• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.61-68
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• 2007

The purpose of this study was to compare the centering abilities of four root canal instrument systems and the amounts of dentin removed after root canal shaping using them. The mesial canals of twenty extracted mandibular first molars having $10-20^{\circ}$ curvature were scanned using X-ray micro-computed tomography (XMCT)-scanner before root canals were instrumented. They were divided into four groups (n = 10 per group). In Group 1, root canals were instrumented by the step-back technique with stainless steel K-Flexofile after coronal flaring. The remainders were instrumented by the crown-down technique with Profile (Group 2), ProTaper (Group 3) or K3 system (Group 4). All canals were prepared up to size 25 at the end-point of preparation and scanned again. Scanned images were processed to reconstruct three-dimensional images using three-dimensional image software and the changes of total canal volume were measured. Pre-and post-operative cross-sectional images of 1, 3, 5, and 7 mm from the apical foramen were com pared. For each level, centering ratio were calculated using Adobe Photoshop 6.0 and image software program. ProTaper and K3 systems have a tendency to remove more dentin than the other file systems. In all groups, the lowest value of centering ratio at 3 mm level was observed. And except at 3 mm level, ProTaper system made canals less centered than the other systems (p < 0.05).

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.577-577
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• 2003

Microcomputed tomography (MCT) made it possible to investigate the morphology of root canals more accurate. The aim of this study was to compare the effects of four root canal shaping methods, the profile system, the ProTaper system, a combination of these, and stainless steel K-files, in the shaping of the mesial root canals of extracted human mandibular first molars, three-dimensionally using MCT. Eight extracted mandibular first molars were scannde using MTC before and after the root cannals were instrumented. Two specimens were prepared using the Profile system and another two specimens were prepared using MCT before and after the root cannals were instrumented. Two specimens were prepared using the Profile system and another two specimens were prepared using the ProTaper system according to manufactures recommendation.(omitted)

• Restorative Dentistry and Endodontics
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• v.35 no.2
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• pp.88-95
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• 2010

The purpose of this study was to compare the root canal shaping ability of 4 rotary NiTi instruments in simulated root canals. For the preparation of thirty two curved root canals, Mtwo instruments using "single length"technique, and Profile, ProTaper Universal, and K3 using crown-down technique (N = 8) were used. All canal samples were prepared by reaching an apical canal size of #30. Pre- and post-instrumentation digital images were recorded and an assessment of canal shape was determined using a computer image analysis program SigmaScan Pro (Systat Software Inc., San Jose, CA, USA). The changes of the dimension of inner walls of canals, (2) the changes of the dimension of outer walls of canals, and (3) the centering ratio were measured at 7 measuring points, and then data were statistically analyzed using one-way ANOVA and Duncan's test. The results were as below; 1. The root canal shaping ability of Profile was significantly faster than that of other rotary NiTi instruments (p < 0.05). 2. The deformation and fracture of all instruments used for this study were not experienced. 3. In the degree of changes of the dimension of inner walls of canals, Profile demonstrated the lowest changes of the dimension of inner walls of canals except at the measuring points of the 1 and 2 mm (p < 0.05). However, the ProTaper Universal showed the highest changes of the dimension of inner walls of canals at all measuring points (p < 0.05). 4. In the degree of changes of the dimension of outer walls of canals, Mtwo demonstrated the lowest changse of the dimension of outer walls of canals except at the measuring point of the 1 mm (p < 0.05). However, Profile exhibited the highest changes of the dimension of outer walls of canals at the measuring points of 3 and 4 mm and ProTaper Universal and K3 showed the largest changes of the dimension of outer walls of canals at the measuring points of 1, 2, 6, and 7 mm (p < 0.05). 5. In degree of centering ratio, Profile demonstrated the least centering ratio comparing with the centering ratio shown by other NiTi instruments at the measuring points of 1, 4, 5, and 6 mm. Results suggest that in the coronal part of canal preparation, active cutting files such as ProTaper Universal may efficiently flare the canal orifice and form a better taper, and in the apical part of the canal, files which have a better centering ability such as Profile may maintain the original canal curvature and reduce the shaping time.

