• 대한치과기공학회지
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• 제40권1호
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• pp.9-15
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• 2018

Purpose: The purpose of this study is to investigate the effect of lithium disilicate glass ceramic polishing on the strength of the final prosthesis. Methods: Fourteen lithium disilicate glass ceramic specimens were prepared. These were randomly divided into two groups of seven(LPG: low polishing group, HPG: high polishing group). In LPG, SiC paper was sequentially polished using 300, 600, 800, 1000 grit, and the specifications of the test piece were adjusted. HPG was sequentially polished using 300, 600, 800, 1000, 1200, 1500, and 2000 grit. Two groups of specimens are executed 3- point bending test. Using the statistical program SPSS 22.0, the average values of the strengths of the two groups were compared in the Mann-Whiteney test. The significance level was set at 0.05. Results: The mean strength value of HPG was measured at $307.14{\pm}23.28MPa$ significantly higher than LPG(p<0.001). Conclusion : The final polishing of the prosthesis is aesthetically important but has proven to play an important role in the flexural strength, early fracture, and prolongation of the prosthesis.

• 구강회복응용과학지
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• 제31권3호
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• pp.231-241
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• 2015

환자의 심미적 요구가 증가함에 따라 전치뿐만 아니라 구치부에서도 자연치아와 유사한 색조와 외형을 재현한 보철물에 대한 필요성이 증가하고 있다. 단일 지르코니아와 CAD/CAM 시스템을 통해 이러한 환자의 요구를 만족시키는 보철물 제작이 가능해졌다. 본 증례는 70세 여자환자로 전치부 보철물이 깨져서 보기 싫고 하악 구치부가 없어서 저작이 불편하다는 주소로 내원하였다. 하악 구치의 상실로 교합평면이 붕괴되었으며 과도한 치아 마모 및 수직고경 상실이 관찰되어 치아 상실 부위에 임플란트를 식립하고 수직고경 증가와 함께 지르코니아 고정성 보철물을 이용한 전악 수복 치료를 진행하였다. 치료 후 3년 간 이상적인 교합이 잘 유지되고 기능적, 심미적으로 만족한 결과를 얻었기에 이를 보고하는 바이다.

• 구강회복응용과학지
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• 제19권3호
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• pp.239-245
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• 2003

The occurrence and pattern of tooth wear are related to cultural, dietary, occupational, and geographic factors, Excessive occlusal wear can result in pulpal exposure, occlusal disharmony, functional inability. Surface loss can be differentiated into 3 general causal categories: i) mechanical loss, which includes attrition, ii) abrasion chemical loss including erosion, and finally iii) a proposed biomechanical category described as abfraction. Considering that mechanical wear is frequently asymptomatic, patients may have parafunctional habit. Structured clinical decision analysis in fixed prosthodontics, as other branches of dentistry do, allows the practitioner to consider the patient's problems more thoroughly based on the clinical data and extenuation factors. This discipline of decision making is intended to complement the experience level and educational background of the clinician in assisting the patient through the decision process. Additionally, CDA helps the clinician define not only the pre-existing condition of the patient prior to irreversible therapy, but also better treatment strategies for the patient over an extended period. The systematic nature of decision analysis stimulates the dentists to pay further attention to those factors, which is germane to the overall complexity of the case, and exclude factors, which have little influence on its final outcome. Further implementation of computerized databases, procedural outcome probabilities based on clinical and laboratory studies and the clinical experience of those who use it, may provide quite a promising future in the field of structured and formalized clinical decision analysis.

