• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.258-268
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• 2018

Purpose: This study systematically examines literatures on the suitability of prostheses and accuracy of obtained impressions to see if digital impressions using intraoral scanners can replace traditional impressions. Materials and methods: A MEDLINE/PubMed search and manual search was performed for studies written in English about accuracy of digital impression published in dental journals from August 1, 1997, to July 31, 2017. Depending on criteria, the data for the selected articles were independently organized into standardized spreadsheets by 2 reviewers. Results: Among the total 35 studies met the inclusion criteria, there were 26 studies comparing the suitability of prostheses, and 9 studies comparing the accuracy of impressions through scan data without prostheses. Most studies used prostheses to compare the accuracy of impression techniques. Conclusion: This review suggests that making single crown or mesio-distally short prostheses with digital impressions is clinically reliable in natural teeth. However, there is still a limit to making mesio-distally long prostheses with digital impressions from the lack of related studies. Digital impression cannot fully replace traditional impressions in implant prostheses yet.

• Journal of Periodontal and Implant Science
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• v.50 no.4
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• pp.238-250
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• 2020

Purpose: This study aimed to evaluate the biocompatibility and the mechanical properties of ultraviolet (UV) cross-linked and biphasic calcium phosphate (BCP)-added collagen membranes and to compare the clinical results of ridge preservation to those obtained using chemically cross-linked collagen membranes. Methods: The study comprised an in vitro test and a clinical trial for membrane evaluation. BCP-added collagen membranes with UV cross-linking were prepared. In the in vitro test, scanning electron microscopy, a collagenase assay, and a tensile strength test were performed. The clinical trial involved 14 patients undergoing a ridge preservation procedure. All participants were randomly divided into the test group, which received UV cross-linked membranes (n=7), and the control group, which received chemically cross-linked membranes (n=7). BCP bone substitutes were used for both the test group and the control group. Cone-beam computed tomography (CBCT) scans were performed and alginate impressions were taken 1 week and 3 months after surgery. The casts were scanned via an optical scanner to measure the volumetric changes. The results were analyzed using the nonparametric Mann-Whitney U test. Results: The fastest degradation rate was found in the collagen membranes without the addition of BCP. The highest enzyme resistance and the highest tensile strength were found when the collagen-to-BCP ratio was 1:1. There was no significant difference in dimensional changes in the 3-dimensional modeling or CBCT scans between the test and control groups in the clinical trial (P>0.05). Conclusions: The addition of BCP and UV cross-linking improved the biocompatibility and the mechanical strength of the membranes. Within the limits of the clinical trial, the sites grafted using BCP in combination with UV cross-linked and BCP-added collagen membranes (test group) did not show any statistically significant difference in terms of dimensional change compared with the control group.

• Journal of Dental Rehabilitation and Applied Science
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• v.38 no.4
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• pp.233-241
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• 2022

Purpose: The purpose of this study was to assess the dimensional change of 3D-printed dentures after post-curing. Materials and Methods: The upper and lower dentures were designed in Exocad DentalCAD software and exported as STL files. The upper and lower dentures were printed from 10 STL files using a DLP-type dental 3D printer. The printed upper and lower dentures were cleaned, and a scan file was created using a model scanner before and after post-curing. The dimensional change was evaluated by superimposing the scanned denture files before and after post-curing and measuring the distance between measurement points on the denture. SPSS was used for statistics, and the level of significance was 5%. Results: The maxillary denture reduced in size during post-curing, with the most notable color change occurring in the posterior palatal region. The reduction in anteroposterior maxillary denture length (A-D, A-E, A-F), as well as the distance between the first molars on both sides (B-C), was statistically significant. After post-curing, the mandibular denture showed more noticeable color change in the posteriorly buccal and lingual region. The decrease of length on the posterior (A-M, A-D, A-E, A-L, A-H, A-I, H-I) and lingual (J-K, L-M) sides of the denture were statistically significant. Conclusion: There was significant dimensional change in both the length and width of the 3D-printed maxillary and mandibular dentures after post-curing in this experiment. Consequently, it is seemed necessary to develop post-curing techniques and materials that reduce such denture deformation.

