• The korean journal of orthodontics
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• v.28 no.2 s.67
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• pp.255-268
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• 1998

This study was investigated to assess the difference of facial height and occlusal plane inclination between normal occlusion group and class II malocclusion group. The subjects consisted of 50 normal occlusion (male 25, female 25) and 50 class II(male 25, female 25) malocclusion patients. All subjects are adult. lateral cephalogram was taken with standard method traced, and digitized for each subjects. The computerized statiscal analysis was carried out with SPSS program. The results were as follows 1. In class II malocclusion group, variables significant different from normal occlusion group were as follows ; SN-FOP, FH-BOP, MP-BOP, AB-BOP, AB-FOP, Facial plane-BOP, FP-FOP 2. In class II malocclusion group, the posterior facial height -especially posterior lower facial height-was significantly smaller than normal occlusion group.(P<0.05) 3. In class II malocclusion group, the angles between occlusal plane and upper and lower incisor, the angle between upper molar and bisected occlusal plane were significantly larger than those of normal occlusion group. (P<0.05) 4. L1 to Mandibular plane (mm) was a unique factor of occlusal plane position that showed significant difference in class II malocclusion group. 5. The correlation between overbite and occlusal plane inclination existed in class II malocclusion group, but the correlation didn't exist in normal occlusion group.

• The korean journal of orthodontics
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• v.37 no.2 s.121
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• pp.150-158
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• 2007

Objective: The aim of this study was to determine the relationship between the status of a unilateral palatally impacted maxillary canine (as seen on the panoramic radiograph) and the orthodontic treatment duration. Methods: A total of 36 subjects were chosen (8 males and 28 females, $13.7{\pm}2.5$ years). All patients had undergone orthodontic traction of the impacted canine after a closed flap surgery. The position of impacted canine on the panoramic radiograph was traced and calculated with regard to the treatment duration. Results: The canine overlap over the lateral incisor (COGr) had significant statistical difference between the short-term and the long-term treatment duration groups (divided by average treatment time of 21 months) (p<0.05). Multiple regression indicated that the variables of significance (with treatment duration as the dependent variable) were the canine vertical height from the occlusal plane $(HCV,\;r^2=0.115;\;p<0.05)$ and the mandibular anterior width $(MnDW,\;r^2=0.142;\;p<0.05)$. The treatment duration, the canine angle to the incisor midline (CA), and HCV decreased from primary dentition (under 12 yrs) to permanent dentition (15 yrs). Howerer, these increased again at the adolescent ages (over 16 yrs). Conclusion: These findings suggested that orthodontic treatment of a palatally impacted canine would show good prognosis at an age of early permanent dentition with the canine showing smaller CA and HCV.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.70-81
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• 2009

Statement of problem: The position and length of cantilever influence on the stress distribution of implants, superstructure and bone. In edentulous mandible, implant-supported cantilever prostheses that based 4 or 6 implants between mental foramens has been attempted. Excessive bite force loaded at cantilever prosthesis causes bone resorption and breakage of superstructure prosthesis around posterior implants. To complement the cantilever length of conventional prosthesis, In 1992, (McCartney) introduced "cantilever-rest-implant" and Malo reported "All-on-Four" in 2003. Purpose: Analyze and compare the stress distribution of conventional cantilever prostheses with rest implant and All-on-$Four^{TM}$ implant prostheses. Material and method: The external loads(300 N vertically, 75 N horizontally) are applied to first molar area. The stress value, stress distribution and aspect of stress dispersion are analyzed by three-dimensional finite element analysis program, ANSYS ver. 10.0. Results: 1. The rest implant and "All-on-Four" implant system are superior to conventional cantilever prostheses to reduce stress on the bone and the superstructure around implants. 2. The rest implant was of the greatest advantage to stress distribution on bone, implant and superstructure. 3. With same number of implants, distally tilted implants are preferred to conventional cantilever prostheses for reducing the length of cantilever.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.693-698
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• 2006

In Class I cavity, the highest C-factor could be obtained and it means the highest polymerization shrinkage stress. In this study, high C-factor model was designed. The pulpose of present study was to determine differences of Microtensile bond strength (MTBS) of class I cavity pulpal and axial wall specimens in primary molar. Twenty clean mandibular 2nd primary molars were randomly divided into two groups Different composite Resins (Filtek Z250, 3M ESPE & Filtek Supreme, 3M ESPE) were bulk filled and photo cured. Axial wall specimens and pulpal specimens were prepared at the same teeth, All specimens were divided into 4 groups and MTBS were evaluated. Group ZP : Filtek Z250-Pulpal wall Group ZA : Filtek Z250-Axial wall Group SP : Filtek Supreme - Pulpal wall Group SA : Filtek Supreme - Axial wall The results were as follows: 1. Mean MTBS of ZP & ZA and SP & SA were significantly different(p<.001). 2. There was no significant difference between MTBS of ZP & SP and ZA & SA.

