• Restorative Dentistry and Endodontics
• /
• v.8 no.1
• /
• pp.139-145
• /
• 1982

Eighty four human maxillary second premolars were injected with china. ink, decalcified, cleared and used in study, in vitro, to determine the number of root canals, the frequency and location of lateral canals, the frequency and location of transverse ansatomoses, the curvature of root canals, the location of apical foramens, and the frequency of apical deltas. The results were as follows: 1. Most of the teeth demonstrated one canals, but the only tooth was found to have two canal. 2. Of the 101 canals studied, 85.1% of the canals were found to have lateral canals and these ramifications were usually located in the apical third of the root. 3. Of the two root canals in one root, 25.4% of the canals were found to have transverse anastomoses and were usually located in the middle third of the root 4. 33.3% of apical foramens were located directly on the root apex and 66.7% of them laterally, and 46.5% of canals showed distal curvature.

• Restorative Dentistry and Endodontics
• /
• v.7 no.1
• /
• pp.139-144
• /
• 1981

Eighty four human maxillary first premolars were injected with china ink, decalcified, cleared and used in study, in vitro, to determine the number of root canals, the frequency and location of lateral canals, the frequency and location of transverse anastomoses, the curvature of root canals, the location of apical foramens, and the frequency of apical deltas. The results were as follows: 1. Most of the teeth demonstrated two canals, but 20.2% of the teeth were found to have one canal. 2. Of the 151 canals studied, 38.4% of the canals were found to have lateral canals and these ramifications were usually located in the apical third of the root. 3. Of the two root canals in one root, 35.7% of the canals were found to have transverse anastomoses and were usually located in the middle third of the root. 4. 15.2% of apical foramens were located directly on the root apex and 84.8% of them laterally, and 52.3% of canals showed distal curvature.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.30 no.4
• /
• pp.637-642
• /
• 2003

Morphology of primary root divergency and curvature determines the pattern of root resorption and periapical lesion, and affects successful root canal treatment. With the purpose of analysing the morphology of primary mandibular second molar roots and canals, the frequency, angle, radius, and start of curvature of the canal were measured. Fifty clinical radiographs were taken from $3{\sim}6$ years old children, followed by digitizing after scanning and analyzing by Scion image Beta 4.02TM(Scion Co. USA). The angle of curvature was determined by Schneider's method and the radius of curvature was determined by Schaefer's method. The results were as follows: 1. The angle of curvatures were $17.3^{\circ}{\pm}5.0$ (mesial), and $27.9^{\circ}{\pm}6.0$ (distal). Distal curvature was significantly larger than mesial.(p<0.05) 2. The radius of curvatures were $8.7mm{\pm}2.5$ (mesial), and $5.8\;mm{\pm}1.5$ (distal). Mesial curvature was significantly larger than distal.(p<0.05) 3. The start of curvatures were $4.1mm{\pm}0.6$ (mesial), and $4.2mm{\pm}0.6$ (distal). There were no difference between two groups. (P<0.05)

• Restorative Dentistry and Endodontics
• /
• v.26 no.5
• /
• pp.418-435
• /
• 2001

Root canal preparation process is of utmost importance in successful treatment of root canal. Also, one of the most important purpose of the root canal preparation is to enlarge the root canal three dimensionally without changing the curvature of the root canal However as the curvature of the root canal increases, there are many difficulties involved in formation of optimum root canal. Therefore in order to solve the above mentioned problems, new developments in methods of root canal preparation and equipments for such purposes were made. Recently, vigorous studies about newly introduced engine-driven nickel-ti-tanium rotary file are conducted. As shown in research results to dates, it is well established that the use of nickel-titanium file is better suited for curved root canal than stainless steel file in maintaining the curvature or root canal and reducing the deformation of root canal. However it is also acknowledged that there are a few discrepancies in research results according to protocol, due to failure to remove variables in experiments. In addition, although it is recommended by the manufacturer that the GT rotary file should maintain a low rotational speed of 150~350rpm and 'light pressure' as light as not to break the lead of a pencil, academic studies about the vertical force which is not yet standardized are not sufficiently explored. Therefore, this research devised and utilized a special research equipment to standardize the appropriate range of vertical force for GT rotary file through experiments by breaking of the lead of a pencil as expressed by the manufacturer and to accurately measure factors involved through repeating and recreating the environment of root canal preparation. Forming nine experimental groups by varying the vertical forces (150g. 220g, 300g) and rpm (150rpm, 250rpm, 350rpm), the effects of changing vertical forces and rpm on working efficiency were measured in terms of time expended in root canal preparation by crown-down method using a transparent resin block with 35 degree curvature and GT rotary file (z-test). The following research using this special research equipment that involved nine experimental groups and varying the vertical force for root canal preparation from 300g which is within the normal vertical force range to 700g and 1000g which fall outside the normal rpm range. The results were as follows : 1. Analysis of the experiment results revealed that the time spent in root canal preparation decreased as the vertical forces and rpm increased (p<0.05). Also, the effects of rpm were greater than those of the vertical forces within the normal vertical force range ($\beta$-weight test). 2. Observation of the deformation of GT rotary file revealed that deformation increases in a direct correlation with the vertical force increase and in a reverse correlation with the rpm decrease. In the case of the vertical forces close to the normal range, the probability of GT rotary file deformation were quite different depending on the rpm changes. In the case of greater vertical forces, the occurrences of deformation of the file were more frequent regardless of the rpm changes. 3. Deformation and breakage of file were also commonly observed in the expended time measurement experiments and GT rotary file deformation experiments in which low speed rpm (150rpm) was used and at the curved portion of the resin block.

