• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.193-198
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• 1984

This study was conducted to compare the chip removal capability of root canal enlarging instruments. Fifty five buccal or mesial canals from upper and lower molar teeth were randomly selected and divided into three groups; Reamer, K-type file and K-flex file. Fifteen canals in each group were individually enlarged with one of three tested instruments and irrigated with 5cc of normal saline solution. After instrumentation, each canal was dried with paper point and the canal was splited longitudinally and the cleanness of root canal surface was evaluated under stereoscope by three observers. The results were as follows; 1. Most of the canals experimented showed varying degree of the presence of debris. 2. The canals prepared with reamers showed the most clean canal surface. 3. There was no significant difference in debridement effect between k-type file and k-flexfile.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.477-486
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• 1998

Recently the development of rotary instrument makes it possible that in root canal treatment operator saves much more time, maintans original curved canal shape and easily prepares continuous tapered root canal. The purpose of this experiment was to examine the smoothness of the internal surface of prepared root canal and the effectiveness of debridement in prepared root canal by SEM for the comparison of hand and Ni-Ti rotary instrument. 25 extracted human teeth were access opened and # 10 K-type file was introduced into canal until it was appeared at the apical foramen. The working length was established by subtracting 0.5mm from this measurement. Group 1. The root canal preparation was done to # 30 with working length and then step-back until # 45 with K-Flexofile (Maillefer, Swiss). Group 2. Root canal preparation was done by Naviflex Ni-Ti file (Brasseler, USA) as the same technique with group 1. Group 3. Canal was prepared by Profile .04 (Maillefer, Swiss) taper until #30. Group 4. With use of Quantec (Tycom, USA) root canal was prepared from file number 1 to 8. In group 1 and 2, the root canal irrigant was NaOCl and the other groups, NaOCl and RC-prep (Premine Dental Products, USA) was used. The prepared teeth were notched with high-speed bur as bucco-lingual direction and fractured with chisel and mallet, then examined with SEM. Group 1 showed smooth internal surface. There were scratches mainly to the axial direction. Group 2 showed similar characteristics to those in group 1. Group 3 showed more smoother and linear cutting surface with bised scratches. Group 4 has the almost same characteristics group 3 and there was no difference in the file design. Ni-Ti rotary root canal instrument prepare the dentinal wall more smoother than hand instrument. The effectiveness of debridement was not fully affected by file design. The isthmus area and accessory canals of the root canal system were not prepared in any group. According to the result, hand and rotary type instrumentation techniques were effective in removal of major amount of tissue from root canal but it was not complete. In the direction of cutting movement there was difference between them.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.789-801
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• 1995

Canals with artificially made internal resorption were filled with 4 techniques(Lateral condensation, Ultrafil, Obtura II, Thermafil) to compare the efficacy of canal filling according to the filling techniques. After canal filling, radiographic examination, dye penetration through the apical portion and percentage of G-P filled area on the internal resorption area were evaluated. To examine the degree of crystal-like structure and the interface between filled G-P and canal wall, SM and SEM images were taken too. The results were as follows : 1. There was no statistically significant difference in apical microleakage among the 4 root canal filling techniques. 2. As a result of radiographic examination, Ultrafil was the best and Obtura II was acceptable but Lateral condensation and Thermafil showed unfavorable canal filling pattern similarly. 3. Ultrafil filled most of artificially made internal resorption area and Obtura II, Lateral condensation, Thermafil in that order filled unfavorably. 4. Degree of crystal like structure was the highest in the group filled with Ultrafil and those of Obtura II and Thermafil were similar and that of gutta percha used in Lateral condensation showed the lowest value. 5. Penetration of gutta percha into the dentinal tubules couldn't be seen in all groups. In the contact surface between the filled G-P and the canal wall, Lateral condensation showed relatively close sealing, Obtura II and Thermafil had irregular contact surface and Ultrafil showed regular filling pattern. 6. Contact surface between the core of Thermafil and the gutta percha showed close relationship without gap formation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.31-38
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• 1990

