• Maxillofacial Plastic and Reconstructive Surgery
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• 제41권
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• pp.40.1-40.7
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• 2019

Background: Through the analysis of clinical data, we attempted to investigate the etiology and determine the risk of severe iatrogenic lingual nerve injuries in the removal of the mandibular third molar. Methods: A retrospective chart review was performed for patients who had undergone microsurgical repair of lingual nerve injuries. The following data were collected and analyzed: patient sex, age, nerve injury side, type of impaction (Winter's classification, Pell and Gregory's classification). Ratios for the respective lingual nerve injury group data were compared with the ratios of the respective data for the control group, which consisted of data collected from the literature. The data for the control group included previous patients that encountered various complications during the removal of the mandibular third molar. Results: The lingual nerve injury group consisted of 24 males and 58 females. The rate of female patients with iatrogenic lingual nerve injuries was significantly higher than the control groups. Ages ranged from 15 to 67 years, with a mean age of 36.5 years old. Lingual nerve injury was significantly higher in the patient versus the control groups in age. The lingual nerve injury was on the right side in 46 and on the left side in 36 patients. There was no significant difference for the injury side. The distoangular and horizontal ratios were the highest in our lingual nerve injury group. The distoangular impaction rate in our lingual nerve injury group was significantly higher than the rate for the control groups. Conclusion: Distoangular impaction of the mandibular third molar in female patients in their 30s, 40s, and 50s may be a higher risk factor of severe lingual nerve injury in the removal of mandibular third molars.

• 한국입자에어로졸학회지
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• 제9권1호
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• pp.23-29
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• 2013

Inertial impaction type mist eliminators are the most effective instruments to separate mist from the gas. In this work, the effect of the horizontal chevron type mist eliminators is characterized experimentally. Droplet size distribution and evaluation of removal efficiency of the chevron type mist eliminators at different gas flows were investigated using an aerosol particle size analyzer and a portable aerosol spectrometer, respectively. The experimental investigations showed that the mist removal efficiency in these instruments is dependent in the droplet size, and the pressure drop is nil.

• 대한기계학회논문집B
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• 제23권7호
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• pp.871-880
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• 1999

In this paper an experimental study is presented of the problem of dynamic behavior of a water droplet impinging upon a heated surface. The experiments are mainly focused on the effects of impinging angle of a droplet and surface temperature on the impact dynamics of the droplet. It Is clarified that the droplet exhibits much different behavior depending on the normal momentum of an impinging droplet before impact. At surface temperature In the nucleate boiling regime. the disintegration of a droplet doesn't occur, whereas the deforming droplet adheres to the surface. The spreading and contraction of the liquid film is repeated a couple of times for the horizontal surface but the expanded droplet just slips without noticeable contraction for the inclined surfaces. In the film boiling regime, the impinging droplet spreads over the surface as a liquid film which is separated from the surface by produced vapor. Depending on the magnitude of the normal momentum of the droplet the disintegration into the several irregular shapes of liquid elements occurs for the horizontal and 30o-inclined surfaces, whereas the impinging droplet for the 60o-inclined surface doesn't break up and tends to recover the original spherical shape.

• Imaging Science in Dentistry
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• 제44권2호
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• pp.171-175
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• 2014

One of the most common oral surgical procedures is the extraction of the lower third molar (LTM). Postoperative complications such as paresthesia due to inferior alveolar nerve (IAN) injury are commonly observed in cases of horizontal and vertical impaction. The present report discusses a case of a vertically impacted LTM associated with a dentigerous cyst. An intimate contact between the LTM roots and the mandibular canal was observed on a panoramic radiograph and confirmed with cone-beam computed tomographic (CBCT) cross-sectional cuts. An orthodontic miniscrew was then used to extrude the LTM prior to its surgical removal in order to avoid the risk of inferior alveolar nerve injury. CBCT imaging follow-up confirmed the success of the LTM orthodontic extrusion.

• Computers and Concrete
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• 제26권5호
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• pp.377-384
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• 2020

A two-dimensional particle flow cod (PFC) is used to study the effect of missile impact on the concrete target. For this purpose firstly calibration of numerical model was performed so that tensile strength of numerical models and experimental sample were the same. Secondly, a concrete model was built. The number of concrete layers and the angle of concrete layers related to horizontal axis were changed. Their numbers were 1, 2, 3 and 4. The angles were 0°, 15°, 30°, 45°, 60°, 75° and 90°. A semi-circle missile was simulated at top of the concrete layers. Its velocity in opposite side of Y direction was 100 m/s. three measuring circles were situated at the below the missile in the model to receive the applied force. The load in the missile and measuring circles together with failure pattern were registered at the beginning of the impaction. The results show that concrete layers number and concrete layers angle have important effect on the failure load while the failure pattern was nearly constant in all of the models.

• 대한치과의사협회지
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• 제11권3호
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• pp.171-175
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• 1973

A 9-year-old girl, in good health, presented a horizontal impaction of the upper left central incisor. History revealed that the patient had been involved in a trauma of the maxillary anterior portion during her childhood. This impacted tooth crown, which was exposed surgically, was bonded by plastic attachments of direct bonding system, and was carefully tried to induce on the dental arch. On the process of the orthodontic treatment the tooth was completely induced and in normal alignment on the arch. The treatment result was very satisfactory; color, vitality, and mobility were normal, periodontal support was good and the cosmetic result was excellent.

