Calcium phosphate 결정 성장 최적화를 위한 Ti 표면의 BaTiO_3 박막 형성에 관한 연구

조진우,양홍서,박영준,황규석,송종은,이용렬 전남대학교 치과대학 2001 구강과학 Vol.13 No.2

This study was purposed to establish an optimized manufacturing process for a negatively charged ferroelectric thin flim on titanium substrate in order to develop a new implant system having the mechanical strength and bone forming ability. Ferroelectric materials show an alignment of positive and negative charges by poling treatment. Based on this property, this study was performed with the assumption that the Ca^2+ ions would be easily attracted on negatively charged surface and the attracted cation might behave as nuclei for bone-like crystal grownth in biological solutions. In order to have an osteoinducibility by the ferroelectric thin film coating, continuous and flawless crystalline thin film should be formed with ferroelectricity, and finally should be adequately poling treated. In this study, BaTiO_3 (BTO) was selected as a ferroelectric material. Before thin film coating process, most favorable poling condition was investiged with the evaluation of the difference in calcium phosphate (Ca-P) formation in simulated body fluid (SBF). Moreover, the parameters to form an optimum thin film were studied. Dense bulk BTO disks were fabricate using cold isostatic pressing(CIP) and sintered in air at 1300℃ for 2 hours. Sintered BTO disk was polished, and he crystallinity, microstructure, and ferroelectric characteristics were evaluated using an X-ray diffraction analysis (XRD), a field emission scanning electron microscope (FE-SEM), and an Impedance analyzer. To find the optimum poling condition for the calcium phosphate crystal formation, sintered bulk BTO specimens were treated with either of following poling conditions; 1) room temperature poling treatment [ polarizing field (Ep) = 25kV/cm, at 25℃ for 2 hours], 2) under Tc medium-temperaturepoling treatment (Ep=20kV/cm, from 85˚C to 25˚C for 2 hour), and 3) above Tc high-temperature poling were immesed in simulated body fluid (SBF) for 30 days, and the formation of calcium phosphate (Ca-P) layer n the surface was evaluated. The crystallinity, microstructure, and ferroelectric characteristic of BTO thin film were evaluated withthe variation of final heat treatment. It was performed after establishing the starting substance-solvent mixing ratio, coating times, and pre-heating temperature optimal to form continuous and flawless BTO thin film adequate for having ferroelectricity. Perparation of BTO thin film was made by dipping-pyrolysis technique using metal naphthenates as starting substances. BTO thin films was spin-coated on Ti substrate by dipping-pyrolysis technique using sol obtained by mixing Ba-naphthenate and Ti-naphthenate as starting substances. Pre-firing temperature of BTO thin film was performed at 450℃ because organic-solvent ws completely volatilized without any crystal growth, and the final heat treatment was performed at 600, 700 or 800℃, respectively. The results are as follows; 1. BTO disk sintered at 1300℃ for 2 hours showed average grain size of about 1㎛ and the relative dielectric constant at 1㎑ was abut 3000∼3500. 2. After immersing the sintered bulk BTO poled at respective conditions in SBF for 30 days, Ca-P layers were present on the negatively charged surfaces. In contrary, positively charged Bto surface did not show any noticeable charge of the surface microstructure after SBF immersion. 3. In he case of poling condition 1 and 2 treated with below Tc, Ca/P ratio showed a relatively low value of 1,.2∼1.5. While, in the case of poling condition 3 treated with above Tc, Ca/P ratio was 1.5∼1.67, which is similar to that of biological apatite. This phenomenon demonstrates that poling the BTO above the temperature of Tc is preferable for the Ca-P formation. 4. For thin film BTO coastin, the starting substance was prepared by an equimolar mixing of the Ba and Ti-naphthenate. Dilution of the starting substance with toluene was most appropriate at sol : toluene ratio of 5.2:4.8 Too thin sol produced porosity in film, and too thick sol resulted cracks in the film. By repeating the coating and pre-firing procedure 15 times, homogeneous film of 0.5㎛ thickness could be fabricated, and perfomed well during the poling treatment without breakdown. 5. The heat-treatmen of the BTO thin film at 700℃ produced a homogeneous crystalline structure without heterogeneous TiO2 formation. The BTO thin film heat-treated at 600℃ showed non-crystallinity and no ferroelectricity. Treatment at 800℃ produced heterogeneous TiO2 phase in the film, which is unfavorabe for having ferroelectricity by the distortion of the perovskite structure. The relative dielectic constant at 1 ㎑ was 152 and 112 by heat-treatment at 700 and 800℃, respectively. In summary, these results demonstrated that poling the ferroelectric B_aT_iO_3 surface negatively is effective for the formation of Ca-P layer in simulated body fluids. Poling condition at a temperature cooling from above Tc down to room temperature is most effective. By optimizing the method of BTO thin film coating on metal substrate for the formation of Ca-P layer, the data of this study might be applied for the manufacture of new bioactive implant system.

