• Restorative Dentistry and Endodontics
• /
• 제30권6호
• /
• pp.435-441
• /
• 2005

본 연구는 친수성 용매가 함유되어 있는 3종의 단일병 접착제의 적용 시간을 증가시켰을 때, 건조 상아질에 대한 재습윤의 효과가 있는지를 미세인장 결합강도의 측정을 통해 알아보고자 시행하였다. 실험대상은 최근에 발거한 상하악의 대구치로, 교합면 1/3부위의 치질을 치아 장축에 수직으로 절단하여 상아질을 노출시킨 후, $32\%$인산 (Unietch, Bisco Inc., Schaumburg, IL, USA)으로 15초간 산부식 하고 수세하였다. 치아는 무작위로 S군 (Single Bond), O군 (One-Step), P군 (Prime & Bond NT)으로 분류하였고, 각 군은 다시 3군 (W: 상아질 표면의 남아있는 과잉의 물을 수분에 적신 거즈를 이용하여 제거한 후, 즉시 단일병 접착제를 적용하고 광중합, D : 30초간 건조 한 후 즉시 단일병 접착제를 적용하고 광중합, 30: 30초간 건조 한 후 단일병 접착제를 30초간 적용하고 광중합)으로 소 분류하였다. 접착제 도포 후, 복합레진을 축조하고 접착계면이 $1mm^2$가 되도록 절단하여 각 군당 20개의 표본을 사용하여 미세인장 결합강도를 측정하였다. 5군,0군의 30초 적용군 (S-30, O-30)은 건조군 (S-D, O-D)보다 높은 미세인장 결합강도를 보였으며, S-30군의 경우 S-D군보다 통계학적으로 유의성 있게 높았다 (P<0.05). 하지만, P군의 30초 적용군 (P-30)은 건조군 (P-D)에 비해 미세인장 결합강도가 통계학적으로 유의성 있게 감소하였다 (P<0.05).

• Restorative Dentistry and Endodontics
• /
• 제30권6호
• /
• pp.477-485
• /
• 2005

근단부위 형성이 완료되고 우식이 없는 하악 대구치 근심치근 50개를 대상으로 주파수 의존형 전자근관장 측정기를 이용하여 측정한 근관장의 정확도를 평가하기 위해 치수강 개방 후 동일한 치아에서 방사선 사진으로 확인한 실측 근관장을 대조군, 각종 전자근관장 측정기로 측정한 근관장을 실험군 ( I군: Root-ZX, II군: Bingo, III군: Propex, IV군: Diagnostic)으로 분류하여 근심협측과 설측의 근관장을 근관의 입구 측으로부터 치근단 1/3까지 확대여부 및 서로 다른 측정시기에 측정하여 비교 평가한 결과 다음과 같은 결론을 얻었다. 하악대구치 근심치근의 협측과 설측 전자근관장은 측정기의 종류, 근관의 입구 측으로부터 치근단 1/3까지의 확대여부 및 측정시기에 상관없이 0.5mm이내의 오차범위를 나타내었으며, 근관치료시 오차한계인 ${\pm}1mm$에서 정확성은 근관의 입구 측으로부터 치근단 1/3까지 미리 확대한 후에 근관장을 측정할 경우와 측정시기가 반복될 경우에 증가되는 경향을 보여 임상에 유용하게 활용할 수 있을 것으로 사료된다.

