• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.648-658
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• 1997

The purpose of this study was to compare the effects of various techniques on the quality and quantity of instrumentation in curved canals. Instrumentation time was evaluated too. Forty eight canals of resin blocks($35^{\circ}$) were divided into three groups and filed. In group A, 16 blocks were instrumented using a step-back technique with stainless steel(SS) K-file(Mani, Matsutani Seisakusho Co.,Japan). In group B, canals were prepared with SS K-files using the Endo-Angle (Nakanishi Dental MFG.CO.,LTD.,Japan). Group C was prepared using N i-Ti engine-driven instruments (Quantec Series $2000^{TM}$ system). Group A and B were filed from # 5 to # 25 at the apex followed by a 1 mm stepback technique, and the coronal half of the canals were flared with Gates Glidden burs(#2,3,4). Group C was instrumented from # 1 to # 8. After the instrumentation time was measured, canals were filled with India ink, and photographed, which to magnify the canal images 8 times. Using these photographs the apical portions were evaluated And scored from 1 to 4 according to the severity of ledging and zipping. On the same photographs, the area of the coronal two thirds of the canals were measured using a personal computer with the computer program Brain and Digitizer (SummaSketch III). The following results were obtained. 1. Instrumentation time was significantly shorter for group C, as opposed to group A and B(ANOVA, P<0.05). 2. The qualitative evaluation of the apical portions of the canals showed no significant difference between the groups(Kruscal-Wallis, p>0.05). 3. The area removed by group C was significantly smaller than group A and B(ANOVA, P<0.05).

• Restorative Dentistry and Endodontics
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• v.35 no.4
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• pp.302-305
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• 2010

Mandibular premolars show a wide variety of root canal anatomy. Especially, the occurrence of three canals with three separate foramina in mandibular second premolars is very rare. This case report describes the root canal treatment of an unusual morphological configuration of the root canal system and supplements previous reports of the existence of such configuration in mandibular second premolar.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.547-547
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• 2003

The aim of this study was to compare the effects of three Ni-Ti instruments on leaning ability by evaluating the volumetric and morphological changes in the apical 6mm of the root canals before and after preparation, using three-dimensionally reconstructed root canals of extracted human teeth. Forty-five teeth were used in this study. They were opened the chambers and removed the all pulp remnants ultrasonically. Subsequently, the canal wall was coated with silver paste and prepared using ProTaper, ProFile and GT rotary files according to the manufacturers instructions. Before and after root canal preparation, all the specimens were scanned with micro computed tomography and examined the differences in dentine volume removed, canal straightening, the proportion of the unchanged area and canal transportation. Quantitative analysis revealed that instrumentation increased in canal volume ranging between 0.081 and $1.866{\;}\textrm{mm}^3$. On average, the large apical preparation produced by ProTaper demonstrated smaller proportions of unchanged surface areas compared to the two other instruments in small canals. But in large canals like maxillary central incisor, the preparation of ProTaper instruments was not enough. ProTaper instrument was tended to increase more in canal volume as compared with the other two instruments but unchanged area was no significant difference. These results showed that three instruments had similar preparation ability and micro computed tomography in combination with the coated wall of root canal using silver paste is a nondestructive and valuable tool to study root canal geometry and changes after preparations in detail.

• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.612-621
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• 2002