The Effect of Static Magnetic Fields on Molecular and Cellular Activities

Park, Jae-Gu,Hwang, Hyeon-sik 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

Optimal force for orthodontic treatment is the force that produces a rapid rate of tooth movement without discomfort to the patient or ensuing tissue damage. Recently considerable interest has been generated in the application of magnets as a way to obtain an optimal force. In vitro assays were made for investigating the effect of static magnetic fields of Sm-Co magnets on molecular and cellular activities. The distance of erythrocyte sedimentation was measured directly, and the activities and the syntheses of Fe^2+ -related enzymes (catalase and No synthase) and non Fe^2+ -related enzyme (lactic dehydrogenase) were assayed by the spectrophotometer. The growth and the proliferation of osteoblast-like cells MC_3 T_3-E_1 were determined by the crystal violet staining and the ^3H-thymidine incorporation. The erythrocytes were exposed to the pole face flux density of 1,400 G (gauss), and the enzymes and osteoblast-like cells MC_3 T_3 E_1 were exposed to the flux density of 7,000 G. The results obtained were as follows : 1. The distance of sedimentation of erythrocyte was not affected by the static magnetic fields. 2. The activities of catalase and lactic dehydrogenase were not affected by the static magnetic fields. 3. The intracellular syntheses of NO synthase and lactic dehydrogenase were not affected by the static magnetic fields. 4. The growth and the proliferation of cultured osteoblast-like cells MC_3 T_3-E_1 were not affected by the static magnetic fields. These results suggested that the molecular and cellular activities were not significantly influenced by the static magnetic fields.

Streptomyces exfoliatus가 생성하는 mutanase에 의한 인공치태 억제 작용

송도원,양규호 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

The main component of dental plaque is the mutan containing the α-1, 3 bond. The following results were obtained by using a blue mutan to assess the factors affecting the mutan-digesting activity of Streptomyces exfoliatus isolated from soil. A clear zone was produced by mutanase-producing Streptomyces exfoliatus on the minimal essential agar containing blue mutan. Streptomyces exfoliatus digested more blue mutan in the minimal essential broth at pH 7.0 than at pH 5.5 or 8.5. Streptomyces exfoliatus digested more blue mutan at 37℃ than at 32℃ or 42℃(P<0.05). When the concentration of CaCl_2 was increased in the minimal essential broth, the digestion of blue mutan was increased(P<0.05). The optimal concentration of KCl was 10mM to digest blue mutan, but a similar amount of blue mutan was digested at the range of 0.1mM to 6.4mM of MgCl_2. When the culture supernatant of Streptomyces exfoliatus was mixed with 2X brain heart infusion broth containing 0.5% yeast extract and 10% sucrose, less artificial plaque was formed by Streptococcus mutans on the orthodontic wire(P<0.05). These results indicated that the secretion of mutanase was identified in culture supernatant of mutan-digesting Streptomyces exfoliatus, suppressing the formation of artificial plaque by Streptococcus mutans.

