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Biomedical subjects

Y I Chang

Publications and source records attributed to Y I Chang.

13 recordsLinked to original sources
PubMed2001

Original sagittal split osteotomy revisited for mandibular distraction.

Introduction: A malformed mandible and an abnormally positioned mandibular foramen make it difficult to plan an ideal osteotomy line for mandibular distraction. In addition, there have been reports of such complications as nonunion, damage and stretch injury of the inferior alveolar nerve and tooth germ damage when conventional osteotomy or corticotomy are used for mandibular distraction. The authors utilized the original sagittal split ramus osteotomy for mandibular distraction. Patients and Methods: Five patients (three unilateral hemifacial microsomia, one bilateral hemifacial microsomia, and one mandibular retrusion) were included in this study of distraction osteogenesis using the sagittal split ramus osteotomy. Extraoral distraction devices were applied to the first four patients. An intraoral device with mono-cortical screw fixation was used for the fifth patient. Result: In all five cases, the results of the distraction were satisfactory. Complications (as listed) of conventional osteotomy when used for distraction were avoided. Satisfactory results were achieved and these were also well maintained postoperatively (mean follow up: 36 months). Conclusion: The authors believe that sagittal osteotomy for mandibular distraction osteogenesis makes it possible, to avoid injury to the inferior alveolar nerve during operation and stretching injury during distraction and to prevent tooth germ injury. It is also possible to diversify the osteotomy line for various force vectors to enlarge the bony contact surface area. Therefore, we suggest that sagittal split ramus osteotomy should be used as a preferred modification of osteotomy for mandibular distraction. Copyright 2001 European Association for Cranio-Maxillofacial Surgery.

Journal Article↗
PubMed2001

Effects of recycling on the mechanical properties and the surface topography of nickel-titanium alloy wires.

The purpose of this study was to investigate the changes in mechanical properties, surface topography, and frictional forces of various nickel-titanium wires after recycling. Three types of nickel-titanium wires were separated into 3 groups: as-received condition (T0, control group), treated in artificial saliva for 4 weeks (T1), and treated in artificial saliva and autoclaved (T2). Strength changes were observed by tensile testing, and surface topography was assessed by scanning electron microscope and 3-D profilogram. Frictional coefficients were tested by friction test, and fatigue by bending fatigue test. Our findings showed that there were no statistically significant differences between the wires in maximum tensile strength, elongation rate, modulus of elasticity, and bending fatigue. Two wires demonstrated increased pitting and corrosion after recycling. The same 2 wires also demonstrated significantly greater surface roughness and maximum frictional coefficients compared with the control wires (P <.05), but the third wire showed no significant difference. However, surface roughness and frictional coefficient of the 2 wires after recycling were not greater than those of the third wire before treatment. Recycling increased the surface roughness and friction coefficients, but these seemed to have limited clinical significance.

Corrosion↗
PubMed1999

Cephalometric evaluation of the anterior open bite treatment.

The present study was aimed at evaluating the treatment changes of anterior open bite malocclusion cases treated by means of the Multiloop Edgewise Arch Wire technique, which is considered one of the more effective treatment modalities for anterior open bite malocclusions. The open bite sample was composed of 16 young adults, 4 males and 12 females. The normal occlusion sample, as a controlled sample was composed of 58 young adults who had pleasing facial profiles and normal occlusions with no experience of orthodontic or prosthodontic treatment. The normal sample was subdivided by the cephalometric vertical facial relationships. Forty adults with cephalometric vertical facial relationships within the normal range of Korean standards were classified as Normal Occlusion Group 1. Eighteen adults with an increased vertical facial relationship but with normal occlusion, were classified as Normal Occlusion Group 2. Thirty-nine reference points were digitized on each film, and the computerized cephalometric analysis was obtained with 8 skeletal, 10 dentoalveolar, 17 teeth angulations, and 4 occlusal plane measurements. Treatment changes were determined by the paired t test, and the structural differences between the four groups were tabulated by the Student's t test. The treatment changes were observed mainly in the dentoalveolar region in the upper and the lower occlusal planes, accompanied by the uprighting of the posterior teeth to the occlusal plane through the distal tipping movement of the entire dentition. After the treatment, there was a tendency for the structural feature of the open bite group to approximate those of the normal occlusion group 2. This ascertains that the treatment changes of open bite malocclusion produced by means of the multiloop edgewise arch wire technique are similar to those found in the natural dentoalveolar compensatory mechanism.

