• The Journal of Advanced Prosthodontics
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• 제12권5호
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• pp.316-321
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• 2020

PURPOSE. The stress distribution and microgap formation on an implant abutment structure was evaluated to determine the relationship between the direction of the load and the stress value. MATERIALS AND METHODS. Two types of three-dimensional models for the mandibular first molar were designed: bone-level implant and tissue-level implant. Each group consisted of an implant, surrounding bone, abutment, screw, and crown. Static finite element analysis was simulated through 200 N of occlusal load and preload at five different load directions: 0, 15, 30, 45, and 60°. The von Mises stress of the abutment and implant was evaluated. Microgap formation on the implant-abutment interface was also analyzed. RESULTS. The stress values in the implant were as follows: 525, 322, 561, 778, and 1150 MPa in a bone level implant, and 254, 182, 259, 364, and 436 MPa in a tissue level implant at a load direction of 0, 15, 30, 45, and 60°, respectively. For microgap formation between the implant and abutment interface, three to seven-micron gaps were observed in the bone level implant under a load at 45 and 60°. In contrast, a three-micron gap was observed in the tissue level implant under a load at only 60°. CONCLUSION. The mean stress of bone-level implant showed 2.2 times higher than that of tissue-level implant. When considering the loading point of occlusal surface and the direction of load, higher stress was noted when the vector was from the center of rotation in the implant prostheses.

• Proceedings of the Optical Society of Korea Conference
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• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.45-48
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• 1990

CO2 laser beam was focused by a ZnSe lens onto the center of the occlusal surface f extracted lower molars. K-type thermocouple was contacted with the pulp chamber and the changes of temperature in the during and after the laser irradiation were measured as function of the power of laser beam, the time of laser irradiation and thickness of the sample. An empirical formula for temperature effect was derived from the measured data.

• Journal of Technologic Dentistry
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• 제6권1호
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• pp.15-18
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• 1984

A denture that shifts easily in response to latterally applied forces can cause a disruption in the border seal or prevent the denture base from Correctly relating to the supporting tissue. The factors that Contribute to stability include ridge height and conformation, base adaptation, residual ridge relationships, occlusion harmony, and Muscle control. These factors can be condensed into the following categories; 1. The relationship of the denture base to the underlying tissue. 2. The relationship of occlusal harmony. 3. The relationship of the denture surface and border to the surrounding muscle. 4. The location of artificial tooth.

• Journal of Oral Medicine and Pain
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• 제7권1호
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• pp.41-46
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• 1982

The patient, 11 yeats old male was examined for routine oral health care. He had been hospitalized for treatment of nephritis. Hos physical condition os mental retarded & undergrowth state. In oral examination, notch on cutting edge and screw-driver shaped crown of maxillary central incisors, narrow crown and dwarfed & pinched occlusal surface of lower first molars and scars(rhagades) on the angle of the lip were shown. We diagnosed the above symptoms as dental defects of congenital syphilis; Huchinson's inscisors and mulberry molar.

• Proceedings of the KACD Conference
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• 대한치과보존학회 2003년도 제120회 추계학술대회 제 5차 한ㆍ일 치과보존학회 공동학술대회
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• pp.566-566
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• 2003

The purpose of this in vitro study was to measure and compare the in vitro micro shear bond strengths of the following dentin bonding systems to different dentin surfaces under simulated pulpal pressure. Occlusal surfaces of 180 extracted human molars were prepared to expose the dentin surface in perpendicular to axis of tooth. Teeth were randomly assigned to 3 equal groups and subdivided into 4 equal groups. 4 adhesive systems(All Bond 2, SEbond, AdheSE, Prompt L-Pop) were used in this study.(omitted)

• Journal of the korean academy of Pediatric Dentistry
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• 제37권2호
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• pp.159-167
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• 2010

The purpose of this study was to identify patterns of caries in the dentition of preschool children using cluster analysis and multidimensional scaling. 815 preschool children aged 36-71 months old were examined for caries experience. The first four clusters in the cluster analysis were (1) molars, (2) upper incisors, (3) lower 1st molars, and (4) upper 1st molars in teeth, (1) occlusal surfaces of lower molars and upper 2nd molars, (2) mesial surfaces of upper central incisors, (3) occlusal surfaces of lower 1st molars, and (4) separation between occlusal surfaces of upper and lower 2nd molars in tooth surfaces, and (1) proximal surfaces of upper anterior teeth, (2) occlusal surfaces of lower molars, (3) buccolingual surfaces of upper anterior teeth and (4) buccolingual, proximal, and occlusal surfaces of upper molars and buccolingual and proximal surfaces of lower molars in tooth surfaces groups. In the multidimensional scaling analysis, teeth could be divided into lower 1st molars, upper 1st molars, upper central incisors, upper lateral incisors, lower 2nd molars, upper 2nd molars, and the rest(canines, lower incisors), tooth surfaces could be divided into occlusal surfaces of lower molars, mesial surfaces of upper central incisors, occlusal surfaces of upper molars, and the rest, and tooth surface groups could be divided into proximal surfaces of upper anterior teeth, buccolingual surfaces of upper anteiror teeth, occlusal surfaces of lower molars, and the rest in the order of the distance from others. In the cluster analysis and the multidimensional scaling analysis, caries patterns were different according to the age.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.1-33
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• 1997

