• Restorative Dentistry and Endodontics
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• v.39 no.4
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• pp.265-269
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• 2014

Objectives: To evaluate the effect of different ultrasonic tip designs on intraradicular post removal. Materials and Methods: The crowns of forty human canine teeth were removed, and after biomechanical preparation and filling, the roots were embedded in acrylic resin blocks. The post spaces were made, and root canal molding was performed with self-cured acrylic resin. After casting (Cu-Al), the posts were cemented with zinc phosphate cement. The specimens were randomly separated into 4 groups (n = 10), as follows: G1 - no ultrasonic vibration (control); G2 - ultrasonic vibration using an elongated cylindrical-shaped and active rounded tip; G3 - ultrasonic vibration with a flattened convex and linear active tip; G4 - ultrasonic vibration with active semicircular tapered tip. Ultrasonic vibration was applied for 15 seconds on each post surface and tensile test was performed in a Universal Testing Machine (Instron 4444 - 1 mm/min). Results: G4 presented the highest mean values, however, with no statistically significant difference in comparison to G3 (p > 0.05). G2 presented the lowest mean values with statistically significant difference to G3 and G4 (p < 0.05). Conclusions: Ultrasonic vibration with elongated cylindrical-shaped and active rounded tip was most effective in reducing force required for intraradicular post removal.

• Restorative Dentistry and Endodontics
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• v.24 no.1
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• pp.222-232
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• 1999

The purpose of this study was to evaluate the effect of heated spreader on the sealing ability of lateral condensation, compared with regular cold spreader. Forty two extracted human teeth with single canal were randomly placed into 3 experimental groups, and four additional teeth were used as positive and negative controls. Each group was prepared with Ni-Ti Profile #40 using step-down technique and obturated with standardized colored gutta-percha cone by standard(cold) lateral condensation technique, warm lateral condensation technique with Endotec and hot spreader soaked in glass bead sterilizer, each with Sealapex sealer. Control groups were not obturated, but prepared. After 2 days in 2% methylene blue, the teeth were invested and made into transparent resin blocks. And then, each block was sectioned horizontally with microtome at 1, 2, 3, 4, 5 mm levels from the apex. The linear extent of dye penetration was examined with stereomicroscope at ${\times}$20 magnification. At each of 5 levels, ratio of the area of gutta-percha was obtained by calculating the area of gutta-percha to the total area of the canal. The data collected were then analyzed statistically using an analysis of variance(ANOVA) and Scheffe test. The results were as follows ; 1. All experimental groups produced the apical microleakage. 2. The mean leakage was 1.57${\pm}$0.76mm for cold spreader group, 0.86${\pm}$0.95mm for Endotec spreader group, and 0.64${\pm}$0.93mm for hot spreader group. The difference between hot spreader group and cold spreader group was statistically significant(p<0.05). 1. At the 1 mm level, the mean ratio of area of gutta-percha was 74.58${\pm}$13.15(%) for cold spreader group, 65.42${\pm}$14.62(%) for Endotec spreader group, and 80.72${\pm}$14.63(%) for hot spreader group. There was statistically significant difference between hot spreader group and Endotec spreader group(p<0.05). 2. At the 2mm level, the mean ratio of area of gutta-percha was 87.86${\pm}$11.22(%) for cold spreader group, 66.55${\pm}$14.02(%) for Endotec spreader group, and 92.93${\pm}$7.24(%) for hot spreader group. There was statistically significant difference between Endotec spreader group and other two spreader groups(p<0.05). 3. At the level 3, 4, 5 mm, there was no statistically significant difference between each group. Within the limits of the results of this experiment, warm lateral condensation technique with hot spreader soaked in a glass bead sterilizer demonstrated favorable apical sealing effect and improved density of gutta-percha mass. Thus, it is thought that this obturation technique is effective for clinical use and beneficial to reduce condensation forces, also economical and easy. Lateral condensation, Heated spreader, canal sealing, Microleakage.

• Restorative Dentistry and Endodontics
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• v.31 no.1
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• pp.1-10
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• 2006

The purpose of this study was to compare the shaping ability of three Ni-Ti file systems used by dental students or the experts and consequently to aid in choosing a proper systems for educational courses of dental students and beginners. Fifty students and ten dentists who have clinical experience over two years prepared 180 simulated root canals in resin blocks with three Ni-Ti systems; $ProFile^{(R)}\;(PF),\;HeroShaper^{(R)}\;(HS),\;K3^{TM}\;(K3)$. After preparation, the Ni-Ti files were evaluated for distortion and canal preparation time was recorded. The images of pre- and post-instrumented canals were scanned and superimposed. Amounts of increased canal widths, deviation, and centering ratio were calculated at apical 1, 3 and 5 mm levels and statistical analysis was performed The results were as follows : 1. HS showed the shortest preparation time and instrumented canal width in K3 was significantly larger than other groups (P<0.05). 2. At 1 and 3mm levels, all groups had outward deviation. In student group, at the 1mm level, PF had the least deviation (P<0.05). 3. In the centering ratio, the PF had the best centering ability compared to the others at 5mm level. At 1 and 3mm levels, HS and PF had better abilities than K3. Student group had better ratio than the expert at 3mm level with PF (P<0.05). Based on the results, it is surmised that the $ProFile^{(R)}$ is the safest and most ideal instrument for students and beginners.

