• Imaging Science in Dentistry
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• v.43 no.2
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• pp.123-128
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• 2013

Double tooth is a dental anomaly consequent to fusion of two or more teeth or gemination of a single tooth. This report describes a unique case of double tooth in relation to a mandibular lateral incisor exhibiting the presence of four root canals. The role of conventional radiography and advanced three-dimensional imaging techniques in the better assessment of complex root canal systems and their aid in endodontic management has also been highlighted.

• 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.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.557-557
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• 2003

I. Objectives The purpose of this study was to evaluate the ratio of gutta-percha area in the canal after canal obturation with Continuous Wave of Condensation Technique with varying depths of plugger penetration. II. Materials and Methods Forty extracted human teeth with single canal were divided into four group of ten teeth each. Root canals were prepared up to size 40 of 0.06 taper with $ProFile^{\circledR}$. After drying, canals of three groups were filled with Continuous Wave of Condensation Technique with System $B^{TM}$ and different plugger penetration depths of 3, 5, and 7mm from the apex.(omitted)

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.600-600
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• 2003

I. Objectives Effective endodontic obturation must provide a complete, three-dimensional filling of the root canal system, preventing the communication of fluids between root canal and surrounding periapical tissues. The objective of this study was to compare the apical leakage with or without the use of dentin adhesive system. II. Materials and Methods Forth extracted human teeth with single canals were decoronated. Root canals were instrumented using GT rotary files and Profile .04 file up to #40, 1mm short of the apex. After each instrumentation, copious irrigation with 5.25% sodium hypochlorite solution and confirmation of apical patency were performed.(omitted)

• Restorative Dentistry and Endodontics
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• v.30 no.3
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• pp.184-192
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• 2005

Intracanal separation of the rotary files is a serious concern in modern endodontic practice. The objective of this study was to compare the life span and fracture patterns of three NiTi rotary files in molar teeth Mesiobuccal roots of upper molar (n = 150) and mesial roots of lower molar (n = 150) were divided into three groups and each group was prepared with Profile, ProTaper, and K3 respectively. Every file was used until separation and/or deterioration of the cutting blade was happened, and then the number of canals to separation and/or unwinding were recorded. Radiographs and Scanning electon microscope (SEM) photographs were taken to evaluate the patterns of separation. The results were as follows: 1. There were no significant differences in numbers of canals to separation and/or unwinding among the groups. 2. Comparing between flaring files, K3 showed significant lower numbers of canals to separation and/or unwinding (p < 0.05), and there was no significant difference between shaping files 3. Separations of instruments were occurred at the midpoint of curvatures within the canals 4. In SEM observations, ductile fractures were seen in most of cases, characterized by shallow dimples. Additional researches is needed to provide a new guideline that informs the appropriate number of times to use NiTi files.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.22 no.1
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• pp.149-160
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• 1992

The purpose of this study was to localize the inferior alveolar canals in relation to the root apices of the mandibular third molars, according to their positions and degrees of impaction using vertical tube shift technique. One hundred three mandibular third molars, from 95 persons consisted of 57 males and 38 females, were clinically and radiographically investigated. The mandibular third molars had no pericoronitis and periapical lesions, and showed an evidence of complete root formation. The obtained results were as follows: 1. In localiztion of the inferior alveolar canals in relation to the root apices of the mandibular third molars, the inferior alveolar canal was located at the buccal side of the root apices of mandibular third molar in 77.7%, below the root apices in 16.5%, and the lingual side of root apices in 5.8%. 2. The positions of the mandibular third molars according to the Winter's Classification were as follows; 36.9% in Class Ⅰ, 21.3% in Class Ⅱ, 14.7% in Class Ⅲ, 4.8% in Class Ⅳ, 1.9% in Class Ⅴ, 17.5% in Class Ⅵ, 2.9% in Class Ⅶ. In localization of the inferior alveolar canals in relation to the root apices of the mandibular third molars according to the Winter's Classification, 92.1 % of Class Ⅰ, 86.4% of Class Ⅱ, 80.0% of Class Ⅲ, and 100.0% of Class Ⅳ and Ⅴ were located at the buccal side. In Class Ⅵ, however, 33.3% was located at the buccal side, 44.5% below the root apices, and 22.2% at the lingual side. 3. The degree of impaction was revealed to be 53.4% in Degree Ⅰ, 36.9% in Degree Ⅱ, and 9.7% in Degree Ⅲ. In localization of the inferior alveolar canals in relation to the root apices of mandibular third molars according to degree of impaction, 98.2% of Degree Ⅰ was located at the buccal side. In Degree Ⅱ, 60.5% was located at the bucal side, 31.6% below the root apices, and 7.9% at the lingual side. In Degree Ⅲ, 30.0% was located at the buccal side, 40.0% below the root apices, and 30.0% at the lingual side.

