• Restorative Dentistry and Endodontics
• /
• v.31 no.5
• /
• pp.378-389
• /
• 2006

The purpose of this study was to compare the sealing ability of root canal obturation with or without the treatment of smear layer. Eighty extracted human teeth with one canal were selected Instrumentation was performed with crown-down technique. After instrumentation, root canals of the NaOCl group and NaOCl-6 group were irrigated with 3% NaOCl. EDTA group and EDTA-6 group were irrigated with 17% EDTA. Then all teeth were obturated using continuous wane obturation technique NaOCl group and EDTA group were immersed in methylene blue solution for 84hours. NaOCl-6 group and EDTA-6 group were immersed in methylene blue solution for 6months. The teeth were sectioned at 1.5 mn (Level 1), 3.0 mm (Level 2) and 4.5 mm (Level 3) from the root apex. The length of dye-penetrated inter-face and the circumferential length of canal at each level were measured using Sigma-Scan Pro 5.0. 1. The mean leakage ratio was decreased cervically. 2. NaOCl group showed higher mean leakage ratio than EDTA group at each level. But there was significant difference at level 1 only (p < 0.05). 3. NaOCl-6 group showed higher mean leakage ratio than EDTA-6 group at each level. But there was significant difference at level 1 only (p < 0.05). 4. NaOCl-6 group showed higher mean leakage ratio than NaOCl group at each level. But there was significant difference at level 1 only (p < 0.05). 5. EDTA-6 group showed higher mean leakage ratio than EDTA group at each level. But there was no significant difference. 6. In NaOCl group and NaOCl-6 group, scanning electron micrographs of tooth sections generally covered with smear layer. In EDTA group and EDTA-6 group, tooth sections showing the penetration of sealers to opened dentinal tubules. The results suggest that removal of smear layer was effective to reduce the apical microleakage of the root canal.

• Restorative Dentistry and Endodontics
• /
• v.31 no.2
• /
• pp.119-124
• /
• 2006

The purpose of this study was to evaluate the effect of newly developed endodontic root canal cleanser (MTAD) on the apical leakage of obturated root canal using an electrochemical method. Canals of 60 extracted single-rooted human teeth were prepared by using a crown-down technique with rotary nickel-titanium files. In Group 1 (positive control group) and 2 (negative centre) group), 5.25% NaOCl was used as a canal irrigant and no canal wall treatment was done. In group 3 only 5.25% NaOCl were used as canal irrigant, canal wall treatment and final rinse. In group 4, specimens were irrigated with 5.25% NaOCl, treated with 5 ml of 17% EDTA for 5 minutes and final rinsed with 5.25% NaOCl Specimens of group 5 were irrigated with 1 3% NaOCl and treated with 5 ml of MTAD for 5 minutes. All root canals are dried with paper points and obtuated with gutta-percha and AH plus as a sealer using a continuous wave of condensation technique except in the group 1. The electrical resistance between the standard and experimental electrodes in canals was measured over a period of 10 days. Rising of apical leakage with time was observed for all the groups. Group 4 and 5 showed lower apical leakage than group 3 but differences between the group 3, 4 and 5 were no statistical significance at any measurement time.

• Restorative Dentistry and Endodontics
• /
• v.24 no.3
• /
• pp.465-472
• /
• 1999

The aim of this study was to determine the shear bond properties of four dentin bonding systems to internal cervical dentin, and to investigate the effect of the pretreatment for removing smear layer and position of dentin on shear bond strength of dentin bonding agents. The materials tested in this study were consisted of four commercially available dentin bonding systems[Allbond 2(AB), Clearfil Linerbond 2(CL), Optibond FL(OP), Scotchbond Multi-purpose(SB)], a restorative light-cured composite resin[Z100]J and a chelating agent[RC-prep(RC)]. Fifty-six freshly extracted human molars were used in this study. Dentin specimens were prepared by first cutting the root of the tooth 1mm below the cementoenamel junction with a diamond bur in a high speed handpiece under air-water coolant, and then removing occlusal part at pulp horn level by means of a second parallel section, The root canal areas were exposed by means of cutting the dent in specimens perpendicular to the root axis. Dentin specimens were randomly assigned to two groups(pretreated group, not-pretreated group) based on the pretreatment method of dentin surface. In pretreated group, RC was applied to dentin surface for 1minute and then rinsed with NaOCl. In not-pretreated group, dentin surface was rinsed with saline Each groups were subdevided into four groups according to dentin bonding systems. Four dentin bonding systems and a restorative resin were applied according to the directions of manufacturer. The dentin-resin specimens were embedded in a cold cure acrylic resin, and were cut with a low speed diamond saw to the dimension of $1{\times}1mm$. The cut specimens were divided into three groups according to the position of internal cervical dentin. The shear bond properties of dentin-resin specimens were measured with Universal testing machine (Zwick, 020, Germany) with the cross head speed of 0.5mm/min. From this experiment. the following results were obtained : 1. In case of shear bond strength, there was no significant difference among dentin bonding systems in not-pretreated groups, whereas in pretreated groups, the shear bond strengths of AB and of SB were statistically significantly higher than those of CL and of OP. 2. The shear bond strengths of AB and of SB in pretreated groups were significantly higher than those in not-pretreated groups. 3. The shear bond strengths of radicular layer of OP were higher than those of occlusal layer of OP in not-pretreated groups, and of AB in pretreated groups. The shear bond strengths of radicular layer of AB and of CL in not-pretreated groups were higher than those in pretreated group.

