• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.3
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• pp.225-232
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• 2011

Purpose: This study was designed to retrospectively evaluate the postsurgical initial stability of the Le Fort I osteotomy with posterior impaction and rigid internal fixation for the correction of mandibular prognathism with midface deficiency. Particular attention was paid to the magnitude and direction of the initial postsurgical change. Methods: 20 healthy patients with mandibular prognathism and midface deficiency participated in this study. All patients underwent Le Fort I osteotomy with posterior impaction and mandibular setback BSSO by one surgeon. Preoperative (T0), immediate postoperative (T1) and follow-up period (T2) cephalograms were taken and analyzed. Change between T0~T1 and T1~T2 was measured and analyzed. Results: Between T0~T1, significant differences were observed in all measurements except the ANS point and mandibular plane angle. Between T1~T2, only the occlusal plane angle was significantly changed. No significant changes were found in all other measurements. Conclusion: This study indicates that Le Fort I osteotomy with posterior impaction is stable at initial stages. Although changes in the occlusal plane angle were observed, it was caused by tooth movement after post-operative orthodontic treatment. However, more studies with larger samples are required to form definitive conclusions. Conclusion: This study indicates that Le Fort I osteotomy with posterior impaction is stable at initial stages. Although changes in the occlusal plane angle were observed, it was caused by tooth movement after post-operative orthodontic treatment. However, more studies with larger samples are required to form definitive conclusions.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.4
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• pp.264-271
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• 2011

Purpose: This study evaluated retrospectively the postsurgical facial hard tissue profile of a Le Fort I osteotomy with/without posterior impaction and rigid internal fixation to correct mandibular prognathism. After observing a difference between the two groups, this measurement was used to prepare a treatment plan for 2-jaw surgery. Patients and Methods: Thirty patients who had undergone orthognathic surgery in Pusan National University Dental Hospital were enrolled in this study. Fifteen patients were treated using a Le Fort I osteotomy with posterior impaction and mandibular setback bilateral sagittal split ramus osteotomy, and the other fifteen patients were treated without posterior impaction. The preoperative (T0), immediate postoperative (T1) and six-month follow-up period (T2) cephalograms were taken and difference between T1-T0 and T2-T2 was analyzed. Results: Both groups was FH-ABp, SNB and ANB showed significant changes in the measurement, whereas only the posterior impaction group showed a change in the SN-U1, occlusal plane, posterior facial height, surgical movement difference from the L1 and B-point. There was no significant statistical change between the immediate postoperative (T1) and six-month follow-up (T2) hard tissue analysis in the two groups. Conclusion: A Le Fort I osteotomy with posterior impaction is considerable for patients with a flat occlusal plane angle, large posterior facial height, prominent B-point, pogonion and labioversed incisal inclination if the indications are well chosen.

• Imaging Science in Dentistry
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• v.41 no.3
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• pp.135-137
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• 2011

Impaction of third molar is a common developmental abnormality. However, ectopic impaction of the mandibular third molar in condylar region is an extremely rare condition. This report describes a case of impacted tooth in the mandibular condyle without any associated pathologic condition. Also, this report presents the spatial relationship of the impacted mandibular third molar to the surrounding anatomic structures using cone beam computed tomography.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.393-403
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• 1991

