Comparative study of 360° virtual reality and traditional two-dimensional video in nonface-to-face dental radiology classes: focusing on learning satisfaction and self-efficacy.

BACKGROUND: Acquiring adequate theoretical knowledge in the field of dental radiography (DR) is essential for establishing a good foundation at the prepractical stage. Currently, nonface-to-face DR education predominantly relies on two-dimensional (2D) videos, highlighting the need for developing educational resources that address the inherent limitations of this method. We developed a virtual reality (VR) learning medium using 360° video with a prefabricated head-mounted display (pHMD) for nonface-to-face DR learning and compared it with a 2D video medium. METHODS: Forty-four participants were randomly assigned to a control group (n = 23; 2D video) and an experimental group (n = 21; 360° VR). DR was re-enacted by the operator and recorded using 360° video. A survey was performed to assess learning satisfaction and self-efficacy. The nonparametric statistical tests comparing the groups were conducted using SPSS statistical analysis software. RESULTS: Learners in the experimental group could experience VR for DR by attaching their smartphones to the pHMD. The 360° VR video with pHMD provided a step-by-step guide for DR learning from the point of view of an operator as VR. Learning satisfaction and self-efficacy were statistically significantly higher in the experimental group than the control group (p < 0.001). CONCLUSIONS: The 360° VR videos were associated with greater learning satisfaction and self-efficacy than conventional 2D videos. However, these findings do not necessarily substantiate the educational effects of this medium, but instead suggest that it may be considered a suitable alternative for DR education in a nonface-to-face environment. However, further examination of the extent of DR knowledge gained in a nonface-to-face setting is warranted. Future research should aim to develop simulation tools based on 3D objects and also explore additional uses of 360° VR videos as prepractical learning mediums.

Mobile educational tool based on augmented reality technology for tooth carving: results of a prospective cohort study.

BACKGROUND: Augmented reality (AR) technology has been shown to be effective in displaying information and presenting three-dimensional objects. Although AR applications are commonly used by learners via mobile devices, plastic models or two-dimensional images are still commonly used in tooth carving practice. Learners practicing tooth carving face a challenge due to the three-dimensional features of teeth as there is a lack of tools available that provide sequential guidance. In this study, we developed an AR-based tooth carving practice tool (AR-TCPT) and compared it to a plastic model to evaluate its potential as a practice tool as well as its user experience. METHODS: To model tooth carving, we created a three-dimensional object from sequential steps that included the maxillary canines and maxillary first premolars (16 steps), mandibular first premolars (13 steps), and mandibular first molars (14 steps). Image markers, created using Photoshop software, were assigned to each tooth. An AR-based mobile application was developed using the Unity engine. For tooth carving, 52 participants were randomly assigned to a control group (n = 26; using a plastic tooth model) or an experimental group (n = 26; using the AR-TCPT). User experience was evaluated using a 22-item questionnaire. Data were comparatively analyzed using the nonparametric Mann-Whitney U test via the SPSS program. RESULTS: The AR-TCPT detects image markers with the mobile device camera and displays three-dimensional objects for tooth fragmentation. Users can manipulate the device to view each step or examine the shape of a tooth. The results of the user experience survey revealed that the AR-TCPT experimental group scored significantly higher in tooth carving experience compared with the control group that used the plastic model. CONCLUSION: Compared with the conventional plastic model, the AR-TCPT provided a better user experience for tooth carving. The tool is highly accessible as it is designed to be used on mobile devices by users. Further studies are required to determine the educational impact of the AR-TCTP on quantitative scoring of carved teeth as well as individual user's carving abilities.

Characterizing the Lateral Border of the Frontalis for Safe and Effective Injection of Botulinum Toxin.

