• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.435-445
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• 2000

The purpose of this study was to compare the leakage of four different obturation techniques in conjunction with immediate apical barrier of ${\beta}$-tricalcium phosphate(TCP) in teeth with open apex. Eighty single-rooted human premolar teeth were prepared and sectioned horizontally, so maximum diameter in apex was 4mm. Apical defects that were similar to open apex, were created with #1/2 round bur and SF104R bur. The apical foramen were opened to a size 80 file extended 3mm beyond the apex. The teeth were placed into the oasis block soaked saline to simulate periapical tissue often associated with pulpless teeth and received apical barriers consisting of TCP followed by obturation using lateral condensation technique, vertical condensation technique, continuous wave technique and thermoplasticized gutta-percha injection technique. Two unobturated teeth served as positive and negative controls. Teeth were immersed in resorcinol-formaldehyde resin for S days at $4^{\circ}C$, and the resin was allowed to polymerize completely for 4 days at room temperature. Teeth were then sectioned horizontally at 1.5mm(level 1), 2.5mm(level 2) and 3.5mm(level 3) from the apex, and examined under a stereomicroscope at ${\times}40$ magnification. The photographs were taken at ${\times}40$ magnification of the filling in each level and scanned. The leakage length in tooth/resin interface was measured at each of the three levels. Each ratio of leakage was obtained by calculating the ratio of the leakage length of canal wall infiltrated with resin to the total length of the canal and was analyzed statistically(One-way ANOVA and Scheffe test). The result were as follows : 1. At the level 1, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), but there was statistically significant(p<0.05). 2. At the level 2, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), and the most leakage in the continuous wave technique group(group 3). There was statistically significant difference between the thermoplasticized gutta-percha injection technique group and the continuous wave technique group(p<0.05). 3. At the level 3, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), but there were no statistically significant differences between other groups(p>0.05). These results suggest that thermoplasticized gutta-percha injection technique which had 1mm apical gutta-percha matrix after the formation of TCP apical barrier, can demonstrate favorable apical sealing.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.337-345
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• 1999

The purpose of this study was to compare the shape of root canal after instrumentation with some engine driven NiTi files. Thirty narrow and curved canals(15-35 degree) of mesial canals of extracted human mandibular first molars were divided into three groups. Group 1: After radicular access with Gates Glidden drill, apical shaping using step back method with Flexo file Group 2: After radicular access with Gates Glidden drill, apical shaping with Profile .04 Group 3: Canal shaping with GT file and Profile .04. Using modified Bramante technique, the root was sectioned at 2 mm from apical foramen, height of curvature, 2 mm from canal orifice. Canal centering ratio, amount of transport, amount of dentin removed, shape of canal were measured and statistical analysis is done using SPSS Program V 7.5. The results were as follows: 1. Canal centering ratio of group 3 was the lowest at coronal part, but there was no statistical difference. Centering ratio of group 2 was the lowest at curve part, and there was statistical difference between group 1(P<0.05). Centering ratio of group 2 was the lowest at apical part, but there was no statistic difference. 2. Amount of transport of group 3 was the lowest at coronal part, but there was no statistical difference. Amount of transport of group 2 was the lowest at curve part, and there was statistical difference between group 1(P<0.05). Amount of transport of group 3 was the lowest at apical part, and there was statistical difference between group 1 and group 2, group 1 and group 3(P<0.05). 3. Amount of dentin removed of group 3 was the lowest at coronal part, bur there was no statistical difference. Amount of dentin removed of group 2 was the lowest at curve part, but there was no statistical difference. Amount of dentin removed or group 2 was the lowest at apical part, and there was statistical difference between group 1 and group 2, group 1 and group 3(P<0.05). 4. The shape of the canals after instrumentation varied among the groups. The majority of canals at coronal and curve part for group 1 were round in shape(7 in 10), those at apical part were oval(8 in 10). The majority of canals at coronal part for group 2 were round in shape(7 in 10) and there was no difference in the number of shape at other part. There was no difference in the number of shape at every part for group 3. As above results, NiTi rotary instrumentation showed a trend to remain more centered in the canal than SS file instrumentation. At using NiTi file, coronal shaping with Gates Glidden drill was not statistically different from shaping with GT file. But shaping with GT file showed tapered canals, so it may be said that shaping with GT file is a safe and valuable instrumentation method.