• Restorative Dentistry and Endodontics
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• v.31 no.2
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• pp.113-118
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• 2006

The aim of this study was to evaluate the ability of newly marketed NRT instruments to maintain the original root canal configuration and curvature during preparation in comparison with the three existing instruments in simulated root canals. Simulated canals in resin blocks were prepared with ProFile. K3, ProTaper and NRT instrument (n = 10 canals in each case). Pre- and post-operative images were recorded, and assessment of canal shape was completed with a computer image analysis program. The data were analyzed statistically using the One-way ANOVA followed by Duncan s test. The ability or instruments to remain centered in prepared canals at 1-, 2-mm levels was significantly better in ProFile groups than in other groups (p < 0.05). The change of centering ratio in NRT groups at 5-mm level was significantly greater than ProFile group and at 6- and 7-mm level than all other groups (p < 0.05). Although the NRT system was comparable to other systems in regards to its ability to maintain the canal configuration of apical portion, this system was more influenced by the mid-root curvature due to its stainless-steel files for coronal preflaring.

• The Korean Journal of Physiology
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• v.8 no.2
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• pp.1-17
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• 1974

This experiment was designed to explore the specific functional interrelations between the vestibular semicircular canals and the extraocular muscles which may disclose the neural organization, connecting the vestibular canals and each ocular motor nuclei in the brain system, for vestibuloocular reflex mechanism. In urethane anesthetized rabbits, a fine wire insulated except the cut cross section of its tip was inserted into the canals closely to the ampullary receptor organs through the minute holes provided on the osseous canal wall for monopolar stimulation of each canal nerve. All extraocular muscles of both eyes were ligated and cut at their insertio, and the isometric tension and EMG responses of the extraocular muscles to the vestibular canal nerve stimulation were recorded by means of a physiographic recorder. Upon stimulation of the semicircular canal nerve, direction if the eye movement was also observed. The experimental results were as follows. 1) Single canal nerve stimulation with high frequency square waves (240 cps, 0. 1 msec) caused excitation of three extraocular muscles and inhibition of remaining three muscles in the bilateral eyes; stimulation of any canal nerve of a unilateral labyrinth caused excitation (contraction) of the superior rectus, superior oblique and medial rectus muscles and inhibition (relaxation) of the inferior rectus, inferior oblique and lateral rectos muscles in the ipsilateral eye, and it caused the opposite events in the contralateral eye. 2) By the overlapped stimulation of triple canal nerves of a unilateral labyrinth, unidirectional (excitatory or inhibitory) summation of the individual canal effects on a given extraocular muscles was demonstrated, and this indicates that three different canals of a unilateral vestibular system exert similar effect on a given extraocular muscles. 3) Based on the above experimental evidences, a simple rule by which one can define the vestibular excitatory and inhibitory input sources to all the extraocular muscles is proposed; the superior rectus, superior oblique and medial rectus muscles receive excitatory impulses from the ipsilateral vestibular canals, and the inferior rectus, inferior oblique and lateral rectus muscles from the contralateral canals; the opposite relationship applies for vestibular inhibitory impulses to the extraocular muscles. 4) According to the specific direction of the eye movements induced by the individual canal nerve stimulation, an extraocutar muscle exerting major role (a muscle of primary contraction) and two muscles of synergistic contraction could be differentiated in both eyes. 5) When these experimental results were compared to the well known observations of Cohen et al. (1964) made in the cats, extraocular muscles of primary contraction were the same but those of synergistic contraction were partially different. Moreover, the oblique muscle responses to each canal nerve excitation appeared to be all identical. However, the responnes of horizontal (medial and lateral) and vertical (superior and inferior) rectus muscles showed considerable differences. By critical analysis of these data, the author was able to locate theoretical contradictions in the observations of Cohen et al. but not in the author's results. 6) An attempt was also made to compare the functional observation of this experiment to the morphological findings of Carpenter and his associates obtained by degeneration experiments in the monkeys, and it was able to find some significant coincidence between there two works of different approach. In summary, the author has demonstrated that the well known observations of Cohen et al. on the vestibulo-ocular interrelation contain important experimental errors which can he proved by theoretical evaluation and substantiated by a series of experiments. Based on such experimental evidences, a new rule is proposed to define the interrelation between the vestibular canals and the extraocular muscles.