• Imaging Science in Dentistry
• /
• v.36 no.1
• /
• pp.55-62
• /
• 2006

Purpose : To find the cause of root curvature by use of panoramic and lateral cephalometric radiograph. Materials and Methods : Twenty six 1st graders whose mandibular 1st molars .just emerged into the mouth were selected. Panoramic and lateral cephalometric radiograph were taken at grade 1 and 6, longitudinally. In cephalometric radio graph, mandibular plane angle, ramus-occlusal plane angle, gonial angle, and gonion-gnathion distance (Go-Gn distance) were measured. In panoramic radio graph, elongated root length and root angle were measured by means of digital subtraction radiography. Occlusal plane-tooth axis angle was measured, too. Pearson correlations were used to evaluate the relationships between root curvature and elongated length and longitudinal variations of all variables. Multiple regression equation using related variables was computed. Results : The Pearson correlation coefficient between curved angle and longitudinal variations of occlusal plane-tooth axis angle and ramus-occlusal plane angle was 0.350 and 0.401, respectively (p<0.05). There was no significant correlation between elongated root length and longitudinal variations of all variables. The resulting regression equation was $Y=10.209+0.208X_1+0.745X_2$ (Y: root angle, $X_1$: variation of occlusal plane-tooth axis angle, $X_2$: variation of ramus-occlusal plane angle). Conclusion : It was suspected that the reasons of root curvature were change of tooth axis caused by contact with 2nd deciduous tooth and amount of mesial and superior movement related to change of occlusal plane.

• Proceedings of the KACD Conference
• /
• 2003.11a
• /
• pp.554-554
• /
• 2003

I. Objectives This study was done to evaluate the shaping ability of ProFile and ProTaper, K-Flexofile during instrumentation in simulated resin canals with different angles of curvature. II. Materials and Methods Ninety simulated root canals with a curvature of 15, 30 and 45 degree (following Schneider's method) were made of epoxy resin ($EPOXICURE^{TM}$, BUEHLER, USA) for this study. The canal length of simulated root canals was adjusted to 18 mm. The beginning point of curvature was positioned at 10mm from the canal orifice.(omitted)

• Restorative Dentistry and Endodontics
• /
• v.35 no.5
• /
• pp.374-379
• /
• 2010

Objectives: Nickel-titanium (Ni-Ti) rotary instruments have some unexpected disadvantages including the tendency to screw-in to the canal. The purpose of this study was to evaluate the influence of root canal curvatures on the screw-in effect of Ni-Ti rotary files. Materials and Methods: A total of 80 simulated root canals in clear resin blocks were used in the study. Canals with curvature of 0, 10, 20 and 30 degrees were instrumented with ProTaper instruments SX, S1, S2 and a ProFile of #25/0.06 to 1.0-2.0 mm beyond the initial point of root curvature. The screw-in force was measured with a specially designed device while canal was instrumented with a ProFile of #30/0.06 at a constant speed of 300 rpm. The data were subjected to one-way ANOVA and Scheffe multiple range test for post-hoc test. Results: Larger degree of canal curvature generated significantly lesser screw-in forces in all groups (p < 0.001). Conclusions: More attention needs to be paid when using rotary instruments in canals with less curvature than canals with more curvatures to prevent or reduce any accidental overinstrumentation.

