Chan-Young Lee

Polymerase Chain Reaction Identification of Microorganisms in Previously Root-Filled Teeth in a South Korean Population

A large body of evidence indicates that microorganisms are the primary causative agents of endodontic treatment failures. This study intended to assess the occurrence of nine putative endodontic pathogens in root-filled teeth associated with periradicular lesions in a South Korean population using a culture-independent molecular approach. Fourteen root-filled teeth with persistent periradicular diseases were selected for retreatment. After removal of the root canal filling, the canals were sampled, and a polymerase chain reaction assay using taxon-specific oligonucleotide primers was used for microbial detection. Bacteria were present in all cases, as revealed by amplification using ubiquitous 16S rDNA primers. The most frequently detected taxon was Enterococcus faecalis (64%), followed by Streptococcus spp. (21%) and Tannerella forsythensis (14%). The results of this study using a highly sensitive identification method are concurrent with those from other geographical locations using diverse identification methods in that E. faecalis is the main species found in cases of root-filled teeth associated with periradicular lesions.

Molecular Epidemiology and Association of Putative Pathogens in Root Canal Infection

The purpose of this study was to investigate the epidemiology of putative pathogens in root canals with apical periodontitis and to determine the associations among the putative pathogens. Eighteen symptomatic and 20 asymptomatic teeth from 36 subjects were studied. This research was performed with polymerase chain reaction and hybridization using rRNA-based oligonucleotide probes. The most frequently found species was Fusobacterium sp. (68.4%), followed by Peptostreptococcus micros (44.7%) and Porphyromonas gingivalis (26.3%). Sixteen teeth (42.1%) contained one or more species of the selected black-pigmented bacteria. Bacteroides forsythus and Treponema sp. were detected in 8 teeth and 6 teeth, respectively. Among the analyzed bacteria, significant relationships were shown in the combination of B. forsythus/P. gingivalis and Treponema sp./P. gingivalis. There was no significant association between any bacteria and any symptoms.

Prognostic factors for clinical outcomes in endodontic microsurgery: a retrospective study.

INTRODUCTION This retrospective study examined the potential prognostic factors on the outcome after endodontic microsurgery and compared the predictors of isolated endodontic lesion with those of both isolated endodontic lesions and endodontic-periodontal lesions. METHODS The data were collected from patients with a history of endodontic microsurgery performed between August 2004 and December 2008 and at least 1 year before being evaluated. Surgical procedures were performed by the endodontic faculty and residents. After surgery, an operation record form was made with the preoperative, intraoperative, and postoperative factors from the clinical and radiographic measures. For statistical analysis of the predisposing factors, the dependent variable was the dichotomous outcome (ie, success vs failure). RESULTS Of 907 cases, 491 were retained at follow-up. At the 0.05 level of significance, age, sex (female), tooth position (anterior), root-filling length (inadequate), [corrected] lesion type (endodontic lesion), root-end filling material (mineral trioxide aggregate and Super EBA; Harry J. Bosworth, Skokie, IL), and restoration at follow-up appeared to have a positive effect on the outcome. On the other hand, with an isolated endodontic lesion, the tooth position (anterior), root-filling length (inadequate), [corrected] and restoration at follow-up were significant factors at the 95% confidence level. CONCLUSIONS Under the control of the significant variables in logistic regression, the potential prognostic factors on the outcome were sex, tooth position, lesion type, and root-end filling material. On the other hand, the tooth position was a pure predictor of an endodontic lesion affecting the clinical outcome.