• Restorative Dentistry and Endodontics
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• v.41 no.1
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• pp.22-28
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• 2016

Objectives: The goal of this study was to compare the density of gutta-percha root fillings obturated with the following techniques: cold lateral (CL) compaction, ultrasonic lateral (UL) compaction, and warm vertical (WV) compaction. Materials and Methods: Thirty-three extracted mandibular first molars, with two separate mesial canals in each, were selected. After instrumentation, the canals were stratified into three groups based on canal length and curvature, and underwent obturation with one of the techniques. No sealer was used in order to avoid masking any voids. The teeth were imaged pre- and post-obturation using micro-computed tomography. The reconstructed three-dimensional images were analyzed volumetrically to determine the amount of gutta-percha present in every 2 mm segment of the canal. P values < 0.05 were considered to indicate statistical significance. Results: The overall mean volume fraction of gutta-percha was $68.51{\pm}6.75%$ for CL, $86.56{\pm}5.00%$ for UL, and $88.91{\pm}5.16%$ for WV. Significant differences were found between CL and UL and between CL and WV (p < 0.05), but not between UL and WV (p = 0.526). The gutta-percha density of the roots treated with WV and UL increased towards the coronal aspect, but this trend was not noted in the CL group. Conclusions: WV compaction and UL compaction produced a significantly denser gutta-percha root filling than CL compaction. The density of gutta-percha was observed to increase towards the coronal aspect when the former two techniques were used.

• Imaging Science in Dentistry
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• v.34 no.1
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• pp.7-12
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• 2004

Purpose: To investigate the anatomical structure of the incisive canal radiographically by a cone beam computed tomography. Materials and Methods: 38 persons (male 26, female 12) were chosen to take images of maxillary anterior region in dental CT mode using a cone beam computed tomography. The tube voltage were 65, 67, and 70kVp, the tube current was 7 mA, and the exposure time was 13.3 seconds. The FH plane of each person was parallel to the floor. The images were analysed on the CRT display. Results: The mean length of incisive canal was 15.87 mm±2.92. The mean diameter at the side of palate and nasal fossa were 3.49 mm±0.76 and 3.89 mm± 1.06, respectively. In the cross-sectional shape of incisive canal, 50% were round, 34.2% were ovoid, and 15.8% were lobulated. 87% of incisive canal at the side of nasal fossa have one canal, 10.4% have two canals, and 2.6% have three canals, but these canals were merged into one canal in the middle portion of palate. The mean angles of the long axis of incisive canal and central incisor to the FH plane were 110.3°±6.96 and 117.45°±7.41, respectively. The angles of the long axis of incisive canal and central incisor to the FH plane were least correlated (r= 0.258). Conclusion : This experiment suggests that a cone beam computed radiography will be helpful in surgery or implantation on the maxillary incisive area.