• Restorative Dentistry and Endodontics
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• v.30 no.6
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• pp.486-492
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• 2005

The purpose of this study was to compare the shaping ability of the two different Ni-Ti file systems and the two different engine systems in simulated canals. A total of four groups of each 10 were tested. Each group was instrumented with HeroShaper and Endo-Mate2 (Croup HE), HeroShaper and Tecnika (Croup HT), ProFile and Endo-Mate2 (Group PE), and ProFile and Tecnika (Croup PT). Canal preparation time was recorded. The images of pre- and post- instrumented root canals were scanned and superimposed. The amounts of increased width and centering ratio were measured and calculated at apical 1, 3 and 5mm levels. These data were statistically analyzed with one-way ANOVA and Duncan's multiple range test The results of this study were as fellows ; 1. Canal preparation time of HT group was the shortest (p<0.05). 2. The amount of increased canal width in HE group was significantly larger than PT group at apical 1mm level (p<0.05) At apical 3mm level, PT group was significantly smaller than other groups (p<0.05). At apical 5mm level, PE group was significantly larger than PT group (p<0.05). 3. The amount of centering ratio in HE group was significantly larger than other groups (p<0.05). At apical 5mm level, HT group was significantly larger than PE group and PT group (p<0.05). Under the condition of this study, torque-controlled endodontic motor is safer than no torque controlled motor, especially when the active file is used.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.546.1-546
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• 2003

Laser doppler flowmeter (LDF) has been applied to the measurement of pulpal blood flow (PBF) in human teeth. As far as we searched, the detection area of the pulp in the blood flow measurement has not been clarified, yet. Therefore, the purpose of this study was to obtain information of the detection area in PBF measurement using LDF. The experiments were performed on the artificial blood circulation in extracted human upper central incisors. The apical portions of examined teeth (n=6) were severed and root canals were enlarged from the apical end to the 2mm incisal to the level of enamel-cement junction. An individual resin cap of each tooth was prepared and a hole was drilled 2mm incisal to enamel-cement junction of the labial side of the cap. The measurement probe of LDF (MBF3D, Moor Instrument, UK) was plugged into the hole of the cap. Heparinized human peripheral blood, which was in advance collected and diluted 3 times with physiological saline, was pumped through the apical foramen of the teeth via a silicone tube and a disposable needle (o.d. 0.7mm) and blood flow signals were monitored. The flux signal significantly increased with the enlargement of the root canal to incisal direction (p<0.01, Friedman analysis). The result indicates that the performance of LDF in PBF with human teeth is limited.

• Restorative Dentistry and Endodontics
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• v.30 no.1
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• pp.38-48
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• 2005

The purpose of this study was to compare and evaluate the shaping ability of the three different Ni-Ti file systems used by undergraduate students. Fifty undergraduate students prepared 150 simulated curved root canals in resin blocks with three Ni-Ti file systems - $ProFile^{(R)}$ (PF), Manual $ProTaper^{(R)}$ (MPT), Rotary $ProTaper^{(R)}$ (RPT). Every student prepared 3 simulated root canals with each system respectively. After root canal preparation, the Ni-Ti files were evaluated for distortion or breakage Assessments were made according to the presence of various types of canal aberrations. The pre- and post-instrumented canal images were attained and superimposed. The instrumented root canal width were measured and calculated for the net transportation (deviation) and the centering ratio. Under the condition of this study, both $ProTaper^{(R)}$ systems allowed significantly more removal of root canal wall than the $ProFile^{(R)}$ system. In the important other aspects such as the centering ratio, there was no significant differences between the systems. Novice dental students were able to prepare curved root canals with any kinds of Ni-Ti file systems with little aberration and great conservation of tooth structure. Students want to learn effective methods and at the same time simple rotary procedures. The rotary $ProTaper^{(R)}$ systems were one of the most compatible to these students from the point of view of cutting ability The $ProFile^{(R)}$ system was also compatible in safe and gentle shaping.

