• Restorative Dentistry and Endodontics
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• 제33권1호
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• pp.45-53
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• 2008

본 연구는 현재 시판되고 있는 여러 개의 상아질 접착제를 임상 술식에서와 같은 방법으로 사용한 후 열 시효처리를 통해 노화 과정을 재현한 다음 접착 계면의 탄성계수를 측정함으로써 가수분해에 따른 물성변화를 관찰 비교하고자 했다. 발거 한 지 2 주일 이내인 영구 대구치 21 개의 상아질 표면이 노출되도록 삭제하였다. 각각 7개의 치아에 시판되고 있는 3가지 상아질 접착제 (OptiBond FL, Clearfil SE, Xeno III)를 적용한 뒤 광중합 복합 레진(Premisa, Kerr, Orange, CA, USA) 를 1 mm 두께로 쌓아 올렸다. 각 치아를 이등분하여 절반 시편은 100,000회의 열 시효 처리를 가하도록 했다. Nanoindentation test를 통하여 각 시편의 adhesive layer와 hybrid layer의 탄성계수를 측정, 비교하였다. 열시효 처리 후 Xeno III군의 탄성계수가 통계학적으로 유의할 만한 감소를 보였다 (p < 0.05). Hydrophilic monomer를 많이 함유한 one-step self-etch adhesive system은 다른 제품에 비해 가수분해에 취약하여 이에 따른 물성 변화를 보이는 것으로 추정되며, 궁극적으로 수복물의 내구성에 영향을 미칠 것으로 여겨진다.

• 구강회복응용과학지
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• 제33권2호
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• pp.114-118
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• 2017

목적: 이 연구의 목적은 타이타늄 구성요소를 가진 지르코니아 지대주가 내부연결 임플란트에 사용되었을 때 나사 풀림에 대해 알아보는 것이다. 열순환 후 타이타늄 소켓을 가진 지르코니아 지대주와 타이타늄 지대주의 나사 풀림과 제거력을 비교 분석하였다. 연구 재료 및 방법: 내측연결 임플란트와 내측연결 타이타늄 지대주, 타이타늄 소켓을 가진 외측연결 지르코니아 지대주를 준비하였다. 내부연결형 임플란트에 5개의 타이타늄 지대주를(대조군), 타이타늄 소켓을 가진 5개의 지르코니아 지대주(실험군)를 각각 연결하고 30 Ncm의 토크로 조인 후 열순환 처리 전후의 지대주 나사 제거력을 측정하였다. 각 시편들은 열순환 장치의 수조에서 $5^{\circ}C$와 $55^{\circ}C$의 물에 60초씩 교대로 2,000회의 열순환을 시행하였다. 각 시편의 나사 풀림을 조사하고 열순환 전후에 나사 제거력을 통계학적으로 분석하였다. 결과: 두 그룹 모두에서 열순환 후 지대주 나사 풀림을 보이지 않았다. 열순환 전후의 나사 제거력 차이는 대조군에서 $-1.34{\pm}2.53Ncm$, 실험군에서 $-1.26{\pm}2.06Ncm$ 로 나타났다. 독립표본 T 통계분석 결과 두 군간에 유의한 차이를 보이지 않았다(P > 0.05). 결론: 이 실험의 결과 내에서 내부연결 임플란트를 위한 지르코니아 지대주 내 타이타늄 소켓이 열순환 후 지대주 나사풀림에 타이타늄 지대주와 비교하여 유의한 영향을 나타내지 않았다.

• 대한치과교정학회지
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• 제30권4호
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• pp.475-481
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• 2000

본 연구는 침수 및 온도변화에 따른 레진 브라켓 wing의 파절양상을 비교하여 구강내 환경이 레진 브라켓 wing의 물성변화에 미치는 영향을 관찰해 보기 위하여 시행되었다. 본 연구의 재료로 레진 브라켓 75개와 금속 브라켓 25개를 사용하였는데, 레진 브라켓은 상온에서 5개월 동안 방치한 경우와 $37^{\circ}C$의 증류수에 6개월 동안 침수시킨 경우, 그리고 $37^{\circ}C$의 증류수에 6개월 동안 침수시킨 상태에서 1개월에 350회씩 총 2,100회의 열순환 시킨 경우의 3가지 군으로 구분하여 처리하였다. 만능물성 시험기를 이용하여 금속 브라켓의 경우 wing의 변형강도를, 레진 브라켓의 경우 파절강도를 각 군별로 측정하고 비교 분석하여 다음과 같은 결과를 얻었다. 1. 금속 브라켓 wing의 변형강도에 비하여 레진 브라켓 wing의 파절강도가 매우 낮게 나타났으며 통계적으로 유의한 차이가 있었다(p<0.001). 2. 상온에서 6개월 동안 방치한 군에 비하여 침수시키거나 침수 및 열순환 시킨 군에서 브라켓 wing의 파절강도가 낮게 나타났으며 통계적으로 유의한 차이를 보였다(p<0.001). 3. 단순침수에 비하여 침수 및 열순한 시킨 군의 브라켓 wing의 파절강도가 더 낮게 나타났으며 통계적으로 유의한 차이가 있었다(p<0.001). 이상의 결과는 구강내 환경에 의하여 레진 브라켓 wing의 물성이 약화되므로 이의 강도증가를 위한 적절한 대책이 필요함을 시사하였다.