Adolescent↗
PubMed1995

Modulation of the ryanodine receptor sarcoplasmic reticular Ca2+ channel in skinned fibers of fast- and slow-twitch skeletal muscles from rabbits.

This study was performed to compare skinned fibers from rabbit adductor magnus (AM) and soleus (SL) muscles with regard to the influence of caffeine, Ca2+ and Mg2+ on the depressive effects of ryanodine (RYA) on the caffeine-induced tension transients. Single skinned fibers were immersed in solutions to load Ca2+ into, and release Ca2+ from the SR (a load-release cycle). Three cycles were sequentially performed in each skinned fiber: (1) a control (no RYA), (2) a conditioning period in which activation was carried out in the presence of ryanodine plus various concentrations of the modulators, i.e. caffeine, Ca2+ or Mg2+, and (3) a test (no RYA) which monitored the release activity retained after the conditioning cycle. The depressive effect of RYA was found to be a function of [ryanodine], [caffeine], or [Ca2+], and an inverse function of [Mg2+], where [] denotes concentration. The half-maximal effects of RYA in AM (5 microM RYA) and SL (10 microM RYA), respectively, occurred at a pCa50 of 5.32 versus 5.43 without caffeine, or pCa50 of 7.24 versus 6.88 and pMg50 of 3.29 versus 3.61 with 25 mM caffeine, at a [caffeine] of 4.96 versus 7.29 mM, and at a [ryanodine] of 31.0 versus 101.6 microM. Thus, the RYA depression in skinned muscle fibers is modulated by caffeine, Ca2+, and Mg2+ in both muscle types, and AM is at least two- to fourfold more sensitive than SL.

Animals↗
PubMed1994

Mechanisms of action of enflurane on vascular smooth muscle. Comparison of rabbit aorta and femoral artery.

BACKGROUND: This study was performed to elucidate the mechanisms of action of enflurane by comparing the vascular smooth muscle responses of conduit arteries of larger (aorta) and smaller (femoral artery) diameter to enflurane using isolated rings and skinned strips. METHODS: Isolated intact rings (endothelium denuded) of aorta and femoral artery from rabbits were activated by various concentrations of norepinephrine (NE) and the effects of enflurane were examined at the steady-state force. In a separate study, the rings were pretreated with verapamil before the NE activation and tested with enflurane. In the saponin-treated arterial strips ("skinned"), the effects of enflurane on Ca2+ uptake or release from the sarcoplasmic reticulum were studied using caffeine-induced tension transients. RESULTS: In isolated aortic rings, enflurane (0.9%-5%) enhanced tension development at low NE concentrations (5 and 30 nM) but depressed it at highest concentration (10 microM). In contrast, enflurane depressed tension development in the femoral artery at all NE concentrations. Enflurane caused significant increase in the NE-activated force in rings pretreated with verapamil. In skinned strips, enflurane (1%-3%) decreased Ca2+ uptake (concentration resulting in 50% depression: 1.8% for aorta and 2.5% for femoral artery) and increased Ca2+ release from the sarcoplasmic reticulum (59%-208% for aorta and 10%-55% for femoral artery). These effects were dose-dependent. Enflurane potentiated ryanodine depression of caffeine-induced tension transients. CONCLUSIONS: Enflurane has similar mechanisms of action in aorta and femoral artery: blocking Ca2+ influx, and causing, at least in part, Ca2+ release from the sarcoplasmic reticulum through the ryanodine-receptor channel. These cellular actions of enflurane account for the depression in femoral artery and enhancement in aorta of NE-activated force in isolated rings.

Animals↗
PubMed1993

Modulation of sarcoplasmic reticulum Ca(2+)-release channels by caffeine, Ca2+, and Mg2+ in skinned myocardial fibers of fetal and adult rats.

