• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.3
• /
• pp.375-380
• /
• 2020

In this study, we tried to evaluate the mechanical properties of Polycarbonate(PC) and acrylonitrile-butadiene-styrene(ABS) plastic materials, which are frequently used as parts of home appliances and machinery, when repeated impacts were applied. A repeating impact tester for this research was designed and manufactured to apply repetitive impacts. Two types of plastic were repeatedly impacted under a constant load, and a tensile test was performed on the plastic material that was impacted. The tensile strength of PC plastic materials that received impact more than 2000 times was reduced by about 45 % and elongation was reduced by about 10 % when compared to impact free specimens. On the other hand, in ABS plastic, a reduction of tensile strength of about 20 % was observed at about 2,000 impacted specimen, but at about 20,000 repetitive impacted specimen, a tensile strength decrease of about 65 % was observed. And the elongation was reduced by 10 % due to the cyclic harding behavior of the material.

• The korean journal of orthodontics
• /
• v.37 no.2 s.121
• /
• pp.159-163
• /
• 2007

Impaction with a severely dilacerated root is seldom reported, especially in the maxillary incisor. It is probably because of the high clinical difficulty associated with bringing the dilacerated tooth into proper position, and the high chance of failure due to ankylosis, external root resolution, and root exposure after orthodontic traction. Even the successful cases may need periodontal surgery to improve the unesthetic gingival shape. However, it has previously been reported that an impacted maxillary central incisor was successfully treated by proper crown exposure and orthodontic traction. This article presents a case of an invertedly impacted maxillary right central incisor with a developing dilacerated root, which was aligned into proper position after orthodontic traction composed of two stages of a closed eruption technique.

• Imaging Science in Dentistry
• /
• v.35 no.4
• /
• pp.199-202
• /
• 2005

Purpose : To report the incidence of radiological findings from screening panoramic radiographs and verify the validity of the panoramic radiography for screening purposes. Materials and Methods : Six thousand one hundred and sixty panoramic radiographs taken from the patients visiting the Health Promotion Center of CNUH were selected for this retrospective study. Panoramic radiographs were examined into the following pathologic conditions : the presence of periodontal bone loss, dental caries, periapical radiolucencies, retained roots, impacted supernumerary teeth, impacted third molars, odontoma, cystic lesions other than radicular cyst, sialoliths, and mixed radiolucent-radiopaque lesions. Number of pathologic conditions and Prevalence values were recorded. Results: The prevalences of pathologic conditions were $72.9\%$ of periodontal bone loss, $32.2\%$ of dental caries, $11.9\%$ of periapical radiolucencies, $10.8\%$ of retained roots, $0.4\%$ of root fracture, $1.0\%$ of impacted supernumerary teeth, $1.0\%$ of impacted third molars, $0.06\%$ of odontoma, $0.08\%$ of cystic lesion other than radicular cyst, $0.2\%$ of prolonged retention of deciduous tooth, $0.1\%$ of sialolith, and $0.04\%$ of mixed radiopaque and radiolucent lesion. Conclusion : Although the panoramic radiograph should not be used to replace intraoral radiographic and clinical examinations, this study showed that many dental pathologic conditions could be detected on panoramic radiographs. The panoramic radiograph might serve as a diagnostic aid in dental health evaluation programs.

• Imaging Science in Dentistry
• /
• v.40 no.2
• /
• pp.89-91
• /
• 2010

Impaction of tooth is a situation in which an unerupted tooth is wedged against another tooth or teeth or otherwise located so that it cannot erupt normally. The supernumerary tooth is also called as hyperdontia and defined as the condition of having additional tooth to the regular number of teeth. The most common supernumerary tooth is a mesiodens, which is a mal-formed, peg-like tooth that occurs between the maxillary incisors. The supernumerary tooth is commonly impacted but they are frequently impacted on maxilla. Ectopic impaction of supernumerary tooth on mandibular condyle, coronoid process, ascending ramus, and pterygomandibular space is very rare condition. In this case, we report a case of impacted supernumerary tooth on mandibular sigmoid notch without definite pathologic change.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.41 no.6
• /
• pp.342-345
• /
• 2015

Adenomatoid odontogenic tumor (AOT) is a rare, benign odontogenic tumor that predominantly appears in the second decade of life in female patients. Most AOTs occur in the anterior part of the maxilla and are usually associated with impacted anterior teeth. There are three types of AOT, follicular, extrafollicular, and peripheral, which are classified based on the location of the lesion and its association with the impacted tooth. We report a rare case of AOT associated with an impacted right mandibular lateral incisor in an 11-year-old female patient.

