• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.2
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• pp.253-261
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• 2006

Estimating the size of unerupted teeth is an essential aspect of orthodontic diagnosis and treatment planning in the mixed dentition. Several methods were introduced and used for the prediction. The most common methods among these would be Moyers probability chart and Tanaka and Johnston equations. These are currently used widely, but they were developed for Caucasians. Because there are clear racial differences in teeth size, the objectives of this study were to produce correlation coefficients between the combined mesiodistal widths of the permanent mandibular incisors and those of the canines and premolars for each quadrant, and prediction tables with regression equations, specifically for Korean. 178 young adults (70 women, 108 men, mean age 21.63 years) were selected from the College of Dentistry, Yonsei University, Seoul, Korea. The mesiodistal crown diameters of the permanent teeth were measured with calipers. Significant sexual dimorphism was found in tooth sizes. The correlation coefficients between the total mesiodistal width of the mandibular permanent incisors and those of the maxillary and mandibular canines and premolars were found to be between 0.52 and 0.64. The standard error of the estimatation was better (0.60) for women and the ${\gamma}^2$ values ranged from 0.27 to 0.41 for both sexes Prediction tables were prepared for Korean. This study showed larger canine and premolar diameters than Tanaka and Johnston's and Moyers' studies which might be due to the racial differences. Further investigations with a larger sample size will be needed for more representative data on the Korean population.

• Journal of Dental Anesthesia and Pain Medicine
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• v.20 no.6
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• pp.367-375
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• 2020

Background: Intraosseous anesthesia (IO) allows the anesthetic solution to be injected directly into the cancellous bone. The anesthetic solution immediately reaches the periapical region, and thus the axonal area of the nerve, where it can temporarily disable the sodium pump. The effect is felt almost without any time delay, and only a small amount of anesthetic solution is required. Methods: This study aims to investigate the efficacy of IO using the AnestoⓇ device after infiltration anesthesia (IA) and/or inferior alveolar nerve block anesthesia (IANB) failed to work in symptomatic irreversible pulpitis (hot tooth). The 33 patients included in the study were treated additionally with 1.7 ml articaine hydrochloride with 1:100,000 epinephrine hydrochloride (UltracainⓇ D-S, Sanofi-Aventis, Frankfurt, Germany) IO. Results: The electrical pulp test showed that 95.76% of the volunteers reacted positively to the combination of IANB or IA with the IO. In women, the additive IO was effective at 97.22%. In men, the IO led to pain elimination in 94.00% of cases. The duration of the IO was less than a quarter of an hour (13.03 min). The IO worked longer in women than in men (13.61 min vs. 12.33 min). Overall, more than every third tooth that needed trepanation was located in the posterior area of the mandible (36.4%). Treatment of hot teeth in this area was associated with an increased pulse rate and increased residual pain. There was a moderate correlation (Spearman-Rho [IRI] = 0.280) between the Visual Analog Scale (VAS) score and bone density, and a significant correlation (IRI = 0.612) between subjective residual pain and bone width. The IO resulted in a moderate, transient increase in the pulse rate by approximately 20 bpm. This is similar to the temporary increase in heart rate after conventional anesthesia techniques in non-preloaded patients and can be considered clinically irrelevant. Conclusion: IO with the AnestoⓇ device as an extension and deepening of local pain elimination is recommended for the treatment of hot teeth.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.1
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• pp.69-76
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• 1999

The mandibular buccal frenum is defined as a fold of mucous membrane at the posterior labial vestibule and attaches the lips and the cheeks to the alveolar mucosa, gingiva, and underlying periosteum. The buccal frenum becomes a problem when its attachment is too close to the marginal gingiva. It may then pull on healthy gingiva, encourage plaque formation and interfere with tooth brushing. Especially, heavy buccal frenum mucogingivally results in insufficent attached gingiva, inadequate vestibular depth and high frenum attachment and also difficulty in eruption of mandibular premolar. Frenotomy, frenectomy and mucogingival surgery are used in treating heavy buccal frenum. Frenotomy with autogenous free gingival graft has been used popularly because of its stable result. But, it is difficult in younger children because of inadequate donor site, difficulty in making recipient site and behavior management. Frenotomy with apically positioned flap is considered as more efficient way for a very young child with heavy buccal frenum. Additionally, modified deep sedation with $N_2O-O_2$ can be used as an adjunct for the effective treatment outcome. Decrease in muscle pull, adequate width of attached gingiva and increased vestibular depth can be expected from this treatment approach.

• Journal of the korean academy of Pediatric Dentistry
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• v.21 no.2
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• pp.547-554
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• 1994

Posterior crossbites are abnormal buccal, or lingual relationship of a tooth or teeth of the maxilla, the mandible, or both when the teeth of the two arches are in occlusion and involve the molars and premolars. Posterior crossbites are classified as dental, muscular(functional), or skeletal. In an effort to avoid occlusal interferences caused by the inadequate arch width, the patient deviates the mandible laterally upon closure to achieve maximum intercuspation. This is described as functional posterior crossbite. Correction of functional posterior crossbites in the primary & early mixed dentition as early as possible after diagnosis has been recommended, because crossbites do not automatically improve with the eruption of the permanent teeth. Functional posterior crossbites, if left untreated, may have deleterious effects on the development and function of the TMJ. The diagnosis and management of three cases is presented. Each patient with functional posterior crossbites is treated using the bilateral maxillary expansion appliance.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.36-45
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• 1996