• The korean journal of orthodontics
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• v.36 no.3 s.116
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• pp.218-227
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• 2006

Although the submentovertex radiograph and surface EMG are not often used due to the difficulty of interpretation, they are accepted as useful diagnostic and analytic aids for skeletal asymmetry. There have been reports which state that they were also useful for the evaluation of vertical skeletal relations. The purpose of this study was to evaluate the correlations between EMG data, measurements from submentovertex radiographs, facial types and facial asymmetry following examination of 60 asymmetric patients. The radiographic corpus length were greater in the nonaffected sides (p<0.001), gonion to interspinosum axis were greater in the affected sides and the mandibular condyle and gonion were located more anteriorly in the non-affected sides than in the affected sides but not significant (p=0.07). The activity of the anterior temporal muscle in rest position was higher in the affected sides than in the non-affected sides (p<0.01). The activity of the masseter muscle at maximum clenching was found to be nonsignificant but it was higher in the affected sides than in the non-affected sides (p=0.09). There was positive correlation between facial index and the intercondylar axes angle (p<0.01). There was positive correlation between masseter muscle activity in maximum occlusion and facial index in the affected and non-affected sides (p<0.05). The results demonstrate that the submentovertex radiograph and EMG can provide useful information for the evaluation of horizontal and vertical skeletal relations.

• The korean journal of orthodontics
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• v.22 no.1
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• pp.109-121
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• 1992

Temporomandibular joint is a major structure to play an important role in the function & stability of the occlusion as well as the stomatognathic system. Therefore, the TMJ is the structure that requires the complete analysis for diagnosing and planning treatment of pathologic changes by TMJ dysfunction and malocclusion. So, in this study, to evaluate TMJ situation in Korean malocclusion, based on the previous accomplishments, students of the dental college of Won-Kwang Univ. are surveyed and selected in terms of Angle's classification of malocclusion, whose TMJ radiographs were taken in the centric occlusion and centric relation. In each maiocclusion groups, the mean and standard deviation of anterior, posterior and superior joint space of the right, left and both side in CO & CR are evaluated and also those of the fossa height and the articular eminence angle of the right, left and both sides are evaluated. The obtained results were as follows: 1. In the correlation coefficient between the malocclusion groups, no other items except the posterior joint space of the right side in CR between in class I and class III are significant. 2. In the correlation coefficient between the right and left side, the each joint space in class I malocclusion group and class II malocclusion group are significant. 3. In the change of each joint space during the transmit from CO to CR, there is a tendency of increasing anterior joint space and decreasing posterior, superior joint spaces in class I, II malocclusion and increasing superior joint space and decreasing anterior, posterior joint space in class III malocclusion, which is significant in the correlation coefficient, but not significant in the T-test. 4. In each malocclusion group, the correlation coefficient between the posterior joint space and the superior joint space in C.R is highly significant. 5. The fossa height of class II malocclusion group is lesser than that of class I or class III, which is not significant in T-test. 6. In the correlation coefficient between Rt. and Lt. side in the fossa height, it is not significant in class I and class III group, but significant in class II malocclusion group. 7. The articular eminence angle of class II malocclusion group is larger then that of class I or class III groups, which is fairly significant. 8. In the correlation coefficient between Rt. and Lt. side in the articular eminence angle, it is significant in each malocclusion group.

• Archives of Plastic Surgery
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• v.38 no.2
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• pp.199-202
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• 2011