• Journal of Oral Medicine and Pain
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• 제25권2호
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• pp.253-263
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• 2000

We collected age determination cases which were done at Yonsei university dental hospital, department of oral medicine from 1976 to 1999 to analyze it's tendency among Koreans. We analyzed 435 clients cases which were stored by age estimation program from January 1993 to December 1999. The results are as follows: 1. There were no significant difference in the sexual distribution (male : 52.0%, female : 48.0%) and more than half percent (51%) were 20's and 30's. 2. Among the age determination clients, those who wanted to decrease their age (50.3%) and those who wanted to increase their age (49.7%) shows similar in number. And the former case were predominant in the female clients, but the latter case in the male clients. Also the clients below six years of age were predominant in the former case, but the clients more than sixty were predominant in the latter case. 3. The purposes of age correction showed different distribution for ages: job or employment for 20's and 30's, marriage for 20's, registration for school for below six, welfare and other social services for 50 and older. 4. Age was estimated by Nolla's growth stage for 12 and under, calcification of the second and third molar for 12~20, and for 20 and over, Takei's tooth abrasion model was used. 5. The alleged age was in accordance with the documents and other information given by clients, but in the 20.6% of the estimation cases, the alleged age was discarded. In the results of the analysis of age determination cases in Koreans, many of the cases resulted from our historical turbulence and social distinctiveness, causing an increase in the necessity for age correction in each age group. For more accurate determination for each age group, further studies with Koreans must be done continuously.

• 한국재료학회지
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• 제33권8호
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• pp.337-343
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• 2023

3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystals) ceramics have excellent mechanical properties including high fracture toughness, good abrasion resistance as well as chemical and biological stability. As a result, they are widely used in mechanical and medical components such as bearings, grinding balls, and hip implants. In addition, they provide excellent light transmittance, biocompatibility, and can match tooth color when used as a dental implant. Recently, given the materials' resemblance to human teeth, these ceramics have emerged as an alternative to titanium implants. Since the introduction of CAD/CAM in the manufacture of ceramic implants, they've been increasingly used for prosthetic restoration where aesthetics and strength are required. In this study, to improve the surface roughness of zirconia implants, we modified the 3Y-TZP surface with a biocomposite of hydroxyapatite and forsterite using room temperature spray coating methods, and investigated the mixed effect of the two powders on the evolution of surface microstructure, i.e., coating thickness and roughness, and biological interaction during the in vitro test in SBF solution. We compared improvement in bioactivity by observing dissolution and re-precipitation on the specimen surface. From the results of in vitro testing in SBF solution, we confirmed improvement in the bioactivity of the 3Y-TZP substrate after surface modification with a biocomposite of hydroxyapatite and forsterite. Surface dissolution of the coating layer and the precipitation of new hydroxyapatite particles was observed on the modified surface, indicating the improvement in bioactivity of the zirconia substrate.

• Restorative Dentistry and Endodontics
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• 제47권3호
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• pp.29.1-29.10
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• 2022

Objectives: This study aimed to investigate the anti-erosive/abrasive effect of resin infiltration of previous deproteinized dentin. Materials and Methods: Dentin slabs were randomly assigned to 3 groups (n = 15): Control (no deproteinization; no resin infiltrant applied), RI (no deproteinization; resin infiltrant applied), and DRI (deproteinization; resin infiltrant applied). After undergoing the assigned treatment, all slabs were subjected to an in vitro cycling model for 5 days. The specimens were immersed in citric acid (0.05 M, pH = 3.75; 60 seconds; 3 times/day) and brushed (150 strokes). Between the challenges, the specimens were exposed to a remineralizing solution (60 minutes). The morphological alterations were analyzed by mechanical profilometry (㎛) and scanning electron microscopy (SEM). Data were submitted to one-way analysis of variance (ANOVA) and Tukey tests (p < 0.05). Results: Control and RI groups presented mineral wear and did not significantly differ from each other (p = 0.063). DRI maintained a protective layer preserving the dentin (p < 0.001). After erosive/abrasive cycles, it was observed that in group RI, only 25% of the slabs partially evidenced the presence of the infiltrating, while, in the DRI group, 80% of the slabs presented the treated surface entirely covered by a resin-component layer protecting the dentin surface as observed in SEM images. Conclusions: The removal of the organic content allows the resin infiltrant to efficiently protect the dentin surface against erosive/abrasive lesions.