• Imaging Science in Dentistry
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• v.32 no.1
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• pp.35-39
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• 2002

Purpose: The altered gantry angle during scanning for some multiplanar reconstruction CT program (CT/MPR) may cause distortion of the image. The aim of this study was to ascertain whether there is a image distortion in a reformatted image when the gantry and the object are equally inclined using ToothPix and DentaScan program. Materials and Methods: A resin block model with four cylindrical holes and a human dry mandible were used. Two MPR software packages, ToothPix and DentaScan program, were used for reformatted panoramic images. The block and the gantry were equally inclined at 0°, 15°, and 30°. Results: With ToothPix program, a resin block model with empty holes and a dry mandible showed inclined images in the reformatted panoramic image. Increasing the gantry angle, the depth and inclination of the holes were increased in the reformatted central panoramic images. However, a resin block model with gutta perch a in its holes and a dry mandible with a wire in its mandibular canal didn't show image distortion. With DentaScan program, image distortion was not seen in any situation. Conclusion: ToothPix program may distort the reformatted image when the gantry angle is not at zero degrees. However, with DentaScan program, the patient may be positioned comfortably and the gantry can be adjusted to the patient positioning.

• Restorative Dentistry and Endodontics
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• v.33 no.6
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• pp.570-579
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• 2008

The purpose of this study was to investigate the distribution of tensile stress of canal obturated maxillary second premolar with access cavity and notch-shaped class V cavity restored with composite resin using a 3D finite element analysis. The tested groups were classified as 8 situations by only access cavity or access cavity with notch-shaped class V cavity (S or N), loading condition (L1 or L2), and with or without glass ionomer cement base (R1 or R2). A static load of 500 N was applied at buccal and palatal cusps. Notch-shaped cavity and access cavity were filled microhybrid composite resin (Z100) with or without GIC base (Fuji II LC). The tensile stresses presented in the buccal cervical area, palatal cervical area and occlusal surface were analyzed using ANSYS. Tensile stress distributions were similar regardless of base. When the load was applied on the buccal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth with class Ⅴ cavity were slightly higher than that of the tooth without class V cavity. When the load was applied the palatal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth without class V cavity were slightly higher than that of the tooth with class V cavity.

• Journal of Korean Society of Forest Science
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• v.34 no.1
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• pp.1-14
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• 1977

These studies were carried out to know the variation of morphological tree forms, needles, cotyledons, seed characters and top height growth of seedlings of Pinus koraiensis S. et Z. by populations in Mt. Jiri. The results are summarized as follows: 1. It was observed that the characteristics of length, needles of serration density of needles, percentage of full seeds length, of seeds, thickness, of seeds length of cotyledons, width of cotyledon, numbers of the stomata line in cotyledons and the top height growth of seedlings were significantly different in individual trees and populations. 2. The characteristics of branch angle specific gravity of wood and resin canal numbers of cotyledons were significantly different in populations. 3. It was that the characteristics of numbers of stomata line, width, of seeds weight, of seeds serration density of cotyledons, numbers of cotyledons were significantly different in individuals. 4. The resin canals of needles showed three principle resin canals in individual trees and population, and the coefficients of variation were not shown in individual trees and populations. Stem forms showed to be a straight form with all populations. 5. The characteristics of cotyledons had generally higher tendency than the characteristics of needles in comparison with coefficience of variation.

• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.323-329
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• 2006

The aim of this study was to evaluate the retrievability of Resilon as a root canal filling material Twenty-seven human single-rooted extracted teeth were instrumented utilizing a crown down technique with Gates-Glidden burs and ProFile system. In group1 (n = 12) canals were obturated with gutta percha and AH-26 plus sealer using a continuous wave technique and backfilled. In group 2 (n = 15) Resilon was used as a filling material. Then teeth were sealed and kept in $37^{\circ}C$ and 100% humidity for 7 days. For retreatment, the samples were re-accessed and filling material was removed using Gates-Glidden burs and ProFiles. Teeth were sectioned longitudinally to compare the general cleanliness and amount of debris $({\times}\;75)$ using SEM. Chi-square test was used $({\alpha}\;=\;0.05)$ to analyze the data. The total time required for removal of filling materials was expressed as mean ${\pm}SD$ (min) and analyzed by the Student t-test $({\alpha}\;=\;0.05)$, Required time for retreatment was $3.25\;{\pm}\;0.32$ minutes for gutta percha/ AH 26 plus sealer and $3.05\;{\pm}\;0.34$ minutes for Resilon. There was no statistically significant difference between the two experimental groups. There was no significant difference between the groups in the cleanliness of the root canal wall. This study showed that Resilon was effectively removed by Gates-Glidden burs and ProFiles.