• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.66-75
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• 2008

This study examined the influence of the apical sizes on the sealing ability of a root canal filling. Thirty-six single rooted teeth with a single canal were divided into 3 groups (n = 12) and instrumented with either the $Profile^{(R)}$ or $LightSpeed^{(R)}$ system to achieve three different apical sizes (master apical file [MAF] of #25, #40, or #60). The teeth were filled with gutta perch a using a modified continuous wave technique. The level of microleakage was determined by immersing ten teeth from each group into India ink for 1 week followed by clearing with nitric acid, ethyl-alcohol, and methylsalicylate. The microleakage was measured using vernier calipers. The data was analyzed statistically using Kruskal-Wallis one-way ANOVA and a Student-Newman-Keuls Method. Two teeth from each group were sectioned horizontally at 1, 2, 3 and 4 mm from the apex in order to observe a cross section. The apical size was significantly (p < .05) influenced the level of microleakage. In the Student-Newman-Deuls Method, MAF sizes of #25 and #40; and MAF sizes of #25 and #60, respectively showed a statistically significant difference. There was no significant difference between #40 and #60. In most cross sections, oval-shaped canals were observed, and the irregularity of the internal surface increased with decreasing apical size. There was also an increase in the area of recess, which is the area where the canal space is not filled with either gutta-percha or sealer. When the root canals are filled using a modified continuous wave technique, canal filling with more consistent and predictable outcome may be expected as the apical preparation size is increased.

• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.189-197
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• 1989

The purpose of this study was to observe the resulting canal shape after using hand, sonic and ultrasonic instrumentation. Thirty canals from extracted human upper or lower 1st and 2nd molars were divided into 3 groups: hand, sonic and ultrasonic instrumentation group. 10 canals of each group were individually prepared with one of three instrumentation methods. After instrumentation and histological processing, apical, middle and coronal third cross sections were examined on the roundness of the canal by microscope. The result were as follows. 1. All experimented groups showed no significant difference in canal roundness regardless of size and level of the canal. 2. Sonic air instrumentation groups revealed Significantly better canal roundness than ultrasonic groups at the middle third of the fine canal. 3. In ultrasonic instrumentation groups, the roundness of the large canal was significantly better than that of fine canal.

• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.137-144
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• 2009

The aim of this study was to investigate the shapes and diameters of the physiological foramen and anatomy of the root canal at 3mm from apex in mandibular first molars. Sixty mandibular first molars were randomly selected. The apical anatomy of 60 mandibular first molars was investigated by means of a stereo microscope (60x magnification). The results were as follows; 1. There was a high percentage of two physiological foramina in mesial (61.67%) and one foramen in distal(71.66%) roots of mandibular first molars. 2. There was a high frequency of accessory foramina in mesial roots with one foramen (26.07%). 3. The diameters of physiological foramen was as follows: - 0.329mm in single mesial foramen - 0.266mm in mesiobuccal foramen and 0.246mm in mesiolingual foramen - 0.375mm in single distal foramen - 0.291mm in distobuccal foramen and 0.237mm in distolingual foramen 4. The most common physiological foramen shape was oval (69.93%). 5. The incidence of isthmus in mesial root at 3mm from apex was 55%. The 3mm-sections contained a complete isthmus 31.66% and a partial isthmus 23.34%. 6. 3mm from the apex, the most common canal shape was oval (50.64%). Knowledge of the apical anatomy of mandibular first molar would be necessary for success of surgical and nonsurgical endodontic treatment.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.495-500
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• 2004

Dens invaginatus is a malformation of tooth resulting from an infolding of the enamel epithelium during tooth development. This malformation shows a broad spectrum of morphologic variations. This invagination frequently allows the entry of irritants and microorganism, which usually lead to necrosis of the adjacent pulp tissue and then to periapical or periodontal abscess. Root canal treatment of such tooth is often difficult because of the un usual form and complicated pulpal space. This article reports 2 cases of dens invaginatus in maxillary lateral incisors. The first case was successfully treated with $Ca(OH)_2$. In the second case, involved tooth was extracted and this extracted tooth was observed using the micro-computed tomography.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.536-545
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• 1997