BACKGROUND: The forehead is a common site for injection of botulinum neurotoxin type A (BoNT-A) to treat hyperactive facial muscles. Unexpected side effects of BoNT-A injection may occur because the anatomy of the forehead musculature is not fully characterized. OBJECTIVES: The authors described the lateral border of the frontalis in terms of facial landmarks and reference lines to determine the safest and most effective forehead injection sites for BoNT-A. METHODS: The hemifaces of 49 embalmed adult Korean cadavers were dissected in a morphometric analysis of the frontalis. L2 was defined in terms of FT (the most protruding point of the frontotemporal region), L0 (the line connecting the infraorbital margin with the tragus), and L1 (the line parallel to L0 and passing through FT) such that L2 was positioned 45° from L1 and passed through FT. RESULTS: The distance from FT to the superior margin of the orbicularis oculi was 12.3 ± 3.3 mm. The frontalis extended more than 5 cm along L2 in 49 of 49 cases (100%), more than 6 cm in 47 cases (95.9%), more than 7 cm in 34 cases (69.4%), more than 8 cm in 11 cases (22.4%), and more than 9 cm in 3 cases (6.1%). The lateral border of the frontalis ran parallel to and within 1 cm of the medial side of L2. CONCLUSIONS: Surface anatomy mapping can assist with predicting the lateral border of the frontalis to minimize the side effects and maximize the efficiency of BoNT-A injections into the forehead.

Quantitative anatomical analysis of facial expression using a 3D motion capture system: Application to cosmetic surgery and facial recognition technology.

The topography of the facial muscles differs between males and females and among individuals of the same gender. To explain the unique expressions that people can make, it is important to define the shapes of the muscle, their associations with the skin, and their relative functions. Three-dimensional (3D) motion-capture analysis, often used to study facial expression, was used in this study to identify characteristic skin movements in males and females when they made six representative basic expressions. The movements of 44 reflective markers (RMs) positioned on anatomical landmarks were measured. Their mean displacement was large in males [ranging from 14.31 mm (fear) to 41.15 mm (anger)], and 3.35-4.76 mm smaller in females [ranging from 9.55 mm (fear) to 37.80 mm (anger)]. The percentages of RMs involved in the ten highest mean maximum displacement values in making at least one expression were 47.6% in males and 61.9% in females. The movements of the RMs were larger in males than females but were more limited. Expanding our understanding of facial expression requires morphological studies of facial muscles and studies of related complex functionality. Conducting these together with quantitative analyses, as in the present study, will yield data valuable for medicine, dentistry, and engineering, for example, for surgical operations on facial regions, software for predicting changes in facial features and expressions after corrective surgery, and the development of face-mimicking robots.

Facial arterial depth and relationship with the facial musculature layer.

BACKGROUND: Previous studies have revealed a variation in the origin and distribution patterns of the facial artery. However, the relationship between the facial artery and the facial muscles has not been well described. The purpose of this study was to determine the facial artery depth and relationship with the facial musculature layer, which represents critical information for dermal filler injection and oral and maxillofacial surgery. METHODS: Fifty-four embalmed adult faces from Korean cadavers (36 male and 18 female cadavers; mean age, 73.3 years) were used in this study. A detailed dissection was performed, with great care being taken to avoid damaging the facial artery underlying the facial skin and muscle. RESULTS: The facial artery was first categorized according to the patterns of its final arterial branches. The branching pattern was classified simply into three types: type I, nasolabial pattern (51.8 percent); type II, nasolabial pattern with an infraorbital trunk (29.6 percent); and type III, forehead pattern (18.6 percent). Each type was further subdivided according to the facial artery depth and relationship with the facial musculature layer as types Ia (37.0 percent), Ib (14.8 percent), IIa (16.7 percent), IIb (12.9 percent), IIIa (16.7 percent), and IIIb (1.9 percent). CONCLUSION: This study provides new anatomical insight into the relationships between the facial artery branches and the facial muscles, including providing useful information for clinical applications in the fields of oral and maxillofacial surgery.

Frontal branch of the superficial temporal artery: anatomical study and clinical implications regarding injectable treatments.