• 대한치과보철학회지
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• 제59권2호
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• pp.153-163
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• 2021

목적: 본 연구는 지르코니아의 거칠기 증가를 위한 4가지 표면처리 방법과 3종의 레진시멘트가 전단결합강도에 미치는 영향을 알아보고자 하였다. 재료 및 방법: 총 120개의 지르코니아 시편을 표면처리 방법에 따라 4개의 군으로 나누었다: 대조군, 아무 처리를 하지 않은 군; APA50군, 50 ㎛ 크기의 Al2O3로 Airborne-particle abrasion (APA) 처리를 시행한 군; APA125군, 125 ㎛ 크기의 Al2O3로 APA 처리를 시행한 군; ZA군, ZrO2 slurry를 적용한 군. 각 군에 3종의 레진시멘트(Panavia F 2.0, Superbond C&B, Variolink N)를 접착하고, 만능시험기를 이용하여 전단결합강도를 측정하였다. 주사전자현미경을 이용해 각 군의 대표 표본의 표면을 관찰하였다. 표면처리 방법과 레진시멘트 종류에 따른 상호작용이 존재하는지 알아보기 위하여 Two-way ANOVA를 실시하였고, 각 군 간의 통계적 차이를 알아보기 위해 One-way ANOVA를 시행하였다. 사후검정으로 Tukey HSD test를 실시하였다(α = .05). 결과: 표면처리에 따른 전단결합강도 비교에서, APA125군, APA50군, ZA군, 대조군 순으로 높은 값을 보였고, APA처리를 시행한 군(APA50군, APA125군) 간에는 통계적으로 유의한 차이가 없었다(P > .05). 또한, ZA군은 대조군보다 유의성 있게 높은 값을 보였다(P < .05). 레진시멘트 종류에 따라서는 Panavia F 2.0, Superbond C&B, Variolink N 순으로 높은 전단결합강도를 보였다(P < .05). APA50군과 APA125군에서는 거칠고 불규칙한 표면이 관찰되었고, ZA군에서는 작고 불규칙한 다공성과 거친 표면이 관찰되었다. 결론: 본 연구의 한계내에서, APA 처리와 ZrO2 slurry를 적용했을 때 지르코니아의 표면 거칠기가 증가됨을 확인할 수 있었고, MDP를 함유한 Panavia F 2.0가 지르코니아와의 가장 높은 전단결합강도를 보였다.

• 대한치과보철학회지
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• 제38권5호
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• pp.595-605
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• 2000

Dental ceramics have good aesthetics, biocompatibility, low thermal conductivity, abrasion resistance, and color stability. However poor resistance to fracture and shrinkage during firing process have been limiting factors in their use, particularly in multiunit ceramic restorations. A new method for making all-ceramic crowns that have high strength and low processing shrinkage has been developed and is referred to as the Vita In-Ceram method. This study was performed to investigate the effect of $CeO_2$ addition in borosilicate glasses on the strength of alumina-glass composites. Porous alumina compacts were prepared by slip casting and sintered at $1,100^{\circ}C$ for 2 hours. Dense composites were made by infiltration of molten glass into partially sintered alumina at $1,140^{\circ}C$ for 4 hours. Specimens were polished sequentially from #800 to #2000 diamond disk. and the final surface finishing on the tensile side was received an additional polishing sequence through $1{\mu}m$ diamond paste. Biaxial flexure test was conducted by using ball-on-three-ball method at a crosshead speed of 0.5mm/min. To examine the microstructural aspect of crack propagation in the alumina-glass composites, Vickers-produced indentation crack was made on the tensile surface at a load of 98.0 N and dwell time of 15 sec, and the radial crack patterns were examined by an optical microscope and a scanning electron microscope. The results obtained were summarized as follows; 1. The porosity rates of partially sintered alumina decreased with the rising of firing temperature. 2. The maximum biaxial flexure strength of 423.5MPa in alumina-glass composites was obtained with an addition of 3 mol% $CeO_2$ in glass composition and strength values showed the aspect of decrease with the increase of $CeO_2$ content. 3 The biaxial flexure strength values of alumina-glass composites were decreased with rising the firing temperature. 4. Observation of the fracture surfaces of alumina-glass composites indicated that the enhancement of strength in alumina-glass composites was due to the frictional or geometrical inter-locking of rough fracture surfaces and ligamentary bridging by intact islands of materials left behind the fracture front.

