• The Journal of the Korea Contents Association
• /
• v.14 no.9
• /
• pp.343-349
• /
• 2014

The dental osseointegration implant should be enough to endure occlusion load and it's required to have efficient design and use of implant to disperse the stress into bones properly. Solidworks as a finite element analysis program for modeling and analysis of stress distribution was used for the research. The simple crown model was designed on applying conjoined condition with tightening torque of 20 Ncm of a abutment screw between a cement retained implant abutment and a fixture. A $45^{\circ}$ oblique loading from lingual to buccal side on buccal cusps of crown and performed finite element analysis by 100 N of external load. The results by a analysis for stress distribution of supporting bones of fixture were as below. The von Mises stress was concentrated on the upper side of supporting compact bone regardless of the diameters and lengths of fixture, and the efficiency result of stress reduction was increase of fixture's diameter than it's length. Therefore, it's effective to use wider fixture as possible to the conditions of supporting jaw bone.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.21 no.2
• /
• pp.131-138
• /
• 1999

The purpose of this study is to evaluate the effects of resorbable plate in the healing process of mandibular fracture. Reduction and rigid fixation was carried out on the artificial mandibular fracture site of the rabbits, using a resorbable screw, 1.5mm in diameter and 4.0mm in length, and an absorbable plate 1.5mm in thickness(Lactosorb$^{(R)}$). En block tissue specimens with plate were taken from the rabbits at 4, 6, 8, and 10 weeks intervals and specimen were observed with light microscope under the hematoxylin-eosin staining, to observe the inflammatory reaction and tissue healing process. The following conclusions were drawn: 1. The subject displayed good healing with no signs of detachment of the fixation plate. 2. At 4 weeks, the plate was covered by the connective tissue. Then at 6 weeks, bone regeneration was discovered around the plate. 3. During the period of healing, no inflammatory reaction or foreign body reaction, as a result of using resorbable plate, were observed. 4. At 8 weeks, the initial phase of the absorption of the plate was observed. Then at 10 weeks, macrophage were observed around the plate, indicating the absorption phase was in process. From the above results, it can be determined that when the resorbable plate is applied to rabbit, full recuperation occurs naturally in the absence of inflammatory reaction and foreign body reaction. The selected study is clinically valuable in proving this procedure.

• The Journal of Advanced Prosthodontics
• /
• v.1 no.1
• /
• pp.10-18
• /
• 2009

STATEMENT OF PROBLEM. Despite an improved bone reactions of Mg-incorporated implants in the animals, little yet has been carried out by the experimental investigations in functional loading conditions. PURPOSE. This study investigated the clinical and histologic parameters of osseointegrated Mg-incorporated implants in early loading conditions. MATERIAL AND METHODS. A total of 36 solid screw implants(diameter 3.75 mm, length 10 mm) were placed in the mandibles of 6 beagle dogs. Test groups included 18 Mg-incorporated implants. Turned titanium implants served as control. Gold crowns were inserted 4 weeks after implant placement and the dogs were immediately put on a food diet. Implants were observed for 10 weeks after loading. Radiographic assessments and stability tests were performed at the time of fixture installation, $2^{nd}$ stage surgery, 4 weeks after loading, and 10 weeks after loading. Histological observations and morphometrical measurements were also performed. RESULTS. Of 36 implants, 33 displayed no discernible mobility, corresponding to successful clinical function. There was no statistically significant difference between test implants and controls in marginal bone levels(P=.46) and RFA values. The mean BIC % in the Mg-implants was $54.5{\pm}8.4%$. The mean BIC % in the turned implant was $45.3{\pm}12.2%$. These differences between the Mg-implant and control implant were statistically significant(P=.005). CONCLUSIONS. The anodized, Mg-incorporated implant demonstrated significantly more bone-to-implant contact(BIC) in early loading conditions. CLINICAL IMPLICATIONS. The results of this study in beagle dogs suggest the possibility of achieving predictable stability of early loaded free-standing dental implants with Mg-incorporated surface.

