• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.27 no.1
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• pp.189-201
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• 1997

The purpose of this study was to evaluate the position and shape of mental foramen in panoramic radiographs. For this study, panoramic radiographs were obtained from the 200 adults and evaluated the position and shape of mental foramen. According to various positional changes in panoramic radiographs of the patients, the author also obtained panoramic radiographs from the 100 adults and then evaluated the positional and shape changes of mental foramen. The following results were obtained: 1. Shapes of mental foramen were observed elliptical(43.3％), round or oval(42.5％), unidentified(7.5％) and diffuse (6.7％) type in descending order of frequency. 2. Horiwntal position of mental foramen were most frequently observed at the 2nd premolar area(54.2％), and area between the 1st premolar and 2nd premolar(43.1％), area between the 2nd premolar and 1st molar(2.7％) in descending order of frequency. 3. Vertical position of mental foramen were most frequently observed at the inferior of apex(88.2％), and at apex (9.7％), overlap with apex(1.9％), superior of apex(0.2％) in descending order of frequency. 4. According to various positional changes in panoramic radiographs of the patients, shape changes of mental foramen were more obviously observed at the forward 10mm and chin down 100 positioned panoramic radiographs. And changes of horiwntal and vertical position were observed in similar to compared with normal positioned panoramic radiographs.

• Journal of dental hygiene science
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• v.16 no.4
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• pp.272-283
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• 2016

This study compared and analyzed the occluding effects of fluoride compounds and desensitizers, which are commonly used in dental clinics, on dentinal tubules. This study also evaluated the persistence of the active ingredients over time by performing toothbrushing with an electric toothbrush. Thirty-five molar teeth, which had been extracted within the past 3 months from healthy people without tooth decays, amalgam fillings, or dental crowns, were divided into 4 pieces each. Of these, 135 teeth pieces were used as study specimens. These specimens were divided into a control group, an untreated group, and 5 experimental groups (acidulated fluoride gel, fluoride varnish, Gluma, Super Seal, and SE-Bond). The specimens were then subjected to toothbrushing equivalent to 1 week (140 times), 2 weeks (280 times), and 4 weeks (560 times), and the occluding effects on dentinal tubules in 3 regions of each specimen were examined under a scanning electron microscope. The fluoride varnish treated group showed the highest degree of dentinal tubule occlusion effects during the first, second, and fourth weeks of toothbrushing, with the SE-Bond treated group showing the second highest degree and the Gluma treated group showing the lowest degree. After 4 weeks of toothbrushing, the Gluma treated group and the Super Seal treated group showed the lowest degrees of dentinal tubule occlusion effects. In summary, the fluoride varnish treated group and the SE-Bond treated group displayed higher occlusion effects even after 4 weeks of treatment than did the other experimental groups. Therefore, it is the authors' belief that fluoride varnish and SE-Bond are effective for treating dentinal hyperesthesia.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.4
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• pp.381-388
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• 2017

Purpose: Unpredictable shrinkage of zirconia during sintering process causes discrepancy. Therefore, there have been attempts to reduce discrepancy by milling zirconia after sintering. However, due to the hardness of sintered zirconia, milling takes longer time, causes damage to the machine and causes chip formation. With customized zirconia block using the mean dimension of prepared natural dentition, it is expected to overcome these shortcomings. Materials and methods: The mean dimension of prepared natural dentition was analyzed as STL file after scanning of prepared teeth treated at SNUDH. The transverse, frontal and sagittal planes were set using Mimics and Photoshop. 3D volume was projected on each plane, and the outer line was measured through external tangent line, and the inner line was measured through inflection point of tangent line. Results: The mean height of prepared incisal (N = 57) is $6.60{\pm}1.05mm$, mesiodistal length is $2.98{\pm}0.73mm$, buccolingual length is $2.04{\pm}0.73mm$. The mean height of prepared premolar (N = 15) is $5.37{\pm}1.49mm$, mesiodistal length is $4.10{\pm}1.78mm$, buccolingual length is $5.86{\pm}1.55mm$. And the mean height of prepared molar (N = 13) is $5.11{\pm}1.29mm$, mesiodistal length is $6.80{\pm}1.18mm$, buccolingual length is $7.34{\pm}1.40mm$. Conclusion: Using the mean dimension of prepared natural dentition, it is expected to be able to fabricate customized zirconia block.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.1
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• pp.11-18
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• 2004