• Restorative Dentistry and Endodontics
• /
• 제31권3호
• /
• pp.169-178
• /
• 2006

본 연구는 EDTA용액의 적용 시간에 따른 도말층의 제거 효과를 비교하여 EDTA용액의 최적 적용 시간을 알고자 시행되었다. 단근치 35개를 NaOCl 용액 하에서 근관 형성 후 대조군은 NaOCl 용액 5 ml로 2분간, 실험군은 30초군, 1분군, 2분군으로 세분하여 17% EDTA 용액 5 ml로 각각 30초, 1분, 2분간 세정하였다. 세정이 끝난 치근의 도말층 제거 정도와 상아 세관의 erosion 정도를 주사전자현미경을 이용하여 관찰한 결과는 다음과 같다. 1. 대조군: 도말층이 전혀 제거되지 않았다. 2. 실험군 1) 중간$\frac{1}{3}$: 세 군 모두에서 도말층이 거의 완전히 제거되었고, EDTA적용 시간이 증가할수록 erosion발생 빈도가 증가하였다. 2) 치근단$\frac{1}{3}$: 2분군이 다른 두 군에 비해 도말층 제거 정도가 우수하였다. 따라서 erosion 발생을 최소화면서 도말층을 효과적으로 제거하기 위해서는 17% EDTA 용액을 2분간 사용하는 것이 적절한 것으로 사료된다.

• Restorative Dentistry and Endodontics
• /
• 제29권6호
• /
• pp.548-552
• /
• 2004

본 연구는 제어방출형 근관소독제(CRD)로 부터 chlorhexidine (CHX)의 방출 속도를 제어하기 위한 3가지 polymer (chitosan, PMMA, PLGA) 의 코팅 효과를 평가하기 위함이다. 80번 paper point (Sure-EndoTM)에 20% CHX를 loading 한 후 각 군당 10개씩 4군으로 분류하였다: Group A: 폴리머를 코팅하지 않은 CRD prototype (control), Group B: chitosan-coated prototype, Group C: PMMA-coated prototype, Group D: PLGA-coated prototype. 모든 시편은 3 ml 증류수가 담긴 큐벳에 넣은 후 3, 6, 10, 20, 30, 40, 50분 마다, 1, 2, 3, 4, 5, 6시간마다 각각 10 μl 씩 채취하고, 1주일 후 다시 10 μl을 채취한 후 UV 흡광도를 이용하여 CHX의 방출 속도를 비교하였다. 실험결과 제어방출형 근관소독제로부터 CHX의 방출속도는 대조군, 키토산, PLGA, PMMA-군 순으로 천천히 일어났으며 PMMA군에서 가장 천천히 일어났다. 결론적으로 제어방출형 근관소독제 표면의 폴리머는 약물 (CHX) 방출속도를 효과적으로 제어하였다.

• Restorative Dentistry and Endodontics
• /
• 제29권6호
• /
• pp.489-497
• /
• 2004

Objective: The purpose of this study was to investigate the viscoelastic properties related to handling characteristics of composite resins, Methods: A custom designed vertical oscillation rheometer (VOR) was used for rheological measurements of composites. The VOR consists of three parts: (1) a measuring unit, (2) a deformation induction unit and (3) a force detecting unit, Two medium viscous composites, Z100 and Z250 and two packable composites, P60 and SureFil were tested. The viscoelastic material function, including complex modulus $E^{*}$ and phase angle ${\delta}$, were measured. A dynamic oscillatory test was used to evaluate the storage modulus (E'), loss modulus (E") and loss tangent ($tan{\delta}$) of the composites as a function of frequency ($\omega$) from 0.1 to 20 Hz at $23^{\circ}C$. Results: The E' and E" increased with increasing frequency and showed differences in magnitude between brands. The $E^{*}s$ of composites at ${\omega}{\;}={\;}2{\;}Hz$, normalized to that of Z100, were 2.16 (Z250), 4,80 (P60) and 25.21 (SureFil). The magnitudes and patterns of the change of $tan{\delta}$ of composites with increasing frequency were significantly different between brands. The relationships between the complex modulus $E^{*}$, the phase angle ${\delta}$ and the frequency \omega were represented by frequency domain phasor form, $E^{*}{\;}(\omega){\;}={\;}E^{*}e^{i{\delta}}{\;}={\;}E^{*}{\angle}{\delta}$. Conclusions: The viscoelasticity of composites that influences handling characteristics is significant different between brands, The VOR is a relatively simple device for dynamic, mechanical analysis of high viscous dental composites. The locus of frequency domain phasor plots in a complex plane is a valuable method of representing the viscoelastic properties of composites.

