• Restorative Dentistry and Endodontics
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• v.37 no.4
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• pp.201-206
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• 2012

Objectives: The purpose was to investigate the preference and usage technique of NiTi rotary instruments and to retrieve data on the frequency of re-use and the estimated incidence of file separation in the clinical practice among general dentists. Materials and Methods: A survey was disseminated via e-mail and on-site to 673 general dentists. The correlation between the operator's experience or preferred technique and frequency of re-use or incidence of file fracture was assessed. Results: A total of 348 dentists (51.7%) responded. The most frequently used NiTi instruments was ProFile (39.8%) followed by ProTaper. The most preferred preparation technique was crown-down (44.6%). 54.3% of the respondents re-used NiTi files more than 10 times. There was a significant correlation between experience with NiTi files and the number of re-uses (p = 0.0025). 54.6% of the respondents estimated experiencing file separation less than 5 times per year. The frequency of separation was significantly correlated with the instrumentation technique (p = 0.0003). Conclusions: A large number of general dentists in Korea prefer to re-use NiTi rotary files. As their experience with NiTi files increased, the number of re-uses increased, while the frequency of breakage decreased. Operators who adopt the hybrid technique showed less tendency of separation even with the increased number of re-use.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.579-588
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• 2007

Statement of problem: A tenderness of the dentin after tapering of teeth for dental prosthesis is a common phenomenon. In practice, the alternative desensitizer may be used for minor pain after tapering of teeth. Purpose: In this study, the desensitizers were used to investigate the affect decreasing of shear bond strength according to the use of various cement, such as resin, Glass Ionomer, and phosphate cement. Material and method: Three different desensitizers were used on this study Compositions of two dentin desensitizers were HEMA(hydroxyethylmethacrylate) and glutaraldehyde. The other one is oxalic acid. Three dentin desensitizers applied on 12 degrees taper teeth. Then, Ni-Cr crowns were bonded with Resin cement, Zinc Phosphate (ZPC) cement and Glass Ionomer (GIC) cement. 120 human premolar teeth were used for specimens. The specimens were divided into four group as the reference and the empirical each with thirty specimens, then further divided into 12 group according to type of desensitizers and cement types. The shear bond strength were measured by Instron multi task instrument. Results: According to the result, the measured shear bond strength in order from the weakest to the strongest in general was ZPC, Resin, and GIC. And it is found that the application of desensitizers on dentin surface does not affect the shear bond strength. Conclusion: Dentin desensitizers that alleviate or prevent a dentin tenderness, usually contains HEMA and glutaraldehyde compounds. Such desensitizers are widely used in clinical studies. By applying the dentin desensitizer on the exposed dentin surface, the dentin capillary are blocked and periodontal membrane and cementum can not be drawn in pulp cavity. Since HEMA and glutaraldehyde may cause harm to the pulp cavity, an alternative desensitizer was developed.

• The korean journal of orthodontics
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• v.46 no.5
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• pp.290-300
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• 2016

Objective: This study aimed to (1) evaluate the effects of maxillary second and third molar eruption status on the distalization of first molars with a modified palatal anchorage plate (MPAP), and (2) compare the results to the outcomes of the use of a pendulum and that of a headgear using three-dimensional finite element analysis. Methods: Three eruption stages were established: an erupting second molar at the cervical one-third of the first molar root (Stage 1), a fully erupted second molar (Stage 2), and an erupting third molar at the cervical one-third of the second molar root (Stage 3). Retraction forces were applied via three anchorage appliance models: an MPAP with bracket and archwire, a bone-anchored pendulum appliance, and cervical-pull headgear. Results: An MPAP showed greater root movement of the first molar than crown movement, and this was more noticeable in Stages 2 and 3. With the other devices, the first molar showed distal tipping. Transversely, the first molar had mesial-out rotation with headgear and mesial-in rotation with the other devices. Vertically, the first molar was intruded with an MPAP, and extruded with the other appliances. Conclusions: The second molar eruption stage had an effect on molar distalization, but the third molar follicle had no effect. The application of an MPAP may be an effective treatment option for maxillary molar distalization.

