• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.249-259
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• 1991

The purpose of this study was to evaluate the incidence and radiographic features of 677 cases of hypercementosis by means of the analysis of full mouth periapical radiograms in 4,236 persons visited the Department of Oral Radiology, School of Dentistry, Kyung Hee University during January 1984 to December 1989. The obtained results were as follows: 1. The incidence of hypercementosis was revealed to be 8.2% in total examined persons, and there was a higher incidence in females (9.4%) than in males (7.1%). 2. The hypercementosis was most frequently occurred in the 6th decades (29.2%), and the incidence was increased by advancing age until 6th decades. 3. There was a higher incidence in the maxilla (59.5%) than in the mandible (40.5%), and maxillary second premolar (18.5%) was the most frequently involved tooth. The maxillary first premolar (11.7%) was next in order to frequency followed by maxillary canine (10.0%) and mandibular first and second premolars (9.6%). 4. In the etiologic factors, 35.0% were inflammation, 31.2% were elongation, 6.2% were trauma from occlusion, 0.1 % were uneruption, and 27.5% were unknown. 5. In the degree of cementum apposition, 35.3% were Type Ⅰ, 29.5% were Type Ⅱ, and 35.2% were Type Ⅲ. 6. In the status of cementum apposition, 3.2% were mesial side, 8.9% were distal side, and 87.9% were mesial & distal side. 7. In the identification of radiographic density between normal cementum and excessive cementum, 12.7% could be identified, and 87.3% could be unidentified.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.1
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• pp.11-19
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• 2007

There are have been reports that the distribution of electromyographical(EMG) activity is determined in a predictable manner by both the location and number of occlusal contacts. However, these reports placed an emphasis on whole dentition. Inclined plane contacts in the frontal plane are classified as A-, B- or C-types. Objectives: The aim of this study was to evaluate the relation between occlusal tooth contact patterns and EMG activity of masseter muscle during maximum voluntary clenching. Methods: Fifteen healthy human subjects(Mean age; 25.3 years) volunteered to participate in this study. Acrylic resin overlays were fabricated for upper 2nd premolars and 1st molars bilaterally, and offered 3 types(A-, B- and AB- type contact). EMG activity of the masseter muscles was recorded bilaterally during maximum voluntary clenching. Statistical analysis was performed using the one-way ANOVA. Results: The group with a A-type contact showed a statistically lower EMG activity of masseter muscle than that of natural group(p<0.05) and that of B- and AB- type groups(p<0.01) on both upper 2nd premolars and upper 1st molars. Conclusions: These results suggest that occlusal tooth contact patterns have an influence on EMG activity of masseter muscle during maximum voluntary clenching.

• The Journal of the Korean dental association
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• v.55 no.6
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• pp.400-410
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• 2017

Approximately 30% of adult patients who want orthodontic treatment have transverse discrepancy with insufficient width of the maxilla. Particularly, in Class III patients requiring orthognathic surgery, the frequency of insufficient width of the maxillary arch related to respiratory problems is high. We report a case of non-surgical maxillary expansion using a Hyrax type expander with an orthognathic surgery, based on the reports that the ratio of non-fused midpalatal suture is not high in adults. A 30 years and 2 months old woman with a long face showed an Angle Class III with a vertical growth pattern. Class III molar and canine relation, anterior edge bite, and mandibular incisor compensatory lingual inclination were observed. The posterior buccal overjet seemed to be appropriate, but I diagnosed that there was a transverse discrepancy, for the following reasons. The inter-canine and inter-molar widths were sufficient but excessive lingual inclination of the mandibular molars was observed when assessing the bucco-lingual inclination based on the center of resistance of the maxillary and mandibular first molar. For this reason, it was expected that intercuspal interference would occur during orthodontic decompensation. Therefore, slow maxillary expansion using Hyrax type expander was performed and 2-jaw rotation surgery was performed to improve aesthetic and occlusion. Adults can also improve width discrepancy by non-surgical methods, which can avoid SARPE requiring additional surgery or segmental surgery lacking stability and predictability.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.4
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• pp.364-373
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• 2019

Unlike class I patients, skeletal class II patients have unstable occlusion thus leading to instability of mandibular complete denture. Therefore, mandibular implant overdenture has been the standard of care due to its advantages in stability and retention. The types of attachments can be divided into two categories: solitary and bar type. The indications vary between two categories. In this clinical report, digital technology was utilized from the implant planning to the choice of appropriate attachment. Implants were placed at the desired location as previously planned in terms of angle and depth. Maxillary removable partial denture and mandibular implant overdenture are expected to have fair prognosis.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.2
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• pp.153-167
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• 2005

