• Journal of Periodontal and Implant Science
• /
• v.37 no.2
• /
• pp.287-295
• /
• 2007

As a general treatment modality of subgingival tooth defect in aethetic area, implant or crown and bridge therapy after extraction of affected tooth can be used. But as more conservative treatment, crown lengthening can be considered and not to lose periodontal attachment and impair aethetic appearance, surgical extrusion can be considered as a treatment of choice. In this case report, 3 cases of surgical extrusion was represented and appropriate time for initiation of endodontic treatment according to the post-surgical tooth mobility was investigated. In 8 patient who has subgingival tooth defect in aethetic area, intracrevicular incision is performed and flap was reflected with care not to injure interproximal papillae. With forcep or periotome, tooth was luxated and sutured in properely extruded position according to biologic width with or without $180^{\circ}$ rotation. 8 cases show favorable short and long term results. In some cases, surgical extrusion with $180^{\circ}$ rotation can minimized extent of extrusion and semi-rigid fixation without apical bone graft seems to secure good prognosis. In 8 cases, endodontic treatment started about 3 weeks after surgery. This time corresponds with the moment when mobility of extruded tooth became 1 degree and this results concide with other previous reports. If it is done on adequate case selection and surgical technique, surgical extrusion seems to be a good treatment modalilty to replace the implant restoration in aethetic area.

• International Journal of Precision Engineering and Manufacturing
• /
• v.2 no.4
• /
• pp.5-11
• /
• 2001

Vibration and noise of gears is doc to the transmission error and the vibration exciting force caused by the periodically alternating tooth stiffness. Transmission error is the rotation delay between driving and driven gear caused by manufacturing error, alignment error in assembly and so on. Tooth stiffness changes with the proceeding mesh of teeth. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification. end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the meshing analysis of gears. Formulated constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth bending strength, surface durability, and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. We also investigate the relation between the aspect ratio and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is expected to be practically useful to resolve the problem of vibration of helical gears.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.11
• /
• pp.199-205
• /
• 2000

The vibration and noise of gears is due to the vibration exciting force caused by the tooth stiffness which changes periodically as the mesh of teeth proceeds and by the transmission error, that is, the rotation delay between driving gear and driven gear caused by manufacturing error and alignment error in assembly and so on. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification, end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the mesh analysis of gears. The constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth fillet stress, surface durability and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. And, since the aspect ratio is an important parameter of tooth modification, we investigate the relation between it and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is to be utilized to resolve the problem of vibration of helical gears.

• The korean journal of orthodontics
• /
• v.34 no.5 s.106
• /
• pp.417-428
• /
• 2004

The purpose of this study was to evaluate the stress distributions at the periodontal ligament (PDL) and displacements of the maxillary first molar when mesially directed force was applied under various molar angulations and rotations. A three dimensional finite element model of the maxiilary first molar and its periodontal ligament was made Upright position, mesially angulated position by $20^{\circ}$ and distally angulated position of the same degree were simulated to investigate the effect of molar angulation. An anteriorly directed force of 200g countertipping moment of 1,800gm-mm (9:1 moment/force ratio) and counterrotation moment of 1,000gm-mm (5:1 moment/force ratio) were applied in each situation. To evaluate the effect of molar rotation on the stress distribution, mesial-in rotation by $20^{\circ}$ and the same amount of distal-in rotation were simulated. The same force and moments were applied in each situation. The results were as follows: In all situations, there was no significant difference in mesially directed tooth displacement Also, any differences in stress distributions could not be found, in other words. there were no different mesial movements. Stress distributions and tooth displacement of the $20^{\circ}$ mesially angulated situation were very similar with those of the $20^{\circ}$ distal-in rotated situation. The same phenomenon was obserned between the $20^{\circ}$ distally angulated situation and $20^{\circ}$ mesial-in rotated situation. When the tooth was mesially angulated, or distal-in rotated, mesially directed force made the tooth rotate in the coronal plane. with its roots moving buccally, and its crown moving lingually. When the tooth was distally angulated, or mesial-in rotated, mesially directed force made the tooth rotate in the coronal plane, with its roots moving lingually and its crown moving buccally. When force is applied to au angulated or rotated molar, the orthodontist should understand that additional torque control is needed to prevent unwanted tooth rotation in the coronal plane.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.51 no.1
• /
• pp.66-79
• /
• 2024