The purpose of this study was to evaluate the incidence and radiographic features of 1,300 cases of supernumerary teeth by means of the analysis of periapical radiograms and/or pantomograms in 69,442 persons visited the Department of Oral Radiology, School of Dentistry, Kyung Hee University during January 1980 to December 1989. This study of supernumerary teeth revealed the following features: 1. The incidence of supernumerary tooth was revealed to be 1.5% in total examined persons, and there was a higher incidence in males (74.0%) than in females (26.0%). 2. The supernumerary teeth were most frequently occurred in the 1 st decade (42.7%), followed by the 2nd decades (20.2%), the 3rd decades (14.1 %), and the 5th decades (7.2%). 3. There was a higher incidence in the maxilla (98.7%) than in the mandible (1.3%), and mesiodens (90.1 %) was the most frequently occurred. The maxillary lateral incisor region (3.1%) was next in order of frequency followed by maxillary distomolar (2.2%), and maxillary paramolar (1.5%). 4. There was a higher incidence of the impaction (82.7%) than that of the eruption (17.3%), and supernumerary tooth in lateral incisor region (87.8%) was the most frequently impacted one. 5. The inverted impaction was occurred in 63.1%, the vertical impaction in 18.1%, and the angulated impaction in 18.8%. In localization, a palatally (lingually) impacted supernumerary tooth was occurred in 85.0%, and middle impacted and buccally (labially) impacted supernumerary tooth showed the same incidence (7.5%). 6. A supplemental tooth was occurred in 3.2%, an accessory tooth in 96.8%, and a supplemental tooth was the most frequently occurred in maxillary lateral incisor and mandibular premolar region. 7. In effects of supernumerary tooth on adjacent tooth, crowding was occurred in 0.4%, diastema in 10.6%, rotation in 5.4%, eruption disturbance in 4.5%, root resorption in 2.5%, and dentigerous cyst in 2.2%.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.367-375
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• 1991

The clinical and radiographic features of 1,171 mesiodenses were studied with periapical radiograms and/or pantomograms in 942 persons visited the Department of Oral Radiology, School of Dentistry, Kyung Hee University during January 1980 to December 1989. The obrained results were as follows; 1. The incidence of mesiodens was higher in males (75.4%) than in females (24.6%). 2. In number of mesiodenses per individual, a single mesiodens was found to be 75.9%, 2-mesiodenses to be 23.8%, and 3-mesiodenses to be 0.2%. 3. In mesiodenses according to erupted and impacted status, the erupted mesiodens was found to be 16.5%, the impacted mesiodens in the interdental alveolar bone to be 66.6%, and in the region below root apex to be 16.9%. 4. In impacted mesiodenses according to direction of tooth crown, the inverted impaction was found to be 68.8%, the vertical impaction to be 15.1%, and the angulated impaction to be 16.1%. Among the impacted mesiodenses, a palatally located impaction was 87.5%, a middle 4.9%, and a labially 7.6%. 5. In mesiodenses according to shape of the tooth crown, a incisor-like type was found to be 1.6%, a canine-like type to be 6.8%, a conical type to be 79.2%, and a tuberculated type to e 12.4%. 6. In effect of mesiodens on adjacent tooth, non-specific influences were found to be 73.4%, crowding to be 0.3%, diastema to be 11.8%, rotation to be 5.7%, delayed eruption to be 3.8%, root resorption to be 2.6%, and dentigerous cyst to be 2.4%.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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• pp.23.1-23.7
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• 2016

Background: The purpose of this retrospective study was to develop a two- and three-dimensional analysis of the airway using cone-beam computed tomography (CBCT) and to determine whether the airway space would be changed in mandibular prognathism after bimaxillary surgery involving maxillary posterior impaction. Methods: Patients requiring orthognathic surgery from 2012 to 2014 were recruited for this study. CBCT scans were obtained at three points: preoperatively (T0), immediate postoperatively (T1), and after 6 months postoperatively (T2). The nasopharynx, oropharynx, and hypopharynx were measured on the CBCT scan for each patient in a repeatable manner. With the midsagittal plane, linear measurements in the middle of each were obtained. For the CBCT, volumetric measurements of each and total airway were obtained. Results: A total of 22 consecutive patients (11 men and 11 women) were included in the present study. The total volume was significantly reduced (p < .001). However, the change of the diameter and volume of the nasopharynx was not statistically significant (p = .160, p = .137, respectively). In the oropharynx, the change of both the diameter and volume showed statistical significance between preoperatively and immediate postoperatively (p < .001, p = .001, respectively) and also preoperatively and after 6 months postoperatively (p = .001, p = .010, respectively). In the hypopharynx, the change of both the diameter and volume showed statistical significance between preoperatively and immediate postoperatively (p = .001, p < .001, respectively) and also preoperatively and after 6 months postoperatively (p = .001, p < .001, respectively). Conclusions: The bimaxillary surgery involving maxillary posterior impaction can reduce the volume of airway in the patients of mandibular prognathism. Although total airway volume was reduced significantly, the changes in the volume and diameter of the nasopharynx were not statistically significant. The maxillary posterior impaction affects on the nasopharyngeal airway minimally.