• Imaging Science in Dentistry
• /
• v.49 no.3
• /
• pp.213-218
• /
• 2019

Purpose: The aim of this study was to evaluate the relationship between the mandibular canal and impacted mandibular third molars using cone-beam computed tomography (CBCT) and to compare the CBCT findings with signs on panoramic radiographs(PRs). Materials and Methods: This retrospective study consisted of 200 mandibular third molars from 200 patients who showed a close relationship between the mandibular canal and impacted third molars on PRs and were referred for a CBCT examination of the position of the mandibular canal. The sample consisted of 124 females and 76 males, with ages ranging from 18 to 47 years (mean, $25.75{\pm}6.15$ years). PRs were evaluated for interruption of the mandibular canal wall, darkening of the roots, diversion of the mandibular canal, and narrowing of the mandibular canal. Correlations between the PR and CBCT findings were statistically analyzed. Results: In total, 146 cases(73%) showed an absence of canal cortication between the mandibular canal and impacted third molar on CBCT images. A statistically significant relationship was found between CBCT and PR findings (P<0.05). The absence of canal cortication on CBCT images was most frequently accompanied by the PR sign of diversion of the mandibular canal(96%) and least frequently by interruption of the mandibular canal wall(65%). Conclusion: CBCT examinations are highly recommended when diversion of the mandibular canal is observed on PR images to reduce the risk of mandibular nerve injury, and this sign appears to be more relevant than other PR signs.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.47 no.1
• /
• pp.15-19
• /
• 2021

Objectives: The aim of this study was to evaluate correlations between anxiety and preoperative pressure pain assessments and postoperative pain and analgesic requirements in impacted lower third molar tooth surgery. Materials and Methods: This prospective study enrolled 60 patients who underwent impacted lower third molar surgery. The preoperative State-Trait Anxiety Inventory-I (STAI-I), pressure pain threshold, and pressure pain tolerance scores were measured. At 2, 4, 6, 12, and 24 hours, and at 6 days following surgery, the patients scored their pain on the visual analogue scale and recorded their analgesic drug usage. The data were evaluated, and the results were statistically analyzed. Results: Of the 60 patients, 38 were female. Mean age was 24.62±7.42 years. The study found no relationship between preoperative pressure pain assessments and postoperative pain (P>0.05). There was also no relationship observed between preoperative STAI-I scores and postoperative pain (P>0.05). However, there was a positive correlation between operation time and total medication taken (P<0.05). Conclusion: Preoperative pressure pain threshold, pressure pain tolerance, and anxiety level had no significant effects on postoperative pain and analgesic requirements in impacted lower third molar surgery.

• The Journal of the Korean dental association
• /
• v.56 no.1
• /
• pp.42-48
• /
• 2018