The objective of this study was to analyze the in vitro and in vivo corrosion products of low and high copper amalgams. The four different types of amalgam alloy used in this study were Fine cut, Caulk spherical, Dispersalloy, and Tytin. After each amalgam alloy and Hg were triturated according to the directions of the manufacturer by means of the mechanical amalgamator(Amalgam mixer. Shinhung Co. Korea), the triturated mass was inserted into a cylindrical metal mold which was 12mm in diameter and 10mm in height. The mass was condensed by 150Kg/cm compressive force. The specimen was removed from the mold and aged at room temperature for about seven days. The standard surface preparation was routinely carried out by emery paper polishing under running water. In vitro amalgam specimens were potentiostatically polarized ten times in a normal saline solution at $37^{\circ}C$(potentiostat : HA-301. Hukuto Denko Corp. Japan). Each specimen was subjected to anodic polarization scan within the potential range -1700mV to+400mV(SCE). After corrosion tests, anodic polarization curves and corrosion potentials were obtained. The amount of component elements dissolved from amalgams into solution was measured three times by ICP AES(Inductive Coupled Plasma Atomic Emission Spectrometry: Plasma 40. Perkim Elmer Co. U.S.A.). The four different types of amalgam were filled in occlusal and buccal class I cavities of four human 3rd molars. After about five years the restorations were carefully removed after tooth extraction to preserve the structural details including the deteriorated margins. The occlusal surface, amalgam-tooth interface and the fractured surface of in vivo amalgam corrosion products were analyzed. In vivo and in vitro amalgam specimens were examined and analyzed metallographically by SEM(Scanning Electron Microscope: JSM 840. Jeol Co. Japan) and EDAX(Energy Dispersive Micro X-ray Analyser: JSM 840. Jeol Co. Japan). 1. The following results are obtained from in vitro corrosion tests. 1) Corrosion potentials of all amalgams became more noble after ten times passing through the in vitro corrosion test compared to first time. 2) After times through the test, released Cu concentration in saline solution was almost equal but highest in Fine cut. Ag and Hg ion concentration was highest in Caulk spherical and Sn was highest in Dispersalloy. 3) Analyses of surface corrosion products in vitro reveal the following results. a)The corroded surface of Caulk spherical has Na-Sn-Cl containing clusters of $5{\mu}m$ needle-like crystals and oval shapes of Sn-Cl phase, polyhedral Sn oxide phase. b)In Fine cut, there appeared to be a large Sn containing phase, surrounded by many Cu-Sn phases of $1{\mu}m$ granular shapes. c)Dispersalloy was covered by a thick reticular layer which contained Zn-Cl phase. d)In Tytin, a very thin, corroded layer had formed with irregularly growing Sn-Cl phases that looked like a stack of plates. 2. The following results are obtained by an analysis of in vivo amalgam corrosion products. 1) Occlusal surfaces of all amalgams were covered by thick amorphous layers containing Ca-P elements which were abraded by occlusal force. 2) In tooth-amalgam interface, Ca-P containing products were examined in all amalgams but were most clearly seen in low copper amalgams. 3) Sn oxide appeared as a polyhedral shape in internal space in Caulk spherical and Fine cut. 4) Apical pyramidal shaped Sn oxide and curved plate-like Sn-Cl phases resulted in Dispersalloy. 5) In Tytin, Sn oxide and Sn hydroxide were not seen but polyhedral Ag-Hg phase crystal appeared in internal space which assumed a ${\beta}_l$ phase.

• The Journal of Korean Academy of Prosthodontics
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• 제47권2호
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• pp.156-163
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• 2009

