, and the most evident deviation was seen in pitch rotation with a mean ± SD of 0.445 ± 0.262°. The workflow took 4.34 ± 0.19 min (mins) for clinical operation and 11.23 ± 0.29 min for laboratory integration.

Conclusion

The present radiation-free protocol with the modified CAD/CAM facebow provided accurate and reproducible transfer of the digitized maxillary dentition to the 3D facial photo with high efficiency.

Comparison of the accuracy of different handheld-type scanners in three-dimensional facial image recognition

PURPOSE

Handheld-type scanners are widely used in clinical practice. This study examined the accuracy of handheld-type scanners using plaster statues to assess their performance in facial recognition.

METHODS

Twelve 4-mm zirconia balls as measuring points were attached to the facial portions of three types of plaster statue. Six digital facial images of each plaster statue were obtained using one of the following five handheld-type scanners: Artec Eva, Artec Spider, Bellus 3D FaceApp, SNAP, and Vectra H1. Four-millimeter spherical objects were manually placed at the measurement points on the scanned data generated using computer-aided design software and coordinate positions were measured using a contact-type high-resolution three-dimensional measurement device. Consequently, the discrepancy between the distance measured using the contact-type device and that measured using the handheld-type scanner was calculated. The scanning time, processing time, and deviation of the distance between the measuring points were analyzed using two-way analysis of variance and t-test with Bonferroni correction.

RESULTS

The scanning and processing times ranged from 15.2 to 42.2 s and 20.7 to 234.2 s, respectively. Overall, 97% of all measured distances by Spider were within ±1.00% deviation; 79%, Vectra; 73%, Eva; 70%, Bellus; and 42%, SNAP.

CONCLUSIONS

The performance of handheld-type scanners using plaster statues varied among the different scanners. The scanning time of Eva and the processing time of Bellus were significantly shorter than those of other scanners. Furthermore, Spider exhibited the best accuracy, followed by Eva, Vectra, Bellus, and SNAP.

Effects of Artificial Extraoral Markers on Accuracy of Three-Dimensional Dentofacial Image Integration: Smartphone Face Scan versus Stereophotogrammetry

Recently, three-dimensional (3D) facial scanning has been gaining popularity in personalized dentistry. Integration of the digital dental model into the 3D facial image allows for a treatment plan to be made in accordance with the patients’ individual needs. The aim of this study was to evaluate the effects of extraoral markers on the accuracy of digital dentofacial integrations. Facial models were generated using smartphone and stereophotogrammetry. Dental models were generated with and without extraoral markers and were registered to the facial models by matching the teeth or markers (n = 10 in each condition; total = 40). Accuracy of the image integration was measured in terms of general 3D position, occlusal plane, and dental midline deviations. The Mann−Whitney U test and two-way analysis of variance were used to compare results among face-scanning systems and matching methods (α = 0.05). As result, the accuracy of dentofacial registration was significantly affected by the use of artificial markers and different face-scanning systems (p < 0.001). The deviations were smallest in stereophotogrammetry with the marker-based matching and highest in smartphone face scans with the tooth-based matching. In comparison between the two face-scanning systems, the stereophotogrammetry generally produced smaller discrepancies than smartphones.

The Effect of Perioral Scan and Artificial Skin Markers on the Accuracy of Virtual Dentofacial Integration: Stereophotogrammetry Versus Smartphone Three-Dimensional Face-Scanning

This study evaluated the effects of different matching methods on the accuracy of dentofacial integration in stereophotogrammetry and smartphone face-scanning systems. The integration was done (N = 30) with different matching areas (n = 10), including teeth image only (TO), perioral area without markers (PN) and with markers (PM). The positional accuracy of the integrated models was assessed by measuring the midline linear deviations and incisal line canting between the experimental groups and laser scanner-based reference standards. Kruskal–Wallis and Mann–Whitney U tests were used for statistical analyses (α = 0.05). The PM method exhibited the smallest linear deviations in both systems; while the highest deviations were found in the TO in stereophotogrammetry; and in PN in smartphone. For the incisal line canting; the canting degree was the lowest in the PM method; followed by that in the TO and the PN in both systems. Although stereophotogrammetry generally exhibited higher accuracy than the smartphone; the two systems demonstrated no significant difference when the perioral areas were used for matching. The use of perioral scans with markers enables accurate dentofacial image integration; however; cautions should be given on the accuracy of the perioral image obtained without the use of markers.

A novel approach quantifying the periorbital morphology: A comparison of direct, 2-dimensional, and 3-dimensional technologies

BACKGROUND

The measurement of anatomical structures is critical in plastic and reconstructive surgery. However, few detailed and standardized measurements have been widely used in the periorbital region. This study aimed to evaluate the feasibility of a novel detailed and standardized protocol with 2D and 3D technologies, and explore the relationship between them and direct measurements.

METHODS

Fifty healthy Caucasians (100 eyes) between 20 and 68 years old were recruited and captured for 3D photographs by VECTRA M3 3D Imaging System. Subsequently, 24 landmarks were located on each 3D photographs following a standardized protocol, and then 19 linear and 3 angular periorbital variables were measured. Furthermore, two-dimensional (2D) and direct measurements were conducted on each subject and compared with 3D measurements and one another.

RESULTS

The grand r means across all measurements were 0.77, 0.78, and 0.88 for direct vs. 2D values, direct vs. 3D values, and 3D vs. 2D values, respectively. The mean absolute differences were 1 mm (ranging from 0.2 mm to 3.7 mm) between direct and 3D measurements, 1 mm (ranging from 0.04 mm to 2.4 mm) between direct and 2D measurements, and 1 mm and 6.6° (ranging from 0.04 mm or 0.5° to 3 mm or 12.8°) between 2D and 3D measurements.

CONCLUSIONS

This study verified the feasibility of this detailed and standardized landmark localization protocol for assessing the periorbital morphology with 2D and 3D technologies. This protocol may work as a bridge communicating with all studies involving any of the three technologies in the future.