An in vivo comparison of working length determination by only root-ZX apex locator versus combining root-ZX apex locator with radiographs using a new impression technique

OBJECTIVE The objective of this study was to compare, in vivo, the accuracy of working length determination using only the Root-ZX electronic apex locator versus adjusting Root-ZX measurements after obtaining a working length radiograph. STUDY DESIGN The working length was determined in 25 premolar root canals using Root-ZX and K-files were fixed at these positions. Radiographs were acquired and interpreted, and the recorded working length measurement was adjusted, if necessary, for a combined measurement. The teeth were then extracted in an effort to determine the position of the file tip to the root canal constriction. On the basis of the position of the file tip to the apical foramen, polyvinylsiloxane impressions of the root apex were taken, or the root was imbedded in acrylic resin and ground in order to measure the position of the file tip to the apical constriction. RESULTS The Root-ZX alone detected the apical constriction within +/- 0.5 mm in 84% of the samples (21 of 25 canals). However, 96% (24 of 25 canals) were within this range when the combination of Root-ZX and radiographs was used. We noted no statistical significance between these 2 methods (P > .05). CONCLUSION Using a Root ZX Electronic Apex Locator combined with radiographs is recommended for the determination of working length, although there was no statistical significance between those 2 groups in this study.

Comparison of the cleaning efficacy of a new apical negative pressure irrigating system with conventional irrigation needles in the root canals

OBJECTIVES This study evaluated the efficacy of EndoVac system in comparison with that of a conventional needle irrigation method when the root canals were enlarged to various sizes. STUDY DESIGN Sixty-nine single-rooted teeth were divided into 3 groups according to the root canal irrigation system (24G and 30G needle and EndoVac). Each group was divided into 3 subgroups according to the MAF size (#25, #40, and #60). Four-micron-thick serial sections were prepared at 1.5 and 3.5 mm from the apical level and photographs were taken for the analysis. The influence of the irrigation system and apical size was evaluated using a 1-way ANOVA test and Tukeys test (P < .05). RESULTS At both levels, significant differences were detected between EndoVac system and conventional needle irrigation in removing debris (P < .05). The relationship between the MAF size and irrigation efficacy was found to have a positive relationship (P < .05). CONCLUSIONS EndoVac left significantly less debris behind than the conventional needle irrigation methods. Although all 3 irrigation methods resulted in clean root canals because the percentage occupied by remaining debris was very low in our specimens, larger apical instrumentation seemed to improve apical root canal debridement.

Periapical status related to the quality of coronal restorations and root fillings in a Korean population.

INTRODUCTION The purpose of this study was to assess the prevalence of apical periodontitis in root canal-treated teeth from the Korean population and to evaluate the relationship between the quality of root canal fillings and coronal restorations and the periapical status of these teeth. METHODS Full-mouth periapical radiographs at the Dental Hospital of Yonsei University, Seoul, South Korea, were examined. A total of 1030 endodontically treated teeth restored with full veneer crown-type restorations were evaluated by 2 independent examiners. Teeth were classified as healthy or diseased according to the periapical status. The quality of endodontic treatment and coronal restorations were also classified via radiographic and clinical evaluation. The data were analyzed using the chi-square test and logistic regression. RESULTS Forty-one percent of all endodontically treated teeth were classified as diseased. Approximately 35.6% of the teeth had endodontic treatments that were rated as adequate. The diseased teeth rate for cases with adequate endodontic treatment was 24.5%, which was significantly lower when compared with teeth with inadequate endodontic treatment (49.9%). The number of teeth with adequate coronal restorations was 706 (68.5%). Teeth with adequate coronal restorations had a significantly decreased prevalence of diseased teeth (34.7%) compared with teeth with inadequate coronal restorations (54.3%). Teeth with both adequate root fillings and restorations showed a significantly better outcome (82.3%) than the others, and teeth with both inadequate root fillings and restorations showed a significantly worse outcome (41.2%) than the others. CONCLUSIONS Data from this Korean population showed a relatively high prevalence of apical periodontitis. The quality of endodontic treatment and coronal restorations were of equal importance and were strong independent predictors of the periapical status.