The precise estimation of the reliability and life of the Ravigneaux planetary gear train used in an automatic transmission is necessary in order to enable accurate material and geometric properties to reliability distrobution and the number of load cycles at failure. These are critical for the proba- bilistic design of complex planetary gear system as Ravigneaux type particularly during various gear ratios. The Ravigneaux planetary gear train has five gears, such as a forward and a reverse sun gear, a short and a long pinion, and an annulus gear. In this paper, the Ravigneaux gear system is analyzed to figure out the reliablity distribution. i.e. the probability of survival in the system without its overhaul. First, the reliablity method based on the Weibull distribution is used in conjuction with the Palmgren's model to predict both the individual reliabilities of its components and the nimber of load cycles when the system failed. Then using the presented method, the life of the Ravigneaux gear system can be determined. Alwo the different design parameters such as tooth face width, material property, and Weibull exponent are applied and reached to optimal ones. Thus, the precise evaluation of the reliability and life of the Ravigneaux planetary gear train used in an automatic transmission can be effectively carried out.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.151-156
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• 1995

This paper presents a methodology for real-time detecting and identifying the runout geometry of an end mill. Cutter runout is a common but undesirable phenomenon in multi-tooth machining such as end-milling process because it introduces variable chip loading to insert which results in a accelerated tool wear,amplification of force variation and hence enlargement vibration amplitude. Form understanding of chip load change kinematics, the analytical sutting force model was formulated as the angular domain convolution of three dynamic cutting force component functions. By virtue of the convolution integration property, the frequency domain expression of the total cutting forces can be given as the algebraic multiplication of the Fourier transforms of the local cutting forces and the chip width density of the cutter. Experimental study are presented to validata the analytical model. This study provides the in-process monitoring and compensation of dynamic cutter runout to improve machining tolerance tolerance and surface quality for industriql application.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.32.1-32.7
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• 2019

Background: Tooth extraction commonly leads to loss of residual alveolar ridge, thus compromising the room available for the implant placement. To combat the post-extraction alveolar loss, alveolar ridge preservation is practiced, with the advent of the biomaterial available. The purpose of this study was to assess the efficiency of calcium phosphosilicate biomaterial in alveolar ridge preservation. Twenty patients indicated for extraction were selected followed by socket grafting using calcium phosphosilicate. Implant placement was done 6 months postoperatively during which a core was harvested from the preserved sockets. Clinico-radiographic measurements of hard and soft tissues were taken at baseline and 6 months post-grafting. Results: There were no significant changes in the radiographic and soft tissue parameters while significant changes in hard tissue parameters with 1.9 mm (p = 0.013) gain in mid-buccal aspect and 1.1 mm (p = 0.019) loss in horizontal bone width were observed. The histomorphometric evaluation depicted the vital bone volume of 54.5 ± 16.76%, non-mineralized tissue 43.50 ± 15.80%, and residual material 2.00 ± 3.37%. Conclusion: The implants placed in these preserved ridges presented 100% success rate with acceptable stability after a 1-year follow-up, concluding calcium phosphosilicate is a predictable biomaterial in alveolar ridge preservation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.45-51
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• 2014

Generally, marine transmissions contain straight shafts and helical gears, meaning that enginerooms require more space. In order to guarantee a levelengine space for conical involute gears or beveloid gears, both of which are important machine parts, a conical gear was used to replace the traditional cylinder gear. Owing to weak points such as the point contact phenomenon of the teeth, a limitation of the width of each tooth in terms of the addendum, the variational modification coefficient,and the difficulty of processing, research about conical involute gears remains at a standstill. Along with the increasing number of applications of conical involute gears, research on conical gear design technology is necessary. In this paper, in an effort to enhance conical gear design technology, research on the 3D modeling and stress analyses of helical conical involute gears were done.

• Imaging Science in Dentistry
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• v.48 no.3
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• pp.191-199
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• 2018

Purpose: This study classified alveolar arch forms and evaluated differences in alveolar bone thickness among arch forms in the anterior esthetic region using cone-beam computed tomography (CBCT) images. Materials and Methods: Axial views of 113 CBCT images were assessed at the level of 3 mm below the cementoenamel junction (CEJ) of the right and left canines. The root center points of teeth in the anterior esthetic region were used as reference points. Arch forms were classified according to their transverse dimensions and the intercanine width-to-depth ratio. The buccolingual alveolar bone thickness of each tooth was measured at 3 mm below the CEJ and at the mid-root level. Differences in the mean thicknesses among arch forms were analyzed. Results: Anterior maxillary arches could be classified as long narrow, short medium, long medium, and long wide arches. Significant differences in buccolingual alveolar bone thickness among the arch groups were found at both levels. The long wide arches presented the greatest bone thickness, followed by the long medium arches, while the long narrow and short medium arches were the thinnest. Conclusion: Arch forms were classified as long narrow, short medium, long medium, and long wide. The buccolingual alveolar bone thickness exhibited significant differences among the arch forms.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.4
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• pp.893-898
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• 1996

The occlusal disharmonies resulted from labially protruded or malpositioned teeth can damage the periodontium and induce the non-inflammatory gingival recession. For these cases, a conservative approach was performed by improving oral hygiene and correcting the axial and positional status of the gingivally recessed teeth and removing the prematurely contacted areas. In some cases, rapid remission of tooth mobility and gradual decrease of gingival recession was observed just after start of treatment. In cases of gingival recession in permanent lower incisors of the children with mixed dentition, the treatment of choice is non-surgical conservative approaches. In cases when the gingival inflammation can be controlled through reinforcing the oral hygiene, when attached gingiva have a potential to increase in width through growth (not more than 1 year after eruption or not yet arrived at adult level), and when the recession can be corrected by moving the teeth from labial cortical plate through orthodontic treatment, the conservative measures would be the first choice. On the contrary, when recession has exceeded beyond the level of CEJ, when the gingival inflammation existed with the cause of poor oral hygiene, when the attached gingiva have little potential to increase (for example, more than 8 years after eruption), and when the conservative measures yielded no benefit after 4-8 weeks of treatment, the surgical approaches should be sought.