• Restorative Dentistry and Endodontics
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• v.38 no.4
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• pp.234-240
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• 2013

Objectives: This study evaluated the effects of intraradicular moisture on the pushout bond strength of a fibre post luted with several self-adhesive resin cements. Materials and Methods: Endodontically treated root canals were treated with one of three luting cements: (1) RelyX U100, (2) Clearfil SA, and (3) G-Cem. Roots were then divided into four subgroups according to the moisture condition tested: (I) dry: excess water removed with paper points followed by dehydration with 95% ethanol, (II) normal moisture: canals blot-dried with paper points until appearing dry, (III) moist: canals dried by low vacuum using a Luer adapter, and (IV) wet: canals remained totally flooded. Two 1-mm-thick slices were obtained from each root sample and bond strength was measured using a push-out test setup. The data were analysed using a two-way analysis of variance and the Bonferroni post hoc test with p = 0.05. Results: Statistical analysis demonstrated that moisture levels had a significant effect on the bond strength of luting cements (p < 0.05), with the exception of G-Cem. RelyX U100 displayed the highest bond strength under moist conditions (III). Clearfil SA had the highest bond strength under normal moisture conditions (II). Statistical ranking of bond strength values was as follows: RelyX U100 > Clearfil SA > G-Cem. Conclusions: The degree of residual moisture significantly affected the adhesion of luting cements to radicular dentine.

• Animal Systematics, Evolution and Diversity
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• v.19 no.1
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• pp.111-117
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• 2003

Some hydromedusae were collected from Shiwhaho (Kyonsgi-do), Korea Strait and Yeosu, Korea during years 2000-2002. They were identified into Sorsia tubulosa (M. Sars, 1835) of the order Anthomedusae, and Liriope tetraphylla (Chamisso and Eysenhardt, 1821) of the order Trachymedusae respectively. They are new to the Korean fauna. The order Trachymedusae is first recorded in Korea. The long tube-like manubrium and four marginal tentacles are characteristics of S. tubuloso. In L. tetraphylla, the four triangle-shaped gonads and their positions upon half of surface of subumbrella, the seven blind centripetal canals in a quadrant and the long fat manubrium are its distinct characteristics. Resulting from this work, the Korean hydromedusae identified so far consist of 13 species of 11 families in five orders.

• Restorative Dentistry and Endodontics
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• v.38 no.4
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• pp.253-257
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• 2013

Maxillary lateral incisors usually exhibit a single root with a single canal. However, maxillary lateral incisor teeth with unusual morphology of root canal system are frequently reported. These cases of variable root canal anatomy can be treated well by nonsurgical endodontic methods. A detailed description of root canal morphology is fundamental for successful endodontic treatment. Treatment using an operating microscope, radiographs from different angles, and cone-beam computerized tomography (CBCT) can produce more predictable endodontic outcomes.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.557-557
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• 2003

I. Objectives The purpose of this study was to evaluate the ratio of gutta-percha area in the canal after canal obturation with Continuous Wave of Condensation Technique with varying depths of plugger penetration. II. Materials and Methods Forty extracted human teeth with single canal were divided into four group of ten teeth each. Root canals were prepared up to size 40 of 0.06 taper with $ProFile^{\circledR}$. After drying, canals of three groups were filled with Continuous Wave of Condensation Technique with System $B^{TM}$ and different plugger penetration depths of 3, 5, and 7mm from the apex.(omitted)

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.381-389
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• 2000