• Journal of Ocean Engineering and Technology
• /
• v.35 no.1
• /
• pp.24-37
• /
• 2021

As one of the development directions of high-performance ships to reduce greenhouse gas emissions, there is research on high-performance propellers. However, in the case of conventional screw propellers, as they have been studied for a long time, there is a limit to improving efficiency only by depending on the conventional design and analysis methods. In this study, we tried to solve the problems using the Coanda effect by spraying a jet on the surface of the hydrofoil. The Coanda hydrofoil consists of a tunnel and jet slit to make jet flow. The computation was performed for each tunnel and slit position, and the efficiency according to the geometry of the hydrofoil was analyzed. In addition, a study on the 3D geometry change was conducted to analyze the performance according to the span direction spraying range and hydrofoil shape. As the height of the slit and the diameter of the tip were lower, when the slit is located in the center of the hydrofoil, the lift force increased and the drag force decreased. The increase rate of lift-to-drag ratio was different according to the shape of the hydrofoil, and the efficiency of the spraying condition of 0.1S-0.5S, which had the least effect on the vortex at the tip of the blade, was high for all 3D hydrofoils. When the geometry of the slit was optimized, and also the shape and spray range of the hydrofoil in 3D was considered, the efficiency of the jet sprayed hydrofoil was increased.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.27 no.5
• /
• pp.385-396
• /
• 2001

The purpose of this experiment was to examine the histological changes and the pattern of expression of proliferating cell nuclear antigen(PCNA) and type I collagen in the elongated bone affected by osteodistraction of the mandibular body in an adult canine model. Seven adult male mongrel dogs weighing over 20kg were used for this experiment. The author excluded 3 animals because they died before the planned time of sacrifice. The custom-made linear extraoral device and 4 bicortical fixation screws 2.3mm in diameter, 50mm in total length, 15mm in screw length were used in each animal. The distal part of the distractor produced a 0.75mm gap between proximal and distal bony segments every $360^{\circ}$ turn of the rotation rod of the device. The mandibular body of the right side from each animal was experimental side and the left side was left intact and served as control. At the experimental side, the mandibular body was osteotomized. After 5-day latency period, the segments were distracted with a rate of 1.1mm/day and a rhythm of two/day for ensuing 7 days. The animals were sacrificed at the 4th. 17th, and 32th day after the end of the distraction. The bony specimens were decalcified, embedded in paraffin, sectioned $5{\mu}m$ thick and stained with Masson trichrome and examined under the light microscope. The immunohistochemical examinations using anti-PCNA antibody and anti-type-I collagen antibody were performed to examine the pattern of the expression of PCNA and type I collagen, respectively. Results : 1. The mean increment of the distance between the proximal and distal screw-holding parts of the distractor was 6.8mm. The average elongation of the mandible in the experimental side was 5.3mm. The loss of elongation was 1.5mm in average. 2. New bone was already observed at the 4th. day after the end of distraction. But, bony union was not completed in the distraction gap at the 32th. day after the end of distraction by radiographic and microscopic examinations. 3. The expression rate of PCNA positive cells in the distraction gap had a tendency of decrease from 35.1-68.8% initially, to 49.1%, and finally to 17.6-27.2%. But at the final period, the tissue of the elongated gap still had the ability of cell proliferation. On the other hand, the expression of PCNA positive cells in the control side were negligible through the experimental period. 4. PCNA positive cells were observed primarily both at the central fibrous zone and at the region of just adjacent to CFZ which initiated new bone formation. 5. The expression pattern of the type I collagen was not zone-specific. They were observed diffusely throughout the elongation gap. 6. The predominant mechanism of new bone formation in the distraction gap was intramembranous. But, some of the regenerated bone was formed by endochondral ossification.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.34 no.3
• /
• pp.306-318
• /
• 2008