The purposes of this study were to evaluate the degree of cavity cleanliness and to observe cavity wall morphology when root-end retrograde cavity preparation was done with ultrasonics. Root resections were done on 20 extracted human maxillary central incisors after canal filling with gutta-percha, and retrocavities were prepared using a slow-speed round bur as a control, and stainless steel ultrasonic tips of power settings of 2 and 6 ($Miniendo^{TM}$, EIE, SA, USA) as experimentals. The degree of the remaining cavity debris and smear layer, and wall morphology were evaluated under the scanning electron microscope. The results were as follows : Cavity prepared with ultrasonics of either power setting showed significantly less smear layer than did slow-speed preparations (p<0.01). However, there was no significant difference in canal debris (p<0.05). Cavity prepared with ultrasonics showed hatcheted appearance of wall, while slow-speed preparation showed relatively plain one.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.2
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• pp.139-145
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• 2002

In a primary teeth, dental caries is rapidly advanced the pulp disease, because the primary teeth have the thinner and the weaker enamel layer and the wider pulp chamber than relatively the permanent teeth. And the pulps of primary teeth are exposed during caries removal or even they are exposed by unexpected movement of the children or by trauma. For successive pulp treatment in primary teeth, it is necessary to understand completely about multiple canal morphology, variation of root canal anatomy and specific problem related to root formation and resorption of primary teeth. In upper primary molar, canal configuration of mesial root has the most variation same as upper molar. If not canal treatment is completely, most of all endodontic treatment should be failed. In a clinical case report, upper primary molars existed persistent pain or bleeding during treatment were founded the second MB canal and were performed the endodontic treatment of theirs. As a result, the upper primary molars have no symptom and good prognosis. In the examination of extracted upper primary molar, we found that 8 of 35 teeth(22.8%) in the upper primary first molars and 22 of 33 teeth(66.6%) in the upper primary second molar had the second mesiobuccal canal. It has revealed the high prevalence of two canals in mesiobuccal roots of upper primary molars. The frequency of occurrence of the second mesiobuccal canal must be taken into consideration when endodontic treatment is planned and as a possible cause of otherwise un explained failure.

• Restorative Dentistry and Endodontics
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• v.35 no.2
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• pp.88-95
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• 2010

The purpose of this study was to compare the root canal shaping ability of 4 rotary NiTi instruments in simulated root canals. For the preparation of thirty two curved root canals, Mtwo instruments using "single length"technique, and Profile, ProTaper Universal, and K3 using crown-down technique (N = 8) were used. All canal samples were prepared by reaching an apical canal size of #30. Pre- and post-instrumentation digital images were recorded and an assessment of canal shape was determined using a computer image analysis program SigmaScan Pro (Systat Software Inc., San Jose, CA, USA). The changes of the dimension of inner walls of canals, (2) the changes of the dimension of outer walls of canals, and (3) the centering ratio were measured at 7 measuring points, and then data were statistically analyzed using one-way ANOVA and Duncan's test. The results were as below; 1. The root canal shaping ability of Profile was significantly faster than that of other rotary NiTi instruments (p < 0.05). 2. The deformation and fracture of all instruments used for this study were not experienced. 3. In the degree of changes of the dimension of inner walls of canals, Profile demonstrated the lowest changes of the dimension of inner walls of canals except at the measuring points of the 1 and 2 mm (p < 0.05). However, the ProTaper Universal showed the highest changes of the dimension of inner walls of canals at all measuring points (p < 0.05). 4. In the degree of changes of the dimension of outer walls of canals, Mtwo demonstrated the lowest changse of the dimension of outer walls of canals except at the measuring point of the 1 mm (p < 0.05). However, Profile exhibited the highest changes of the dimension of outer walls of canals at the measuring points of 3 and 4 mm and ProTaper Universal and K3 showed the largest changes of the dimension of outer walls of canals at the measuring points of 1, 2, 6, and 7 mm (p < 0.05). 5. In degree of centering ratio, Profile demonstrated the least centering ratio comparing with the centering ratio shown by other NiTi instruments at the measuring points of 1, 4, 5, and 6 mm. Results suggest that in the coronal part of canal preparation, active cutting files such as ProTaper Universal may efficiently flare the canal orifice and form a better taper, and in the apical part of the canal, files which have a better centering ability such as Profile may maintain the original canal curvature and reduce the shaping time.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.317-322
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• 1999