터널형 2급와동 충전재의 탄성계수와 전단결합강도 및 수복치의 변연융선 파절강도에 관한 연구

이가연,양규호 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

An alternative design to conventional class Ⅱ cavity preparation for proximal carious lesions is the tunnel preparation. It preserves the marginal ridge intact, thus making it possible to maintain the natural contact relationship with the adjacent tooth and minimize tooth reduction. This in vitro study was purposed to evaluate the effect of the materials' elastic constants and shear-bond strength on the marginal ridge fracture resistance of teeth restored by the tunnel technique, and to find the materials of choice for tunnel restorations. Resinomer??, Ketac-silver??, Miracle-Mix??, and Tytin?? were used as restorative material. The elastic constants of each restorative material were evaluated by ultrasonic pulse measurement. Young's modulus and bulk modulus of the restorative materials were evaluated in three specimens for each material type. The shear-bond strength of the restorative materials to the dentin surface was measured after thermocycling 400 times between 6 and 60℃, using ten specimens for each material type. For measuring marginal ridge strength, 60 sound extracted molar teeth were distributed into six groups by size. Sound molar teeth were used as a Control group and unfilled prepared teeth were grouped as Unrestored. Another four groups were named Resinomer group, Ketac-Silver group, Miracle Mix group, and Tytin group by type of restorative material . Tunnel cavity preparation was done with #½, 2, and 4 round burs in sequence. Initial access to proximal surface was made through an occlusal access preparation started at least 2 mm from the marginal ridge, and the proximal opening was formed about 2.5 mm below the marginal ridge. After restoration and thermocycling, marginal ridge strength was measured using a universal testing machine. The results were as follows : 1. The young's modulus of Tytin?? was 63.95 GPa, followed by Ketac-Silver?? 27.60 GPa, Miracle-mix?? 18.48 GPa, and Resinomer?? 10.74 GPa showing significant differences between the groups (P<0.05). The bulk modulus of the materials showed the same order as Young's modulus. The value of Tytin?? showed 59.57 GPa indicating that it will deform less than other materials under the same stress. It was followed by Ketac-Silver?? 23.57 GPa, Miracle Mix?? 12.50 GPa, and Resinomer?? 11.60 GPa. 2. The Resinomer group had a shear-bond strength of 7.41 MPa which was significantly higher than those of the Ketac-Silver group(1.80 MPa) and the Miracle Mix group(2.84 MPa)(P<0.01). All the specimens of Tytin group detatched from the dentin surface during themocycling. 3. The mean marginal ridge strength of the Unrestored group(46.14 kgf) was significantly lower than that of the Control group(84.24 kgf)(P<0.01). The marginal ridge strength of teeth restored by the tunnel technique was, in order, Ketac-Silver group 74.06 kgf, Miracle Mix group 73.36 kgf, Resinomer group 63.47 kgf, and Tytin group 58.76 kgf. The Ketac-Silver, Miracle Mix, and Resinomer groups showed no significant difference with the Control group(P>0.05), but the Tytin group showed significantly lower strength compared to the Control group(P<0.05). The results showed that the marginal ridge strength of the teeth restored by the tunnel technique was not significantly lower than that of sound teeth. They also demonstrated that the bonding strength of the restorative material to the tooth surface should be high and the modulus of elasticity should not be lower than that of the tooth in order to restore the marginal ridge strength to its natural condition.

치아이동 후 고정방법이 성견 치주인대섬유의 재배열에 미치는 영향

이기헌,황현식 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

The purpose of this study was to evaluate the effect of splinting methods on the rearrangement of periodontal fibers after experimental tooth movement. Orthodontic force was applied by placing closed coil spring between upper third incisor and canine in seven dogs, weighing 20 kg or more. After 3 weeks of force application, 0.0215 inch multistrand wire and polyethylene ribbon were bonded to each side, as a flexible and rigid splinting respectively in 6 experimental animals. The remaining 1 served as the control group. Each 2 animals were sacrificed at 4, 8 and 12 weeks after splinting respectively and prepared histologically for hematoxyline-eosin and Masson's trichrome staining. The results of this study were obtained as follows : 1. After tooth movement, periodontal space was narrowed and periodontal fibers were thick on pressure side, while elongated fibers were observed on tension side. 2. After 4 weeks of retention, the rearrangement of periodontal fibers was observed in the flexible splinting group but not in the rigid splinting group. 3. After 8 weeks of retention, the rearrangement of periodontal fibers was observed in both groups but the difference could not detected between two groups. 4. During the retention period, the rearrangement of periodontal fibers was faster in tension side than in pressure side. These results show that the rearrangement of periodontal fibers is also obtained by rigid splinting after tooth movement. It is suggested that the rigid splinting by polyethylene ribbon can be used as a way of postorthodontic retention.