Ryanodine causes depression of the caffeine-induced tension transient (ryanodine depression) in skinned muscle fibers, because it blocks the sarcoplasmic reticulum (SR) Ca(2+)-release channels [Su, J. Y. (1988) Pflügers Arch 411:132-136, 371-377; (1992) Pflügers Arch 421:1-6]. This study was performed to examine the sensitivity of SR Ca(2+)-release channels to ryanodine in fetal compared to adult myocardium and to investigate the influence of Ca2+, caffeine, and Mg2+ on ryanodine depression in skinned fibers. Ryanodine (0.3 nM-1 microM) caused a dose-dependent depression in skinned myocardial fibers of the rat, and the fetal fibers (IC50 approximately 74 nM) were 26-fold less sensitive than those of the adult (IC50 approximately 2.9 nM). The depression induced by 0.1 microM or 1 microM ryanodine was a function of [caffeine], or [Ca2+] (pCa < 6.0), which was potentiated by caffeine, and an inverse function of [Mg2+]. At pCa > 8.0 plus 25 mM caffeine, a 20% ryanodine depression was observed in both the fetal and adult fibers, indicating independence from Ca2+. Ryanodine depression in skinned fibers of the fetus was less affected than that seen in the adult by pCai, [caffeine]i, or 25 mM caffeine plus pCai or plus pMgi (IC50 approximately pCa 4.5 versus 5.1; caffeine 12.7 mM versus 2 mM; pCa 6.7 versus 7.3; and pMg 3.9 versus 3.3 respectively). The results show that the SR Ca(2+)-release channel in both fetal and adult myocardium is modulated by Ca2+, caffeine, and Mg2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

The effect of cationic electrolytes on the adhesion of cells.

The adhesion rate of cells under charge regulation onto a spherical collector with constant potential is investigated in this paper. Particularly, the effect of the presence of cationic electrolytes in the suspension medium on the adhesion rate is examined. The result reveals that the presence of cationic electrolytes in the suspension medium raises the electrostatic repulsion force between cell and collector surface, when the separation distance between them is small than a critical value. This has the effect of decreasing the adhesion rate of cells. The adhesion rate of cells is quite sensitive to the value of Hamaker constant, especially at a high ionic strength value.

Journal Article↗
PubMed1990

The effect of multivalent cations on adhesion time for cellular adhesion to solid surfaces.

The dynamic behavior of the adhesion of a charge-regulated cell to a solid surface of constant potential is investigated. In particular, the effect of the presence of multivalent cations in the suspension medium on adhesion time is discussed. By neglecting the effect of hydrodynamic retardation and assuming that the bulk liquid phase is stagnant, we show that the presence of multivalent cations has the effect of retarding cell adhesion. At a fixed level of ionic strength, the adhesion time increases with the increase of the concentration of multivalent cations in the suspension medium, and decreases with the increase in magnitude of the Hamaker constant. For a fixed concentration of cations, the adhesion time decreases with the increase of ionic strength. The effect of the magnitude of Hamaker constant on adhesion time is appreciable if both the ionic strength and the concentration of cations are high.

Animals↗
PubMed1990

[Soft X-ray study on fetal cranio-facial growth and development].

This study was undertaken to ascertain the changes of fetuses in craniofacial dimension and to evaluate the growth and development during fetal period. Lateral cephalograms by soft X-ray were taken from 64 fetuses and were measured in linear and angular aspects. The following conclusions were obtained. 1. The linear increase rates of anterior cranial base length exceeded those of the posterior cranial base length. 2. Growth increments on horizontal dimension were greater than vertical dimension in the maxilla. 3. The cranial base angle was almost constant after fetal period 13 weeks with the average angle of 130 degrees. 4. The angle between anterior cranial base and palatal plane was decreased gently during fetal period.

Cephalometry↗
PubMed1989

The effect of cationic electrolytes on the electrostatic behavior of cellular surfaces with ionizable groups.

Based on the assumption that the electrostatic charges on the surface of sheep leukocytes arise from the dissociation of ionogenic groups, together with the presence of divalent cation (or trivalent cation) in the suspending medium of low ionic strength (or high ionic strength), the non-linear Poisson-Boltzmann equation for cell interaction with a solid surface with constant potential (or constant charge) is numerically solved in this paper. The cellular surface potential and the repulsive (or attractive) force is expressed as the function of separation distance. Because of shrinking the thickness of the electrostatic double layer at high ionic strength, the presence of cationic electrolyte has a less influential role on both the cellular surface potential and interaction force than at low ionic strength. However, due to the continuous equilibration of the ionogenic groups on the cellular surface as separation distance decreases, the presence of cationic electrolyte will not always reduce the interaction force during the whole adhesion period. The distance at which the cationic electrolyte changes its effect from positive to negative is termed the critical separation distance in this paper.

Animals↗