The purpose of this study was to compare the v-shape thread with the square shape thread of fixture in the view of stress distribution pattern using finite element stress analysis. The finite element model was designed with the parallel placement of two standard fixtures(4.0 mm diameter ${\times}$ 11.5 mm length) on the region of mandibular 1st and 2nd molars. Three dimensional finite element model was created with the components of the implant and surrounding bone. This study simulated loads of 200 N at the central fossa in a axial direction (load A), 200 N at the buccal offset load that is 2 mm apart from central fossa in a axial direction (load B), 200 N at the buccal offset load that was 4 mm apart from central fossa in a axial direction (load C). These forces of load A',B',C' were applied to a $15^{\circ}$ inward oblique direction at that same site with 200 N. Von Mises stress values were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study : 1. The highest stress concentration occurred at the cervical region of the implant fixture. 2. Von Mises stress value of off-site region was higher than that of central fossa region. 3. Square shape thread type showed more even stress distribution in the vertical and oblique force than V-shape thread type. 4. Stress distribution was the most effective in the case of buccal offset load (2, 4 mm distance from central fossa) in the square shape thread type. 5. V-shape thread type revealed higher von Mises stress value than square shape thread type in all environmental condition. The results from numerical analyses concluded that square shape thread type had the lower destructive stress and more stress distribution between the fixture and bone interface than V-shape thread type. Therefore, square shape thread type was regarded as optimal thread configuration in biomechanical concepts.

• Journal of Dental Rehabilitation and Applied Science
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• v.16 no.2
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• pp.113-122
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• 2000

The reinforced composte resin as the esthetic operative material continuously has been studied because the porcelain fused metal prosthesis is widely used for its excellent esthetics, rigidity and marginal integrity, but it has low fracture resistance against the tensile strength and stress, attrition of the opposite teeth. The reinforced composite resin is well adapt with the dental alloy but it is low the shear bond strength with the dental alloy vs the porcelain fused metal prosthesis, and then has been studied continuously. The purpose of the study was to examine how metal was the higher shear bond strength among the dental alloy was used to the reinforced composite resin and to find the effect that the particle size of sandblasting influenced the shear bond strength. We built up the reinforced composite resin with 4 mm in diameter, 3 mm in height on circular alloy with 5 mm in diameter, 2 mm in height. Type II gold, type IV gold, and Ag-Pd alloy was used as alloys and $50{\mu}m$, $110{\mu}m$, $250{\mu}m$ of the particle size was sandblasted at each alloy in bonding between alloy and resin. We made 90 secimens of 10 per each group and we measured the shear bond strength using the Instron($M100EC^{(R)}$, Mecmesin Co., England). The obtained results were as follows : 1. In comparison among each alloys, Ag-Pd alloy had the highest shear bond strength and the shear bond strength was decreased significantly in the sequence of the type II gold and type IV gold(P<0.001). 2. In comparison according to the size of sandblasting particle, (1) In Ag-Pd alloy, shear bond strength was decreased in the sequence of $110{\mu}m$, $250{\mu}m$, $50{\mu}m$ and there were significant difference in all the group. (P<0.05) (2) In type II gold, it was decreased in the sequence of $250{\mu}m$, $50{\mu}m$, $110{\mu}m$ and there were significant difference. (P<0.05) (3) In type IV gold, it was decreased in the sequence of $110{\mu}m$, $50{\mu}m$, $250{\mu}m$. There were significant difference between the group of $110{\mu}m$ and $50{\mu}m$, the group of $110{\mu}m$ and 250, but there were no significant difference in the group of $50{\mu}m$ and $250{\mu}m$. 3. The highest shear bond strength according to the size of sandblasting particle was $110{\mu}m$ in Ag-Pd alloy and type IV gold, $250{\mu}m$ in type II gold.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.323-337
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• 2010

The objective of this study was to examine the availability of the new impression coping by comparing with conventional coping in implant pick-up impression technique. Five implant fixtures were installed on #14, 21, 23, 25, 27 in acrylic resin model. That model with 5 fixtures was standard model, which was divided 3 groups; using new flag type impression coping, conventional impression coping splinted with self-curing resin, conventional impression coping without splinting. We made metal circular cones for calculation 3-dimensional coordinates by attaching to implant fixtures or analogs. Three-dimensional relationships of each model were calculated. Data was analyzed by multiple ANOVA and Bonferroni. The accuracy of impression between using new flag type impression coping and conventional impression coping did not show differences in 3 - dimensional analysis.Within limitations of this study, the new flag type impression coping is available in implant pick-up impression technique.