성견의 외과적 치근이개부 골결손에 차폐막과 골이식재를 이용한 조직유도재생술시 치유양상

정은희,정현주 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

The present study was to evaluate the healing patterns of guided tissue regeneration(GTR) using resorbable Vicry??(polyglactin 910) mesh and nonresorbable expanded polytetrafluoroethylene(ePTFE) membrane with or without bone grafting using autogeneous bone and demineralized freeze-dried bone allograft(DFDBA) in the grade Ⅱ furcation defects. Mucoperiosteal flaps were reflected buccally in the mandibular 2nd, 3rd and 4th premolar areas and furcation defects were created surgically by removing 5 × 6mm alveolar bone in 4 dogs. Root surfaces were thoroughly debrided of periodontal ligament and cementum, and notches were placed on root sruface at the most apical bone level. In the right and left mandibular quadrant, each tooth was received Vicryl?? mesh(ACE Surgical Supply Co., USA) only, Vicryl?? mesh with DFDBA, Vicryl?? mesh with autogeneous bone grafts, ePTFE membrane(Gore-tex?? membrane, W.L. Gore & Associates Inc., USA) only, ePTFE membrane with DFDBA or ePTFE membrane with autogeneous bone grafts. For the fluorescent microscopic examination, fluorescent agents were injected at 2, 4 and 8 weeks after surgery. Four weeks after surgery, 2 dogs were sacrificed and ePTFE membranes were removed from remaining 2 dogs, which were sacrificed at 12 weeks after surgery. Undecalcified tissues were embedded in cethylmethacrylate and 10㎛ thick sections were cut in a buccolingual direction. These sections were stained with hematoxylin-eosin stain and Masson's trichrome stain, and evaluated by descriptive histology and linear measurements. The results were as follows : 1) Vicryl?? mesh group showed less connective tissue attachment than ePTFE membrane group. 2) The combination of GTR using Vicryl?? mesh and osseous grafts resulted in new attachment and new bone formation more than GTR using Vicryl?? mesh only. 3) GTR using ePTFE membrane, with or without osseous grafts, enhanced periodontal regeneration. 4) Root resorption and dentoalveolar ankylosis were observed in the areas treated with the combination of GTR and DFDBA. It was suggested that the effect of adjunctive bone grafting in GTR procedure depends on the materials and the physical properties of barrier membranes. Vicryl?? mesh performed a barrier function and the use of adjunctive bone grafting may enhance the periodontal regeneration.

동종탈회냉동건조골편을 이용한 가토 하악골 불연속 결손부 수복재건에 관한 연구

박광,정성수 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

This study was purposed to evaluate the mechanical effects and calcium contents of demineralized bone matrix on the repair of discontinuous mandibular defects in a rabbit model. In experimental group Ⅰ, the 6 mm discontinuous bone defect was created in the mandibular body and then grafted with arutogenous iliac bone. In experimental group Ⅱ, the same bone defects was made and grafted with demineralized allogeneic bone. The experimental animals were sacrified at 4 weeks and 8 weeks postoperatively. To evaluate the effects of autogenous and demineralized allogeneic bone graft on the discontinuous mandible, the biomechanical study to compare the mechnical strenths, and the degree of calcium contents by atomic absorption spectrometry were performed. The biomechanical studies demonstrated that the bone induced by autogenous bone achieved 68% of normal bone and the demineralized allogeneic bone matrix bone(DABM) achieved 35% of normal bone at 8 weeks. Atomic absorption spedtrometric study revealed that both the autogenous and demineralized bone demonstrated very small concetration of calcium at fourth weeks. However, there were gradual increase of calcium concentration after 8 weeks. It showed that the autogenous grafts are worthy using in mandibular discontinuous defects, while demineralized allogeneic bone has some possibility to repair the discontinuous defects.

Mutanase를 생성하는 Microbispora rosea의 분리, 동정 및 효소의 특성 연구

정진,오종석 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

A microorganism producing mutanase was isolated from soil on RL, agar containing blue mutan as sole carbon source and identified as Microbispora rosea on the basis of the cultural, morphological and physiological observations. Mutanase production was enhanced when Microbispora rosea was cultured in the media containing 0.01% glucose, 10mM KCl, 0.1mM MgCl_2, 16mM CaCl_2 and 0.2% mutan. The enzyme was purified by (NH_4)_2SO_4 precipitation, anion exchange column chromatography on Mono Q following DEAE cellulose column chromatography and gel filtration on superose 12 column. The molecular weight of the purified enzyme was 48,000Da by SDS-PAGE and the amino-terminal sequences were Ser-Pro-Gly-Asn-Ser-Pro-Gly-Ala. The optimum pH and temperature for enzyme activity were 5.5 and 40℃, respectively. The enzyme was stable up to 50℃ on heat treatment at pH 5.5 for 30 min. The enzyme activity was inhibited by the presence of Zn^++, Fe^++ at 10mM. Tween 20 increased enzyme activity in contrast with the effect of SDS and Triton X-100. In vitro, the purified mutanase had strong inhibitory effect on the formation of artificial plaque while the reduction of preformed glucan was weak. The mutanase from Microbispora rosea had an effect on the formation of glucan as well as reduction of glucan produced by other Streptococcus mutans.