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.991-999
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• 1998

Tooth impaction may lead to malocclusion, root resolution, cyst or aberrant changes in adjacent teeth. Clinical and radiographic examinations are used to locate the impaction, and appropriate treatment plans must be made to relocate the impacted tooth. When surgically exposing the impacted tooth, periodontal considerations to conserve maximum amount of soft and hard tissue are used. Oral hygiene instructions are emphasized to maintain sound periodontal health. Securing enough space for the impacted tooth and proper anchorage is important. Proper use of force and mechanics is crucial to prevent such complications as root resolution. Various patterns of orthodontic traction may be employed as situation permits. Most impaction cases can be managed with orthodontic traction to restore function and esthetics, provided that early detection and proper diagnosis and treatment planning are made.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.600-604
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• 2003

Tooth impaction is defined as a cessation of the eruption of a tooth at the level of the oral mucosa or alveolar bone. Maxillary canines are the most frequently impacted teeth next to the third molar. Maxillary canine impaction is associated with congenital missing of lateral incisors, peg lateralis and genetic factors such as ectopic positioning of a tooth germ. The clinicians have an important role in early detection of tooth impaction for prevention of esthetic and functional problems. There are specific methods to treat impacted tooth for different conditions. In this case, an 11-year-old girl with a horizontally impacted maxillary right canine in a palatal position was treated through orthodontic traction along with surgical button attachment procedure. On regaining of eruption space, canine traction was performed. At the completion of treatment, the canine was positioned fairly within the arch with proper keratinized gingiva and complications such as root resorption were not observed.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.598-604
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• 2004

Impaction of mandibular first molar is relatively rare and its overall frequency has been reported to be 0.01%. The etiology of impaction are lack of eruption space, physical obstacles such as supernumerary teeth, odontomas or odontogenic tumors, hereditary factors, functional disturbances of endocrine glands and traumas. Impaction of mandibular first molar can result in a short lower facial height, formation of a follicular cyst, pericoronal inflammation, resorption of the roots of neighboring teeth and malocclusion. The treatment options available for impacted teeth include surgical exposure, orthodontic forced eruption, surgical repositioning and surgical removal of unerupted molar. This report presents two cases of distally tilted and impacted mandibular first molars which were treated by surgical exposure. In these cases, we could observe spontaneous eruption of the impacted mandibular first molars after surgical exposure.

• Particle and aerosol research
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• v.18 no.4
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• pp.129-136
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• 2022

The line width of circuits in semiconductor devices continues to decrease down to a few nanometers. Since nanoparticles attached to the patterned wafer surface may cause malfunction of the devices, it is crucial to remove the contaminant nanoparticles. Physical cleaning that utilizes momentum of liquid for detaching solid nanoparticles has recently been tested in place of the conventional chemical method. Dropwise impaction has been employed to increase the removal efficiency with expectation of more efficient momentum exchange. To date, most of relevant studies have been focused on drop spreading behavior on a horizontal surface in terms of maximum spreading diameters and average spreading velocity of drop. More important is the local liquid velocity at the position of nanoparticle, very near the surface, rather than the vertical average value. In addition, there are very scarce existing studies dealing with microdroplet impaction that may be desirable for minimizing pattern demage of the wafer. In this study, we investigated the local velocity distribution in spreading liquid film under various impaction conditions through the CFD simulation. Combining the numerical results with the particle removal model, we estimated an effective cleaning diameter (ECD), which is a measure of the particle removal capacity of a single drop, and presented the predicted ECD data as a function of droplet's velocity and diameter particularly when the droplets are microns in diameter.