Effect of different temperatures and penetration depths of a System B plugger in the filling of artificially created oval canals

OBJECTIVES The purpose of this study was to compare the gutta-percha-filled area in oval canals while varying the temperature and penetration depth of the System B plugger. STUDY DESIGN Seventy-five resin blocks, with artificially created oval canals, were obturated by using a continuous wave technique. In groups 1, 2, and 3, the plugger was introduced to a depth of 4 mm from the apex at set temperatures of 100, 200, and 350 degrees C, respectively. In group 4, the plugger was inserted to a depth of 2 mm from the apex at a set temperature of 200 degrees C. Group 5 was obturated in the same way as group 2, and then an additional cold plugging was performed to a depth of 3 mm from the apex. The cross sections of the obturated canals were photographed, and the percentage of the gutta-percha-filled area (PGP) was measured. RESULTS No significant differences were found between the 3 different temperature settings (P >.05). At 1 mm from the apex, group 4 showed the highest PGP (95.57% +/- 6.86), followed by group 5 (84.72% +/- 12.19), and group 2 (67.33 +/- 13.03) (P <.05). CONCLUSION In artificially created oval canals, plugger temperature within the range used in this study did not affect the PGP. However, the penetration depth of the plugger was significantly related to PGP.

Néel temperature of high Mn austenitic steels

The predictive equations for the Néel temperature (TN) of high Mn austenitic steels were reviewed and reevaluated using 116 different measured TN values. The previous equations gave good predictions for TN values of high Mn-low C austenitic steels, but not for those of medium and low Mn-high C austenitic steels, including TWIP steels with less than 20 at.% Mn. Therefore, an improved TN equation for medium and low Mn-high C as well as high Mn-low C was newly suggested. To improve the accuracy of the new equation, especially for high C TWIP steels, the TN values of three different high C TWIP steels were experimentally measured using a superconducting quantum interference device (SQUID) because there are few measured TN values of high C TWIP steels in the literature.

In vivo quantitative evaluation of live and dead bacteria in root canal infection by using propidium monoazide with real-time PCR.

INTRODUCTION For selective detection of viable bacteria with molecular methods, propidium monoazide (PMA) treatment has been successfully applied to a wide range of bacteria. The purpose of this study was to compare the quantity of live cells with the total amounts of both live and dead cells before and after chemomechanical preparation by using PMA in combination with real-time polymerase chain reaction (qPCR). METHODS Twenty-one teeth with pulp necrosis and a periapical lesion were included. Bacterial sampling of the root canals was performed before (S1) and after (S2) chemomechanical root canal treatment. Each sample was separated into 2 different tubes. PMA was added to one of the tubes, and the other was left untreated. Then, DNA extraction and qPCR were performed. To evaluate the validity of the PMA treatment, the defined mixtures containing different ratios of live and dead cell suspensions of Enterococcus faecalis were either subjected to PMA treatment or not subjected to PMA treatment, followed by qPCR quantification. RESULTS A paired t test showed a highly significant difference in the mean threshold cycle values between S1 with and without PMA (P = .0002), and this difference (0.89) was similar to that (0.96) obtained from the samples consisting of 80% live cell suspension and 20% dead cell suspension of E. faecalis. The threshold cycle values between the S2 samples with and without PMA were also significantly different (P = .0134), and this difference (0.37) was similar to that obtained from the 100% live cell suspension of E. faecalis (0.42). CONCLUSIONS PMA in conjunction with qPCR appeared to be useful in analyzing the primary infections of root canals because there were significant amounts of dead bacteria in the root canals. Although the use of PMA treatment in post-preparation samples significantly reduced the detection of dead bacteria, this difference was still small, so further studies should be carried out to confirm the necessity of PMA treatment.

Hypoesthesia after IAN block anesthesia with lidocaine: management of mild to moderate nerve injury

Hypoesthesia after an inferior alveolar nerve (IAN) block does not commonly occur, but some cases are reported. The causes of hypoesthesia include a needle injury or toxicity of local anesthetic agents, and the incidence itself can cause stress to both dentists and patients. This case presents a hypoesthesia on mental nerve area followed by IAN block anesthesia with 2% lidocaine. Prescription of steroids for a week was performed and periodic follow up was done. After 1 wk, the symptoms got much better and after 4 mon, hypoesthesia completely disappeared. During this healing period, only early steroid medication was prescribed. In most cases, hypoesthesia is resolved within 6 mon, but being aware of etiology and the treatment options of hypoesthesia is important. Because the hypoesthesia caused by IAN block anesthesia is a mild to moderate nerve injury, early detection of symptom and prescription of steroids could be helpful for improvement of the hypoesthesia.