• 대한치과보철학회지
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• 제37권2호
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• pp.200-211
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• 1999

For many years permanent soft denture liners has been widely used in dental practice directly or indirectly because of its function in absorbing and distributing the impact force. However, it reveals problems such as lack of permanency and decreased bond strength in long term use. The purpose of this study is to measure the bond strength and failure between denture base resin and several permanent liners. Lucitone 199 was used as denture base resin with soft acrylic liners (Triad, Tokuso Rebase) and silicone elastomers (Tokuyama, Ufi Gel C) bonded to measure the tensile strength before and after thermocycling. The thermocycling was done in 2000 cycles at $5^{\circ}C,\;26^{\circ}C\;and\;55^{\circ}C$ and the measured tensile strength values before and after thermocycling were compared. The mode of failure was investigated in the separated specimens. The results are as follows. 1. As to tensile strength, the strongest material is Tokuso Rebase followed by Triad, Tokuyama, Ufi Gel C in before thermocycling and the order of Triad, Tokuso Rebase, Tokuyama, Ufi Gel C in after thermocycling state. There was significant difference between the values of Triad, Tokuso Rebase and Tokuyama, Ufi Gel C(p<0.05). 2. As to degree of displacement, Ufi Gel C showed most displacement with or without thermo-cycling treatment and also the difference was significant with the other materials(p<0.05). 3. As to comparisons before and after thermocycling, Tokuso Rebase and Tokuyama showed significant difference in bond strength, whereas Triad and Tokuso Rebase showed significant difference in the degree of displacement(p<0.05). 4. In debonded specimens, Triad and Ufi Gel C showed adhesion failure and Tokuyama showed cohesion failure. Both failures were observed in Tokuso Rebase with adhesion failure up to 70%. The results of this study showed that degree of bond strength between permanent soft denture liner and denture base resin were variable. There was a significant difference between soft acrylics and silicone elastomers with regard to bond strength. Further research in improving bond strength of widely used silicone elastomers and in developing the method of measuring bond strength between denture base resin and the lining materials is needed.

• 대한치과교정학회지
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• 제35권4호
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• pp.295-301
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• 2005

• The Journal of Advanced Prosthodontics
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• 제10권1호
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• pp.65-72
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• 2018

PURPOSE. The aim of this in vitro study was to investigate the fracture resistance under chewing simulation of implant-supported posterior restorations (crowns cemented to hybrid-abutments) made of different all-ceramic materials. MATERIALS AND METHODS. Monolithic zirconia (MZr) and monolithic lithium disilicate (MLD) crowns for mandibular first molar were fabricated using computer-aided design/computer-aided manufacturing technology and then cemented to zirconia hybrid-abutments (Ti-based). Each group was divided into two subgroups (n=10): (A) control group, crowns were subjected to single load to fracture; (B) test group, crowns underwent chewing simulation using multiple loads for 1.2 million cycles at 1.2 Hz with simultaneous thermocycling between $5^{\circ}C$ and $55^{\circ}C$. Data was statistically analyzed with one-way ANOVA and a Post-Hoc test. RESULTS. All tested crowns survived chewing simulation resulting in 100% survival rate. However, wear facets were observed on all the crowns at the occlusal contact point. Fracture load of monolithic lithium disilicate crowns was statistically significantly lower than that of monolithic zirconia crowns. Also, fracture load was significantly reduced in both of the all-ceramic materials after exposure to chewing simulation and thermocycling. Crowns of all test groups exhibited cohesive fracture within the monolithic crown structure only, and no abutment fractures or screw loosening were observed. CONCLUSION. When supported by implants, monolithic zirconia restorations cemented to hybrid abutments withstand masticatory forces. Also, fatigue loading accompanied by simultaneous thermocycling significantly reduces the strength of both of the all-ceramic materials. Moreover, further research is needed to define potentials, limits, and long-term serviceability of the materials and hybrid abutments.

• 대한치과보철학회지
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• 제42권2호
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• pp.142-153
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• 2004

Statement of problem: Increasing demand of esthetic restorations made lots of kinds of ceramic materials. Among them, zirconia has been being focused by many dentists. But, mechanical properties of zirconia were still unclear. Purpose : The purposes of this study were to analyze the flexural strength of various zirconia ceramics which had been currently used for clinic i.e., In-Ceram Zirconia(Vita Zahnfabrik, Bad $S\"{a}ckingen$, Germany), Celay Zirconia(Vita Zahnfabrik, Bad $S\"{a}ckingen$, Germany) and CAD/CAM Zirconia (Adens Zi-Ceram. Seoul , Korea). Material and methods: The four point bending test(ASTM Cl161) was used to measure the flexural strength of a specimen before and after circular heat treatment and fatigue loading. Results : 1. The average value of flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia in dry condition were 806.5 MPa, 669.9 MPa, 605.6 MPa, respectively. There was a statistically significant difference in strength among the types (P<0.05). 2. After thermocycling, the average flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia were 791.2 MPa, 604.2 MPa, 605.4 MPa, respectively. CAD/CAM Zirconia showed statistically significant higher strength(P<0.05). The others showed no significant difference after thermocycling(P>0.05). 3. After fatigue loading in wet condition. the average flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia were 806.0 MPa, 674.9 MPa, 601.7 MPa, respectively. There was a significant difference in strength among the types(P<0.05). 4. There was no statistically significant difference in strength of the specimens according to experimental methods except for before and after thermocycling in Celay Zirconia(P>0.05). Conclusion: Besides high esthetic quality, zirconia had sufficiently high mechanical strength.

