• 대한치과교정학회지
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• 제48권5호
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• pp.292-303
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• 2018

Objective: Biplanar imaging systems allow for simultaneous acquisition of lateral and frontal cephalograms. The purpose of this study was to compare measurements recorded on three-dimensional (3D) cephalograms constructed from two-dimensional conventional radiographs and biplanar radiographs generated using a new biplanar imaging system with those recorded on cone-beam computed tomography (CBCT)-generated cephalograms in order to evaluate the accuracy of the 3D cephalograms generated using the biplanar imaging system. Methods: Three sets of lateral and frontal radiographs of 15 human dry skulls with prominent facial asymmetry were obtained using conventional radiography, the biplanar imaging system, and CBCT. To minimize errors in the construction of 3D cephalograms, fiducial markers were attached to anatomical landmarks prior to the acquisition of radiographs. Using the 3D $Ceph^{TM}$ program, 3D cephalograms were constructed from the images obtained using the biplanar imaging system (3D $ceph_{biplanar}$), conventional radiography (3D $ceph_{conv}$), and CBCT (3D $ceph_{cbct}$). A total of 34 measurements were obtained compared among the three image sets using paired t-tests and Bland-Altman plotting. Results: There were no statistically significant differences between the 3D $ceph_{biplanar}$ and 3D $ceph_{cbct}$ measurements. In addition, with the exception of one measurement, there were no significant differences between the 3D $ceph_{cbct}$ and 3D $ceph_{conv}$ measurements. However, the values obtained from 3D $ceph_{conv}$ showed larger deviations than those obtained from 3D $ceph_{biplanar}$. Conclusions: The results of this study suggest that the new biplanar imaging system enables the construction of accurate 3D cephalograms and could be a useful alternative to conventional radiography.

• Clinics in Shoulder and Elbow
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• 제21권3호
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• pp.113-119
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• 2018

Background: This study was undertaken to evaluate the positional relationship between planes of the glenoid component (the scapular plane and the perpendicular plane to the glenoid) and its surrounding structures. Methods: Computed tomography (CT) images of both shoulders of 100 patients were evaluated using the 3-dimensional CT reconstruction program ($Aquarius^{(R)}$; TeraRecon). We determined the most lateral scapular bony structure of the scapular plane and measured the shortest distance between the anterolateral corner of the acromion and the scapular plane. The distance between the scapular plane and the midpoint of the line connecting the posterolateral corner of acromion and the anterior tip of the coracoid process (fulcrum axis) was also evaluated. The perpendicular plane was then adjusted to the glenoid and the same values were re-assessed. Results: The acromion was the most lateral scapular structure of scapular plane and perpendicular plane to the glenoid. The average distance from the anterolateral corner of the acromion to the scapular plane was $10.44{\pm}5.11mm$, and to the plane perpendicular to the glenoid was $9.55{\pm}5.13mm$. The midpoint of fulcrum axis was positioned towards the acromion and was measured at $3.90{\pm}3.21mm$ from the scapular plane and at $3.84{\pm}3.17mm$ from the perpendicular plane to the glenoid. Conclusions: Our data indicates that the relationship between the perpendicular plane to the glenoid plane and its surrounding structures is reliable and can be used as guidelines during glenoid component insertion (level of evidence: Level IV, case series, treatment study).

• Journal of Dental Anesthesia and Pain Medicine
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• 제16권2호
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• pp.111-116
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• 2016

Background: Inferior alveolar nerve block (IANB) of the mandible is commonly used in the oral cavity as an anesthetic technique for dental procedures. This study evaluated the success rate of the first IANB administered by dental practitioners. Methods: Volunteer dental practitioners at Mahidol University who had never performed an INAB carried out 106 INAB procedures. The practitioners were divided into 12 groups with their advisors by randomized control trials. We recorded the success rate via pain visual analog scale (VAS) scores. Results: A large percentage of the dental practitioners (85.26%) used the standard method to locate the anatomical landmarks, injecting the local anesthetic at the correct position, with the barrel of the syringe parallel to the occlusal plane of the mandibular teeth. Further, 68.42% of the dental practitioners injected the local anesthetic on the right side by using the left index finger for retraction. The onset time was approximately 0-5 mins for nearly half of the dental practitioners (47.37% for subjective onset and 43.16% for objective onset), while the duration of the IANB was approximately 240-300 minutes (36.84%) after the initiation of numbness. Moreover, the VAS pain scores were $2.5{\pm}1.85$ and $2.1{\pm}1.8$ while injecting and delivering local anesthesia, respectively. Conclusions: The only recorded factor that affected the success of the local anesthetic was the administering practitioner. This reinforces the notion that local anesthesia administration is a technique-sensitive procedure.

