• 한국콘텐츠학회논문지
• /
• 제10권11호
• /
• pp.235-242
• /
• 2010

이 연구는 전문가 미백(in-office bleaching)에 사용하는 35% 과산화수소(hydrogen peroxide, HP)를 제2인산칼슘(dicalcium phosphate dihydrate, DCPD)와 혼합하여 치아의 미백 효과와 미세경도를 평가하고자 하였다. 소구치로부터 30개의 치아시편을 제작하여 3군으로 분류하였다(n=10). 35%과산화수소에 DCPD를 0.1, 1wt% 첨가하여 실험군으로 하고 하루 60분간 치아미백을 실시하였다. 치아 미백제에 pH를 측정하였고, 미백 적용한 치아 표면에는 색과 미세경도를 측정하였다. pH는 DCPD 함유한 군에서 DCPD의 함유량이 증가할수록 함유되지 않은 군에 비해 pH 수치가 증가하였다. 색조변화량 (${\Delta}$E)을 비교한 결과, 미백 전에 비해 미백 후 색조 변화를 보였고(p<0.05), 결과적으로 색 변화에 있어 DCPD를 함유한 군과 함유되지 않은 군 사이에 통계적으로 유의한 차이는 없었다(p>0.05). 법랑질의 표면미세경도를 분석한 결과, 모든 군에서 미백 후 미세경도의 감소를 보였고(p<0.05), DCPD를 혼합한 군은 함유되지 않은 군에 비해 경도 감소의 폭이 훨씬 적게 나타났다. 이상의 결과로부터 DCPD를 함유한 35%과산화수소의 치아미백제는 치아미백 효과가 있고, pH를 상승시켜서 법랑질의 표면 경도를 덜 감소시키므로 치아미백제의 구성성분으로 실용할 수 있을 것으로 사료된다.

• 한국치위생학회지
• /
• 제13권2호
• /
• pp.351-360
• /
• 2013

Objectives : The purpose of this study was to evaluate the effects of tooth bleaching agent contained 15% carbamide peroxide on the color, microhardness and surface roughness of tooth-colored restorative materials by using pH cycling model. Methods : Four types of tooth-colored restorative materials, including a composite resin(Filtek Z350 ; Z350), a flowable composite resin(Filtek P60 : P60), a compomer(Dyract$^{(R)}$ AP ; DY), and a glass-ionomer cement(KetacTM Molar Easymix ; KM). were used in the study. Eighty-eight specimens of each material were fabricated, randomly divided into two groups(n=44): experimental group(15% carbamide peroxide) and control group(distilled water). These groups were then divided into four subgroups(n=11). All groups were bleached 4 hours per day for 14 days using pH cycling model. The authors measured the color, microhardness, and roughness of the specimens before and after bleaching. The data were analyzed with ANOVA and T-test. Results : Z350 and P60 showed a slight color change(${\Delta}E^*$), whereas DY and KM showed significantly color change(p<0.05). Among them, the greatest color change was observed in DY. Percentage microhardness loss(PML) of the distilled water group was 1.8 to 5.1%, and 15% peroxide peroxide group was 5.0 to 25.2%. Microhardness of DY and KM showed a statistically significant decrease(p<0.05). Roughness was increased in all groups after bleaching. Z350 and P60 does not have a significant difference(p>0.05), however DY and KM significantly increased more than the 0.2 ${\mu}m$(p<0.05). Conclusions : The effects of bleaching on restorative materials were material dependent. It is necessary to consider the type of the material before starting the treatment.

• 대한소아치과학회지
• /
• 제31권2호
• /
• pp.280-289
• /
• 2004

치과용 수복재료가 요구하는 심미성과 치아의 보존 및 편의성 등의 여러 조건들을 만족시키기 위해서 치과용 복합레진은 적절한 중합이 이루어져 물리적 기계적 성질을 충족하고, 색조의 안전성, 중합시의 수축과 이에 따른 변연 적합도 문제를 해결할 수 있어야 한다. 본 연구에서는 광중합 복합레진 Z250의 색상과 두께를 달리 하여 광투과도와 중함도를 각각 적외선 분광분석법과 미세경도 측정을 통해 비교하여 다음과 같은 결과를 얻었다. 1. 플라즈마 아크 중합기의 사용 시 3초 중합과 6초 중합의 경우로 나누어 실험하였으며 6초 중합에 있어서 할로겐 중합 20초와 유사한 광투과도 및 미세경도를 나타내었다. 2. 광중합 복합레진의 색상을 A1, A2, A3, A3.5로 나누어 실험한 결과 레진의 표면에서는 색상별로 광투과도나 경도의 차이가 나타나지 않았으나, 2, 3, 4mm로 깊이가 증가함에 따라 색상에 따른 광투과도나 경도의 차이가 확연하게 나타났고 특히 색상이 어두워질수록 4mm의 깊이에서 중합도가 더욱 낮았다. 3. 중합깊이의 비교를 위하여 0, 2, 3 4mm깊이로 나누어 실험한 결과, 2mm이상의 깊이에 있어서는 미반응 단량체의 양이 유의하게 많은 것으로 나타났다. 4. 광중합 복합레진의 광투과도를 알아보는 FTIR을 통한 단량체 전환도와 미세경도 측정사이에는 유의한 상관관계를 보였다.