• Restorative Dentistry and Endodontics
• /
• 제23권1호
• /
• pp.433-442
• /
• 1998

The purpose of this study was to observe the changes of acidity of resin cement(Time Line), glass ionomer cement(GC Fugi Lining LC), zinc phosphate cement(Fleck's zinc cement). zinc oxide eugenol cement(Sultan,Chemists.) in vivo and in vitro. Class I cavities with 3mm depth were prepared on the occlusal surfaces of 20 recently extracted human Mn. molar teeth and 20 human Mn. 3rd molar teeth in oral cavity. The prepared cavities were divided into 4 groups of each 5 teeth using the above 4 cavity liners. Each cement was mixed in accordance with manufacturer's direction at the room temperature of $23^{\circ}{\pm}5^{\circ}C$ and filled into the cavity in a width of 1 mm. The microelectrode of pH meter was inserted into the prepared cavity which was filled with mixed cement, and the acidity of cement was measured for 3 days from the beginning of cement mix in vitro and in vivo. The measured acidity was then statistically analyzed by ANOVA. The results were as follows. 1. In vitro, the pH of zinc oxide eugenol cement was statistically lower than that of the three other groups at 2min, 4min, 6min, 8min, 10min, 12min, 18min, 20min. (p<0.05). 2. The pH of zinc oxide eugenol cement in vivo was statistically higher than that in vitro at 16min,16min, 20min(p<0.05). 3. The pH of zinc phosphate cement in vivo was statistically higher than that in vitro at 4min, 20min(p<0.05). 4. In vitro and in vivo, there was no significant difference in the pH between the resin cement and the glass ionomer cement(p>0.05). 5. The initial acidity was not high, but almost neutral in all kinds of the cements.

• Restorative Dentistry and Endodontics
• /
• 제23권1호
• /
• pp.443-460
• /
• 1998

The purpose of this study was to estimate the changes of tensile bond strength according to the difference in lining materials and lining area. Seventy non-carious extracted human molars were used in the present study, and they were randomly assigned into 2 experimental groups according to the difference in lining materials. Each experimental group was subdivided into 3 groups according to the difference in lining area. Circular cavities were prepared on the dentin surface to a diameter of 1.5mm, 2.0mm, 2.5mm and the prepared cavities were filled with Fuji II LC( Glass Ionomer Cement : GIC) or Dycal. Dentin specimens without circular cavity were used as control group. The primer and bonding agent of All-Bond 2 and composite resin (Z-100, 3M Dental Products, U. S. A.) were applied to the exposed dentin surface with or without lining. Tensile bond strengths for the experimental specimens were then measured. To examine the interface between dentin and liner & between liner and composite resin, two specimens from each group were fabricated and observed under the SEM. The results were as follows. 1. Tensile bond strength for the specimens lined with GIC was higher than that for specimens lined with Dycal. However, there was no significant difference between two groups(p>0.05). 2. Tensile bond strength for the specimens lined with GIC in a diameter of 1.5mm(GIC-1.5mm lining group) was statistically higher than that for the GIC-2.0mm lining group and GIC-2.5mm lining group(p<0.05). 3. Tensile bond strength for the specimens lined with Dycal in a diameter of 2.5mm (Dycal-2.5mm lining group)was statistically lower than that for Dycal-1.5mm lining group and Dycal-2.0mm lining group(p<0.05). 4. It was possible to observe the good adhesion of the resin composite to the GIC and the presence of a fissure between GIC and dentin all along the interface. Interfacial gaps of 7.2-$72.2{\mu}m$ between GIC and dentin were observed. The interfacial gap between GIC and dentin at the cavity base was greater. However, the gap was gradually decreased toward the occlusal portion. 5. It was possible to observe the poor adhesion of the resin composite to the Dycal. The detachment of Dycal was occurred all along the composite resin-Dycal interface, and the gaps of 2.0-$30.1{\mu}m$ were formed. In all the specimens, polymerization shrinkage of resin composite caused the detachment of Dycal from the body of Dycal. At a Dycal-dentin interface. it was possible to observe the good adhesion. but poor adhesion with interfacial gap of 2.9-$26.8{\mu}m$ was observed partially.