• Journal of Oral Medicine and Pain
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• v.17 no.2
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• pp.119-128
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• 1992

In order to evaluate the relationship of age with the developmental stage on mandibular second molars in female, the author examined the radiographs in standard films taken by intraoral paralleling technic and analysed the development of 620 roots of 310 females ranged from 10 to 18 years. The development was divided into 7 stages : Crown complete (Cr.C.), Root lengthed 1/4(R.1/4), Root length 1/2 (R.1/2), Rooth length 3/4 (R.3/4), Rooth length complete (R.C), Apex 1.2 closed (A. 1/2), Apical closure complete (A.C) The obtained results were as follows : 1. The formation of roots in fulllength of mandibular second molars was completed at 14.21-year-age in mesial root and at 14.96-year-age in distal root. 2. The formation of apical foramen of mandibular second molars was completed at 17.11-year-age in mesial root and at 17.53-year-age in distal root. 3. The mesial root of mandibular second molar was generally developed earlier than distal root (p<0.01) 4. Coefficients of correlation and regression equations between for age(Y) and the developmental stage of mandibular second molar(X) were "Y=1.53X+6.54, r=0.91 (p<0.01)" in mesial root and "Y=1.52X+7.11, r=0.92(p<0.01)" in distal root respectively.l root respectively.

• Restorative Dentistry and Endodontics
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• v.29 no.2
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• pp.147-152
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• 2004

The purpose of this study was to investigate the quantity of debris which was extruded apically after canal instrumentation using different types of enlarging instrument in endodontic resin models. Five groups of 9 endodontic resin models were instrumented using each different technique : hand instrumentation without early coronal flaring. hand instrumentation after early coronal flaring. and three nickel-titanium engine-driven instrumentations (Hero 642, Protaper, $K^$). Debris extruded from apical foramen during instrumentation was collected on preweighed CBC bottle, desiccated and weighted using electronic balance. The results were analyzed using Kruskal-wallis test and Mann-Whitney U rank sum test at a significance level of 0.05. The results were as follows: 1. All of instrumentation techniques produced apically extruded debris. 2. Group without early coronal flaring extruded significant more debris than groups with early coronal flaring. 3. There was no significant difference among early coronal flaring groups. The early coronal flaring is very important to reduce the amount of debris extruded apically.

• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.20-27
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• 2008

The purpose of this study was to evaluate the consistency of two electronic apex locators in vitro model. Materials consisted of fifty two extracted premolars and two electronic apex locators; Root ZX (J. Morita, Osaka, Japan) and E-Magic Finder Deluxe (S-Denti. Cheonan, Korea). After access preparation, the teeth were embedded in a saline-mixed alginate model. Canal lengths of each tooth were measured at "0.5" and "Apex" mark of the apex locators, respectively so that each tooth had two measurements from 0.5 and Apex points. The file was fixed at final measurement using a glass ionomer cement. The apical 4 mm from the apex was exposed to measure the distance from the file tip to the major apical foramen of each tooth. Average distances and standard deviations were used to evaluate the consistency. Results showed that all measurements of both Root ZX and E-Magic Finder located the major foramen the range of ${\pm}0.5\;mm$ level. Both apex locators showed better consistency at Apex mark than at 0.5 mark. The average distance of file tip-major foramen was - 0.18 mm at 0.5 mark and - 0.07 mm at Apex mark in Root ZX, - 0.25 mm at 0.5 mark and - 0.02 mm at Apex mark in E-Magic Finder. Standard deviation was 0.21 at 0.5 mark and 0.12 at Apex mark in Root ZX, 0.12 at 0.5 mark and 0.09 at Apex mark in E-Magic Finder.