• Journal of Life Science
• /
• v.17 no.2 s.82
• /
• pp.174-178
• /
• 2007

Treatment of malformin A1 is known to increase ethylene production 130% at 4 hr and 56% at 8 hr after treatment in maize root compared to untreated plants. The ethylene production by malformin A1 was maximum level at 4 hr and slowly decreased up to 8 hr. Calcium ion regulators such as A23187 (calcium ionophore) and verapamil (calcium channel blocker) stimulated ethylene production. Treatment of both calcium ion regulators increased about 30% of ethylene production at 4 hr, and 20% at 8 hr. Both calcium ion regulators did not stimulate malformin A1-induced ethylene production at 4 hr as malformin A1 itself did. However, the treatment of calcium ion regulators with malformin A1 maintains the ethylene production for 8 hr. These results suggested that the proper concentration of calcium might need to confer the effect of malformin A1 on the ethylene production. Malformin A1 suppressed the gravitropic curvature of maize root about 58% at 4 hr and 42% at 8 hr compared to control plant. Verapamil inhibited the gravitropic curvature about 54% at 4 hr and 23% at 8 hr compared to control, respectively. But A23187 could not. In addition, verapamil showed more inhibition in malformin A1-induced gravitropic curvature than A23187 in malformin A1 induced. These data suggested that calcium ion regulators affect the malformin A1-induced ethylene production and gravitropic curvature, and give the evidence that calcium ion play an important role in gravitropic curvature in maize root.

• Restorative Dentistry and Endodontics
• /
• v.30 no.4
• /
• pp.327-334
• /
• 2005

This study investigated the effect of anticurvature filing method on preparation of the curved root canal using ProFile. Thirty six resin blocks were divided equally into three groups by instrumentation motions: anticurvature filing motion. circumferential filing motion and straight up-and-down motion. Each resin block was sectioned at 8mm level from the apex and at the greatest curvature of the canal and reassembled in metal mold by a modified Bramante technique. All groups were instrumented with the ProFile system. At each levels. image of sectioned surface were taken using CCD camera under a stereomicroscope at $\times40$ magnification and stored. Distances of transportation at the inner and outer area of curvature and the centering ratio were determined and compared by statistical analysis. along with the assessment of the increase of root canal cross-sectional area. The results were as follows; 1. In all groups. there was no statistical difference in the mean increase of root canal cross-sectional area. the centering ratio. and the mean distances of transportation at the inner area of curvature at each level. 2. At 8mm level from the apex. the mean distances of transportation at the outer area of curvature decreases in following order anticurvature filing motion. circumferential filing motion. straight up-and­down motion but. no significant difference at the greatest curvature of the canal among three groups. Effect of anticurvature filing motion using ProFile does not seem to be different from other instrumentation motions at the inner area of curvature in curved root canal.

• Restorative Dentistry and Endodontics
• /
• v.46 no.1
• /
• pp.5.1-5.13
• /
• 2021

Objectives: The aim of the current study was to assess whether the amount of extruded debris differs for straight and severely curved root canals during retreatment using H-files, R-Endo, Reciproc and ProTaper Universal Retreatment (PTU-R) files. Additionally, the area of residual filling material was evaluated. Materials and Methods: Severely curved (n = 104) and straight (n = 104) root canals of maxillary molar teeth were prepared with WaveOne Primary file and obturated with gutta-percha and AH Plus sealer. Root canal filling materials were removed with one of the preparation techniques: group 1: H-file; group 2: R-Endo; group 3: Reciproc; group 4: PTU-R (n = 26). The amount of extruded material and the area of the residual filling material was measured. The data were analyzed with 2-way analysis of variance (ANOVA) and 1-way ANOVA at the 0.05 significance level. Results: Except for Reciproc group (p > 0.05), PTU-R, R-Endo, and H-file systems extruded significantly more debris in severely curved canals (p < 0.05). Each file system caused more residual filling material in severely curved canals than in straight ones (p < 0.05). Conclusions: All instruments used in this study caused apical debris extrusion. Root canal curvature had an effect on extruded debris, except for Reciproc system. Clinicians should be aware that the difficult morphology of the severely curved root canals is a factor increasing the amount of extruded debris during the retreatment procedure.