The purpose of this study was to compare the histomorphological change of curved root canal preparation using GT rotary File, Profile .04 taper and stainless steel K-file. 45 mesial canals(over 20 degree) of extracted human mandibular first molars were mounted in resin using a modified Bramante muffle system and divided into three groups. The roots were cross-sectioned at 2.5mm 5mm and 8mm levels from apical foramen. Tracings of the canals were made from preinstrumentation pictures of the cross section. The canals were prepared using a step-back technique with stainless steel K file(group 1), Profile .04 taper rotary file(group 2) and GT rotary file(group 3). Tracings of the prepared canals were made from postinstrumentation picture. Canal centring ratio. amount of transportation, area of dentin removed and shape of canal were measured and statistically were evaluated with Student-Newman-Keuls test using Sigma Stat(Jandel Scientific Software, USA). The results were as followings : 1 Amount of transportation of group 2 was the lowest at apical part, but there was no statistical difference. The direction of transportation was the outside of curvature at apical part. 2. Centering ratio at the apical part of group 1 was the highest, and there was statistical differences between apical and middle part, apical and coronal part(p＜0.05). Centering ratio at the middle part of group 3 was the lowest, and there was statistical difference between apical and middle part(p＜0.05). Centering ratio of group 2 was the lowest at apical part, but there was no statistical difference. 3. Amount of dentin removed of group 1 was the highest at coronal, middle and apical part among three groups, and there was statistical difference(p＜0.05). 4. The majority of the cross-sectioned canal shape after instrumentation were irregular at coronal, middle and apical part. But there are more number of round shaped canals at group 3 than other group.

• Restorative Dentistry and Endodontics
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• v.29 no.4
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• pp.378-385
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• 2004

The purpose of this study was to compare the effects of preparation with GT files and profiles .04 in shaping of root canals and reconstruct the three-dimensional root canal system using micro computed tomography 40 canals of the extracted human mandibular molars were used, and randomly distributed into two experimental groups. In group 1. canals were prepared by GT files. In group 2, Profiles .04. were used. Apical preparation size was #30. For each tooth pre and post operative cross-sectional images were obtained by the micro CT at 50 micron intervals. Pre and post operative cross-sectional images of 1, 2, 3, 5, and 8mm from the apex were compared. For each section. canal area and centering ratio were determined. For each tooth pre- and post-operative root canal volume from the furcation to the apex of the roots was calculated by three-dimensional image software. Following results were obtained: 1. At 8mm from the apex, area of dentin removed by GT rotary file was significantly larger than that by Profile .04. And at the other levels there was not a significant difference. 2. There was a trend for GT rotary file to remain more centered in the canals than Profile .04 at all levels. But at 3mm level. there was a statistically significant difference. 3. In root canal volume increments after instrumentation, there was no significant difference between two groups.

• Korean Journal of Veterinary Research
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• v.37 no.2
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• pp.269-280
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• 1997

The development and change of the cartilage canals ralated to chondrocyte growth and the major histological pattern were investigated in the calcaneus of the Korean native cattle fetuses from CRL 28mm to 175mm. The results as follows; 1. The cartilage canal first appeared in the caudal subperichondral region of the sustentaculum tali of the CRL 28mm fetus, and well developed after the period. 2. The three major cartilage canals, one entered from the head of calcaneous into where achilles tendon insert and the others from the caudal region of sustentaculum tali and the calcaneal sulcus, growth distinctively. The latters participated in the ossification center prior to the former. 3. The number of cells in this canals and the size increased synchronously with chondrocytic hypertrophy. In the intermediate and deep canals, the chondrogenic change showed distinctinvely. Our results demonstrated that the cartilage canals from the lower part were important the formation of the ossification center, and the growth and development of canals associated with the hypertropic changes of chondrocytes in the calcaneus of the Korean native cattle fetus.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.388-395
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• 1997

Maintaining the original canal path during instrumentation is a challenge in narrow curved canals. This study compared the maintenance of the original canal path of curved root canals during instrumentation with two kinds of stainless steel K-files(Brassler USA & Mani Japan), K-flexofiles(Maillefer Swiss) and Ni-Ti files(Brassler USA, Savannah, GA) using circumferential filing technique to # 40 MAF on 60 extracted human molars. Buccal and mesial canals with minimal initial curvature of 20 degrees were used. The maximal initial curvature was 41.5 degrees. Sixty curved canals divided into four groups according to file type(Group 1 : Ni-Ti file, Group 2 : K-flexofile, Group 3: K-file(Brassler), Group 4 : K-file(Mani)). Radiographs of canals were obtained before and after canal shaping. And postoperative radiographs were compared with preoperative radiographs using superimposition method. Data analysis was performed using Covariance analysis and paired-comparison test. The results observed were as follow ; 1. The angle of curvature was better maintained with Ni-Ti file than with stainless steel files. (p<0.01) 2. There was no significant difference in maintaining canal curvature between K-flexofile, Brassler$^{(R)}$ K-file and Mani$^{(R)}$ K-file, although there was some differences in mean values of postoperative canal curvature. 3. Paired-comparison t test revealed significant differences within each of the three stainless steel file types when comparing the mean differences before and after instrumentation, but no significant differences were observed within Ni-Ti file group.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.659-669
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• 1997