Dens invaginatus is a developmental anomaly resulting from an invagination of the enamel organ. The incidence is highest with maxillary permanent lateral incisors. The reported occurrence ranges from 0.04 to 10%. This anomaly may involve the pulp and periapical tissues and cause pulpal inflammation, loss of vitality, apical and lateral periodontitis, periapical abscesses and cysts and stimulate internal resorption. Oehlers describes dens invaginatus as occurrence in three forms. In treating type 3 invaginatus, treatment strategy can be determined by considering the complexity and accessibility of invagination. In this case, showing simple invagination, it could be treated by simple endodontic treament confining to invagination without loss of vitality of tooth. After treatment of the present case, the results were as follows: 1. In type 3 dens invagiantus, if the tooth is vital and there is no evidence of communicating between invagination and pulp, we can save the vitality of the tooth and resolve the lesion by endodontic treament confining to the invagination. 2. In the invagination with opened apex, the closure of apex can be induced by apexification procedure doing this, we can avoid the neccessity of surgical intervention.

• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.577-586
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• 2002

The purpose of this in vitro study was to compare the effects of root canal cleanness following two Ni-Ti rotary instruments with different rake angle. Thirty-six sound, extracted human premolars with single root were randomly divided into three groups. The used rotary instruments were HEROShaper (Group 1, Micro-Mega, Besancon, France, n=12) and ProFile (Group 2, Maillefer, Ballaigues, Switzerland, n=12). Control group (n=12) was only extirpated with barbed broach (Mani, Matsutani Seisakusho Co., Japan) Group 1 & 2 teeth were prepared to a #40/.04 taper at the apex followed by 1 mm using crown-down technique. After canal preparation and frequent irrigation with 5.25% sodium hypochlorite, the roots split longitudinally into a bucco-lingual direction. Root halves were cross-sectioned in apical third portion again. All root specimens were processed for SEM investigation and photographed. Separate evaluations by one endodontist were undertaken for smear layer on prepared walls with a five score-index for each using reference photograph in root halves. The penetration depth of smear layer into dentinal tubules was also estimated in the other halves. Following results were obtained: 1. Smear layer was observed on all the prepared walls with two experimental groups except control group. 2. Smear layer characteristics in two experimental groups; 1) HEROShaper group showed snowy, dusty appearance and were shown open dentinal tubuli on the prepared walls of almost specimens, and the thickness of smear layer covering onto dentinal surfaces was within 1-2 ${\mu}m$ in a few specimens. 2) ProFile group showed shiny, burnished appearance and complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli in all specimens. The penetration of smear layer into dentinal tubules was found in all specimens and the thickness was at 2-4 ${\mu}m$ in all specimens. These results demonstrated that a completely clean root canal could not be achieved regardless of positive or negative rake angle, which is in accordance with the majority of previous studies on root canal cleanliness In conclusion, through irrigation with antibacterial solutions or chelating agents is recommended to remove the smear layer on prepared canal wall in spite of Ni-Ti instrumentation.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.97-105
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• 2017

Purpose: The purpose of this study was comparing the efficacy of passive irrigation (PI) and passive ultrasonic irrigation (PUI) for ability to remove debriment of canals. Materials and Methods: Mandibular premolars were decoronated and standardized to 16 mm length. After root canal enlargement and half separating longitudinally, standardized groove of 4 mm length, 0.2 mm width and 0.5 mm depth were formed on the dentin wall of one half. Three depressions in the canal wall of the opposite half, 0.3 mm in diameter and 0.5 mm in depth, were formed. After each groove and depression was filled with dentin debris, two sections of each half were reassembled using impression putty material. In group 1 the canals were irrigated with 2.5% NaOCl by PI. In group 2 the canals were irrigated with 2.5% NaOCl by PUI. Before and after root canal irrigation, the root canal wall of the section was taken with a microscope and a digital camera as images. The amount of dentin debris remaining in grooves and depressions was assessed using a scoring system. Results: There was no significant difference between PI and PUI except for the middle 1/3 of the root canal (P = 0.004). Conclusion: At the middle 1/3 of the root canal, PUI removed more dentine debris than PI. But the removal efficiency of dentin debris is not significantly different between the PUI and PI at the apical area of root canal in mandibular premolars.