• 대한치과교정학회지
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• 제20권3호
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• pp.427-446
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• 1990

The objective of this study was to understand the major changes of craniofacial dimensions and spatial growth pattern during the late embryonic and fetal period of human fetures. This study was performed with the selective materials of normal fetuses received from the Registry of Congenital Malformation of Seoul National University Hospital. The specimens consisted of nineteen embryos and sixty-six fetuses. The photomicrographs from mid-segittal sections of embryos were used for angular measurement, and the lateral cephalograms taken with soft X-ray were also measured in liners and angular aspects. All of the anatomical landmarks for the tracing of the photomicrographs and cephalograms were referred to the previous reports on literature. The sequential changes of prenatal craniofacial dimensions and agles were analysed statistically and discussed on the focus about the developmental growth directions of human ore-facial structure arised from heterogeneous origins. The results are as follows, 1) Cranial base angle was almost formed at about 6 weeks old embryos with the average angle of $127.4{\pm}6.33^{\circ}$ (n=3) and it was almost constant onwards. 2) The linear increase rates of anterior cranial base length and anterior facial height exceeded those of the posterior cranial base length and posterior facial height, and the maxilla grows more rapidly on the horizontal dimension than the vertical dmension during the fetal period. 3) The angular relationship between the anterior cranial base and palatal plane decreasedslightly during the fetal period, disclosing $11^{\circ}$ at 12th week gestation and $5^{\circ}$ at 41th weeks gestation. 4) Genial angle was maintained almost constantly at about $130^{\circ}$ during the fetal period from 12 weeks to 41 weeks of gestation.

• 대한치과보철학회지
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• 제27권1호
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• pp.55-81
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• 1989

Recently the instantaneous center concept has been to understand the biomechanics by which a tissue derangement causes a mechanical derangement in human joint. Therefore, to understand the biomechanics of temporomandibular joint (T.M.J.) as a part of human joint, it is necessary to clarify the instantaneous center of rotation (I.C.R.) in the mandibular movement. Twenty male subjects without T.M.J. disorder and mandibular deviation during the mandibular movement were selected for this study. The habitual opening and closing paths were recorded on the paper of the sagittal metal plate by two pencil markers connected to the resin open clutch attached on the lower teeth, which was designed for this study. The coordinates of the 33-target points and the 109-anatomical landmarks were obtained using a Summagraphic digitizer connected to a 18AT computer. The original raw data of the opening and closing paths were smoothed by B-spline curve fitting technique and then the I.C.R. pathways were determined mathematically by the computer using algorithm for finding the I.C.R. of a planer rigid body model. Also the opening and closing movements of the mandible were simulated according to the determined I.C.R. The results obtained from this study were as follows. 1. At the early opening and the last closing, I.C.R's were almost distributed around the mastoid process outside the mandibular body without the presence in the region of the mandibular condyle. 2. The I.C.R. pathway showed variable patterns to each subject at the opening and closing movements. 3. The K constant with uniform pattern was obtained by the rotation angle times the radius, which was assumed to the index of the mandibular movement. 4. The opening and closing movements of the mandible were simulated by the I.C.R. pathways at the habitual opening and closing movements. 5. The mandibular condyle was rotated or translated accordng to the relative rotation angle and radius of the determinant factors of K contant.

• Imaging Science in Dentistry
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• 제50권4호
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• pp.323-330
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• 2020

Purpose: The mastoid region is ideal for studying sexual dimorphism due to its anatomical position at the base of the skull. This study aimed to determine sex in the Iranian population based on measurements of the mastoid process using different data mining algorithms. Materials and Methods: This retrospective study was conducted on 190 3-dimensional cone-beam computed tomographic (CBCT) images of 105 women and 85 men between the ages of 18 and 70 years. On each CBCT scan, the following 9 landmarks were measured: the distance between the porion and the mastoidale; the mastoid length, height, and width; the distance between the mastoidale and the mastoid incision; the intermastoid distance (IMD); the distance between the lowest point of the mastoid triangle and the most prominent convex surface of the mastoid (MF); the distance between the most prominent convex mastoid point (IMSLD); and the intersecting angle drawn from the most prominent right and left mastoid point (MMCA). Several predictive models were constructed and their accuracy was compared using cross-validation. Results: The results of the t-test revealed a statistically significant difference between the sexes in all variables except MF and MMCA. The random forest model, with an accuracy of 97.0%, had the best performance in predicting sex. The IMSLD and IMD made the largest contributions to predicting sex, while the MMCA variable had the least significant role. Conclusion: These results show the possibility of developing an accurate tool using data mining algorithms for sex determination in the forensic framework.

• 대한치과교정학회지
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• 제52권4호
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• pp.249-257
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• 2022

Objective: The purpose of this study was to evaluate and compare the dimensional accuracy between thermoformed and direct-printed aligners. Methods: Three types of aligners were manufactured from the same reference standard tessellation language (STL) file: thermoformed aligners were manufactured using Zendura FLX^TM (n = 12) and Essix ACE^TM (n = 12), and direct-printed aligners were printed using Tera Harz^TM TC-85DAP 3D Printer UV Resin (n = 12). The teeth were not manipulated with any tooth-moving software in this study. The samples were sprayed with an opaque scanning spray, scanned, imported to Geomagic^® Control X^TM metrology software, and superimposed on the reference STL file by using the best-fit alignment algorithm. Distances between the aligner meshes and the reference STL file were measured at nine anatomical landmarks. Results: Mean absolute discrepancies in the Zendura FLX^TM aligners ranged from 0.076 ± 0.057 mm to 0.260 ± 0.089 mm and those in the Essix ACE^TM aligners ranged from 0.188 ± 0.271 mm to 0.457 ± 0.350 mm, while in the direct-printed aligners, they ranged from 0.079 ± 0.054 mm to 0.224 ± 0.041 mm. Root mean square values, representing the overall trueness, ranged from 0.209 ± 0.094 mm for Essix ACE^TM, 0.188 ± 0.074 mm for Zendura FLX^TM, and 0.140 ± 0.020 mm for the direct-printed aligners. Conclusions: This study showed greater trueness and precision of direct-printed aligners than thermoformed aligners.