The eruption of permanent teeth represents the movement in the alveolar bone before appearance in oral cavity, to the occlusal plane after appearance in oral cavity, and additive movement after reaching th the occlusal plane. Tooth eruption is mostly controlled by genetic signals. The eruption stage is divided to preeruptive alveolar stage, alveolar bone stage, mucosal stage according to the process of growth and development. If the disturbance is occured in any stage of eruption, tooth does not erupt. The cause of eruption disturbance are ectopic position of the tooth germ, obstruction of the eruption path and defects in the follicle or PDL. In the treatment of eruption disturbance, surgical procedures are commonly used. There are three kind of surgical procedure ; surgical exposure, surgical repositioning, surgical exposure and traction Surgical exposure is basic procedure. This involves removal of mucosa, bone, lesion that are surrounding the teeth, dental sac when necessary to maintain a patent channel between the crown and the normal eruptive path into the oral cavity. To ensure this patency, many techniques including cementation of a celluloid crown, packing with gutta-percha or zinc oxide-eugenol, or a surgical pack, are used. When surgical exposure is conducted, operators should not expose any part of cervical root cement and not injure periodontium or root of adjunct tooth. After surgical exposure, tooth should be surrounded by keratinized gingiva. There is direct relationship between the extent of development of pathophysiologic aberrations and the intensity of the manipulative injury inflicted on the tooth by surgical treatment, so operator should consider this thing. In these cases, surgical exposure is conducted on Maxillary 1st milars that have a eruption disturbance and improve the eruption disturbance effectively.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.4
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• pp.619-627
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• 2008

The objective of this study was to compare the microleakage of five adhesive systems in the enamel and dentin of permanent teeth. Class V cavity preparations with occlusal margins in enamel and gingival margins in dentin were prepared on both buccal and lingual surfaces of 25 extracted human molar teeth. The tested adhesives were: Adper Scotchbond Multi-purpose Plus Adhesive (SM), Adper Single bond 2 (SB), Clearfil SE Bond (SE), Adper Prompt L-Pop (PL) and G-Bond (GB). The results were as follows: 1. At the enamel margins, PL showed the highest leakage value(0.85), and others showed values of SB(0.55), GB(0.50), SM(0.35) and SE(0.25) in decreasing order. There were statistically significant differences in PL vs. SM and PL vs. SE(p<0.05). 2. At the dentin margins, GB showed the highest leakage value(2.10), and others showed values of SE(1.45), PL(1.40), SB(1.05), SM(0.70) in decreasing order. There were statistically significant differences in GB vs. SB and GB vs. SM(p<0.05). 3. Dentin margins showed high dye penetration rate than enamel margins in all material tested groups and there were statistically significant differences for SE, PL and GB.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.5
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• pp.581-596
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• 1999