• Restorative Dentistry and Endodontics
• /
• 제23권1호
• /
• pp.424-432
• /
• 1998

To get a satisfactory result in the composite resin restorations, it is necessary to choose correct shade. At present, most of the commercial composite resins are based on the Vita Lumin shade guide or Bioform shade guide, but color differences might be expected even using the same shade in various materials. In this study, five kinds of light-cured composite resins with A2 and B3 shade were used to measure and compare the color each other while one porcelain served as a control. All composite resins (Spectrum TPH (SP), VeridonFil- Photo (VE), Z100 (Z100), Charisma (CH), Prodigy (PRO)) were filled in to the metal mold (12 mm diameter, 2 mm depth), followed by compression, polymerization and polishing with wet sandpaper. The specimens of porcelain were fabricated by using the refractory mold for porcelain. After 24 hours, the specimens were placed on the spectrocolorimeter and spectral reflectance were measured under CIE illuminant D65. After measuring the values of $L^*$, $a^*$, $b^*$ and ${\Delta}E^*$, following results were obtained; 1. The $L^*$, $a^*$ and $b^*$ values of both shade of porcelain specimens showed significantly higher than those of resin specimens(p<0.05). 2. In comparing the resin specimens of the A2 shade, differences were significant except $L^*$ values of SP-CH and PRO-VE, $a^*$ values of the VE-SP and $b^*$ values of the VE-Z100 and SP-PRO(p<0.05), 3. In comparing the resin specimens of the B3 shade, differences were significant except $L^*$ values of PRO-SP, $a^*$ values of the SP-PRO and Z100-VE and b* values of the PRO-SP(p<0.05). 4. In comparing the resin specimens of the A2 shade, color differences between materials (${\Delta}E^*$) showed the lowest value of 1.66, and the highest was 5.16. ${\Delta}E^*$ values of the materials of VE-PRO, CH-PRO, SP-PRO, SP-Z100 and SP-CH were lower than 3.3. 5. In comparing the resin specimens of the B3 shade, the lowest value of the ${\Delta}E^*$ was 0.57 and the highest was 5.92. ${\Delta}E^*$ values of Z100-CH and SP-PRO were lower than 3.3. The present study revealed there was perceptible color difference between materials even if they have the same designated shade based on Vita shade guide. The results of the present study suggested that it would be necessary to establish the reproducible and constant color specification system for an esthetic restoration.