• Archives of Plastic Surgery
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• 제50권3호
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• pp.254-263
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• 2023

Background The three-dimensional (3D) evaluation of skeletal stability after orthognathic surgery is a time-consuming and complex procedure. The complexity increases further when evaluating the surgery-first orthognathic approach (SFOA). Herein, we propose and validate a simple time-saving method of 3D analysis using a single software, demonstrating high accuracy and repeatability. Methods This retrospective cohort study included 12 patients with skeletal class 3 malocclusion who underwent bimaxillary surgery without any presurgical orthodontics. Computed tomography (CT)/cone-beam CT images of each patient were obtained at three different time points (preoperation [T0], immediately postoperation [T1], and 1 year after surgery [T2]) and reconstructed into 3D images. After automatic surface-based alignment of the three models based on the anterior cranial base, five easily located anatomical landmarks were defined to each model. A set of angular and linear measurements were automatically calculated and used to define the amount of movement (T1-T0) and the amount of relapse (T2-T1). To evaluate the reproducibility, two independent observers processed all the cases, One of them repeated the steps after 2 weeks to assess intraobserver variability. Intraclass correlation coefficients (ICCs) were calculated at a 95% confidence interval. Time required for evaluating each case was recorded. Results Both the intra- and interobserver variability showed high ICC values (more than 0.95) with low measurement variations (mean linear variations: 0.18 mm; mean angular variations: 0.25 degree). Time needed for the evaluation process ranged from 3 to 5 minutes. Conclusion This approach is time-saving, semiautomatic, and easy to learn and can be used to effectively evaluate stability after SFOA.

• Imaging Science in Dentistry
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• 제53권2호
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• pp.101-108
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• 2023

Purpose: The aim of this study was to conduct a scoping review and meta-analysis to provide overall estimates of the recall and precision of artificial intelligence for detection and segmentation using oral and maxillofacial cone-beam computed tomography (CBCT) scans. Materials and Methods: A literature search was done in Embase, PubMed, and Scopus through October 31, 2022 to identify studies that reported the recall and precision values of artificial intelligence systems using oral and maxillofacial CBCT images for the automatic detection or segmentation of anatomical landmarks or pathological lesions. Recall (sensitivity) indicates the percentage of certain structures that are correctly detected. Precision (positive predictive value) indicates the percentage of accurately identified structures out of all detected structures. The performance values were extracted and pooled, and the estimates were presented with 95% confidence intervals(CIs). Results: In total, 12 eligible studies were finally included. The overall pooled recall for artificial intelligence was 0.91 (95% CI: 0.87-0.94). In a subgroup analysis, the pooled recall was 0.88 (95% CI: 0.77-0.94) for detection and 0.92 (95% CI: 0.87-0.96) for segmentation. The overall pooled precision for artificial intelligence was 0.93 (95% CI: 0.88-0.95). A subgroup analysis showed that the pooled precision value was 0.90 (95% CI: 0.77-0.96) for detection and 0.94 (95% CI: 0.89-0.97) for segmentation. Conclusion: Excellent performance was found for artificial intelligence using oral and maxillofacial CBCT images.

• The Journal of Advanced Prosthodontics
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• 제16권3호
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• pp.139-150
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• 2024

PURPOSE. The purpose of this diagnostic study was to assess the accuracy and time efficiency of a digital method to draw the denture foundation extension outline on preliminary casts compared with the conventional technique. MATERIALS AND METHODS. A total of 28 preliminary edentulous casts with no anatomical landmarks were digitized using a laboratory scanner. The outlining of the entire basal seat of the denture was performed on preliminary casts and digitized. Casts with no extension outline were digitized and outlines were drawn using software (DWOS, Straumann). The accuracy of the extension outlined between both techniques was evaluated in the software (GOM Inspect; GOM GmbH) by file superimposition. Specificity and sensitivity tests were applied to measure accuracy. The paired t-test (95% CI) was used to compare the mean total area and the working time. RESULTS. The accuracy ranged from 0.57 to 0.92. The buccal and labial frenulum showed a lower value in the maxilla (0.57); while the area between the retromolar pad and buccal frenulum (0.64) showed a lower score in the mandible. The maxillary denture foundation and the working time for both arches were significantly longer for the digital method (P < .001). CONCLUSION. The denture foundation extension outline exhibited a sufficiently excellent accuracy for the digital method, except for the maxillary anterior region. However, the digital method required a longer working time.