• Gut and Liver
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• v.12 no.6
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• pp.722-727
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• 2018

Background/Aims: Although endoscopic bilateral stent-instent placement is challenging, many recent studies have reported promising outcomes regarding technical success and endoscopic re-intervention. This study aimed to evaluate the technical accessibility of stent-in-stent placement using large cell-type stents in patients with inoperable malignant hilar biliary obstruction. Methods: Forty-three patients with inoperable malignant hilar biliary obstruction from four academic centers were prospectively enrolled from March 2013 to June 2015. Results: Bilateral stent-in-stent placement using two large cell-type stents was successfully performed in 88.4% of the patients (38/43). In four of the five cases with technical failure, the delivery sheath of the second stent became caught in the hook-cross-type vertex of the large cell of the first stent, and subsequent attempts to pass a guidewire and stent assembly through the mesh failed. Functional success was achieved in all cases of technical success. Stent occlusion occurred in 63.2% of the patients (24/38), with a median patient survival of 300 days. The median stent patency was 198 days. The stent patency rate was 82.9%, 63.1%, and 32.1% at 3, 6, and 12 months postoperatively, respectively. Endoscopic re-intervention was performed in 14 patients, whereas 10 underwent percutaneous drainage. Conclusions: Large cell-type stents for endoscopic bilateral stent-in-stent placement had acceptable functional success and stent patency when technically successful. However, the technical difficulty associated with the entanglement of the second stent delivery sheath in the hook-cross-type vertex of the first stent may preclude large cell-type stents from being considered as a dedicated standard tool for stent-in-stent placement.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.2
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• pp.169-181
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• 2008

The aim of this study was to compare the retention and stability of implant overdenture according to the shape and the number of magnetic attachment. The experimental groups were designed for the number of implants(1, 2, 4) and shape of magnetic attachments(flat, cushion, dome type) resulting in 9 subgroups. 45 attachments were tested attached to $Br{\aa}nemark$ system implants which were planted on a mandibular model. Each attachment was composed of the magnet assembly embedded in a overdenture sample and the abutment keeper screwed into the implants. Dislodging tensile forces were applied to the overdenture samples using an Instron(cross-head speed 50.80mm/min) in 3 directions simulating function: vertical, oblique, and anterior-posterior. The loading was repeated 10 times in each direction for 45 samples. The values of maximum dislodging force of each subgroup were processed statistically using SPSS V. 12.0 at the 0.05 level of significance. The results of this study were as follows: 1. Flat type magnetic overdenture was the most retentive when subjected to vertically directed forces and dome type was the lest retentive when subjected to obliquely directed forces(p<0.05). 2. In case of planting one implant, flat type had a higher vertically retentive force than anterior-posteriorly retentive force. In case of planting two implants, flat type and dome type had a higher vertically retentive force and in case of planting four implants, flat type and cushion type had a higher vertically retentive force than anterior-posteriorly retentive force(p<0.05). 3. The incremental number of dental implant, without regards to the three types of magnetic attachment shapes, showed higher retention of overdenture(p<0.05). From the results, if a patient need much more retention of implant overdenture, flat type magnetic overdenture would be a good treatment. In case of the bruxism where excessive lateral forces are already present, dome type could be expected to produce better results. In case of planting one implant, flat type is more stable than the other shape of magnet and in case of two implant, flat type and dome type are more stable and in case of four implants, flat type and cushion type are more stable. Planting more than two implants and using flat type magnetic attachment would provide better retention and stability of implant overdenture

• Clinical and Experimental Pediatrics
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• v.48 no.2
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• pp.158-164
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• 2005

Purpose : We reviewed the therapeutic results of various Duct-Occlud coils(pfm AG, $K{\ddot{o}}ln$, Germany) to evaluate the efficacy of the most-recently modified Duct-Occlud coil(Nit-Occlud) in the transcatheter closure of patent ductus arteriosus(PDA), including large defects more than 4 mm in diameter. Methods : Two hundred and five patients who underwent percutaneous PDA occlusion using Duct-Occlud devices from March 1996 to December 2003 were enrolled and four types of Duct-Occlud [Standard(S), Reinforced(R), Reinforced reverse cone(RR) and Nit-Occlud(N)] were used in this study. The patients were followed up by echocardiogram and physical examination before discharge, one month, six months and 12 months after the procedure. Results : The rate of residual shunt according to the type of Duct-Occlud were as follows : S-54%, R-72%, RR-50%, N-14%(P<0.05 compared with other devices) at one month, S-25%, R-44%, RR-37%, N-0%(P<0.05 compared with other devices) at six months, S-8%, R-8%, RR-4%, N-0%(P<0.05 compared with S and R) at 12 months and later. Nit-Occlud coil showed the complete occlusion of PDA after six months of follow-up, even in 12 patients with relatively large PDA(>4 mm). Conclusion : The transcatheter closure of PDA using Duct-Occlud was an effective treatment and our study revealed that a Nit-Occlud coil which showed higher rate of occlusion even in PDA with large diameters over than 4 mm, was a more effective modality compared to previous devices.