• Restorative Dentistry and Endodontics
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• v.47 no.2
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• pp.19.1-19.15
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• 2022

Objectives: The aim of this study was to evaluate and compare the apical constriction (AC) and apical canal morphology of maxillary first and second molars, using micro-computed tomography (micro-CT). Materials and Methods: The anatomical features of 313 root canals from 41 maxillary first molars and 57 maxillary second molars of patients with known age and sex were evaluated using micro-CT, with a resolution of 26.7 ㎛. The factors evaluated were the presence or absence of AC, the morphotypes, bucco-lingual dimension, mesio-distal dimension, and the profile (shape) of AC and the apical root canal. The apical root canal dimensions, location of the apical foramen (AF), AC to AF distance, and presence of accessory canals in the apical 5 mm were also assessed. Descriptive and analytical statistics were used for data evaluation. Results: AC was present in all 313 root canals. Patients' age and sex did not significantly impact either AC or the apical canal dimensions. The most common AC morphotype detected was the traditional (single) constriction (52%), followed by the parallel (29%) morphotype. The mean AC dimensions in maxillary first molars were not significantly different from those in maxillary second molars. Sixty percent of AF were located within 0.5 mm from the anatomic apex. Conclusions: The most common morphotype of AC detected was the traditional constriction. Neither patients' age nor sex had a significant impact on the dimensions of the AC or the apical root canal. The majority of AF (60%) were located within 0.5 mm from the anatomic apex.

• 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.24 no.4
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• pp.578-584
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• 1999

The purpose of this experiment was to determine: (1) the safe automatic apical reverse setting that prevents overinstrumentation of the root canal, using Tri Auto ZX$^{(R)}$ and (2) the effect of various irrigant on such instrumentation. The instrumentation was carried out with the automatic apical reverse setting of 0.5, 1.0, 1.5, and 2.0. The root canal irrigants used in usual manner were normal saline(0.9%), NaOCl(2.5%), and RC Prep$^{(R)}$. For each reverse setting and each irrigant, ten teeth were used with the total of 120 teeth. The distance between the file tip and the apical constriction was determined by stereomicroscope using the point that the file began to rotate in reverse direction. When the reverse setting mode was set to 0.5, 18 of 30 were overinstrumented. If these were discriminated by irrigant, 10 of 6 with 0.9% saline, 10 of 6 with NaOCl, and 10 of 6 with RC Prep$^{(R)}$ has the file tip located 0.57${\pm}$0.30mm, 0.73${\pm}$0.39mm, and 0.26${\pm}$0.25mm beyond the apical constriction respectively. In 1.0 setting 15 of 29 were over the apical constriction, and the distribution was 6 in saline, 5 in NaOCl, and 4 in RC Prep$^{(R)}$. The mean distance over the apical constriction was 0.28${\pm}$0.13mm with saline, 0.75${\pm}$0.61mm with NaOCl, and 0.25${\pm}$0.17mm with RC Prep$^{(R)}$. When the autoatic reverse mode was set to 1.5, and 2.0, 5, and 1 teeth were found to be overinstrumented in respective settings. But there were large variations in overinstrumented distances when an attempt was made to compare the effect of irrigants on this overinstrumentations and they were meaningless for the small sample size. When all of the autoreverse setting were combined to compare the number of overinstrumented teeth with each irrigant, there were no significant differences (14 for normal saline, 12 for NaOCl, 13 for RC Prep$^{(R)}$). When 0.5 or 1.0 automatic apical reverse setting mode was used the Tri Auto ZX$^{(R)}$ in clinical application, the possibility of overinstrumentation beyond the apical constriction exists in 55.9% of cases. Therefore 1.5 or 2.0 setting is safer for the preparation inside the canal but this type setting needs additional apical hand preparation of the root canal because the accuracy is lower than 0.5 or 1.0 setting.

• Restorative Dentistry and Endodontics
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• v.37 no.2
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• pp.68-73
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• 2012

Objectives: The purpose of this study was to assess the accuracy of Root ZX (J. Morita Corp.) according to the location of major foramen and open apex. Materials and Methods: 81 mandibular premolars with mature apices were selected. After access preparation, 27 teeth were instrumented to simulate open apices. 54 teeth were classified according to location of major foramen under surgical microscope (${\times}16$). The file was fixed at the location of apical constriction by Root ZX using glass ionomer cement .The apical 4 mm of the apex was exposed and photo was taken and the distance from file tip to the major foramen was measured by calibrating metal ruler on graph paper. The results were statistically analyzed using ANOVA and Scheffe test at p < 0.05 level. Results: Mean distance from file tip to major foramen was 0.308 mm in Tip foramen group (I), 0.519 mm in Lateral foramen group (II) and 0.932 mm in open apex group (III). Root ZX located apical constriction accurately within ${\pm}0.5mm$ in group I of 85.71%, in group II of 59.09%, and in group III of 33.33%. There was a statistically significant difference between group I and III (p < 0.05). Conclusion: Root ZX located apical constriction accurately regardless of location of major foramen. However, Root ZX couldn't find it in open apex. Clinicians have to use a combination of methods to determine an appropriate working length at open apex. It may be more successful than relying on just electronic apex locator.