• 한국표면공학회지
• /
• 제13권3호
• /
• pp.146-154
• /
• 1980

The effects of various electrodeposition conditions (deposition temperature and cathode current density) on preferred orientation and microhardness of electrodeposited Ni-Sn and Sn-Zn alloys were studied. At deposition temperatures from 25$^{\circ}$ to 95$^{\circ}C$ and constant cathode current density of 270 and 530 A/$m^2$ Ni-Sn and Sn-Zn were codeposited in chloride-fluoride acid and stannate-cyanide alkaline electrolyte bath respectively. Ni-Sn alloy deposited at temperatures from 25$^{\circ}$ to 35$^{\circ}C$ was composed of single phase of $Ni_3Sn_4$ with 73 wt.% Sn and the one deposited at temperatures from 45$^{\circ}$ to 95$^{\circ}C$ was made of multiphase mixture of NiSn, $Ni_3Sn_2$ and $Ni_3Sn_4$ with nearly equiatomic composition (65.5 wt.% Sn). The random orientation of thermody-namically metastable NiSn phase (hexagonal structure) predominated at deposition temperature range 25$^{\circ}$-45$^{\circ}C$, and the strong (110) preferred orientation was found at 65$^{\circ}$-85$^{\circ}C$ and then disappeared again at 95$^{\circ}C$. The microhardness of Ni-Sn deposits increased with deposition temperature up to 85$^{\circ}C$, and then decreased at constant cathode current density. The preferred orientation and the maximum microhardness were discussed in terms of lattice contractile stress which result from desorption of hydrogen atom absorbed in deposit lattice. The Sn content of Sn-Zn alloy deposits increased with deposition temperature up to 75$^{\circ}C$, and then decreased at constant cathode current density of 530 A/$m^2$. It also decreased with cathode current density up to 530 A/$m^2$, and then increased at constant deposition temperature of 25$^{\circ}C$. Sn-Zn alloy deposits were composed of two-phase mixture of ${beta}$-Sn and Zn. The preferred orientations of ${beta}$-Sn (tetragonal structure) changed with deposition temperature. The microhardness of Sn-Zn deposits decreased with deposition temperature. It also increased with cathode density up to 530 A/$m^2$, and then decreased at constant deposition temperature of 25$^{\circ}C$. The microhardness of Sn-Zn deposits was observed to be determinded more by the Sn content than by the preferred orientation.

• Restorative Dentistry and Endodontics
• /
• 제36권2호
• /
• pp.108-113
• /
• 2011

연구목적: 여러 광개시제 시스템에 의해 활성화되는 복합 레진을 기존의 single-peak LED와 최신의 dual-peak LED로 광중합하였을 때의 누프 미세 경도와 수중 보관 후의 색 안정성 차이를 알아보기 위한 것이다. 연구 재료 및 방법: Camphorquinone이 광개시제로 포함되어 있는 Z100과 다른 광개시제가 포함되어 있는 것으로 알려진 Tetric Ceram과 Aelite LS Posterior를 유리판 위에서 테플론 주형(직경 8 mm, 두께 2 mm) 내로 충전하고, single-peak LED와 dual-peak LED로 광중합하였다. 중합 후 누프 미세 경도를 측정하였고 한 달 후 색 변화를 측정하였다. 광중합기간의 미세 경도와 색 변화 차이를 student t-test로 분석하였다. 결과: 모든 레진에서 dual-peak LED로 광중합하였을 때 미세 경도가 높게 나타났다. 색 안정성 역시 dual-peak LED로 광중합하였을 때 높게 나타났으나 Aelite LS Posterior에서만 통계학적으로 유의한 차이가 있었다. 결론: 다른 광개시제가 포함되어 있는 복합 레진을 dual-peak LED로 광중합한 경우 미세 경도와 색 안정성에 있어서 더 좋은 결과를 얻을 수 있었다.

• 한국표면공학회지
• /
• 제35권3호
• /
• pp.158-164
• /
• 2002

Nanocomposites consisting of a nanocrystalline brass matrix (grain size ; 20-100nm) with sub-micron sized Al2O3 particles (60-200nm) were prepared by pulsed current electrodeposition. The microhardness of the nanocomposite with a grain size of 90-100nm was approximately 1.7 times higher than that of a comparable electrodeposit with no particles. However, significant variations in microhardness were not observed between the nanocomposites with grain sizes of 20 nm and the comparable electrodeposit.