The purpose of this study was to investigate the stress distribution of the abutment and sup-porting tissues according to the slopes and types of the guiding plane of distal extension removable partial dentures. The 3-dimensional finite element method was used and the finite element models were prepared as follows. Model I : Kratochvil type guiding plane with $90^{\circ}$ to residual ridge Model II : Kratochvil type guiding plane with $95^{\circ}$ to residual ridge Model III : Kratochvil type guiding plane with $100^{\circ}$ to residual ridge Model IV : Krol type guiding plane with $90^{\circ}$ to residual ridge Distal extension partial denture which right mandibular first and second molar were lost was used and the second premolar was prepared as primary abutment with RPI type retainer. Then 150N of compressive force was applied to central fossae of the first and second molars and von Mises stress and displacement were measured. The results were as follows 1. Model I and Model IV showed a similar stress distribution pattern and the stress was concentrated on the apex of the root of the abutment. 2. The stress was increased and concentrated on mesial side of the root of the abutment in Model II. The stress was concentrated on buccal and mesiobuccal side of the root of the abutment in Model IV. 3. In Model I, the root of the abutment displaced and twisted a little in clockwise. In Model IV, the root of the abutment displaced to distolingually at apical region of the root and mesiobuccally at cervical region of the root. 4. In Model II, the root of the abutment displaced to mesiolingually at apical region of the root and more displaced and twisted in counterclockwise at cervical region of the root. In Model III, the root of the abutment displaced to mesiobucally at apical region of the root and more displaced and twisted in clockwise at cervical region of the root.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.3
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• pp.181-188
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• 2010

Purpose: The purpose of this study was to compare the stress distribution characteristics of four different abutment connections on SS-$III^{(R)}$ fixture under occlusal loading, using 3-dimensional finite element method. Materials and methods: The fixture of SS-$III^{(R)}$ (Osstem, Korea) with 4 mm diameter and 11.5 mm length and 4 types of abutments were analyzed; Solid, Com-Octa, ComOcta Gold, and Octa abutment. The models were placed in the area of first molar in the mandible. The 4 loading conditions were; (1) the vertical loading of 100 N on the central fossa, (2) the vertical loading of 100 N on the buccal cusp, (3) the $30^{\circ}$ inclined loading of 100 N to lingual side on the central fossa, and (4) the $30^{\circ}$ inclined loading of 100 N to the lingual side on the buccal cusp. The 3G.Author program was used, the von-Mises stress was calculated and the stress contours were plotted on each part of the implant systems and the surrounding bone structures. Results: Regardless of abutment types and loading conditions, higher stress concentration was observed at the cortical bone. In cancellous bone, the highest stress was observed at apical portion and the maximum stress occurred at the implant neck. The higher internal stress was observed in the fixtures than in the bone. The lowest stress was observed at loading condition 1 and the stress concentration was also lower than any other loading conditions. Conclusion: Within the limitation of the result of this study, it seems that the abutment connection type does not affect much on the stress distribution of bone structure.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.3
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• pp.199-206
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• 2010

This study investigated the effects of strontium on osteoblastic phenotypes of cultured human periostealderived cells. Periosteal tissues were harvested from mandible during surgical extraction of lower impacted third molar. Periosteal-derived cells were introduced into cell culture. After passage 3, the periostealderived cells were further cultured for 28 days in an osteogenic induction DMEM medium supplemented with fetal bovine serum, ascorbic acid 2-phosphate, dexamethasone and at a density of $3{\times}10^4$ cells/well in a 6-well plate. In this culture medium, strontium at different concentrations (1, 5, 10, and 100 ${\mu}g$/mL) was added. The medium was changed every 3 days during the incubation period. We examined the cellular proliferation, histochemical detection and biochemical measurements of alkaline phosphatase (ALP), the RT-PCR analysis for ALP and osteocalcin, and von Kossa staining and calcium contents in the periostealderived cells. Cell proliferation was not associated with the addition of strontium in periosteal-derived cells. The ALP activity in the periosteal-derived cells was higher in 5, 10, and 100 ${\mu}g$/ml strontium-treated cells than in untreated cells at day 14 of culture. Among the strontium-treated cells, the ALP activity was appreciably higher in 100 ${\mu}g$/ml strontium-treated cells than in 5 and 10 ${\mu}g$/ml strontium-treated cells. The levels of ALP and osteocalcin mRNA in the periosteal-derived cells was also higher in strontium-treated cells than in untreated cells at day 14 of culture. Their levels were increased in a dose-dependent manner. Von Kossa-positive mineralization nodules were strongly observed in the 1 ${\mu}g$/ml strontium-treated cells at day 21 and 28 of culture. The calcium content in the periosteal-derived cells was also higher in 1 ${\mu}g$/ml strontium-treated cells at day 28 of culture. These results suggest that low concentration of strontium stimulates the osteoblastic phenotypes of more differentiated periosteal-derived cells, whereas high concentration of strontium stimulates the osteoblastic phenotypes of less differentiated periosteal-derived cells. The effects of strontium on osteoblastic phenotypes of periosteal-derived cells appear to be associated with differentiation-extent.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.441-452
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• 1998