• Restorative Dentistry and Endodontics
• /
• v.34 no.6
• /
• pp.484-490
• /
• 2009

The purpose of this study was to evaluate the effect of soft chelating irrigant on the sealing ability of root fillings by using a glucose leakage test. A total of 45 single-rooted teeth were selected for the study. The teeth were decoronated leaving a total length of 13mm. The root canals prepared using K3 NiTi rotary instruments to an apical dimension of size 45(0.06 taper). The specimens were then randomly divided into 3 experimental groups of 13 roots each and 2 control groups of 3 roots each. Specimen in each group were prepared with different irrigation protocols : group 1, 2.5% NaOCl; group 2, 2.5% NaOCl and 17% EDTA: group 3, 2.5% NaOCl and 15% HEBP. The root canals were filled with gutta-percha and AH Plus sealer using lateral condensation. After 7 days in $37^{\circ}C$, 100% humidity, the coronal-to-apical microleakage was evaluated quantitatively using a glucose leakage model. The leaked glucose concentration was measured with spectrophotometry at 1, 4, 7, 14, 21 and 28 days. There was a tendency of increase in leakage in all experimental groups during experimental period. HEBP-treated dentin showed no significant difference with EDTA-treated dentin during experimental period. From the 21th day onward, HEBP-treated dentin showed significantly lower leakage than smear-covered dentin. HEBP-treated dentin displayed a similar sealing pattern to EDTA-treated dentin and a better sealing ability than smear-covered dentin. Consequently, a soft chelator(HEBP) could be considered as the possible alternative to EDTA.

• Restorative Dentistry and Endodontics
• /
• v.26 no.4
• /
• pp.350-359
• /
• 2001

목적 - 근관형성시 근관내 상아질벽에는 항상 도말층(smear layer)이 형성되는데, 이는 상아질, 치수조직 잔사, 조상아세포 돌기, 때로는 미생물 등으로 구성되며, 주사전자현미경상으로는 비규칙적이며, 무정형의 구상(granular)구조물로 관찰된다. 본 연구에서는 도말층의 유무에 따른 혐기성 미생물, Prevotella nigrescens의 근관내 상아질 부착정도를 주사전자현미경으로 평가하고자 한다. 지금까지 사용되었던 실험방법에 비하여 보다 임상적 환경에 가까운 실험방법을 고안, 신빙성 있는 연구결과를 기대할 수 있도록 하였다. 방법 - 치주질환이나 외상 등의 원인으로 발거된 상, 하악 전치 18개를 사용하였다. 각 치아의 치관부를 백악법랑경계부위에서 절단하고, 1군(5개치아)은 10ml의 생리식 염수를, 2군(5개치아)과 3군(5개치아)은 10ml의 3.5% NaOCl을 근관관주용액으로 사용하여 근관형성을 하였다. 근관형성 완료후 1군과 2군은 10ml의 생리식염수로, 3군은 10ml의 0.5M EDTA용액으로 final flush를 시행하여, 3군의 도말층을 제거하였다. 치근수직절단과 ethylene oxide(EO) gas 소독후 1, 2, 3군의 시편(각군10개시편)을 Prevotella nigrescens가 부유된 Brain Heart Infusion with Yeast estract, Hemin and Menadione(BHIYHM) broth내에 37$^{\circ}C$에서 3시간 동안 incubation했다. 4, 5, 6군은 실험과정을 검증하기 위한 대조군으로써, 4군(1개치아)과 5군(1개치아)은 1군, 2군과 같이 각각 생리식염수와 NaOCl만을 이용한 근관형성으로 도말층을 잔존시키고, 6군(1개치아)은 3군과 같이 NaOCl과 EDTA를 적용하여 도말층을 제거한 후, 치근 수직절단과 EO gas 소독을 시행했다. 모든 시편(1, 2, 3, 4, 5, 6군)을 통상의 방법에 따라 처리한 후 주사전자현미경을 통하여 관찰, 근관내면에 부착되어 있는 Prevotella nigrescens의 개수, 모양, 상아세관 및 도말층과의 관계 등을 관찰, 비교, 분석하였다. 결과는 t-test와 one-way ANOVA를 통하여 통계처리 하였다. 결론 - 1. 근관형성 후 근관내 상아질 표면 전체는 도말층으로 덮여 있는 양상을 보였다. 2. 3.5% NaOCl과 0.5M EDTA를 적용하여 근관내 도말층을 효과적으로 제거할 수 있었으며, 상아세관 개구부가 확연히 노출되어 있는 소견을 관찰할 수 있었다. 3. 도말층이 덮인군에서 미생물의 부착이 유의성 있게 높았다(P<0.05). 4. 근관 형성중 형성되어 근관 상아질을 덮고 있는 도말층이 미생물의 부착을 증가시켜, 근관 재감염의 기회를 증가시킴을 알 수 있었다.