BACKGROUND: The frontal branch of the superficial temporal artery (Fbr) is vulnerable to damage triggered by iatrogenic manipulation by both dermal filler and BoNT-A injection. The purpose of this study was to elucidate the branching pattern of Fbr and to determine its location and course on the lateral border of the frontal belly of the occipitofrontalis muscle (FB). METHODS: Sixty-four hemifaces from 38 Korean cadavers (26 males and 12 females; mean age 71.9 years) were dissected, and the location and course of the Fbr were identified with reference to the lateral border of the FB. RESULTS: The ramification of the frontal branch from the superficial temporal artery (STA) occurred 36.9 ± 14.24 mm (mean ± SD) superior and 17.2 ± 8.2 mm anterior to the posterior-most point of the tragus [i.e., tragion (Tg)]. The Fbr was observed as a single branch in 96.9% of cases and reached its destination at a single point in 71.9%. It reached the Fbr 14.8 ± 7.7 mm superior to the uppermost point of the eyebrow and 15.8 ± 9.1 mm from the lateral epicanthus. The Fbr bifurcated into superior and inferior branches before reaching the FB in 25.0% of cases. In two cases (3%), the Fbr ramified from the STA within 1 mm of the Tg. The diameter of the superior division of Fbr was 1.6 ± 0.5 mm at the lateral border of the FB and 1.8 ± 0.6 mm at other locations. CONCLUSION: Physicians performing injection treatments such as botulinum toxin type A and dermal filler injection to the posterior frontal area should be aware of the various distributions of the Fbr.

The risorius muscle: anatomic considerations with reference to botulinum neurotoxin injection for masseteric hypertrophy.

BACKGROUND: The botulinum neurotoxin Type A (BTX) injection into the masseter muscle often causes a change in the facial expression. There is as yet no precise anatomic evidence to support this etiologic factor of constrained facial expressions. OBJECTIVE: The aim of this study was to clarify the location and boundaries of the risorius muscle and its topographical relationship with the surrounding structures. MATERIALS AND METHODS: This study involved the dissection of 48 hemifaces. The locations of origin and insertion points of the risorius muscle were measured, and the masseter muscle was divided into 6 equally sized rectangular areas. RESULTS: Cases where the masseter muscle was covered by the risorius muscle were classified into the following 4 types: in Type A, Area III was partially covered by the risorius (17.8%); in Type B, Area VI was partially covered (20.0%); in Type C, Areas III and VI were partially covered (53.3%); and in Type D, Areas II, III, and VI were covered (6.7%). CONCLUSION: These findings suggest that the medial part of the masseter muscle represents a hazard zone into which the injection of BTX may affect the risorius muscle, potentially resulting in iatrogenic unnatural facial expressions.

Description of a novel anatomic venous structure in the nasoglabellar area.

Injectable dermal fillers are frequently used to reduce the appearance of various facial creases and rhytids. However, venous complications can develop while injecting dermal filler, especially in the nasoglabellar area. The aims of this study were to determine the anatomic patterns of the veins in the nasoglabellar area and to elucidate their detailed location with reference to various facial landmarks. Forty-one heads from Korean and Thai cadavers were dissected. When the anastomosing vein between the bilateral angular veins (AVs) was located in the nasoglabellar area, it was designated the intercanthal vein (ICV). The bilateral AVs continued as the facial vein without any communicating branches in 12 cases (29.3%). At the radix of the nose, the AV communicated with the ICV, connecting them bilaterally. The ICV was found above (type IIA) and below (type IIB) the intercanthal line in 26 (63.4%) and 3 (7.3%) cases, respectively. The ICV can be regarded as a candidate causative site for the frequent complications associated with dermal filler injection in the nasoglabellar area, and utmost care should be taken when injecting in this area, such as when performing radix augmentation and softening wrinkles in the glabellar area.

New anatomical insights on the course and branching patterns of the facial artery: clinical implications of injectable treatments to the nasolabial fold and nasojugal groove.

BACKGROUND: Improper manipulation of injectable treatments to the face can result in disastrous vascular complications. The aim of the present study was to elucidate the detoured course of the facial artery and to provide detailed metric data regarding facial artery location with a view to helping physicians avoid iatrogenic vascular accidents during injectable treatments. METHODS: Sixty specimens from 35 embalmed cadavers (24 male and 11 female cadavers; mean age, 70.0 years) and one fresh male cadaver (age, 62 years) were used for this study. RESULTS: In 56 cases (93.3 percent), the branches of the facial artery were observed at the vicinity of the nasolabial fold. The facial artery was located 3.2 ± 4.5 mm (mean ± SD) lateral to the ala of the nose and 13.5 ± 5.4 mm lateral to the oral commissure. It crossed the nasolabial fold in 33.9 percent of cases, and ascended within 5 mm of the nasolabial fold in 42.9 percent. The facial artery and detoured branches were found in 18 cases (30.0 percent). In the cases with detoured branches, the facial artery turned medially over the infraorbital area at 39.2 ± 5.8 mm lateral to the facial midsagittal line and 35.2 ± 8.2 mm inferior to the plane connecting the medial epicanthi of both sides. The nasojugal portion of the detoured branch traveled along the inferior border of the orbicularis oculi and then ascended toward the forehead, forming the angular artery. CONCLUSION: This detailed vascular anatomy of the facial artery will promote safe clinical manipulations during injectable treatments to the nasolabial fold and nasojugal groove.