This study aimed to assess the prevalence and distribution pattern of dental anomalies in the permanent teeth of patients with non-syndromic cleft lip with or without cleft palate. Additionally, it aimed to compare differences in dental anomalies between cleft and non-cleft areas, considering gender and cleft phenotype. Panoramic radiographs of 164 patients diagnosed with non-syndromic orofacial clefts were retrospectively analyzed by a single examiner to confirm dental anomalies. The dental anomalies investigated included tooth agenesis, supernumerary teeth, microdontia, rotation, ectopic eruption, and enamel hypoplasia. Cleft phenotypes were categorized into 7 types based on medical and dental records. A significantly higher prevalence of supernumerary teeth was observed in males than females within non-cleft areas (p = 0.017), with no significant differences in other dental anomalies. In non-cleft area, patients with cleft palate exhibited a high prevalence of tooth agenesis (p < 0.0001) and microdontia (p = 0.012) compared to other cleft phenotypes. Maxillary incisor rotation was closely associated with adjacent tooth agenesis in unilateral cleft lip and palate cases (p = 0.034). This study suggests that the additional subphenotype based on dental anomalies in patients with orofacial cleft may serve as applicable clinical markers.

• Journal of Oral Medicine and Pain
• /
• v.23 no.2
• /
• pp.143-155
• /
• 1998

This study was performed to investigate the factor that might affect mandibualr body rotation. For the study, 115 patients with temporomandibular disorders and 35 dental students without angy signs and symptoms of temporomandibular disorders were randomly selected as the patient group and the contreol group, respectively. Preferred chewing side, Angle' classification, lateral guidance pattern, and affected side were clinically recorded, and the amount of Mandibular body rotational torque movement was measured in wide opening and closure, in right and left excursion with vertical and lateral distance in frontal plane, right and left rotational angel in horizontal and in frontal plane. Masticatory muscle activity of anteriorocclusal contact pattern on maximal hard biting were also observed synchronously with BioEMG and T-Scan , respectively. The observed items were muscle activity of anterior temporalis and superficial masseter, and tooth contact status related to contact number, force, duration, and occlusal unbalance between right and left arch. The data collected were analyzed by SAS statistical program. The results of this study were as follows : 1. Mean value of vertical distance in frontal plane in wide opening and closure was more in control subjects than in patients, but there was no difference for rotational angle. In right excursion, rotational angles were greater in patient group than in control group. 2. Comparison among the subjects by preferred chewing side did not reveal any significant difference, but comparison among patients by affected side showed more rotational amount in bilaterally affected patients than in unilaterally affected patients. 3. Comparison among the subjects by Angle's classification or lateral guidance pattern revealed no difference. There was also no difference between preferred chewing side and contralateral side, and between affected side and contralateral side. 4. Positive correlation in madibular rotational torque movements were observed among vertical distance, total horizontal rotation angle, electromyographic activity of anterior temporalis, tooth contact number, and tooth contact force but total frontal rotation angle almost did not show any correlation with other variables except vertical distance.

• The Journal of the Korean dental association
• /
• v.54 no.8
• /
• pp.592-603
• /
• 2016

Pathologic tooth migration (PTM) caused by periodontal disease is a relatively common disease with a prevalance rate of 30~55%. It is one of the reasons for periodontal treatment of patients. PTM occurs when various factors related to the position of the tooth are altered and clinical features of PTM include facial flaring, diastema, proximal tilting, rotation, and extrusion of teeth. The purpose of this study was to assess the treatment of teeth of hopeless prognosis through the practice of modified intentional replantation on pathologic migrated tooth. This study presents cases using modified intentional replantation for the treatment of pathologic tooth migration caused by severe periodontitis. Modified intentional replantation is a technique that prepares extraction socket by using an implant drill. Based on 3 cases performed with modified intentional replantation, an improvement of clinical periodontal indicators such as probing pocket depth, bleeding on probing, tooth mobility, and pathologic teeth migration was observed after surgery. Also, the patients were satisfied with the functional and esthetic improvement.