• 한국진공학회지
• /
• 제7권s1호
• /
• pp.179-182
• /
• 1998

Boron carbide coating has some very attractive properties for nuclear and semiconductor industry. The potential of atmosheric plasma spray as manufacturing methods for $B_4C$ coating was discussed. In this work, the boron carbide coating with low porosity, high microhardness and good life of thermal shock resistance was deposited by the control of spraying distance. The relationship between the properties of $B_4C$ coatings and their spraying distance was studied.

• Restorative Dentistry and Endodontics
• /
• 제44권4호
• /
• pp.41.1-41.13
• /
• 2019

Objectives: This paper presents a systematic review and meta-analysis of the effect of preheating on the hardness of nanofilled, nanoceramic, nanohybrid, and microhybrid resin composites. Materials and Methods: An electronic search of papers on MEDLINE/PubMed, ScienceDirect, and EBSCOhost was performed. Only in vitro studies were included. Non-English studies, case reports, clinical trials, and review articles were excluded. A meta-analysis of the reviewed studies was conducted to quantify differences in the microhardness of the Z250 microhybrid resin composite using the Comprehensive Meta-Analysis software. Results: Only 13 studies met the inclusion criteria for this systematic review. The meta-analysis showed that there were significant differences between the non-preheated and preheated modes for both the top and bottom surfaces of the specimens (p < 0.05). The microhardness of the Z250 resin composite on the top surface in the preheated mode (78.1 ± 2.9) was higher than in the non-preheated mode (67.4 ± 4.0; p < 0.001). Moreover, the microhardness of the Z250 resin composite on the bottom surface in the preheated mode (71.8 ± 3.8) was higher than in the non-preheated mode (57.5 ± 5.7, p < 0.001). Conclusions: Although the results reported in the reviewed studies showed great variability, sufficient scientific evidence was found to support the hypothesis that preheating can improve the hardness of resin composites.

• Restorative Dentistry and Endodontics
• /
• 제45권1호
• /
• pp.12.1-12.8
• /
• 2020

Objectives: The aim of this in vitro study was to evaluate the microhardness and surface roughness of composite resins before and after tooth bleaching procedures. Materials and Methods: Sixty specimens were prepared of each composite resin (Filtek Supreme XT and Opallis), and BisCover LV surface sealant was applied to half of the specimens. Thirty enamel samples were obtained from the buccal and lingual surfaces of human molars for use as the control group. The surface roughness and microhardness were measured before and after bleaching procedures with 35% hydrogen peroxide or 16% carbamide (n = 10). Data were analyzed using 1-way analysis of variance and the Fisher test (α = 0.05). Results: Neither hydrogen peroxide nor carbamide peroxide treatment significantly altered the hardness of the composite resins, regardless of surface sealant application; however, both treatments significantly decreased the hardness of the tooth samples (p < 0.05). The bleaching did not cause any change in surface roughness, with the exception of the unsealed Opallis composite resin and dental enamel, both of which displayed an increase in surface roughness after bleaching with carbamide peroxide (p < 0.05). Conclusions: The microhardness and surface roughness of enamel and Opallis composite resin were influenced by bleaching procedures.

• Restorative Dentistry and Endodontics
• /
• 제2권1호
• /
• pp.38-49
• /
• 1976

Central and lateral incisors of 20, 40 and 60 age groups were bisected pararelly to long axis and middle portion of mesio-distal of teeth. And author measured the hardness of various areas in enamel and dentin with vickers hardness tester. Measured levels were divided into the labio-middle portion, middle portion of incisal edge and linguo-middle portion in enamel and dentin of all age groups. The results were as follows; 1) Total average hardness of enamel for 20, 40 and 60 age groups were respectively Hv. 366.5${\pm}$5.75, Hv. 372.9${\pm}$8.16 and Hv. 389.8${\pm}$10.27. 2) Total average hardness of dentin for 20, 40 and 60 age groups were respectively Hv. 51.0${\pm}$2.14, Hv. 54.0${\pm}$1.87 and Hv. 55.3${\pm}$2.23. 3) Total microhardness values in enamel and dentin of 60 age group was highered than 20 and 40 age groups. 4) The hardness values of enamel and dentin in all age groups were detected lower value on the middle portion of incisal edge than the labio-middle portion and linguo-middle portion. 5) Microhardness values of enamel was highered gradually from the dentinoenamel junction to the outer surface and it lowered at the outermost surface in all age groups. The microhardness values of dentin were the highest values at 600${\mu}$ from dentino-enamel junction and the lowest values at near the pulp chamber in all age groups.