Dong-Sung Park

Immediate implant placement into infected and noninfected extraction sockets: a pilot study

OBJECTIVE This study compared the osseointegration of immediate implants in dogs in infection-free sites and in sites with periradicular lesions which were removed by simulated periradicular surgery. STUDY DESIGN Periradicular surgeries were performed to remove intentionally induced periradicular lesions, followed by teeth extraction and immediate implant placement with (experimental group 1) or without (experimental group 2) membranes. In the control group, implants were placed at healthy extraction sockets. After 12 weeks, the animals were killed and the results of histomorphometric study were analyzed by Kruskal-Wallis test. RESULTS Both the control and the experimental implants were clinically acceptable. The control group showed significantly higher bone-implant contact (BIC; 76.03 +/- 7.98%) than the experimental groups 1 (59.55 +/- 14.21%) and 2 (48.62 +/- 20.22%) (P < .05). CONCLUSIONS Despite the lower BIC of the experimental groups, this pilot study showed the possibility that immediate implant placement might be successful in extraction sockets with periradicular lesions. Further studies with larger sample sizes are required.

The experimental study for the effect of tooth-brushing on the laser irradiated dentin surface

Dentin hypersensitivity is one of the most painful and least predictably treated chronic conditions in dentistry. It has been thought to be partially caused by the opening of dentinal tubules. If the exposed dentin surfaces and the number of opened dentinal tubules are increased, the patient feels more discomfort, especially during air blast, mechanical stimulation, thermal extremes or intense osmotic stimulation. In order to decrease the hypersensitivity, various attempts at blocking the dentinal tubules or changing the content of the dentinal tubules have taken place. Several medicaments and materials have been recommended to block the dentinal tubules. However, most of them have proved to be ineffective or have a short duration. Dederich et al. used the Nd:YAG laser to make the dentinal walls of the root canals smooth due to melting and recrystalizing of the dentinal surface. Harvey et al. demonstrated that the treated dentin with Nd:YAG laser appeared to have meltThe experimental study for the effect of tooth-brushing on the laser irradiated dentin surface

An electrochemical study of the sealing ability of three retrofilling materials

The purpose of this study was to evaluate the apical sealing ability of Super-EBA, MTA and Dyract-flow as retrofilling materials. Forty-eight extracted human teeth with straight and single root canal were used in this study. The root canals were prepared to a #40 apical canal size and obturated with gutter-percha. Apicoectomies were performed and root end cavities were prepared to a depth of 3mm using an ultrasonic device. The root end cavities were filled with Super-EBA, MTA or Dyract-flow. Leakage was measured using an electrochemical technique for 4 weeks. According to this study, the results were as follows. 1. Increasing leakage with time was observed in all groups. 2. No significant difference was noted among the 3 groups with time (p =0.216). 3. No significant difference was noted among the 3 groups when measured within the same time interval (p =0.814). The results of this study suggest that the sealing ability of Dyract-flow is equal to that of Super-EBA and MTA, and Dyract-flow may be an alternative to other materials for root-end filling.

The effect of MTAD on the apical leakage of obturated root canals: an electrochemical study

The purpose of this study was to evaluate the effect of newly developed endodontic root canal cleanser (MTAD) on the apical leakage of obturated root canal using an electrochemical method. Canals of 60 extracted single-rooted human teeth were prepared by using a crown-down technique with rotary nickel-titanium files. In Group 1 (positive control group) and 2 (negative control group), 5.25% NaOCl was used as a canal irrigant and no canal wall treatment was done. In group 3, only 5.25% NaOCl were used as canal irrigant, canal wall treatment and final rinse. In group 4, speci- mens were irrigated with 5.25% NaOCl, treated with 5 ㎖ of 17% EDTA for 5 minutes and final rinsed with 5.25% NaOCl. Specimens of group 5 were irrigated with 1.3% NaOCl and treated with 5 ml of MTAD for 5 minutes. All root canals are dried with paper points and obtuated with gutta-per- cha and AH plus as a sealer using a continuous wave of condensation technique except in the group 1. The electrical resistance between the standard and experimental electrodes in canals was mea- sured over a period of 10 days. Rising of apical leakage with time was observed for all the groups. Group 4 and 5 showed lower apical leakage than group 3 but differences between the group 3, 4 and 5 were no statistical significance at any measurement time.

Fracture resistance of crown-root fractured teeth repaired with dual-cured composite resin and horizontal posts

The purpose of this study was to investigate the fracture resistance of crown-root fractured teeth repaired with dual-cured composite resin and horizontal posts. 48 extracted human premolars were assigned to control group and three experimental groups. Complete crown-root fractures were experimentally induced in all control and experimental teeth. In the control group, the teeth (n=12) were bonded with resin cement and endodontically treated. Thereafter, the access cavities were sealed with dual-cured composite resin. In composite resin core - post group (n=12), the teeth were endodontically treated and access cavities were sealed with dual-cured composite resin. In addition, the fractured segments in this group were fixed using horizontal posts. In composite resin core group (n=12), the teeth were endodontically treated and the access cavities were filled with dual-cured composite resin without horizontal posts. In bonded amalgam group (n=12), the teeth were endodontically treated and the access cavities were sealed with bonded amalgam. Experimental complete crown-root fractures were induced again on repaired control and experimental teeth. The ratio of fracture resistance to original fracture resistance was analyzed with KruskalWallis test. The results showed that teeth in control and composite resin core - post group showed significantly higher resistance to re-fracture than those in amalgam core group (