• The korean journal of orthodontics
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• v.47 no.3
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• pp.195-206
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• 2017

Facial asymmetry can be classified into the rolling-dominant type (R-type), translation-dominant type (T-type), yawing-dominant type (Y-type), and atypical type (A-type) based on the distorted skeletal components that cause canting, translation, and yawing of the maxilla and/or mandible. Each facial asymmetry type represents dentoalveolar compensations in three dimensions that correspond to the main skeletal discrepancies. To obtain sufficient surgical correction, it is necessary to analyze the main skeletal discrepancies contributing to the facial asymmetry and then the skeletal-dental relationships in the maxilla and mandible separately. Particularly in cases of facial asymmetry accompanied by mandibular yawing, it is not simple to establish pre-surgical goals of tooth movement since chin deviation and posterior gonial prominence can be either aggravated or compromised according to the direction of mandibular yawing. Thus, strategic dentoalveolar decompensations targeting the real basal skeletal discrepancies should be performed during presurgical orthodontic treatment to allow for sufficient skeletal correction with stability. In this report, we document targeted decompensation of two asymmetry patients focusing on more complicated yaw-dependent types than others: Y-type and A-type. This may suggest a clinical guideline on the targeted decompensation in patient with different types of facial asymmetries.

• Restorative Dentistry and Endodontics
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• v.29 no.3
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• pp.267-272
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• 2004

The purpose of this in vitro study was to evaluate the effect of surface defects and cross-sectional configuration of NiTi rotary files on the fatigue life under cyclic loading. Three NiTi rotary files ($K3^{TM},{\;}ProFile^{\circledR},{\;}and{\;}HERO{\;}642^{\circledR}$) with ＃30/.04 taper were evaluated. Each rotary file was divided into 2 subgroups : control (no surface defects) and experimental group (artificial surface defects), A total of six groups of each 10 were tested. The NiTi rotary files were rotated at 300rpm using the apparatus which simulated curved canal (40 degree of curvature) until they fracture. The number of cycles to fracture was calculated and the fractured surfaces were observed with a scanning electron microscope. The data were analyzed statistically. The results showed that experimental groups with surface defects had lower number of cycles to fracture than control group but there was only a statistical significance between control and experimental group in the $K3^{TM}$ (p<0.05), There was no strong correlation between the cross-sectional configuration area and fracture resistance under experimental conditions. Several of fractured files demonstrated characteristic patterns of brittle fracture consistent with the propagation of pre-existing cracks. This data indicate that surface defects of NiTi rotary files may significantly decrease fatigue life and it may be one possible factor for early fracture of NiTi rotary files in clinical practice.

• Journal of Oral Medicine and Pain
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• v.48 no.3
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• pp.96-105
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• 2023

Purpose: Mandibular advancement devices (MAD) are known to be insufficiently effective in all patients with obstructive sleep apnea (OSA). This study aimed to compare the treatment outcomes of MAD therapy according to OSA severity and to investigate the risk factors for the lack of response to MAD therapy. Methods: A total of 29 patients diagnosed with OSA received an adjustable two-piece MAD treatment. Sleep parameters measured with the home sleep apnea test device, including apnea-hypopnea index (AHI) and oxygen saturation (SpO₂), and daytime sleepiness using the Epworth Sleepiness Scale (ESS) were retrospectively assessed both before and after the MAD treatment. Results: The patients were classified into three groups according to AHI severity: mild (n=16, AHI<15), moderate (n=6, 15≤AHI<30), and severe OSA (n=7, AHI≥30). MAD therapy significantly improved the sleep parameters (p<0.001 for AHI and p=0.004 for minimum SpO₂) and daytime sleepiness (p<0.001 for ESS). Furthermore, successful outcomes (reduction in AHI>50% and AHI<10 events/h) were achieved in 83.3% and 71.4% of moderate and severe OSA cases, respectively. Of 13 patients with moderate and severe OSA, 10 were classified as responders and 3 as non-responders. The non-responders had significantly lower baseline value of SpO₂ (p=0.049 for average SpO₂ and p=0.007 for minimum SpO₂) and higher baseline AHI (p=0.049) than the responders. Conclusions: The results of the present study suggest that MAD is effective in the majority of patients with OSA of varying severities. The success of MAD therapy does not seem to depend solely on AHI severity. In addition to AHI, minimum SpO₂ may be a prognostic measure of the efficacy of MAD treatment in clinical dental practice.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.99-107
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• 2009