Lateral condensation with gutta-percha and sealer has been shown to provide an excellent apical seal; however, the lateral condensation technique has demonstrated less favorable apical leakage results in curved canals when compared with straight canals. Placement of endodontic spreaders to within 1 to 2mm of the root canal working length has been advocated for optimum gutta-percha obturation. Due to their stiffness, stainless-steel(SS) spreaders will often fail to achieve this position in curved canals. Newly marketed nickel-titanium(NT) spreaders may offer an advantage in this regard due to the increased flexibility of these instruments. The purpose of this study was to evaluate the effect of NT finger spreader on the sealing ability in lateral condensation technique, compared with conventional SS finger spreader. Twenty four standardized resin models simulating curved canals(30 degree) were randomly placed into 2 groups and instrumented to a #30 master apical file size with Ni-Ti Profile .04 taper series using step down technique. Each groups was obturated with standardized gutta-percha cone by standard lateral condensation technique using SS finger spreader, NT finger spreader. And then, each model was sectioned horizontally with microtome at 1, 2, 3, 4, 5mm levels from the apex. At each of 5 levels, ratio of the area of gutta-percha was obtained by calculating the area of gutta-percha to the total area of the canal. The data collected were then analyzed statistically using a t test for independent samples. The results as follows ; 1. The total mean ratio of area of gutta-percha was 89.20${\pm}$7.00(%) for SS spreader group. 92.20${\pm}$5.17(%) for NT spreader group. There was statistically significant difference between each group(p<0.05). 2. At 3mm level, the mean ratio of area of gutta-percha was 88.32${\pm}$5.41(%) for SS spreader group, 95.25${\pm}$2.60(%) for NT spreader group. There was statistically significant difference between each group(p<0.05). At 1,2,4mm levels, NT spreader group showed greater mean ratio of area of gutta-percha than SS spreader group, too. But there was no statistically significant difference. 3. At 5mm level, the mean ratio of area of gutta-percha was 91.83${\pm}$3.42(%) for SS spreader group, 87.91${\pm}$3.68(%) for NT spreader group. There was statistically significant difference between each group(p<0.05). This study concluded that the NT spreader demonstrated somewhat favorable apical sealing effect than SS spreader in prepared curved canals. The clinical use of NT spreaders may enhance our ability to create better apical seals in curved canals, but further studies in this area will help clarify some of the remaining areas with which practitioners are concerned, such as compaction forces exerted by NT spreaders.

• Restorative Dentistry and Endodontics
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• v.31 no.2
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• pp.113-118
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• 2006

The aim of this study was to evaluate the ability of newly marketed NRT instruments to maintain the original root canal configuration and curvature during preparation in comparison with the three existing instruments in simulated root canals. Simulated canals in resin blocks were prepared with ProFile. K3, ProTaper and NRT instrument (n = 10 canals in each case). Pre- and post-operative images were recorded, and assessment of canal shape was completed with a computer image analysis program. The data were analyzed statistically using the One-way ANOVA followed by Duncan s test. The ability or instruments to remain centered in prepared canals at 1-, 2-mm levels was significantly better in ProFile groups than in other groups (p < 0.05). The change of centering ratio in NRT groups at 5-mm level was significantly greater than ProFile group and at 6- and 7-mm level than all other groups (p < 0.05). Although the NRT system was comparable to other systems in regards to its ability to maintain the canal configuration of apical portion, this system was more influenced by the mid-root curvature due to its stainless-steel files for coronal preflaring.

• Restorative Dentistry and Endodontics
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• v.19 no.2
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• pp.429-446
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• 1994

The purpose of this study was to evaluate the sealing effect of warm lateral condensation technique by Endotec spreader, comparing with other canal filling techniques. One hundred and forty extracted human teeth with single canal were instrumented and randomly divided into four groups according to canal filling techniques including lateral condensation with sealer, warm lateral condensation with sealer, warm lateral condensation without sealer, and injection-molded thermoplasticized gutta-percha without sealer. Obturated canals were exposed to 2 % methylene blue solution at $37^{\circ}C$ for 24 hours and measurement of the degree of microleakage was done linearly and volumetrically with stereozoom microscope and UV-spectrophotometer respectively. The results were as follows ; When sealer was used, the canals obturated by warm lateral condensation showed less leakage linearly and volumetrically than the canals obturated by standard lateral condensation with no statistically significant difference. The obturated canals by warm lateral condensation with sealer showed less leakage linearly and volumetrically than the canals obturated by warm lateral condensation without sealer and by injection-molded thermoplasticized gutta-percha without sealer with statistical significance (p<0.05). No statistical difference revealed that the group filled with the use of the Endotec had significantly less leakage than any of the other groups. There was a significant correlation between the linear measurement and volumetric measurement(r=0.4459, p<0.05).