A comparison of canal centering abilities of four root canal instrument systems using X-ray micro-computed tomography

The purpose of this study was to compare the centering abilities of four root canal instrument systems and the amounts of dentin removed after root canal shaping using them. The mesial canals of twenty extracted mandibular first molars having curvature were scanned using X-ray micro-computed tomography (XMCT)-scanner before root canals were instrumented. They were divided into four groups (n = 10 per group). In Group 1, root canals were instrumented by the step-back technique with stainless steel K-Flexofile after coronal flaring. The remainders were instrumented by the crown-down technique with Profile (Group 2), ProTaper (Group 3) or K3 system (Group 4). All canals were prepared up to size 25 at the end-point of preparation and scanned again. Scanned images were processed to reconstruct three-dimensional images using three-dimensional image software and the changes of total canal volume were measured. Pre-and post-operative cross-sectional images of 1, 3, 5, and 7 mm from the apical foramen were com pared. For each level, centering ratio were calculated using Adobe Photoshop 6.0 and image software program. ProTaper and K3 systems have a tendency to remove more dentin than the other file systems. In all groups, the lowest value of centering ratio at 3 mm level was observed. And except at 3 mm level, ProTaper system made canals less centered than the other systems (p

Comparison of ultrasonic and sonic root end preparations using anaerobic bacterial leakage model

최근 치근단 와동 형성 시 초음파 또는 음파 기구를 이용하는 것이 보편화 되어 있고 여러 측면에서 평가되어져 왔다. 본 연구의 목적은 혐기성 세균을 이용한 미세 누출 모델을 이용하여 초음파와 음파 기구를 사용, 치근단 와동 형성을 하 였을 때 두 기구의 사용이 충전된 치근단 와동의 미세 누출에 미치는 영향을 비교 평가하는 것이다. 48개의 단근치의 근관을 crown-down 방법을 이용 Profile로 .06 black까지 근관 성형을 시행하고 수직 가압법을 사용하여 gutta-percha와 AH26 sealer를 이용하여 근관 충전을 시행하였다. 각 충전된 시편의 치근단 3mm를 절제하 였다. 각 시편은 이미로 4군으로 나누었으며 1군에서는 치근단 와동을 초음파 기구로 형성하였고 2군에서는 음파 기구로 형 성하였다. 3군은 음성대조군으로 4군은 양성대조군으로 분류하였다. 형성된 치근단 와동은 공기 분사침을 이용하여 건 조 후 super EBA 시멘트로 충전하였으며 Anaerobic chamber에서Fusobacterium nucleatum (VPI 10197)을 사용 한 혐기성 세균 미세누출 모델을 이용하여 30일간 미세 누출을 관찰한 결과, 초음파 기구를 사용한 군에서는 80%에서 음파 기구를 사용한 군에서는 75%에서 미세누출이 나타났으나 통계적으로 유의성 있는 차이는 보이지 않았다.

IL-1 and TNF-α release in human polymorphonuclear leukocytes after exposure to calcium hydroxide treated Porphyromonas endodontalis lipopolysaccharide

Bacterial lipopolysaccharide (LPS) plays a major role in stimulating the synthesis and release of the principal osteoclast-activating cytokines, namely, interleukin 1 and tumor necrosis factor- from immune cells. Although rnonocytes/macrophages are the main producers of these cytokines, recent evidence has indicated that polymorphonuclear leukocytes (PMN) have the ability to release IL-1 and TNF-. Calcium hydroxide has been shown to be an effective medicament in root canal infections, reducing the microbial titre within the canal. It has been proposed that the therapeutic effect of Ca(OH) may also be the result of direct inactivation of LPS. The purpose of this study was to investigate whether treatment of Porphyromonas endodontalis LPS with calcium hydroxide alters its biological action as measured by human PMN secretion of IL-1 and TNF-, and it was compared with Escherichia coli LPS. P. endodontalis ATCC 35406 was cultured in anaerobic condition, and LPS was extracted using the hot-phenol water extraction method and purified. Purchased E. coli LPS was also purified. 100 /ml of each LPS in pyrogen free water were incubated with 25mg/ml Ca(OH) at 37 for 7 days. The supernatants were subjected to ultrafiltration, and the isolates were lyophilized and weighed. PMNs were obtained from peripheral blood by centrifugation layered over Lymphoprep. The cells were resuspended (410 cells/ml) in RPMI 1640 followed by treatment with various concentrations of LPS (0, 0.1, 1, 10/ml) for 24 hours at 37 in 5% incubator. The supernatants of cells were collected and the levels of IL-1, IL=1 and TNF- were measured by enzyme-linked immunosorbent assay. The results were as follows ; 1. The levels of IL-1, IL-1, TNF- from PMN treated with each LPS were significantly higher than those released from unstimulated PMN of the control group (p0.05) 3. The levels of secretion for all three cytokines were affected in a dose-dependent manner in PMN stimulated with each LPS (p0.05). 4. The levels of all three cytokines released from PMN stimulated with p. endodontalis LPS were significantly lower than those released from PMN stimulated with E coli LPS (p