흰쥐 구치와 주위조직에서 신경조직의 발생에 관한 면역조직화학적 연구

김태경,이은주 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

The distribution patterns of nerve fibers immunoreactive to calcitonin gene-related peptide (CGRP), substance P(SP) and neuropeptide Y(NPY) were studied and compared with innervation visualized by antibody to neurofilament protein-200(NFP) in developing dental structure in rats aged 13 to 27 days. A substantially greater part of the nerve fibers was immunoreactive to NFP and CGRP than to SP and NPY in all stage of dental development. In the bell stage, nerve fibers immunoreactive to NFP and CGRP were found in the dental follicle but not in the dental papilla and stellate reticulum. In the advanced bell stage, after initiation of dentine and enamel formation, regular NFP and CGRP-immunoreactive fibers were found in the periphery and beneath of dental papilla in the dental follicle. In the stage that crown formation was completed and the root formation began, SP and NPY-immunoreactive fibers were first observed mainly in connection with larger blood vessles in the basal part of pulp. Concomitantly with the begining of root formation, a subodontoblastic nerve plexus immunoreactive to NFP and CGRP was formed and NFP and CGRP-immunoreactive fibers were found within the odontoblastic layer. At the stage of root development and eruption, NFP and CGRP-immunoreactive fibers were rich in the subodonoblastic nerve plexus, odontoblastic layer and apical third of periodontal ligament. While SP and NPY-immunoreactive fibers occured occasionally around the blood vessels in the pulp. When the teeth occluded fully, much more NFP and CGRP-immunoreactive fibers occured at the odontoblastic layer and subodontoblastic nerve plexus in the pulp horns and coronal pulp and apical third of periodontal ligament. No apparent difference in the occurrence and distribution of SP and NPY-immunoreactive fibers was found in comparison with those of preceding developmental stage. Hence, it may be concluded that the developing innervation of NFP and CGRP-immunoreactive fibers is well correlated with the stage of development of individual teeth.

측두하악장애 환자에서 두부자세 변화가 초기 교합접촉에 미치는 영향

최원호,기우천 전남대학교 치과대학 1995 전남치대논문집 Vol.7 No.1

The pusrpose of this study was to evaluate an effect of change on head posture initial occlusal contacts with measuring the distances between initial occlusal contacts and maximum intercuspal position at different head posture in TMDs patient. For this study, 24 patients from age 13 to 36 were selected, they were examined health history taken, patients who have sign and symptoms of TMDs were examine before the study. For the normal group, 21 adults from age 23 to 25 were selected. They have normal or classⅠmolar relationship, and have no symptoms of TMJ or masticatory muscles, and some of them had restorations less than 3 areas on each tooth, and have no other prosthetic restorations. Difference on distance between initial occlusal contact and maximum intercuspal position with mandibular kinesiograph(MKG??)(K6 diagnostic system, Myo-tronic Inc., U.S.A.) in upright, supine, 45˚extension, 30˚flexion position of the head were measured. The Frankfort horizontal plane was used as a reference plane. The results were as follows 1. There were significant differences between initial occlusal contacts of the normal and patient group on upright position and 30˚ flexion of the head(p<0.05, p<0.01). 2. The positions of the initial occlusal contacts have a tendency to place anterior and inferior to maximal intercuspal position in upright position and 30˚ flexion of the head as well as posterior and inferior in supine position and 45˚ extension of the head in the noraml and patient groups. 3. There were significant differences among the initial occlusal contacts between upright and supine position ; upright and 45˚ extension of the head(p<0.05) ; supine position and 30˚ flexion of the head, and 30˚ flexion and 45˚ extension of the head in the patient group(p<0.01). The results have shown that after treatment on the supine position, it may be necessary to check occlusal contact on the upright position as well as flexion of the head. It may need careful adjustment in occlusal condition on upright position of TMDs patient.