The power water flowed out from the multipurpose darn influences the ecosystem approximately because of the low water temperature. An appropriate counter measure to the rising water temperature is needed for growing crops especially when the temperature is below 18˚C in the source of the irrigation water This observational study is practiced in Yong-Doo water warming canal and pond in the down stream of Choong-Ju multipurpose dam and is practiced for analyse and compare the rising effects in actural water temperature by actual measurement with the rising effects of planned water temperatuer by the basic theoritical method and for the help to present the direction in plan establishment through investigate the results afterwards. The results are as follows. 1.The degree of the rise of the water temperature can be decided by $\theta$x=$\theta$o +K L--v.h (T-$\theta$˚)Then, K values of a factor representing the characteristics of the water warming canal were 0.00002043 for the type I. and 0.0000173 for the type II. respectively. 2.A variation of water temperature which produced by the difference effective temperature and water temperature in the water warming canal was $\theta$x1 = 16.5 + 15.9(1-e -0.00018x), $\theta$x2 =18.8 + 8.4( 1-e -0.000298x)for the type I. and $\theta$x, = 19.6 + 12.8 ( 1-e -0.00041x) for the type II. 3.It was shown that the effects of the rise of water temperature for the type I. water warming canal were greater than that of type II. as a resultes of broadening the surface of the canal compared with the depth of water, coloring the surface of water canal and installing the resistance block. 4.In case of the type I. water warming canal, the equation between the air temperature and the degree of the rise of water temprature could be made ;Y= 0.4134X + 7.728 In addition, in case of the type II. water warming canal, the correlation was very low. 5.A monthly variation of the water temperature in the water warming canal was the highest in August during the irrigation period and the water temperature rose with the air temperature until August. However, it was blunted after then. 6.A rising degree of water temperature of the practical value in the water warming pond was higher than that of the theoritical equation by 69% for the type I. and 57% for the type II. Accordingly, it was possible to acquire the result near the practical value.$\theta$w-$\theta$o=[1-exp{ -h(1+2$\psi$) . X($\theta$w-$\theta$0)XC Here, C values are 1.69 for the type I. and 1.57 for the type II. 7.It was shown that the effect of the rise of water temperature was favorable when the thermal absorption was to be good by coloring the surface of the water warming pond and removing the bottom osmosis. 8.By enlarging the surface of water in comparison with the depth, and by having dead area of water in the water warming pond, this structure in the water warming pond is helpful for the rise of water temperature.

• Imaging Science in Dentistry
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• v.37 no.4
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• pp.217-220
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• 2007

Purpose: The purpose of this study was to compare the location of the mandibular canal in Class III malocclusion to its location in normal occlusion for adults. Materials and Methods: For this study 32 skeletal Class III patients and 26 normal patients were observed. Four measurements were taken on cross sectional tomography between the first and second molars: the distance from the mandibular canal to the inner surface of both the buccal and lingual cortices, the distance from the mandibular canal to the inferior border of the mandible, and the buccolingual width of the mandible. The buccolingual location of the canals was classified as lingual, central, or buccal. Each measurement was analyzed with an independent t test to compare Class III malocclusion to normal occlusion. Results: Compared to the control group, the prognathic group had a shorter distance from the canal to the inner surface of the lingual cortex and to the base of the mandible. A higher percentage of the canals were located lingually in the prognathic group. Conclusion: This study showed that the mandibular canal was located more lingually and inferiorly in prognathic patients than in patients with normal occlusion. These results could help surgeons to reduce injuries to the inferior alveolar nerve.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.26-32
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• 2008

Middle Route Project, the largest water conveyance system in China delivers the water of Changjiang River to North China. In order to create canal operation simulation system, mathematical models are established based on the analysis of hydraulics about steady flow, unsteady flow, and check gate. By simulating the canal operation behavior, we improved the check gate control algorithm and predicted the change process of water surface and flow profile which is very valuable to actual canal operation.

• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.77-84
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• 1986

This study was designed to compare the antimicrobial effect of the several root canal cements and to determine the duration of their activity. After Strep. sanguis 9811 was streaked on the surface of BHI agar and Plain agar, PVC tubes filled with root canal cements were applied and cultured for 48 hours, aerobically. Following results were obtained, 1. All of the examined root canal cements had antimicrobial activity with varying degree. 2. The antimicrobial activity of N2 was larger than any other root canal cements. Nogenol and Tubliseal showed the lowest activity. ZOE, AH26, Procosol and PCA cement showed the moderate antimicrobial activity. (P>0.05) 3. At one day after mixing the root canal cements, all of the root canal cements except N2 and PCA cement showed greatly reduced antimicrobial activity. 4. At three days after mixing, PCA cement showed the reduced antimicrobial activity. N2 showed the reduced activity at 7 days after mixing.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.126-132
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• 2013