• Restorative Dentistry and Endodontics
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• v.37 no.1
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• pp.24-28
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• 2012

Objectives: The aim of this study was to test the hypothesis, that the effectiveness of irrigation in removing smear layer in the apical third of root canal system is dependent on the depth of placement of the irrigation needle into the root canal and the enlargement size of the canal. Materials and Methods: Eighty sound human lower incisors were divided into eight groups according to the enlargement size (#25, #30, #35 and #40) and the needle penetration depth (3 mm from working length, WL-3 mm and 9 mm from working length, WL-9 mm). Each canal was enlarged to working length with Profile.06 Rotary Ni-Ti files and irrigated with 5.25% NaOCl. Then, each canal received a final irrigation with 3 mL of 3% EDTA for 4 min, followed by 5 mL of 5.25% NaOCl at different level (WL-3 mm and WL-9 mm) from working length. Each specimen was prepared for the scanning electron microscope (SEM). Photographs of the 3mm area from the apical constriction of each canal with a magnification of ${\times}250$, ${\times}500$, ${\times}1,000$, ${\times}2,500$ were taken for the final evaluation. Results: Removal of smear layer in WL-3 mm group showed a significantly different effect when the canal was enlarged to larger than #30. There was a significant difference in removing apical smear layer between the needle penetration depth of WL-3 mm and WL-9 mm. Conclusions: Removal of smear layer from the apical portion of root canals was effectively accomplished with apical instrumentation to #35/40 06 taper file and 3 mm needle penetration from the working length.

• The Journal of the Korean dental association
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• v.54 no.8
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• pp.658-665
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• 2016

Treatment of immature permanent teeth with irreversibly damaged pulp has been challenging in dental practice because of the lack of apical constriction, thin dentinal walls, and short roots. This may lead to the extrusion of filling materials, and fracture of the root due to its more fragile feature during shaping of the root canal. Apexification with calcium hydroxide or MTA is one of the treatment options for these cases. Although favorable results of apexification have been reported, these treatment procedures do not guarantee the increase of root length and/or width even after a long term period. Thus, treated teeth are still prone to fractures. Recently, pulp revascularization has been proposed as an alternative treatment for immature teeth with necrotic pulp and periapical pathosis. Pulp revascularization allows the stimulation of the apical development and the root maturation. There have been many treatment protocols using various materials such as antibiotics and calcium hydroxide medicament. In this case report, literature review about pulp revascularization and two related cases are presented.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.150-160
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• 1996

The present study was to evaluate the accuracy of the frequency dependent type apex locator, Root-ZX. The subjects included 505 root canals of 238 teeth treated by the Department of Conservative Dentistry, and 22 human premolars which were schduled to be extracted for the orthodontic reasons. The results were as follows ; 1. The working lengths determined by Root-ZX were compared with radiographic readings. Of the total 505 root canals, 66 % showed coincidence within ${\pm}0.5mm$ and the average readings of Root-ZX were $0.13mm{\pm}1.05$ longer than those of radiographic readings. 2. The length difference between the file tip determined by Root-ZX and the apical constriction in extracted teeth were measured. Of the total 24 root canals, 70.8 % showed coincidence within ${\pm}0.5mm$ and the average readings of Root-ZX were $0.12mm{\pm}0.50$beyond the apical constriction. 3. The vitality of the teeth did not show any statistical difference(p>0.05) in the accuracy of the Root-ZX readings. The presence of the periapical lesions, however, significantly lowered the percentage of ${\pm}0.5mm$ accuracy in Root-ZX measurements.(p<0.05). In the presence of periapical lesions, the percentage within ${\pm}0.5mm$ was significantly lower.

• Journal of Chest Surgery
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• v.50 no.1
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• pp.22-29
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• 2017

Background: The aim of this study was to analyze the preoperative attributes and clinical impacts of complete pericardiectomy in chronic constrictive pericarditis. Methods: A total of 26 patients were treated from January 2001 to December 2013. The pericardium was resected as widely as possible. When excessive bleeding or hemodynamic instability occurred intraoperatively, a cardiopulmonary bypass (CPB; n=3, 11.5%) or an apical suction device (n=8, 30.8%) was used. Patients were divided into 2 groups: those who underwent ${\geq}80%$ resection of the pericardium (group A, n=18) and those who underwent <80% resection of the pericardium (group B, n=8). Results: The frequency of CPB use was not significantly different between groups A and B (n=2, 11.1% vs. n=1, 12.5%; p=1.000). However, the apical suction device was more frequently applied in group A than group B (n=8, 30.8% vs. n=0, 0.0%; p=0.031). The postoperative New York Heart Association functional classification improved more in group A (p=0.030). Long-term follow-up echocardiography also showed a lower frequency of unresolved constriction in group A than in group B (n=1, 5.60% vs. n=5, 62.5%; p=0.008). Conclusion: Patients with chronic constrictive pericarditis demonstrated symptomatic improvement through complete pericardiectomy. Aggressive resection of the pericardium may correct constrictive physiology and an apical suction device can facilitate the approach to the posterolateral aspect of the left ventricle and atrioventricular groove area without the aid of CPB.

• Korean Journal of Dental Materials
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• v.45 no.4
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• pp.275-286
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• 2018

The purpose of this study was to evaluate the effect of needle tip design and position, and irrigant flow rate on apical pressure (AP) during root canal irrigation. Five human mandibular premolars were instrumented up to #35 (0.06 taper) using nickel-titanium rotary instruments. Three different needles according to change of needle tip design (notched, side-vented, and flat) were positioned at the point of 1, 3, and 5 mm from the apical constriction (needle tip position). For each needle tip design and position, APs were measured with varying flow rates of 0.05, 0.1, 0.2, and 0.3 ml/s. When the other conditions were controlled, AP increased with decreasing needle tip position or increasing irrigant flow rate (p<0.05). The AP of flat needle was the highest, followed by notched, side-vented needle for the same needle tip position and irrigant flow rate. The APs at needle tip position of 1 mm or with more than 0.1 ml/s flow rate were higher than central venous pressure (5.88 mmHg) for all conditions. Flat needle was not recommended for clinical use due to sharp increase of AP with changing needle tip position and irrigant flow rate. For safe and effective root canal irrigation, irrigant should be applied with the needle tip position of 3 mm and flow rate of less than 0.05 ml/s.

• 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.