Three-dimensional courses of zygomaticofacial and zygomaticotemporal canals using micro-computed tomography in Korean.

The zygomatic nerve (ZN), which originates from the maxillary nerve at the pterygopalatine fossa, enters the orbit through the inferior orbital fissure. Within the lateral region of the orbit, the ZN divides into the zygomaticofacial (ZF) and zygomaticotemporal (ZT) nerves. The ZF and ZT nerves then pass on to the face and temporal region through the zygomaticoorbital foramen and enter their own bony canals within the zygomatic bone. However, multiple zygomaticofacial and zygomaticotemporal canals (ZFCs and ZTCs, respectively) can be observed, and their detailed intrabony courses are unknown. The aim of this study was clarify the three-dimensional intrabony courses and running patterns of the ZFCs and ZTCs, both to obtain a detailed anatomical description and for clinical purposes. Fourteen sides of the zygomatic bones were scanned as two-dimensional images using a micro-computed tomography (CT), with 32-µm slice thickness. Intrabony structures of each canals were three-dimensionally reconstructed and analyzed using Mimics computer software (Version 10.01; Materialise, Leuven, Belgium). We found that some ZTC was originated from ZFC. In 71.4% of the specimens, the ZTC(s) divided from the intrabony canal along the course of the ZFC(s). In other cases, 28.6% of ZTCs were opened through each corresponding ZT foramen. Zygomaticofacial canal originates from zygomaticoorbital foramen, divided into some of ZTCs, and is finally opened as ZF foramen. This new anatomical description of the intrabony structures of the ZFC(s) and ZTC(s) within the zygomatic bone by micro-CT technology provided helpful information to surgeons performing clinical procedures such as Le Fort osteotomy and reconstructive surgeries in the midface region.

Realization of masticatory movement by 3-dimensional simulation of the temporomandibular joint and the masticatory muscles.

Masticatory muscles are closely involved in mastication, pronunciation, and swallowing, and it is therefore important to study the specific functions and dynamics of the mandibular and masticatory muscles. However, the shortness of muscle fibers and the diversity of movement directions make it difficult to study and simplify the dynamics of mastication. The purpose of this study was to use 3-dimensional (3D) simulation to observe the functions and movements of each of the masticatory muscles and the mandible while chewing. To simulate the masticatory movement, computed tomographic images were taken from a single Korean volunteer (30-year-old man), and skull image data were reconstructed in 3D (Mimics; Materialise, Leuven, Belgium). The 3D-reconstructed masticatory muscles were then attached to the 3D skull model. The masticatory movements were animated using Maya (Autodesk, San Rafael, CA) based on the mandibular motion path. During unilateral chewing, the mandible was found to move laterally toward the functional side by contracting the contralateral lateral pterygoid and ipsilateral temporalis muscles. During the initial mouth opening, only hinge movement was observed at the temporomandibular joint. During this period, the entire mandible rotated approximately 13 degrees toward the bicondylar horizontal plane. Continued movement of the mandible to full mouth opening occurred simultaneously with sliding and hinge movements, and the mandible rotated approximately 17 degrees toward the center of the mandibular ramus. The described approach can yield data for use in face animation and other simulation systems and for elucidating the functional components related to contraction and relaxation of muscles during mastication.

Dosimetric perturbations due to an implanted cardiac pacemaker in MammoSite(®) treatment.