Anodic spark deposition method(ASD) surface treated titanium implant possesses a considerable osteoconductive potential that promoting a high level of implant osseointegration in normal bone. The purpose of this study was to observe the ASD implant's osseointegration in the osteoporosis-induced animal model. Twenty four rats, 10 weeks of age, were ovarectomized and 5 weeks later divided into two groups : ASD implant group and control implant group. Titanium screw implants (diameter; 2.0 mm, length, 3.5 mm; pitch-height, 0.4 mm) were designed for this study. Experimental implants were ASD treated and no treatment on control implants. ASD implants and control implants were placed in to left tibiae of rats. The rats were sacrificed at different time interval(1, 2, 4 and 8 weeks after implantation) for histopathologic observation and immunohisto-chemistrical observation, with collagen type Ⅰ, fibronectin, integrin ${\alpha}_2{\beta}_1$ and integrin ${\alpha}_5{\beta}_1$ antibodies. The results obtained from this study were as follow: 1. Histopathologic findings, overall tissue response and the pattern of bone formation in both groups were similar. In ASD group, more newly formed bone was seen at 1 week and 2weeks than control group. 2. The levels of type Ⅰ collagen and fibronectin expression were the most abundant at 2weeks and decreased gradually in both groups. Fibronectin and type Ⅰ collagen expression in ASD group were stronger than control group but no significance. 3. The levels of integrin ${\alpha}_2{\beta}_1$ and Integrin ${\alpha}_5{\beta}_1$ expression were most abundant at 2 weeks and decreased gradually in both groups. No significant difference was observed in both groups. From this results, anodic oxidized titanium implants were more advantages in early stage of bone formation than control group, but have no significance in tissue responses and late bone formations. It could be stated that although anodic oxidized titanium implant possesses considerable osteoconductive potential but in osteoporotic bone condition dental implant procedure should performed after improving or treating the osteoporotic bone condition.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.34 no.3
• /
• pp.276-284
• /
• 2008

Purpose: The purpose of this study was to observe the effect of calcium and vitamin D to the titanium implant osseointegration in the osteoporosisinduced animal model. Material and method: Thirty-two rats, 10 weeks of age, were divided into two groups: experimental group was ingested additional calcium and vitamin D, and a control group was not. Titanium screw implant(diameter, 2.0 mm; length, 3.5 mm; pitch-height 0.4 mm) were placed into tibia of 32 rats, 16 in the control group and 16 in the experimental group. The rats were sacrificed at 1, 2, 4 and 8 weeks after implantation for histopathologic examination, histomorphometric analysis and immunohistochemistry with fibronectin and collagen type I antibody. Result: In histopathological findings, newly formed bone was seen at 2 weeks and became lamellar bone at 4 weeks, and mature trabecullar bone was seen at 8 weeks in experimental group. In control group, thickness of regenerated bone increased till 4 weeks gradually and trabecullar bone was seen at 8 weeks. In histomorphometric analysis, marrow bone density increased significantly in experimental group compared to control group. Fibronectin immunoreactivity was strong at 2 weeks in experimental group and reduced after 4 weeks gradually. But it was maintained continuously from 2 to 8 weeks in control group. Collagen type I immunoreactivity was very strong from 2 to 4 week in experimental group. And the amount of Collagen type I expression was more abundant in experimental group. Conclusion: The results of this study suggest that calcium and vitamin D supplementation promote bone healing around titanium implants in osteoporosis induced animals.

• The Korean Journal of Physiology and Pharmacology
• /
• v.1 no.6
• /
• pp.603-611
• /
• 1997

The motor evoked potentials (MEPs) have been advocated as a method of monitoring the integrity of spinal efferent pathways in various injury models of the central nervous system. However, there were many disputes about origin sites of MEPs generated by transcranial electrical stimulation. The purpose of present study was to investigate the effect of major extrapyramidal motor nuclei such as lateral vestibular nucleus (VN) and medullary reticular nucleus (mRTN) on any components of the MEPs in adult Sprague-Dalwey rats. MEPs were evoked by electrical stimulation of the right sensorimotor cortex through a stainless steel screw with 0.5mm in diameter, and recorded epidurally at T9 - T10 spinal cord levels by using a pair of teflon-coated stainless steel wire electrodes with 1mm exposed tip. In order to inject lidocaine and make a lesion, insulated long dental needle with noninsulated tips were placed stareotoxically in VN and mRTN. Lidocaine of $2{\sim}3\;{\mu}l$ was injected into either VN or mRTN. The normal MEPs were composed of typical four reproducible waves; P1, P2, P3, P4. The first wave (P1) was shown at a mean latency of 1.2 ms, corresponding to a conduction velocity of 67.5 m/sec. The latencies of MEPs were shortened and the amplitudes were increased as stimulus intensity was increased. The amplitudes of P1 and P2 were more decreased among 4 waves of MEPs after lidocaine microinjection into mRTN. Especially, the amplitude of P1 was decreased by 50% after lidocaine microinjection into bilateral mRTN. On the other hand, lidocaine microinjection into VN reduced the amplitudes of P3 and P4 than other MEP waves. However, the latencies of MEPs were not changed by lidocaine microinjection into either VN or mRTN. These results suggest that the vestibular and reticular nuclei contribute to partially different role in generation of MEPs elicited by transcranial electrical stimulation.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.33 no.3
• /
• pp.199-209
• /
• 2011