• Restorative Dentistry and Endodontics
• /
• v.32 no.4
• /
• pp.327-334
• /
• 2007

The purpose of this study was to evaluate the effect of burs on microleakage of Class V resin restorations when a self-etching primer adhesive was used. Forty Class V cavities were prepared with four different cutting burs on extracted third molars, and divided into one of four equal groups (n = 10); Group 1-plain cut carbide bur (no. 245), Group 2-cross cut carbide bur (no. 557), Group 3-fine diamond bur (TF-21F), Group 4-standard diamond bur (EX-41). The occlusal and gingival margin of cavities was located in enamel and dentin, respectively. Cavities were treated with Clearfil SE Bond and restored with Clearfil AP-X. Specimens were thermocycled, immersed in a 2% methylene blue solution for 24 hours, and bisected longitudinally. They were observed leakages at enamel and dentinal margins. Data were analyzed using Mann-Whitney and Wilcoxon signed ranked test. The results of this study were as follows; 1. At enamel margin, microleakage of group 4 was statistically higher than those of group 1, 2 and 3 (p < 0.01). 2. At dentinal margin, microleakage of group 4 was statistically higher than group 3 (p < 0.01), but group 1 and 2 were not statistically different with group 3 and 4. 3. Enamel microleakage was statistically higher than dentinal microleakage in group 1, 2 and 3 (p < 0.05), but statistical difference between the microleakage of enamel and dentinal margin was not in Group 4. In conclusion, the use of coarse diamond bur showed high microleakage at both enamel and dentinal margin when Clearfil SE Bond was used in class V cavity.

• Restorative Dentistry and Endodontics
• /
• v.32 no.4
• /
• pp.377-384
• /
• 2007

Present tooth bonding system can be categorized into total etching bonding system (TE) and self-etching boding system (SE) based on their way of smear layer treatment. The purposes of this study were to compare the effectiveness between these two systems and to evaluate the effect of number of themocycling on microleakage of class V composite resin restorations. Total forty class V cavities were prepared on the single-rooted bovine teeth and were randomly divided into four experimental groups: two kinds of bonding system and another two kinds of thermocycling groups. Half of the cavities were filed with Z250 following the use of TE system, Single Bond and another twenty cavities were filled with Metafil and AQ Bond, SE system. All composite restoratives were cured using light curing unit (XL2500, 3M ESPE, St. Paul, MN, USA) for 40 seconds with a light intensity of $600mW/cm^2$. Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Half of teeth were thermocycled 500 times and the other half were thermocycled 5,000 times between $5^{\circ}C$ and $55^{\circ}C$ for 30 second at each temperature. Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (${\mu}A$) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level. From this study, following results were obtained: There was no interaction between variables of bonding system and number of thermocycling (p = 0.485). Microleakage was not affected by the number of thermocycling either (p = 0.814). However, Composite restoration of Metafil and AQ Bond, SE bond system showed less microleakage than composite restoration of Z250 and Single Bond, TE bond system (p = 0.005).