• The Journal of Advanced Prosthodontics
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• 제7권3호
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• pp.224-232
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• 2015

PURPOSE. The purpose of this study was to find out the effect of immediate dentin sealing (IDS) on bond strength of ceramic restoration under various thermocycling periods with DBA (dentin bonding agent system). MATERIALS AND METHODS. Fifty freshly extracted human mandibular third molars were divided into 5 groups (1 control and 4 experimental groups) of 10 teeth. We removed enamel layer of sound teeth and embedded them which will proceed to be IDS, using All Bond II. A thermocycling was applied to experimental groups for 1, 2, 7, 14 days respectively and was not applied to control group. IPS Empress II for ceramic was acid-etched with ceramic etchant (9.5% HF) and silane was applied. Each ceramic disc was bonded to specimens with Duo-link, dual curable resin cement by means of light curing for 100 seconds. After the cementation procedures, shear bond strength measurement and SEM analysis of the fractured surface were done. The data were analyzed with a one-way ANOVA and Tukey multiple comparison test (${\alpha}$=.05). RESULTS. There were no statistically significant differences between 4 experimental groups and control group, however the mean value started to decrease in group 7d, and group 14d showed the lowest mean bond strength in all groups. Also, group 7d and 14d showed distinct exposed dentin and collapsed hybrid layer was observed in SEM analysis. CONCLUSION. In the present study, it can be concluded that ceramic restorations like a laminate veneer restoration should be bonded using resin cement within one week after IDS procedure.

• 대한치과보철학회지
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• 제45권2호
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• pp.216-227
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• 2007

Statement of problem: For the long-term success of removable partial dentures, the bonding between metal framework and denture base resin is one of the important factors. To improve bonding between those, macro-mechanical retentive form that is included metal framework design has been generally used. However it has been known that sealing at the interface between metal framework and denture base resin is very weak, because this method uses mechanical bonding. Purpose: Many studies has been made to find a simple method which induces chemical bond, now various bonding system is applied to clinic. In this experiment, shear bond strengths of heat-cured denture base resin to the surface-treated Co-Cr alloy were measured before and after thermocycling. Chemically treated groups with Alloy $Primer^{TM}$, Super-Bond $C&B^{TM}$, and tribochemically treated group with $Rocatec^{TM}$ system were compared to the beadtreated control group. The data were analyzed with two-way ANOVA. Result: 1. Shear bond strength of bead-treated group is highest, and Alloy $Primer^{TM}$ treated group, Super-Bond $C&B^{TM}$ treated group, RocatecTM system treated group were followed. Statistically significant differences were found in each treated group(p<0.05). 2. Surface treatment and thermocycling affected shear bond strength(p<0.05), however there was no interaction between two factors(p>0.05). 3. Shear bond strengths of bead-treated group and Alloy $Primer^{TM}$ treated group showed no statistically significant difference before and after thermocycling(p>0.05), and those of Super-Bond $C&B^{TM}$ treated group and $Rocatec^{TM}$ system treated group showed statistically significant difference after thermocycling(p<0.05).

• Structural Engineering and Mechanics
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• 제64권6권
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• pp.819-826
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• 2017

The effects of thermocycling procedure and material shade on the mechanical properties and wear resistance of resin-based dental restorative materials are investigated. The modulus of elasticity, hardness, plasticity index and wear resistance are determined for the conventional composite, the nanohybrid composite and the nanofilled dental composites. Disc-shape samples are prepared from each material to investigate the effects of thermocycling procedure on the mechanical properties and wear resistance of different types of dental restorative materials. In this respect, a group of samples is thermocycled and the other group is stored in ambient conditions. Then nano-indentation and nano-scratch tests are performed on the samples to measure their mechanical properties and wear resistance. Results show that the A1E shade of the dental nanocomposite possesses higher modulus of elasticity and hardness values compared to the two other shades. According to the experimental results, the mean values for the modulus of elasticity and hardness of the A1E shade of the nanocomposite are 13.71 GPa and 1.08 GPa, respectively. The modulus of elasticity and hardness of the conventional dental composite increase around 30 percent in the oral environment due to the moisture and temperature changes. The wear resistance of the dental composites is also significantly affected by moisture and temperature changes in the oral conditions. It is observed that thermocycling has no significant effect on the hardness, plasticity index and wear resistance of the nanohybrid composite and the nanocomposite dental materials.