Purpose: Hyoid bone is a U-shaped bone in the anterior of the neck. Hyoid bone fractures are exceedingly rare and represent only 0.002% of all fractures because of its protective position relative to the mandible and its suspension by elastic musculature. We report a patient who presented hyoid bone fracture associated with hypoglossal nerve palsy. We also discuss the possible complication and treatment. Methods: A 69-year-old man was transferred from another institution because of persistent purulent discharge from the left chin. He had a history of trauma in which a knuckle crane grabbed his face and neck in the construction site. A CT scan at the time of the accident demonstrated a comminuted fracture of the right side of the mandible and hyoid bone fracture at the junction between body and right greater cornua. The displaced fracture of hyoid bone and fullness in the pre-epiglottic space were noted, probably indicating some edema. The patient was transferred into ICU after treatment of emergency tracheostomy because the patient showed respiratory distress rapidly. When the patient was hospitalized in our emergency room, he complained of dysphagia and pain when swallowing. On examination of oral cavity, the presence of muscle wasting with fasciculation of the tongue was noted and the tongue deviates to the left side on protruding from the mouth. Pharyngolarygoscopy was performed to make sure that there was no evidence of progressive swelling and pharyngeal laceration. Results: The patient underwent surgical removal of dead and infected tissue from the wound and reconstruction of mandibular bony defect by iliac bone grafting. Hyoid bone fracture was managed conservatively with oral analgesics, soft diet and restricted movement. Hypoglossal nerve palsy was resolved within 7 weeks after trauma without complications. Conclusion: Closed hyoid bone fracture is usually uncomplicated and thus it can be treated conservatively. Surgical intervention for hyoid bone fracture is recommended for patient with airway compromise, pharyngeal perforation and painful symptoms which show no response to conservative care. Furthermore, since respiratory distress syndrome may develop quickly, close observation is required. Besides, hypoglossal nerve palsy is a rarely recognized complication of hyoid bone fracture.

• Imaging Science in Dentistry
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• v.39 no.3
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• pp.149-156
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• 2009

Purpose : The purpose of this study was to develop a stent-based image guided surgery system and to apply it to oral and maxillofacial surgeries for anatomically complex sites. Materials and Methods : We devised a patient-specific stent for patient-to-image registration and navigation. Three-dimensional positions of the reference probe and the tool probe were tracked by an optical camera system and the relative position of the handpiece drill tip to the reference probe was monitored continuously on the monitor of a PC. Using 8 landmarks for measuring accuracy, the spatial discrepancy between CT image coordinate and physical coordinate was calculated for testing the normality. Results : The accuracy over 8 anatomical landmarks showed an overall mean of $0.56{\pm}0.16\;mm$. The developed system was applied to a surgery for a vertical alveolar bone augmentation in right mandibular posterior area and possible interior alveolar nerve injury case of an impacted third molar. The developed system provided continuous monitoring of invisible anatomical structures during operation and 3D information for operation sites. The clinical challenge showed sufficient accuracy and availability of anatomically complex operation sites. Conclusion : The developed system showed sufficient accuracy and availability in oral and maxillofacial surgeries for anatomically complex sites.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.3
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• pp.186-194
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• 2015

Purpose: To evaluate the effects of implant location and length on stress distribution and displacement in osseointegrated-implants that were associated with mandibular distal extension removable partial dentures (DERPD). Materials and Methods: A sagittally cut model with the #33, #34 teeth and a removable partial denture of the left mandible was used. Seven models were designed with NX 9.0. Models A, B, C had implants with lengths of 11, 6, 4 mm, respectively, under the denture base of the #37 artificial tooth. Models D, E, F had implants with lengths of 11, 6, 4 mm, respectively, under the denture base of the #36 artificial tooth. Model G did not have any implants. Axial force (250 N) was loaded on #36 central fossa. The finite element analysis was performed with MSC Nastran. Von Mises stress maps were plotted to visualize the results. Results: The models of #37 implant placement showed much lower stress concentration on the surrounding bone of the implant compared with #36. The #36 implant position tended to reduce displacement more than #37. Conclusion: When an IARPD is designed, the distal positioning of implant placement has more advantages in the edentulous bone of DERPD on the prognosis of short implants and the stress distribution of edentulous alveolar bone. Using implants with longer lengths are important for stress distribution. However, Additional studies are necessary of the effects of length on implant survival.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.4
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• pp.464-473
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• 2018

The purpose of this study was to investigate the distribution of eruption disturbance and to analyze its causes, treatment methods, and duration of orthodontic traction, based on 703 patients with eruption disturbance who were treated in the pediatric dental clinic of Seoul National University Dental Hospital between July 2011 and June 2016. Eruption disturbance in pediatric patients was most prevalent in the maxillary canine, followed by the maxillary central incisor and maxillary first molar. Eruption disorder of the maxillary canine was more common in females (p < 0.001), whereas the maxillary central incisor (p = 0.009), maxillary first molar (p < 0.001) and mandibular first molar (p = 0.028) were more common in males than females. The most common causes of eruption disturbance were abnormality of the eruption pathway and the presence of obstacles in the pathway. Orthodontic traction was the most prevalent treatment choice for eruption disorder, mostly done for the maxillary central incisors. The duration of orthodontic traction was shorter with younger age (p < 0.001) and lower crown position (p < 0.001). It is important for pediatric patients to detect eruption disorders early through regular checkup, and it is necessary to initiate treatment at an appropriate time with an accurate diagnosis and treatment plan.