• 한국대기환경학회지
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• 제26권2호
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• pp.219-233
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• 2010

Understanding the Nano size particles is of great interest due to their chemical and physical behaviors such as compositions, size distributions, and number concentrations. Therefore, accurate measurements of size distributions and number concentrations in ultrafine particles are getting required because expected losses such as diffusion for the instrument system from ambient inlet to detector are a significant challenge. In this study, the data using the computed settling losses, impaction losses, diffusion losses for the sampling lines (explored different sampling line diameters, horizontal length, number of bending, line angles, flow rates with and without a bypass), and diffusion losses for the Scanning Mobility Particle Sizers are examined. As expected, the settling losses and impaction losses are very minor under 100 nm, however, diffusion loss corrections for the sampling lines and the size instrument make a large difference for any measurement conditions with high numbers of particles smaller mobility size. Both with and without the loss corrections, which can affect to size distributions and number concentrations are described. First, 80% or more of the smallest particles (less than 10 nm) can be lost in the condition of a flow rate of 0.3 liter per minute and the length of sampling line of 1.0 m, second, total number concentrations of measurements are quite significantly affected, and the mode structure of the size distribution changes dramatically after the loss corrections applied. With compared to the different measurements, statistically diffusion loss corrections yield a required process of the ambient particle concentrations. Based on the current study, as an implication, a possibility of establishing direct revelation mechanisms is suggested.

• Imaging Science in Dentistry
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• 제53권2호
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• pp.137-144
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• 2023

Purpose: This study aimed to evaluate the anatomic circle around the impacted lower third molar to show, document, and correlate essential findings that should be included in the routine radiographic assessment protocol as clinically meaningful factors in overall case evaluation and treatment planning. Materials and Methods: Cone-beam computed tomographic images of impacted lower third molars were selected according to specific inclusion criteria. Impacted teeth were classified according to their position before assessment. The adjacent second molars were assessed for distal caries, distal bone loss, and root resorption. The fourth finding was the presence of a retromolar canal distal to the impaction. Communication with the dentist responsible for each case was done to determine whether these findings were detected or undetected by them before communication. Results: Statistically significant correlations were found between impaction position, distal bone loss, and detected distal caries associated with the adjacent second molar. The greatest percentage of undetected findings was found in the evaluation of distal bone status, followed by missed detection of the retromolar canal. Conclusion: The radiographic assessment protocol for impacted third molars should consider a step-by-step evaluation for second molars, and clinicians should be aware of the high prevalence of second molar affection in horizontal and mesioangular impactions. They also should search for the retromolar canal due to its associated clinical considerations.

• Imaging Science in Dentistry
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• 제44권1호
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• pp.61-65
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• 2014

Purpose: This study was performed to evaluate the position of impacted mandibular third molars in different skeletal facial types among a group of Iranian patients. Materials and Methods: A total of 400 mandibular third molars in 200 subjects with different types of facial growth were radiographically investigated for their positions according to their types of facial growth on the basis of the ${\beta}$ angle. The subjects were divided into three groups (class I, II, and III) according to ANB angle, representing the anteroposterior relationship of the maxilla to the mandible. Meanwhile, the subjects were also divided into three groups (long, normal, and short face) according to the angle between the stella-nasion and mandibular plane (SNGoGn angle). ANOVA was used for statistical analysis. Results: The mean ${\beta}$ angle showed no significant difference among class I, II, and III malocclusions (df=2, F=0.669, p=0.513). The same results were also found in short, normal, and long faces (df=1.842, F=2, p=0.160). The mesioangular position was the most frequent one in almost all of the facial growth patterns. Distoangular and horizontal positions of impaction were not found in the subjects with class III and normal faces. In the long facial growth pattern, the frequency of vertical and distoangular positions were not different. Conclusion: In almost all of the skeletal facial types, the mesioangular impaction of the mandibular third molar was the most prevalent position, followed by the horizontal position. In addition, ${\beta}$ angle showed no significant difference in different types of facial growth.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제20권4호
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• pp.284-290
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• 1998

The purpose of this study was to assess the soft tissue changes using twenty skeletal class III malocclusion patients who treated with bimaxillary surgery for the correction of dentofacial deformities. Patients were divided into two groups. One was impaction and advancement of maxilla with mandibular set-back (Group 1), the other was downward and advancement of maxilla with mandibular set-back (Group 2). Preoperative and postoperative one year cephalometric data were analyzed and compared. Results obtained were as follows: 1. The ratio of horizontal changes of soft tissue to hard tissue at Nt to ANS, Ls to UI, Li to LI, sPog to Pog were 1:0.60, 1:0.79, 1:0.47, 1:0.63 in group 1 respectively, and 1:0.59, 1:0.48, 1:0.83, 1:1.09 in group 2 respectively. Soft tissue changes were highly predictable at the upper lip, lower lip, and chin area. 2. The ratio of vertical changes of soft tissue to hard tissue at Nt to ANS, Li to LI were 1:0.72, 1:0.06 in group 1, and others showed no statistically significant difference. 3. The ratio of horizontal changes of Ls to hard tissue movements at LI(h) was 1:-0.82 in group 1 and at UI(h), LI(h) were 1:0.48, 1:0.01 in group 2. These ratios of group 1 were greater than those of group 2. 4. The direction of horizontal change of Li was the same as that of hard tissue change. The ratio of horizontal changes of Li to LI was 1:0.47 in group 1 and others showed no statistically significant difference. 5. The changes of upper lip thickness and length were -1.6mm, -1.4mm in group 1, and -1mm, -2.7mm in group 2. 6. The ratios of thickness of upper lip to ANS, UI, LI were 1:-0.83, 1:-0.37, 1:0.11 in group 1. There was similar trend in group 2, and there were no statistically significant difference. These results suggest that prediction of changes in soft tissue of upper lip, lower lip, and chin were 79%, 47%, and 63% in group 1, and 48%, 83%, and 109% in group 2. There was a tendency to decrease in thickness and increase in length of the upper lip.