INTRODUCTION The most commonly impacted tooth is the third molar. An impacted third molar can ultimately cause acute pain, infection, tumors, cysts, caries, periodontal disease, and loss of adjacent teeth. Local anesthesia is employed for removing the third molar. This study aimed to evaluate the efficacy and safety of 2% lidocaine with 1:80,000 or 1:200,000 epinephrine for surgical extraction of bilateral impacted mandibular third molars. METHODS Sixty-five healthy participants underwent surgical extraction of bilateral impacted mandibular third molars in two separate visits while under local anesthesia with 2% lidocaine with different epinephrine concentration (1:80,000 or 1:200,000) in a double-blind, randomized, crossover trial. Visual analogue scale pain scores obtained immediately after surgical extraction were primarily evaluated for the two groups receiving different epinephrine concentrations. Visual analogue scale pain scores obtained 2, 4, and 6 h after administering an anesthetic, onset and duration of analgesia, onset of pain, intraoperative bleeding, operator's and participant's overall satisfaction, drug dosage, and hemodynamic parameters were evaluated for the two groups. RESULTS There were no statistically significant differences between the two groups in any measurements except hemodynamic factors (P > .05). Changes in systolic blood pressure and heart rate following anesthetic administration were significantly greater in the group receiving 1:80,000 epinephrine than in that receiving 1:200,000 epinephrine ($P{\leq}01$). CONCLUSION The difference in epinephrine concentration between 1:80,000 and 1:200,000 in 2% lidocaine liquid does not affect the medical efficacy of the anesthetic. Furthermore, 2% lidocaine with 1:200,000 epinephrine has better safety with regard to hemodynamic parameters than 2% lidocaine with 1:80,000 epinephrine. Therefore, we suggest using 2% lidocaine with 1:200,000 epinephrine rather than 2% lidocaine with 1:80,000 epinephrine for surgical extraction of impacted mandibular third molars in hemodynamically unstable patients.

• Imaging Science in Dentistry
• /
• v.46 no.4
• /
• pp.251-258
• /
• 2016

Purpose: The aim of this study was to examine the radiographic features associated with impacted premaxillary supernumerary teeth, to determine the relationship between their characteristics and their effects on permanent incisors, and to investigate the types of orthodontic treatment that patients received after the extraction of impacted supernumerary teeth. Materials and Methods: The clinical records and radiographs of 193 patients whose impacted premaxillary supernumerary teeth were removed were retrospectively reviewed, and 241 impacted supernumerary teeth were examined. Cone-beam computed tomographic images and panoramic radiographs were examined to determine the number, location, sagittal position, orientation, and morphology of the supernumerary teeth. Their effects on permanent incisors and the orthodontic treatment received by patients after the extraction of the supernumeraries were also investigated. Results: Supernumerary teeth were most frequently observed in the central incisor region, in the palatal position, in the inverted orientation, and were most commonly conical in shape. The most common complication was median diastema, followed by displacement and delayed eruption of the adjacent incisors. Ten (71.4%) of the 14 odontomas showed delayed eruption of the adjacent incisors. Displacement of the incisors was more frequently observed in association with supernumerary teeth with tuberculate or supplemental shapes. Orthodontic traction was most frequently performed after the removal of odontomas. In 32 cases (13.3%), permanent incisors erupted after the orthodontic creation of sufficient space. Conclusion: Median diastema was most common complication. The delayed eruption of incisors was common in supernumerary teeth with a vertical orientation and an odontoma shape.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.41
• /
• pp.29.1-29.10
• /
• 2019

Background: Reduction in postoperative complications is of vital considerations in impacted third molar teeth surgery. The aim of this study was to compare postoperative complications of impacted third molar surgeries for bone removal using laser, piezoelectric equipment, and conventional rotary instruments. Methods: To address the research purpose, the investigator designed the prospective double-blind clinical trial study. The sample size was determined 20 (40 teeth) by sampling formula in any kind of operation. The data of patients were obtained in the different periods in terms of pain, trismus, swelling, ecchymosis, and patient's satisfaction and then analyzed using SPSS 20 software via paired t test and Wilcoxon and McNemar's tests. Results: The pain immediately after surgery and 2 days and 7 days after surgery was higher in the laser group. The swelling immediately after surgery was more in the laser group but not significant. The amount of mouth opening immediately after surgery and 2 days and 7 days after surgery was significantly lower in the laser group than in the piezosurgery group. The total duration of surgery and duration of osteotomy were significantly longer in the laser group. The patient's satisfaction from surgery with piezosurgery was more than that with laser, but this difference was not significant. Conclusion: Due to the rising demand for impacted wisdom tooth surgery, the present study suggests that hard tissue laser surgery and piezosurgery can clear the future of impacted molar surgery, and these approaches are more efficient in reducing postoperative complications compared to the conventional surgeries.