The c-fos is known as neuronal marker of second neurons which is activated by noxious peripheral stimulation. To investigate the changes of c-fos el(pression in the trigeminal nucleus complex during tooth movement, immunohistochemical study was performed. Experimental rats(9 weeks old, 210 gm 21 rats) were divided into seven groups(normal, 1 hour group, 3 hour group, 6 hour group, 12 hour group, 1 day group,3 day group). Rats in the normal group were anesthesized without orthodontic force. Rats in the experimental groups were applied orthodontic force (approximately 30 gm) to upper right maxillary molar. Frozen sections of brain stem were immunostained using rabbit antisera. The changes of c-fos expression were observed with respect to rostrocaudal distribution, laminar organization, md duration of orthodontic force application. The study results were as follows $\cdot$The c-fos nuclei in the dorsal part were observed from ipsilateral transition zone of subnucleus interpolaris and subnucleus caudalis to $C_1$ cervical dorsal horn rostrocaudally. The maximal peak point was the rostral part of subnucleus caudalis. The greatest proportion of c-fos cells were located within lamina I and II. $\cdot$The c-fos nuclei in the dorsal Part were observed from the most caudal part of subnucleus interpolaris to the middle part of the subnucleus caudalis. $\cdot$The number of c-fos immunoreactive dot increased at 1 hour group, reached its maximum at the 3 and 6 hour groups, and showed a decreasing trend after 12 hours. These results imply that nociceptive stimulation caused by continuous orthodontic force might be modulated by transition zone of subnucleus interpolaris and subnucleus caudalis, subnucleus caudalis, $C_1$ spinal dorsal hem.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.3
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• pp.317-326
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• 2011

The mental foramen and anterior loop of the mandibular canal are important landmarks for mandibular surgical procedures. The purpose of this study was to analyze the shape and position of the mental foramen and anterior loop of the mandibular canal on the computed tomography (CT) images, and apply the results clinically. CT images of 96 patients (33 male, 36 female, age range 17~43 years, mean $24.6{\pm}4.99$ years) were enrolled. The horizontal and vertical position of the mental foramen, as well as the distance from the root apices were measured. The distance of the anterior loop of the mandibular canal to the root apices, and the buccal angle were measured. The mental foramen was found mostly below the second premolar observed in 81 cases (46.0%), between the first and second premolars in 67 cases (38.0%), and between the second premolar and first molar in 19 cases (10.2%). The mean distance between the mental foramen and the lower border of the mandible was $12.20{\pm}1.77$ mm, the mean distance between the mental foramen and root apex was $5.16{\pm}0.98$ mm. The mean distance of the anterior loop of the mandibular canal was $5.80{\pm}2.00$ mm. The buccal angle measured at $47.7{\pm}9.07^{\circ}$. The distance between the root apex and mental foramen measured as $5.16{\pm}0.98$ mm on panoramic radiography, and $6.2{\pm}3.07$ mm on CT. The mean distance between the mental foramen and mandibular canal was $5.39{\pm}1.62$ mm. When performing surgical procedures such as installing dental implants, it is important to minimize surgical trauma, especially the risk of damage to the mental nerve. To optimize the surgical outcome, a careful assessment of the shape and position of the mental foramen and the anterior loop of the mandibular canal must be made. CT images are useful for finding such anatomic structures.