• Restorative Dentistry and Endodontics
• /
• 제23권1호
• /
• pp.401-412
• /
• 1998

The aim of this study was to measure the regional micro-shear bond strength of dentin bonding agents to dentin, and to investigate the relationship between the micro-shear bond strength and two dentinal characteristics ; Vickers hardness and remaining dentin thickness. Twenty-four freshly extracted, noncarious human molars were selected for this study. The materials tested in this study consisted of two commercially available dentin bonding agents (MAC-BOND, ONE-STEP) and two restorative light-cured composite resins (AELITEFIL, Z100). The occlusal or side surface of tooth crown was sectioned to expose dentin, and the exposed surface was finally polished with # 600 sandpaper. Four groups of application methods were used combining the filling materials and the dentin bonding agents. The composite resin-attached tooth specimens were embeded in a cold cure acrylic resin, and were cut with a low speed diamond saw to the dimension of 1mm $\times$ 1mm. Nine specimens were obtained from each tooth. The cut specimens were divided into three groups depending on the position of the dentin bonding surface. The micro-shear bond strength, remaining dentin thickness, and dentinal hardness were measured. Experimental results were then statistically analyzed with ANOVA. t-test, Scheffe test, and regression analysis. From this experiment, the following results were obtained : 1. In the case of occlusal surface bonding, the pooled micro-shear bond strength of ONST-AELIT group (16.62 MPa) was significantly higher than that of MACB-AELIT group (9.91 MPa) (p<0.05). However, there was no significant difference in the micro-shear bond strength depending on the dentin position (p>0.05). 2. In the case of side surface bonding of crown, the pooled micro-shear bond strength of four different bonding groups was not significantly different among each other (p>0.05). However, in three of the test groups (ONST-AELIT, MACB-Z100, ONST-Z100), the micro-shear bond strength to the lower 1/3(III) position was significantly lower than that to middle 1/3(II) position of surface (p<0.05). 3. In the ONST-AELIT bonding group, the pooled micro-shear bond strength to the occlusal surface was significantly lower than that to the side surface of crown (p<0.05). 4. There was no significant correlation between the micro-shear bond strength and dentin hardness / remaining dentin thickness (p>0.05).

• Restorative Dentistry and Endodontics
• /
• 제23권1호
• /
• pp.366-378
• /
• 1998

Thermocondensation root canal filling technique have been used to fill accessary canals or to obtain homogeneous root caral fillings. But these thermocondensation technique inevitably produce heat in the canal which can be transmitted through the dentin and cementum and consequently damage periodontal ligamental cells and osteoblasts. In this study, System $B^{TM}$(Analytic technology, WA.D.S.A.) was used to evaluate the reaction of periodontal ligament tissue to "Continous Wave condensation technique" introduced by Buchanan, and the transmitted root surface temperature was measured according to measured root thicknesses. 12 Mandibular incisors of two adult dogs were used for the experiment. 6 controls were filled by lateral condensation technique with sealer.3 specimens were apically filled by Continuous Wave technique at $200^{\circ}C$ for 5 seconds and remaining 3 specimens were additionally backfilled using System $B^{TM}$(Analytic technology, WA.D.S.A.) was used to evaluate the reaction of periodontal ligament tissue to "Continous Wave condensation technique" introduced by Buchanan, and the transmitted root surface temperature was measured according to measured root thicknesses. 12 Mandibular incisors of two adult dogs were used for the experiment. 6 controls were filled by lateral condensation technique with sealer.3 specimens were apically filled by Continuous Wave technique at $200^{\circ}C$ for 5 seconds and remaining 3 specimens were additionally backfilled using System $B^{TM}$ at $100^{\circ}C$ for 20 seconds. Six weeks later, the dogs were sacrificed and the teeth stained with Hematoxylin and Eosin for histologic examination. 6 extracted human teeth were used to measure the transmitted temperature. After cutting off the crown, the canals were prepared and divided into 3 groups with root thickness of 1.5mm, 1.0mm, 0.5mm, 2 teeth in each group. Inside each root canal, System $B^{TM}$ was heated as with the temperature for the apically condensed and the back filled group, and the transmitted heat was measured on the external surface of the root. The temperature of System $B^{TM}$ heat spreader at $200^{\circ}C$ and $100^{\circ}C$ was also measured at root temperature. It can be concluded as follows: 1. In the thin area (200-$250{\mu}m$) of the root, root resorption could be seen even with heating at $200^{\circ}C$ for 5 seconds. 2. When the spreader was heated at $200^{\circ}C$ for 5 seconds and additionally at $100^{\circ}C$ for 20 seconds for backfill, all teeth showed root resorption regardless of their root thickness. 3. The transmitted external root surface temperature was higher as the root thickness decreased and as the heating time increased. In the thermocompaction technique using System $B^{TM}$, the spreader should be heated for the minimal time and used only in the apical area. The heated spreader shouldn't inserted to the binding point of the canal and backfilling should be done with other means of minimally heated gutta percha technique.