PURPOSE: To investigate dose perturbations for pacemaker-implanted patients in partial breast irradiation using high dose rate (HDR) balloon brachytherapy. METHODS: Monte Carlo (MC) simulations were performed to calculate dose distributions involving a pacemaker in Ir-192 HDR balloon brachytherapy. Dose perturbations by varying balloon-to-pacemaker distances (BPD = 50 or 100 mm) and concentrations of iodine contrast medium (2.5%, 5.0%, 7.5%, and 10.0% by volume) in the balloon were investigated for separate parts of the pacemaker (i.e., battery and substrate). Relative measurements using an ion-chamber were also performed to confirm MC results. RESULTS: The MC and measured results in homogeneous media without a pacemaker agreed with published data within 2% from the balloon surface to 100 mm BPD. Further their dose distributions with a pacemaker were in a comparable agreement. The MC results showed that doses over the battery were increased by a factor of 3, compared to doses without a pacemaker. However, there was no significant dose perturbation in the middle of substrate but up to 70% dose increase in the substrate interface with the titanium capsule. The attenuation by iodine contrast medium lessened doses delivered to the pacemaker by up to 9%. CONCLUSIONS: Due to inhomogeneity of pacemaker and contrast medium as well as low-energy photons in Ir-192 HDR balloon brachytherapy, the actual dose received in a pacemaker is different from the homogeneous medium-based dose and the external beam-based dose. Therefore, the dose perturbations should be considered for pacemaker-implanted patients when evaluating a safe clinical distance between the balloon and pacemaker.

Sihler-stain study of buccal nerve distribution and its clinical implications.

OBJECTIVE: The aim of this study was to elucidate the precise distribution of the buccal nerve (BN) and its anatomic relationship with the infraorbital nerve (ION) and mental nerve (MN). STUDY DESIGN: Eight human specimens were subjected to Sihler staining, which is a highly accurate method for visualizing the distribution of nerve fibers without alteration of the nerve. RESULTS: It was found that the BN mainly proceeded medially from its point of entrance near the parotid duct opening to the angular area of mouth, giving off tiny branches along its trajectory. Some of these branches were distributed in upper angular area, over the cheilion, intermingling with branches of the ION. Intermingling of the BN and the MN was also observed in the premolar area of the lower lip. CONCLUSIONS: This new information regarding the distribution of BN should be taken into consideration when evaluating the possible effects of BN damage.

Medial muscular band of the orbicularis oculi muscle.

Despite the importance of anatomic variations in the muscular bands around the orbicularis oculi muscle (OOc), little is known about them. The morphology and variations therein of the medial muscular band of the OOc were thus examined in the current study. Sixty-one hemifaces of Korean cadavers were dissected to enable examination of the anatomic organization of the muscles around the OOc. A medial muscular band of the OOc was observed in 40 cases (65.6%). Three patterns of attachment were found. In type A (14 cases, 23%), it attached to the frontal belly without being attached to the medial canthal tendon; in type B (14 cases, 23%), it originated from the medial canthal tendon at the lower portion of the OOc and inserted into the cheek skin, and in type C (12 cases, 19.7%), it was also observed to insert into the cheek skin and attach to the frontal belly without being attached to the medial canthal tendon. The distance between the inferior edge of the OOc and the subnasale was 16.3 (SD, 4.3) mm and 14.5 (SD, 4.4) mm in cases with and without a medial muscular band, respectively. A space was observed on the inferolateral side of the OOc in about 67.2% of cases. These findings regarding the medial muscular band of the OOc increase further the anatomic variations associated with this region. In addition, it appears that this medial muscular band of the OOc can help to prevent drooping of the OOc.

A piezoelectric motor-based microactuator-generated distractor for continuous jaw bone distraction.

Distraction osteogenesis is widely applied to correct oral and maxillofacial deformities, and intermittent distraction protocols have been used in various clinical applications. There are many challenges for continuous distraction of the jaw bone such as when using hydraulic motors and motor-driven plates. The size of the motor is critical to the ability to miniaturize the complete distractor system, and the importance of size makes it difficult to extrapolate the results of animal models to the clinical situation. This study developed a microactuator-generated distractor (MAGD) for continuous jaw bone distraction. The MAGD system consists of control software based on Microsoft Windows and a Squiggle piezoelectric motor. The system allows various intermittent and continuous distraction protocols to be simply selected using the control software. The maximum force of the laboratory-scale MAGD is 3 N, and the device is ready for adoption in small-animal distraction models such as the rat and mouse. The MAGD needs further refinement before it can be applied to humans, but a fully implanted MAGD system will reduce soft-tissue complications resulting from exposure of the extraoral component. Moreover, the MAGD will support the patient's social activities and require only minimal cooperation from the patient.