The goals of root canal instrumentation are complete debridement of pulp tissue, removal of microbes and affected dentin, and proper cleaning and shaping of the root canal space before obturation. Instrumentation with stainless steel files has been shown to produce undesirable results in canals, regardless of the improved technique or modified file type used. Nickel-Titanium(Ni-Ti) alloy has been shown to be exceptionally elastic, having a lower bending moment and lower permanent set after torsion, compared with similar gauge stainless steel. The purpose of this study was to evaluate the change of root canal prepared by Ni-Ti rotary and stainless steel instruments. Thirty-four single rooted teeth of similar shape and canal size were divided into three groups. The teeth were scanned by computed tomography before instrumentation. In group 1, canals were instrumented using a step-back technique with K-file. In group 2, canals were prepared with K-flex file using the same technique as group 1. Group 3 was prepared with nickel-titanium(Ni-Ti) rotary instrument using a manufacture's instruction. Instrumented teeth were again scanned using computed tomography, and reformated images of the uninstrumented canals were compared with images of the instrumented canals. K-flex file and Ni-Ti file caused significantly less canal transportation than K-file in the 8mm root canal section from the apex(p<0.05). K-flex file and Ni-Ti file produced more centered canal preparation than K-file in the 2mm section(p<0.05). Ni-Ti file maintained more precisely the center of the canal than K-flex file in the 10mm section (p<0.05). There was no difference in the removed volume of canals among each groups.

• Ocean and Polar Research
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• v.24 no.1
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• pp.63-71
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• 2002

This preliminary study on the changes of macrobenthic assemblages in experimental sediment fences was conducted as a part of tidal marsh restoration project. Intertidal sediment fences were designed to increase the efficiency of trapping sediments on unvegetated tidal flats in order to raise sediment elevation and to allow colonization of intertidal vegetation. Although increment of soil surface level was not observed over the first three months of the study, it was possible to obtain some effects of the sediment fence. Three months later, the particle sizes of the surface sediment at experimental plots became much finer compared to unfenced areas on the natural mudflats located in the same tide level as that of the plots. The difference was much greater on the plot with drainage canals than on the plot without ones. Species diversity of the experimental plots became much higher than that of natural sites. Perinereis aibuhitensis and Glauconome chinensis which were absent from initial community appeared with high density in the plot with drainage canals. Those species were significantly different in abundance between the experimental plot and the natural mudflat. Changes in species composition were not detected in another experimental plot without drainage canals.

• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.121-133
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• 1989

In order to compare the accessory canal filling effects of the three root canal filling methods with gutta-percha, the author fabricated artificial root canal mold with the first and second accessory canals of chrome-cobalt alloy. After the artificial root canal was filled with gutta-percha by lateral condensation, vertical condensation and low-temperature thermoplasticized gutta-percha injection-molded method, twenty five times respectively, the gutta-percha forced into the first and second accessory canals were measured with caliper for length. The results were as follows: 1. The filling in both accessory canals was most effective in low-temperature thermoplasticized gutta-percha injection-melded method followed in such order as: vertical condensation method and lateral condensation method (p < 0.01). 2. The filling effect of the second accessory canal was more or less higher than that of the first one (p < 0.05). 3. Low-temperature thermoplasticized gutta-percha injection-molded method was fastest in time needed for root canal filling followed by lateral condensation method and vertical condensation method.