• Journal of Dental Rehabilitation and Applied Science
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• v.39 no.4
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• pp.267-275
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• 2023

To obtain better esthetic results when immediately placing a dental implant, the soft tissue surrounding the implant must be conditioned during healing of the extraction socket. To this end, the emergence profile can be customized through immediate restoration of the provisional prosthesis, and good clinical results can be obtained at the time of definitive restoration in the future, resulting in high patient satisfaction. In this case, horizontal root fracture occurred after trauma to both maxillary central incisors. Immediate implant placement and loading was planned considering aesthetics and alveolar bone condition. By taking an impression using a digital intraoral scanner, a digital diagnostic wax-up was performed to make a more aesthetic prosthesis without applying external force to the traumatized teeth. Based on this, the ideal placement location was determined and immediate implant placement was performed using a 3D printed surgical guide. The provisional prosthesis was restored 5 days after placement, and the definitive zirconia crown was restored through soft tissue conditioning and customization using the shape of the provisional prosthesis for 3 months.

• The korean journal of orthodontics
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• v.43 no.5
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• pp.235-241
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• 2013

Objective: The purpose of this study was to investigate whether extension of the custom base is necessary for enhancement of bond strength, by comparing the debonding forces and residual adhesives of 3 different lingual bracket systems. Methods: A total of 42 extracted upper premolars were randomly divided into 3 groups of 14 each for bonding with brackets having (1) a conventional limited resin custom base; (2) an extended gold alloy custom base: Incognito${TM}$; and (3) an extended resin custom base: KommonBase${TM}$. The bonding area was measured by scanning the bracket bases with a 3-dimensional digital scanner. The debonding force was measured with an Instron universal testing machine, which applied an occlusogingival shear force. Results: The mean debonding forces were 60.83 N (standard deviation [SD] 10.12), 69.29 N (SD 9.59), and 104.35 N (SD17.84) for the limited resin custom base, extended gold alloy custom base, and extended resin custom base, respectively. The debonding force observed with the extended resin custom base was significantly different from that observed with the other bases. In addition, the adhesive remnant index was significantly higher with the extended gold alloy custom base. Conclusions: All 3 custom-base lingual brackets can withstand occlusal and orthodontic forces. We conclude that effective bonding of lingual brackets can be obtained without extension of the custom base.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.175-176
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• 2006

The aim of the 3D medical imaging is to facilitate the creation of clinically usable image-based algorithm. Clinically usable imaging algorithm for image analysis requires a high degree of interaction to verify and correct results from registration algorithms, such as the Insight Toolkit (ITK) and the Visualization Toolkit (VTK) which are the class libraries. ITK provides segmentation algorithms and VTK has powerful 3D visualization. However, to apply those libraries to the medical images such as Computerized Tomography (CT), the algorithm based on the interactive construction and modification of data objects are necessary. In this paper we showed the 3D registration about mandibular premolar of human teeth acquired by micro-CT scanner. Also, we used the ITK to find the contour of pulp layer of premolar, furthermore, the 3D imaging was visualized with VTK designed to create one kind of view on the data of 3D visualization. Finally, we evaluated that the volume model of pulp layer would be useful for the tooth morphology in dental medicine.

• Imaging Science in Dentistry
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• v.41 no.3
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• pp.101-106
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• 2011

Purpose : This study evaluated the potential use of the computed tomography indices (CTI) on cone beam CT (CBCT) images for an assessment of the bone mineral density (BMD) in postmenopausal osteoporotic women. Materials and Methods : Twenty-one postmenopausal osteoporotic women and 21 postmenopausal healthy women were enrolled as the subjects. The BMD of the lumbar vertebrae and femur were calculated by dual energy X-ray absorptiometry (DXA) using a DXA scanner. The CBCT images were obtained from the unilateral mental foramen region using a PSR-$9000N^{TM}$ Dental CT system. The axial, sagittal, and coronal images were reconstructed from the block images using $OnDemend3D^{TM}$. The new term "CTI" on CBCT images was proposed. The relationship between the CT measurements and BMDs were assessed and the intra-observer agreement was determined. Results : There were significant differences between the normal and osteoporotic groups in the computed tomography mandibular index superior (CTI(S)), computed tomography mandibular index inferior (CTI(I)), and computed tomography cortical index (CTCI). On the other hand, there was no difference between the groups in the computed tomography mental index (CTMI: inferior cortical width). Conclusion : CTI(S), CTI(I), and CTCI on the CBCT images can be used to assess the osteoporotic women.