Morphometric analysis of the anterior region of the maxillary bone for immediate implant placement using micro-CT.

The purpose of this study was to elucidate the relationship between the maxillary incisor roots and surrounding alveolar structures using microscopic computerized tomography (micro-CT) for the immediate implant placement. Nineteen maxillae from 14 Korean cadavers were used in this study. All specimens were scanned and reconstructed into a three-dimensional (3D) structure using a micro-CT system. The roots of the maxillary central and lateral incisors became dramatically narrower from 6 mm above the cementoenamel junctions to the apex. The roots of the maxillary incisors and canine were located at the labial one fifths region of the alveolar bone. The angle formed by the longitudinal root axis and the alveolar bone was greatest at the maxillary canine. On the basis of the results of this study, guidelines for immediate implant placement can be suggested on the implant diameter and drilling angle to minimize damage of the alveolar plate.

Morphometric analysis of the Korean mandibular ramus for distraction osteogenesis using micro-computed tomography.

When performing distraction osteogenesis, the osteotomy is normally applied to the cortical bone posterior to the mandibular second molar. We measured the topographic thickness of the cortical and trabecular bone of the mandibular ramus and at the mandibular canal (MC) to provide crucial anatomic data aimed at minimizing complications and elucidating the most appropriate site for placing the distractor. Forty sides of the mandibles were prepared from 20 Korean cadavers (10 men and 10 women with a mean age of 68 years). The specimens were scanned and reconstructed into three-dimensional images using a micro-computed tomography system. Coronal and horizontal sectional images of the mandibular ramus were taken at thickness intervals of 2 mm from the reconstructed three-dimensional images. Image analysis software was used to measure the thicknesses of the cortical and trabecular bone and to identify the locations of the MC within the body and the mandibular ramus on each section. The mean thicknesses of the buccal cortical plate, trabecular bone, and lingual cortical plate were 2.9 mm (men, 3.0 mm; women, 2.8 mm), 9.1 mm (men, 9.8 mm; women, 8.5 mm), and 2.2 mm (men, 2.3 mm; women, 2.1 mm), respectively. The distance from the buccal surface of the mandible to the MC increased from 5.3 to 10.0 mm (men, 5.3-10.0 mm; women, 5.3-9.1 mm) when moving progressively anterosuperior from the mandibular angle region. Morphometric analyses of the mandibular ramus can provide crucial data when performing mandibular osteotomy and locating an appropriate placement site for a distractor device during the distraction-osteogenesis procedure.

Intramuscular communicating branches in the flexor digitorum profundus: dissection and Sihler's staining.

PURPOSE: This study was designed to clarify the anatomy of the intramuscular communicating branch (ICb) between the median and ulnar nerves in the flexor digitorum profundus (FDP), and morphologically demonstrate the location of connection. METHODS: Twenty Korean cadavers were dissected and a further 8 were subjected to modified Sihler's staining to investigate the pattern of innervation of the ICb and the location of its communicating points in muscle. RESULTS: The median and ulnar nerves divided into small branches before entering FDP muscle. Of these small branches, one or two met inside the muscle. This communicating pattern could be classified into three types: type I, communicating branches in both the proximal and distal regions; type II, at least one communicating branch in the proximal region; type III, at least one communicating branch in the distal region. Of 20 dissected specimens, no case of type I was observed, but 3 cases of type II and 15 cases of type III were found. No ICbs at all were found in two of the dissected specimens. In eight stained specimens, one was classified as type I, two as type II, and five as type III. The proximal communicating branches were located at 34.1% from the interepicondylar line, inside the third muscle bundle. The distal communicating branches were located at 66.0% from the interepicondylar line, between third and fourth muscle bundles. CONCLUSIONS: These findings could provide critical anatomical information regarding the nerve distribution of FDP focused on the ICbs.