PURPOSE. Post surface conditioning is necessary to expose the glass fibers to enable bonding between fiber post and resin cement. The purpose of the present study was to evaluate the effect of different surface conditioning on tensile bond strength (TBS) of a glass fiber reinforced post to resin cement. MATERIALS AND METHODS. In this in vitro study, 40 extracted single canal central incisors were endodontically treated and post spaces were prepared. The teeth were divided into four groups according to the methods of post surface treatment (n=10): 1) Silanization after etching with 20% $H_2O_2$, 2) Silanization after airborne-particle abrasion, 3) Silanization, and 4) No conditioning (Control). Adhesive resin cement (Panavia F 2.0) was used for cementation of the fiber posts to the root canal dentin. Three slices of 3 mm thick were obtained from each root. A universal testing machine was used with a cross-head speed of 1 mm/minute for performing the push-out tests. Two-way ANOVA and Tukey post hoc tests were used for analyzing data (${\alpha}$=0.05). RESULTS. It is revealed that different surface treatments and root dentin regions had significant effects on TBS, but the interaction between surface treatments and root canal regions had no significant effect on TBS. There was significant difference among $H_2O_2$ + Silane Group and other three groups. CONCLUSION. There were significant differences among the mean TBS values of different surface treatments. Application of hydrogen peroxide before silanization increased the bond strength between resin cements and fiber posts. The mean TBS mean values was significantly greater in the coronal region of root canal than the middle and apical thirds.

• Restorative Dentistry and Endodontics
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• v.28 no.3
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• pp.232-240
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• 2003

This study is to investigate the canal system in the mesiobuccal root of the maxillary first molar. 61 maxillary first molars were randomly selected. Serial transverse sections were made perpendicular to the long axis of the mesiobuccal root. Each section was placed in 3% sodium hypochlorite for 24 hours and rinsed in water and dried. The resected surface was stained with 2% methylene blue dye and examined with stereomicroscope. 1 Canal configuration analysis showed that 36.1% of the specimen classified as type I, 16.4% as type II , 37.7% as type III and 9.8% as type IV. 2. Type II canal was merged in one canal within 1 to 4mm of the apex. 40% of type II canal converged at 2mm of the apex. 3. Type IV canal was divided into two canal within 2 to 4mm of the apex. 66.6% of type IV canal branched off at 2mm of the apex. 4. None of the sections had more than two main root canal. 5. 48.4% of the sections in 3mm with two canals contained an isthmusand more than 70% with two canals has isthmus at 4 to 5mm sections. 63.9% of the mesiobuccal root of maxillary first molar had two canaland 76.5% of sections with two canals in 5 MM had an isthmus. Because of this complexity the clinician should always search for extra canal carefullyand root canal system, including an isthmus, should be cleaned and shaped completelyand obturated three dimensionally for successful endodontic treatment.

• Restorative Dentistry and Endodontics
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• v.6 no.1
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• pp.7-16
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• 1980

The author observed the periodontal tissue reactions to the root canal sealers after root perforations were made intentionally in dogs. The perforations were made on 74 teeth from 7 dogs. The experiments were performed in two different modes of procedure: In Group I, the perforations were made through the root canal to the alveolar bone. In Group II, the perforations were made from site of alveolar bone to the root canals. The perforated canals in Group I were filled with gutta-percha and root canal cements; Calxyl (Calcium Hydroxide in Ringer's solution), Zinc Oxide -Eugenol cement (Z.O.E.), Kerr sealer (Rickert's paste) and AH 26 (Epoxy Resin preparations). The perforated canals in Group II were sealed with Calxyl, Z.O.E, Kerr sealer and AH26. Histologic examinations of periodontal tissue reactions were observed at various time intervals. The results were as follows; l. Cementum deposition on the perforated root surface in Group II cases showed slightly earlier than that of Group I. Healing tendency of injured alveolar bone in Group II was greater than that of Group I. 2. According to the time increase after experiment, the cementum deposition on the site of perforated dentin in Group II with intact pulp was notably thickened. Secondary dentin deposition on the root canal surface where the dentinal tubles were cut was also found in similar pattern. 3. In the cases of perforated canals sealed with Calxyl both in Group I and Group II, It revealed the earliest cementum-deposition among 4 different root canal cements. In the cases of perforated canals sealed with Kerr sealer and AH26, the cementum-deposition on the root surface was not found. 4. Proliferation of epithelium around the perforated area was first seen at 5-week cases in Group I, and at 3-week cases in Group II. 5. In all cases, dentin resorption on the site of perforated root surface was always occured.