Purpose: Osteoporosis, is a major health problem for the elderly and post-menopausal women and shown to alter the properties of bone as well as impair bone healing around titanium implants in both human and animals. The objective of this study was to examine the effect of LIPUS with adipose-derived stem cells on the healing process around a titanium implant in rats with osteoporosis. Methods: Sixteen osteoporosis-induced rats were divided into two groups: an adipose-derived stem cell injected with Low Intensity Pulsed Ultrasound (LIPUS) application group and a control group. Titanium screw implants (diameter, 2.0 mm: length, 3.5 mm, Cowell Medi, Korea) were placed into both tibia of 16 rats, on 8 rats as the control group and the other 8 rats as the experimental group. Rats were sacrificed at different intervals from 1, 2, 4 and 8 weeks after implantation for histopathologic and immunohistochemical analyses. Results: Histopathological analysis revealed newly formed bone in experimental group earlier than that in control group. Especially at 1 week after implantation, more amounts of new bone matrix and collagen around the implant in the experimental group were seen compared with the control group. Immunohistochemical analysis showed that the levels of osteoprotegerin (OPG) expression in the experimental group were increased at early stages compared with that of control group until 2 weeks after implantation. But after 2 weeks, the expression level of OPG similar in both groups. The expression levels of receptor activator of nuclear factor kB ligand (RANKL) were stronger in the experimental group than the control group until 2 weeks after implantation. After 4 weeks, expression of RANKL in experimental group was similar to the control group. Conclusion: The results of this study suggest that LIPUS with Adipose-Derived Stem Cells in implantation could promote bone healing around titanium implants in rats with osteoporosis.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.36 no.5
• /
• pp.392-401
• /
• 2010

Introduction: Diabetes mellitus, as a major health problem for the elderly has been shown to alter the properties of the bone and impair bone healing around a titanium implant in both humans and animals. The aim of this study was to examine the effect of adipose-derived stem cells on the healing process around a titanium implant in streptozotocin-induced diabetic rats. Materials and Methods: Thirteen rats were divided into two groups: adipose-derived stem cells injected group and a control group. A titanium screw implant (diameter: 2.0 mm, length: 3.5 mm) was placed into both tibia of 13 rats: 13 right tibia as the control group and 13 left tibia as the experimental group. The rats were sacrificed at different intervals (1, 2, and 4 weeks) after implantation for histopathology observations and immunohistochemistric analysis. Results: The histopathological findings revealed earlier new formed bone in the experimental group than the control group. In particular, at 1 week after implantation, the experimental group showed more newly formed bone and collagen around the implant than the control group. In immunohistochemistric analysis, osteoprotegerin (OPG) expression in the experimental group increased early compared to that of the control group until 2 weeks after implantation. However, after 2 weeks, OPG expression in the experimental group was similar to OPG expression in the control group. The receptor activator of nuclear factor ${\kappa}B$ ligand (RANKL) expression in the experimental group increased early compared to that of the control group, and then decreased at 2 weeks. After 2 weeks, the level of RANKL expression was similar in both groups. Conclusion: These results suggest that adipose-derived stem cells in implantation can promote bone healing around titanium, particularly in diabetes mellitus induced animals.