Statement of problem: Recently, there have been increased esthetic needs for posterior dental restorations. The failure of posterior dental ceramic restoration are possible not only by the characters of the component materials but also by the type of food. Purpose: The research aim was to compare the in vitro fracture resistance of simulated first molar crowns fabricated using 4 dental ceramic systems, full-porcelain-occlusal-surfaced PFG, half-porcelain-occlusal-surfaced PFG, Empress 2, Ice Zirkon and selected Korean foods. Material and methods: Eighty axisymmetric crowns of each system were fabricated to fit a preparation with 1.5- to 2.0-mm occlusal reduction. The center of the occlusal surface on each of 15 specimens per ceramic system was axially loaded to fracture in a Instron 4465, and the maximum load(N) was recorded. Afterwards, selected Korean foods specimens(boiled crab, boiled chicken with bone, boiled beef rib, dried squid, dried anchovy, round candy, walnut shell) were prepared. 15 specimens per each food were placed under the Instron and the maximum fracture loads for them were recorded. The 95% confidence intervals of the characteristic failure load were compared between dental ceramic systems and Korean foods. Afterwards, on the basis of previous results, 14Hz cyclic load was applied on the 4 systems of dental ceramic restorations in MTS. The reults were analyzed by analysis of variance and Post Hoc tests. Results: 95% confidence intervals for mean of fracture load 1. full porcelain occlusal surfaced PFG Crown: 2599.3 to 2809.1 N 2. half porcelain occlusal surfaced PFG Crown: 3689.4 to 3819.8 N 3. Ice Zirkon Crown: 1501.2 to 1867.9 N 4. Empress 2 Crown: 803.2 to 1188.5 N 5. boiled crab: 294.1 to 367.9 N 6. boiled chicken with bone: 357.1 to 408.6 N 7. boiled beef rib: 4077.7 to 4356.0 N 8. dried squid: 147.5 to 190.5 N 9. dried anchovy: 35.6 to 46.5 N 10. round candy: 1900.5 to 2615.8 N 11. walnut shell: 85.7 to 373.1 N under cyclic load(14Hz) in MTS, fracture load and masticatory cycles are: 1. full porcelain occlusal surfaced PFG Crown fractured at 95% confidence intervals of 4796.8-9321.2 cycles under 2224.8 N(round candy)load, no fracture under smaller loads. 2. half porcelain occlusal surfaced PFG Crown fractured at 95% confidence intervals of 881705.1-1143565.7 cycles under 2224.8 N(round candy). no fracture under smaller loads. 3. Ice Zirkon Crown fractured at 95% confidence intervlas of 979993.0-1145773.4 cycles under 382.9 N(boiled chicken with bone). no fracture under smaller loads. 4. Empress 2 Crown fractured at 95% confidence intervals of 564.1-954.7 cycles under 382.9 N(boiled chicken with bone). no fracture under smaller loads. Conclusion: There was a significant difference in fracture resistance between experimental groups. Under single load, Korean foods than can cause fracture to the dental ceramic restorations are boiled beef rib and round candy. Even if there is no fracture under single load, cyclic dynamic load can fracture dental posterior ceramic crowns. Experimental data with 14 Hz dynamic cyclic load are obtained as follows. 1. PFG crown(full porcelain occlusion) was failed after mean 0.03 years under fracture load for round candy(2224.8 N). 2. PFG crown(half porcelain occlusion) was failed after mean 4.1 years under fracture load for round candy(2224.8 N). 3. Ice Zirkon crown was failed after mean 4.3 years under fracture load for boiled chicken with bone(382.9 N). 4. Empress 2 crown was failed after mean 0.003 years under fracture load for boiled chicken with bone(382.9 N).

• Journal of the korean academy of Pediatric Dentistry
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• 제26권1호
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• pp.53-61
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• 1999

Newley developed dentin bonding system which contains self-etching primer performed the removing of smear layer and etching procedure at once. So, it make possible more simple and shorter working time, the stronger bonding strength than conventional dentin bonding system. Cavities were prepared in the buccal and lingual surface of 30 extracted primary molars, and randomly assigned into three equal groups of 10 each. All cavities were filled with Z-100 composite resin following manufacturer's specifications after priming of three different dentin bonding system. Specimens stored for 7 days in 37 degree C water, thermocycled for 1000 cycles between 5 degree C and 55 degree C, immersed in 50% silvernitrate solution for 24 hours, and embedded in resin before being sectioned longitudinally. Data were analyzed by t-test and ANOVA. Mac-Bond II and Clearfil Linear-Bond II showed less microleakage at the occlusal and gingival margins compared to Scotchbond Multi Purpose. All dentin bonding systems showed significantly less microleakage at the occlusal margins compared to the gingival margins. But, there were no significantley difference between each group.

• The Journal of Korean Academy of Prosthodontics
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• 제32권2호
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• pp.181-194
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• 1994

The purpose of this study was to compare the retention and fitness of crown treated with various desensitizing agents on natural teeth. Varnish, dentin primer, bonding agent and potassium oxalate treated groups and control group with no treatment were used. The retention test was executed with the Instron test machine(Instron Co.,U.S.A.) on 24 hours after cementation with zinc phosphate cement. After retention test, the teeth and crowns were washed and recemented. The cemented crowns were embedded in clear resin and sectioned with a diamond saw. The occlusal and marginal fitnesses, were measured indirectly with a stereomicroscopic photographs. The result of this study were obtained as follows : 1. The retention of control group was higher than any other desensitizing agent treated group. 2. The differences of retention among varnish, dentin primer, bonding agent and potassium oxalate treated groups were not statistically significant. 3. There were no statistically significant difference in fitness at occlusal surface and margin among control, varnish, dentin primer, bonding agent and potassium oxalate treated groups. According to these results, desensitizing agents used to protect the pulp from irritation of luting agents may adversely affect the retention of castings. Therefore, desensitizing agents should be used in limited areas carefully.