• The korean journal of orthodontics
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• v.32 no.6 s.95
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• pp.401-411
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• 2002

Precise bracket positioning is essential in modem orthodontics. However, there can be alterations in the vertical position of a bracket due to several reasons. The purpose of this study was to evaluate the effect of variations in the vertical bracket position on the crown inclination in Korean patients with normal occlusion. From a larger group of what was considered to be normal occlusions obtained from the Department of Orthodontics, College of Dentistry, Seoul National University, each of the final 10 subjects (6 males and 4 females, with an average age of 22.3 yews) was selected. The dental models of each of the subjects were scanned three-dimensionally by a laser scanner, and measurements drawn from these were made on the scanned dental casts of the subjects were input into the computer program. From this the occlusal plane and the bracket plane were determined. The tooth plane was then constructed to measure the crown inclination on the bracket plane of each tooth. From a practical standpoint, information was obtained on the extent to which the torque of a tooth would be changed as the bracket position was to be moved vertically (in ${\pm}0.5mm,\;{\pm}1.0mm,\;{\pm}1.5mm$) from its ideal position. A one way analysis of the variance (ANOVA) was used to compare each group of the different vertical distances from the bracket plane on a specific tooth. Duncan's multiple comparison test was then performed. There were statistically significant differences in the crown inclination among the groups of different vertical distances for the upper central incisor, upper lateral incisor, upper canine, upper first and second molars, lower first and second premolars, and lower first and second molars (p<0.05). On the upper anterior teeth, upper molars, lower premolars and lower molars, the resultant torque values due to the vertical displacement of the bracket were different depending on the direction of the displacement, occlusal or gingival. This study implies that the torque of these teeth should be handled carefully during the orthodontic treatment. In circumstances in which the bracket must be positioned more gingivally or occlusally due to various reasons, it would be useful to provide the chart of torque alteration of each tooth referred to in this study with its specified bracket prescription.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.2
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• pp.105-110
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• 2015

Purpose: The purpose of this study was to evaluate the 3 dimensional accuracy of impression taking on the newly developed healing abutment and impression coping combined system comparing conventional pick-up type impression. Materials and methods: For 10 patients who had a single missing tooth on molar area, dental implants (SuperLine; Dentium, Seoul, Korea) were placed and healing abutment (MyHealing; Raphabio Co., Seoul, Korea) abutments were connected. After 3 months, transfer type impression with MyHealing and pick-up type impression with impression coping were performed twice in the same patients, and master models were fabricated. Customized prosthetic abutments (Myplant; Raphabio Co., Seoul, Korea) were milled and connected to the master casts. Through a dental scanner (Scanner S600; Zirkonzahn, South Tyrol, Italy), the master casts were converted into virtual casts. The length and angulation differences between casts were measured using 3 dimentional analysis program (Geomagic Qualify 12; Geomagic, Morrisville, NC, USA). Statistical significance was calculated using Kruskal Wallis test and Mann-Whitney U test (${\alpha}$=.05). Results: The length differences between the two systems were 0.032 mm in sagittal plane, and 0.029 in coronal plane, and 0.023 mm in horizontal plane. The angulation differences were $0.755^{\circ}$ in sagittal plane, and $1.275^{\circ}$ in coronal plane, and $0.420^{\circ}$ in horizontal plane. Conclusion: The accuracy of newly developed healing abutment system is similar to that of conventional pick-up impression. The new system can reduces chair time by not using separate impression coping.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.132-142
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• 2003

This study is performed to investigate the characteristics of the palatal morphology of the children with anterior crossbite in Hellman dental age IIIA by 3-dimensional laser scanner. Totally 40 study casts were taken; 20 were from children with crossbite and another 20 were from normal occlusion as a control. Each cast was scanned by 3 dimension laser scanner and shaped by the 3 dimension image by rapidform 2000 program(INUS, Korea). And finally it was calculated by Rhino 3D program(Rhinoceros, USA). The intercanine, intermolar cross-sectioned transverse plane and sagittal plane were measured. Due to the variations in palatal morphology, each group was standardized into 25mm, 35mm, 35mm. By sectioning standardized curves of the Palatal morphology per 1mm, the palatal depth of each point was calculated. Through these complex methods, the mean curves of the palatal morphology could be obtained and the values were statistically compared and evaluated by T-test with 95% of significance level. The results were as follows: 1. In the intercanine cross-sectioned transverse plane, the mean curve of palatal morphology of crossbite group was flatter V shape than that of control group, however, there was no statistical significance was found between two groups(P>0.05). 2. In the intermolar cross-sectioned transverse plane, the mean curve of palatal morphology of crossbite was deeper all over the area than that of control group, and the statistical significance was found in the middle area from point 8 to 21(P<0.05). 3. In the sagittal plane, the mean curve of palatal morphology of crossbite group was more deepening as approaching posteriorly than that of control group, and the statistical significance was found in all over the area(P<0.01).