• Restorative Dentistry and Endodontics
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• v.26 no.1
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• pp.77-85
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• 2001

The purpose of this in vitro study was to compare the apical leakage in extracted teeth filled with gutta-percha subsequent to dressing with one of three different calcium hydroxide preparations. Thirty six extracted teeth with single canal were used in this study. After working length determination, canals were prepared with K flexo files to a #40 at the working length. Step-back flaring was produced by using #45, #50 K flexo files and #2, #3, #4 Gates Glidden burs. The teeth were randomly divided into 3 groups of 10 each : the remaining six teeth were used for negative and positive leakage control: Group 1, dressed with pure calcium hydroxide powder (Sigma, USA) mixed with distilled water; Group 2, dressed with Metapaste (Metadent, Korea) ; Group 3, dressed with Vitapex (Neo Dental, Japan). Teeth were sealed with Caviton (GC, Japan) and incubated in 100% humidity, at 37$^{\circ}C$ for 1 wk. All kinds of calcium hydroxide were removed from the canal with a MAF and 5% NaOCl. The canals were filled with AH-26$^{\circledR}$ sealer and gutta-percha using lateral condensation technique, incubated in 100% humidity, at 37$^{\circ}C$ for 2 days for the sealer to be set. The teeth were coated twice with nail varnish except for an area of approximately 2mm surrounding the apical foramen. All specimens were placed in 2% methylene blue solution for 2 days. The root were sectioned longitudinally, the amount of apical leakage was measured to the most coronal part of the root canal to which the dye had penetrated. The independent measurements were made for each root using a stereomicroscope ($\times$40 magnification) and the average was recorded for statistical analysis. The results were as follows ; 1. The mean of apical leakage in group of pure calcium hydroxide ranged 0.102$\pm$0.156mm, in Metapaste$^{\circledR}$ ranged 0.062$\pm$0.069mm, and in Vitapex$^{\circledR}$ ranged 0.067$\pm$0.072mm. 2. Group of pure calcium hydroxide exhibited more leakage than those of 2 manufactured calcium hydroxide preparations, but it was not statistically significant. 3. Group of water-based Metapaste$^{\circledR}$ showed lesser leakage than that of oil-based Vitapex$^{\circledR}$, but it was not statistically significant.

• Restorative Dentistry and Endodontics
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• v.24 no.4
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• pp.628-632
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• 1999

Currently electronic apex locators have been widely used to determine working length in endodontic treatment. According to Manufacture's recommendation, it is beneficial to find the working length before instrumenting the canal. However, in crown-down pressureless technique, working length of tooth is established following coronal instrumentation 3mm short of radiographic apex. In narrow canals, mechanically formed constriction might be established by coronal instrumentation in some distance from anatomical constriction. The purpose of this study was to evaluate the accuracy of Root-ZX in the canal with mechanical constriction following considerable coronal enlargement with ProFile .06 series. The 40 root canals in 30 extracted mandibular molars were accessed, and their actual length (AL) established by passing a size 10 file just through the minor apical foramen. The teeth were then embedded in an acrylic container with normal saline. The initial canal length(IL) was measured with Root-ZX by negotiating a size 10 file to the apical constriction. The canal was sequentially enlarged to size 40 with ProFile .06 file 3mm short of actual length. The enlarged final canal lengths (FL) were obtained with a size 15 file. The average values of IL, FL were calculated and compared using Repeated measures Analysis of Variance followed Turkey's Studentized Range test. The results were obtained as follows: 1. The initial canal length was 0.12mm shorter than actual canal length(P>0.05). 2. The differences between initial canal length and final canal length were not significant(P>0.05). 3. As a result of this study, regardless of mechanically formed constriction. Root-ZX differentiated between mechanical and anatomic constriction.