• The korean journal of orthodontics
• /
• v.34 no.3 s.104
• /
• pp.219-227
• /
• 2004

The purpose of this study was to evaluate the spatial changes of mesial-in rotated maxillary molar and opposite anchor tooth during derotation by the precision transpalatal arch (TPA) with the use of a new typodont simulation system, the Calorific machine system, which was designed to observe the whole process of tooth movement. The maxillary right first molar was used for the anchor tooth and the maxillary left first molar was used for the mesial-in rotated tooth, and the angle of rotation was increased to 20,40, and 60. A passive precision TPA was fabricated and then activated by bending the left arm to 20, 40, and 60. Each experiment was repeated five times under the same conditions and analyzed by ANOVA and Tucky's Studentized Range (HSD) test. In the occlusal plane, when the bending angle of precision TPA was increased, the mesiobuccal cusp of the rotated molar moved more buccally (p<0.001) and less distally (p<0.001) while the distolingual cusp moved in the mesiopalatal direction. In the sagittal plane, the palatal roots of the derotated molar moved mesially (p<0.001). In the traverse plane, the derotated molar showed slight extrusion (p<0.001). The upper right first molar, which was used as an anchor tooth, showed clinically insignificant movement across all three planes.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.38 no.1
• /
• pp.62-67
• /
• 2011

Early eruption refers to an accelerated eruption of a tooth beyond the normal eruption period. The clinical findings of an early erupted tooth with little formation of crown and/or root include severe mobility, pain on chewing, hypocalcification of the enamel, and inclination, displacement, and rotation of the tooth. The radiographic findings include underdeveloped root and insufficient bone support. Early eruption of a permanent tooth can cause several complications such as chronic trauma, pain, edema, an increased rate of premolar impaction and tooth displacement and/or rotation. Therefore, when a permanent tooth erupts earlier than its normal eruption period with accompanying symptoms, appropriate treatments should be done as soon as possible. A female patient of age 7 without any systemic disease was referred from a local dental clinic with chief complaint of severe mobilities and pain in both upper first premolars. According to the clinical and radiographic examinations, the permanent teeth erupted earlier with barely formed roots, severe mobilities, edema, and pain. This case is to report the successful accomplishment of root formations and stabilization of teeth after applying intraoral fixed appliances using bands and spurs for 14 months.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.05a
• /
• pp.65-66
• /
• 2010

To improve the gear noise quality, gear tooth grinding machine are widely used in automotive industry. While using the gear profile grinding machine to improve the gear tooth quality of the transmission, several defects such as chattering, tooth waves that cause the gear noise occasionally happened. But it is very difficult to solve that problem, because there is no one who knows the setting up the optimal grinding condition appropriately. The abnormal manufacturing conditions which make the gear noise make the engineer to spend a lot of time, effort, and money. Due to demands for solving the serious abnormal gear noise happened in the new FF 6th stage automatic transmission in the mass product stage, the vibration checking process in the worm wheel axis, work rotation and fixed axis of the grinding machine were adapted to find the root causes. As a result, gear profile wave are affected by the work rotation axis's unbalance which is caused by worm wheel feeding speed. And a primary and the secondary grinding feeding speed, cutting oil, work fixed forces are also proved as the important factors. After setting up the grinding condition reported in this paper, it was adapted successfully to the grinding machine to manufacture the new FF 6th speed automatic transmissions' output gear. The gear noise was dramatically disappeared and the process and results will offer good guides to the engineers who manufacture the gear with the grinding machine.