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Biomedical subjects

H M Kyung

Publications and source records attributed to H M Kyung.

6 recordsLinked to original sources
PubMed2006

An evaluation of localized debonding between fibre post and root canal wall by finite element simulation.

AIM: To investigate the effect of localized bonding defects between fibre post and root canal wall on the stress distribution in the radicular dentine. METHODOLOGY: A tooth restored with a fibre post together with the alveolar bone were axisymmetrically modelled. A total of four models with localized debonding at the post to canal wall interface in different locations were analysed: Model A: perfect bonding layer over the entire interface; Model B: debonding at the cervical 1/3 of the interface; Model C: debonding at the mid 1/3; and Model D: debonding at the apical 1/3. A tooth restored without using a post was also included as the control (Model E). A load of 50 N was applied to the top of the full veneer cast crown at angles of 0, 15, 30, and 45 degrees with the tooth's longitudinal axis. The stress distribution across the fibre post and root dentine was compared. RESULTS: Higher stresses were generated in the radicular dentine as a function of the load angle. The differences in the stress distribution were negligible between the four models and virtually the same as that for model E (control). CONCLUSIONS: In this simulation, localized debonding at the fibre post to root canal wall interface, regardless of its location along the post, had little effect on the stress distribution in the root dentine.

Dental Bonding↗
PubMed1992

Differential effects of 1 alpha, 25-dihydroxycholecalciferol and 24R,25-dihydroxycholecalciferol on the proliferation and the differentiated phenotype of rabbit craniofacial chondrocytes in primary culture.

The response of chondrocytes from the craniofacial complex to vitamin D3 has been investigated in vitro. Chondrocytes were isolated from nasal septal cartilage (NSC), sphenooccipital synchondrosis (SOS) and mandibular condylar cartilage (MCC) of New Zealand rabbits weighing from 250-350 g. Treatment of NSC-chondrocytes with 1,25-(OH)2D3 or 24,25-(OH)2D3 for 6 days from days 4 to 10 in medium containing charcoal-treated FBS increased DNA synthesis dose-dependently at the concentrations of 10(-9) M to 10(-8) M, or 10(-11) M to 10(-9) M, respectively. 1,25-(OH)2D3 inhibited GAG synthesis dose dependently at the concentrations of 10(-11) M to 10(-8) M. 24,25-(OH)2D3 had no effect on GAG synthesis in NSC-chondrocytes. 1,25-(OH)2D3 increased DNA synthesis in SOS-chondrocytes at a concentration of 10(-10) M and inhibited GAG synthesis. 24,25-(OH)2D3 had no significant effect on DNA and GAG syntheses of SOS-chondrocytes. 1,25-(OH)2D3 slightly increased GAG synthesis at a concentration of 10(-10) M in MCC-chondrocytes but had no effect on DNA synthesis. 24,25-(OH)2D3 had no effect on DNA and GAG synthesis in MCC-chondrocytes at concentrations of 10(-11) M to 10(-9) M. These finding suggest that vitamin D3 metabolites, 1,25-(OH)2D3 and 24,25-(OH)2D3 play an important role in the growth of craniofacial cartilage by differently stimulating proliferation and expression of the differentiated phenotype of chondrocytes from NSC, SOS and MCC.

24,25-Dihydroxyvitamin D 3↗
PubMed1992

Stimulation of alkaline phosphatase activity by ascorbic acid and suppression by 1,25-dihydroxycholecalciferol in rabbit craniofacial chondrocytes in culture.

To clarify the role of vitamins D and C in chondrocyte hypertrophy of craniofacial cartilage, we have studied cultured chondrocytes from rabbit mandibular condylar cartilage (MCC), sphenooccipital synchondrosis (SOS) and nasal septal cartilage (NSC) under conditions in which these cells mature into hypertrophic chondrocytes. In cultures of MCC- and SOS-chondrocytes, alkaline phosphatase (ALPase) activity started to increase on day 9 at confluence and the cessation of cell division, and reached a maximum on day 18. The degree of the increase of ALPase activity on day 18 was higher in MCC-chondrocytes than in SOS-chondrocytes. ALPase activity was very low level in NSC- and CGC-chondrocytes. Ascorbic acid induced a marked increase in ALPase activity in MCC-, SOS-, NSC- and CGC-chondrocytes. The ALPase activities in MCC- and SOS-chondrocytes with 50 micrograms/ml ascorbic acid were 2.5-times those in its absence. Those in NSC- and CGC-chondrocytes were 10 times and 20 times, respectively. When chondrocytes were cultured with 10% charcoal-treated serum, ALPase activity decreased less than that in cultures with 10% normal serum in MCC-, SOS-, NSC- and CGC-chondrocytes. Treatment of 1,25-(OH)2D3 for 9 days from days 4 to 13 in MCC-chondrocytes and for 14 days from days 4 to 18 in SOS-, NSC- and CGC-chondrocytes inhibited ALPase activity dose-dependently at the concentrations of 10(-12) M to 10(-8) M in MCC- chondrocytes, 10(-10) M to 10(-8) M in SOS- and CGC-chondrocytes, 10(-11) M to 10(-9) M in NSC-chondrocytes. These findings suggest that 1,25-(OH)2D3 and ascorbic acid may be involved in the control of cartilage growth and terminal differentiation.

Alkaline Phosphatase↗
PubMed1989

[Individual indirect bonding technique (IIBT) using set-up model].

There has been much progress in Edgewise Appliance since E.H. Angle. One of the most important procedures in edgewise appliance is correct bracket position. Not only conventional edgewise appliance but also straight wire appliance & lingual appliance cannot be used more effectively unless the bracket position is accurate. Improper bracket positioning may reveal much problems during treatment, especially in finishing state. It may require either rebonding after the removal of the malpositioned bracket or the greater number of arch wire and the more complex wire bending, causing much difficulty in performing effective treatments. This made me invent Individual Indirect Bonding Technique with the use of multi-purpose set-up model in order to determine a correct and objective bracket position according to individual patients. This technique is more accurate than former indirect bonding techniques in bracket positioning, because it decides the bracket position on a set-up model which has produced to have the occlusal relationship the clinician desired. This technique is especially effective in straight wire appliance and lingual appliance in which the correct bracket positioning is indispensible.

Dental Bonding↗