• Restorative Dentistry and Endodontics
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• v.31 no.1
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• pp.66-71
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• 2006

To evaluate the ratio of gutta-percha area in the canal after canal obturation with Continuous Wave of Condensation Technique (CWCT) with varying depths of plugger penetration, forty root canals of extracted human teeth were prepared up to size 40 of 0.06 taper with $ProFile^{(R)}$. Canals of three groups were filled with CWCT with System $B^{TM}$ (Analytic Tech. , USA) and different plugger penetration depths of 3, 5, or 7 mm from the apex. Canals of one group were filled with lateral condensation technique as a control The felled teeth were cross-sectioned at 1, 2 and 3 mm levels from the apical foramen. The ratio of gutta-percha area in the canal was analyzed using $Auto^{(R)}$ Cad 2000. Data were analyzed with one-way ANOVA and Duncan's multiple range test. At all levels, higher gutta-percha area ratio was found with deeper plugger penetration depth in CWCT, and cold lateral condensation group showed higher ratio than group of plugger penetration to apical 7 mm in CWCT. At apical 1 mm and 2 mm levels, group of plugger penetration to apical 3 mm showed significantly high or gutta-percha area ratio than those of apical 7 mm and lateral condensation (p<0.05). It is concluded therefore that, under the conditions of the present study, deeper plugger penetration depth results in more favorable and efficient obturation in CWCT.

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.371-376
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• 2009

We evaluated in vitro microleakage of Mineral Trioxide Aggregate (MTA) powder with 4-methacryloxyethyl trimellitate anhydride (4-META) / methyl methacrylate (MMA) & tri-n-butylborane (TBB) resin as a retrograde filling material by using methylene blue dye method. Fifty-two single rooted, extracted teeth were instrumented and obturated with gutta percha and AH plus sealer. The apical 3mm of each root was resected and 3mm deep ultrasonic root end preparation was done. External surface of roots was coated with nail varnish. Prepared teeth were randomly divided into five groups; Negative control: completely covered with nail varnish; Positive control: coated with nail varnish except for apical foramen; Group 1 (retrofilled with Portland cement); Group 2 (retrofilled with MTA); Group 3 (retrofilled with MTA powder mixed with 4-META/MMA & TBB resin). Immediately after completion of root-end filling, all specimens were submerged in methylene blue dye for 72 hours in $37^{\circ}C$incubator. The roots were longitudinally sectioned and measured for extent of dye penetration by three different examiners under microscope (${\times}$10). The results were statistically analyzed using one way ANOVA and Turkey's HSD test. No leakage was evident in negative control and complete leakage in positive control group. Group 3 showed significantly less leakage than group 1 and 2 (p < 0.01). There was no significant difference between group 1 and 2 (p > 0.01). It was concluded that MTA powder with 4-META/MMA & TBB resin was excellent in reducing initial apical microleakage.

• Restorative Dentistry and Endodontics
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• v.31 no.5
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• pp.390-397
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• 2006

The purpose of this study was to evaluate the accuracy and the consistency of four different electronic apex locators in an in vitro model. Fourty extracted premolars were used for the study. Four electronic apex locators (EAL) were Root ZX, Smarpex, Elements Diagnostic Unit (EDU), and E-Magic Finder Deluxe (EMF). After access preparation, the teeth were embedded in an alginate model and the length measurements were carried out at '0.5' and 'Apex' mark using four EALs. The file was cemented at the location of the manufacturers' instruction (Root ZX, EDU, EMF: 0.5 mark, SmarPex: Apex mark). The apical 4mm of the apex was exposed and the distance from the file tip to the major foramen was measured by Image ProPlus (${\times}100$). The distance from the file tip to the major foramen was calculated at 0.5 and Apex mark and the consistency of 0.5 and Apex mark was compared by SD and Quartile of Box plots. In this study, Root ZX and EMF located the apical constriction accurately within ${\pm}0.5 mm$ in 100%, whereas SmarPex and EDU located in 90% and in 70% respectively. For Root ZX and EMF, there was no significant difference between the consistency of 0.5 and Apex mark. However, for the EDU and SmarPex, Apex mark was more consistent than 0.5 mark. From the evaluation of the consistency in this study, for Root ZX and EMF, both 0.5 and Apex mark can be used as a standard mark. And for EDU and SmarPex, the Apex mark can be recommended to be used as a standard mark.