Statement of problem: Restoring and replacing teeth with fixed prostheses commonly used in dental practice. Because of improper oral hygiene care and inaccurate laboratory procedure, complications of fixed prostheses were found in the mouth of patients. Although many efforts have been continually made to obtain the data of long term prognosis of fixed prostheses, it was difficult to do it. Purpose: The purpose of this study was to evaluate the clinical status of fixed prostheses. Material and methods: In order to assess the clinical status of fixed prostheses, a total of 161 individuals(aged 17-85, 99 women and 62 men with 1596 unit of fixed prostheses, and 1169 abutments) who first visited the Department of Prosthodontics, Pusan National University Hospital, between April to September, in 2007 were examined. Results and conclusion: The results of this study were as follows: 1. Length of service of fixed prostheses was $8.6{\pm}0.6$ years(mean), 10.0 years(median). 2. Location of fixed prostheses was found to have no statistically significant influence on longevity of fixed prostheses(P>.05). But, the success rate was high in posterior region and in mandible where the failure rate was high in combination(P<.05). 3. Longevity of fixed prostheses made of metal was longest(mean: $13.0{\pm}9.3$, median: 14.0), gold, precious ceramic, non-precious ceramic trailing behind(P<.05). 4. Number of units in fixed prostheses was found to have no statistically significant influence on longevity of fixed prostheses(P>.05). But, the success rate was high in Single-unit and the failure rate was high in over 3-unit(P<.05). 5. Condition of opposing dentition was found to have no statistically significant influence on longevity of fixed prostheses(P>.05). But, the success rate was high in natural dentition(P<.05). 6. Defective margin(28.2%), dental caries(23.0%), periodontal disease(19.3%), periapical disease(16.9%) were frequent complications. In 30.1% of the cases, abutment state after removing fixed prostheses was needed to be extracted.

• The korean journal of orthodontics
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• v.38 no.5
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• pp.337-346
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• 2008

Objective: The purpose of this study was to determine whether an exogenous electric current to the alveolar bone surrounding a tooth being orthodontically treated can enhance tooth movement in human and to verify the effect of electric currents on tooth movement in a clinical aspect. Methods: This study was performed on 7 female orthodontic patients. The electric appliance was set in the maxilla to provide a direct electric current of $20{\mu}A$. The maxillary canine on one side was assigned as the experimental side, and the other as control. The experimental canine was provided with orthodontic force and electric current. The control side was given orthodontic force only. Electrical current was applied to experimental canines for 5 hours a day. The amount of canine movement was measured with an electronic caliper every week. Results: The amount of orthodontic tooth movement in the experimental side during 4 weeks was greater by 30% compared to that of the control side. The amount of increase in tooth movement in the experimental side was statistically significant. The amount of tooth movement in the experimental side during the first two weeks was !Bleater than that in the following two weeks. The amount of weekly tooth movement in the control side was decreased gradually. Conclusions: These results suggested that the exogenous electric current from the miniature electric device might accelerate orthodontic tooth movement by one third and have the potential to reduce orthodontic treatment duration.

• Journal of the korean academy of Pediatric Dentistry
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• v.42 no.1
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• pp.1-9
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• 2015

This study was conducted for the purpose of providing basic data that aims to develop the clinical practice education program and improve satisfaction for clerkship by evaluating the satisfaction of students who participated in learning using role-play in the clerkship of the department of pediatric dentistry. 85 senior dental students participated in this study. The students were divided into 17 groups and randomly performed role-plays in their role. After each role-play, a questionnaire designed to evaluate students' satisfaction on interest and appropriacy and satisfaction on usefulness towards role-play were completed by 77 students. The mean score of total satisfaction was 3.38 on a 5 point Likert scale. The mean score satisfaction on interest and appropriacy was 3.99 and the mean score satisfaction on usefulness was 3.79. The satisfaction score in the role group of parents was the highest and there was a significant difference in mean scores by the role groups (p < 0.05). Students evaluated the role-play as an interesting and useful educational tool in clerkship. It is necessary to undergo further trials and complement programs to upgrade the quality of dental clerkship.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.3
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• pp.334-346
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• 2023

The aim of this study was to assess the correlation between serum levels of insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), and hand-wrist radiographs using a skeletal maturity indicator (SMI) and the middle phalanx of the third finger (MP3). Hand-wrist radiographs and blood samples from 205 patients aged 7 - 17 years were retrospectively analyzed by two dentists using the SMI stages, MP3 stages, and serum IGF-1 and IGFBP-3 levels. Serum IGF-1 levels were highest at the SMI 6 - 8 and MP3 - G stage and lowest at the SMI 1 - 3 and MP3 - F stage (p < 0.0001). Serum IGFBP-3 levels were highest at the SMI 9 - 10 and MP3 - I stage and lowest at the SMI 1 - 3 and MP3 - FG stage (p = 0.010, 0.030). As a result of Pearson correlation analysis, a relatively high correlation was found between skeletal maturity using the SMI and MP3 stages and serum IGF-1 levels (r = 0.698, 0.622, p < 0.0001). According to the results of this study, serum IGF-1 levels can be used as an auxiliary measure to evaluate the skeletal maturity of children and adolescents in dentistry. The range from the mean serum IGF-1 level of 472 ㎍/L in SMI 6 stage to the mean IGF-1 level of 510.63 ㎍/L in MP3 G stage could be considered as the peak height velocity in clinical practice.