• 구강회복응용과학지
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• 제29권1호
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• pp.69-79
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• 2013

본 연구의 목적은 각각 다른 표면처리를 한 지르코니아를 레진시멘트로 접착한 후 전단결합강도를 평가, 비교하는 것이다. 디스크 모양의 산화 지르코늄(3-TZP, Kyoritsu, Tokyo, Japan) 시편 120 개를 다음과 같이 표면처리 하였다. (1)110 ${\mu}m$ 산화 알루미나 분사 처리 (2)Silica coating(RocatecTM, 3M ESPE) (3)처리하지 않음 시편을 한 군당 10 개씩 총 6 개군으로 나누어 두 개의 지르코니아 시편을 자가 접착형 레진 시멘트(RelyX U-200, 3M ESPE)로 합착하였다. (1)처리하지 않음/처리하지 않음 (2)처리하지 않음/110 ${\mu}m$ 산화 알루미나 분사처리 (3)처리하지 않음/Silica coating (4)110 ${\mu}m$ 산화 알루미나 분사 처리/110 ${\mu}m$ 산화 알루미나 분사 처리 (5)110 ${\mu}m$ 산화 알루미나 분사 처리/Silica coating (6)Silica coating/Silica coating. 각 군의 전단결합강도를 만능시험기로 측정하였다. 표면처리에 따른 결합강도의 차이를 살펴보기 위해 일원변량분석(One-way ANOVA)을 이용하고 사후 분석으로 Tukey HSD test를 실시하였다. Silica coating을 한 두 개의 시편을 접착한 군이 가장 높은 결합 강도를 보였다(P<0.05). 표면 처리하지 않은 시편을 접착한 군과 두 개의 시편 모두 알루미나 분사 처리한 시편을 접착한 군은 서로 간에 유의한 차이를 보이지 않았으며, 그 외의 군에 비해서는 유의하게 낮았다(P<0.05). 본 연구의 결과에 따르면 Silica coating은 자가중합형 레진시멘트를 이용하여 접착한 두 지르코니아 간의 결합을 증진시키는데 효과적이었다.

• 구강회복응용과학지
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• 제25권2호
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• pp.157-169
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• 2009

본 논문의 목적은 코팅처리의 기계적 성질과 임플란트 지대주나사의 코팅처리가 고정체와의 결합안정성에 미치는 영향을 연구하고자 함이다. 이를 위해 Megagen 임플란트 시스템과 직경 15 mm, 높이 1 mm의 티타늄원판을 사용하였다. 지대주 나사와 원판에 TiN, TiCN, 및 TiC를 코팅하여 실험군으로, 코팅처리하지 않은 것을 대조군으로 하였다. 실험군은 지대주나사를 32 Ncm로 체결한 후 풀림회전력과 조임회전각을 측정하고, 10만 번씩 저작 모방 시험을 실시하여 풀림회전력의 변화를 관찰하였다. 조임회전각은 TiCN, TiC코팅나사에서 코팅하지 않은 나사보다 크게 나타났다(p<0.05). 그러나 풀림회전력은 TiCN, TiC코팅나사에서 코팅하지 않은 나사보다 낮게 나타났다(p<0.05). 저작 모방 시험후 코팅한 나사에서 코팅하지 않은 나사보다 풀림 회전력이 더 높게 나타났으며 풀림회전력은 건조상태와 습윤상태 사이에 유의한 차이가 없었다. 이상의 결과로 TiC 코팅군은 저작 모방 시험 전에는 풀림회전력이 낮았지만 저작 모방 시험 후에는 낮은 마찰계수로 인한 높은 풀림회전력과 조임회전각을 가져 임플란트 지대주나사의 결합안정성에 영향을 미치는 효율적인 방법임을 시사한다.