• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.2
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• pp.111-118
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• 2013

Purpose of present study is to investigate the effects of thread pitch in coronal portion in scalloped implant with 2 different connections on loading stress using 3 dimensional finite element analysis. Scalloped implant with 4 different thread pitches (0.4mm, 0.5mm, 0.6, and 0.7mm) in the coronal part was modeled with 2 different implant-abutment connections. Platform matching connection had the same implant and abutment diameter so that they were in flush contact at the periphery while platform mismatching connection had smaller abutment diameter than implant so that their connection was made away from periphery of implant-bone interface. Occlusal loading of 100N force was applied vertically and 30 degree obliquely to all 8 models and the maximum von Mises bone stress was identified. Loading stress as highly concentrated in cortical bone. Platform mismatching scalloped implant with small thread pitch (0.4mm) model had consistently lowest maximum von Mises bone stress in vertical and oblique loads. Platform matching model had lowest maximum von Mises bone stress with 0.6mm thread pitch in vertical load and with 0.4mm thread pitch in oblique load. Platform mismatching connection had important roles in reducing maximum von Mises bone stress. Scalloped implant with smaller coronal thread pitch showed trend of reducing maximum von Mises bone stress under load.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.1
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• pp.60-70
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• 2007

Statement of problem: The cement-type abutment would be needed for the reduction of its body in order to correct the axis and to assure occlusal clearance. In the case of intraoral preparation, there is a potential risk that generated heat could be transmitted into the bone-implant interface, where it can cause deterioration of tissues around the implant and failed osseointegration. Purpose: The purpose of this study was to assess the difference of the heat transmitting effect on external and internal connection implant types under various conditions. Material and method: For evaluating the effects of alternating temperature, the thermocoupling wires were attached on 3 areas of the implant fixture surface corresponding to the cervical, middle, and apex. The abutments were removed 1mm in depth horizontally with diamond burs and were polished for 30 seconds at low speed with silicone points using pressure as applied in routine clinical practice. Obtained data were analyzed using Mann-Whitney rank-sum test and Wilcoxon / Kruskal-Wallis Tests. Result: Increased temperature on bone-implant interface was evident without air-water spray coolant both at high speed reduction and low speed polishing (p<.05). But, the difference between connection types was not shown. Conclusion: The reduction procedure of abutment without using proper coolant leads to serious damage of oral tissues around the implant irrespective of external and internal connection type.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.12
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• pp.71-74
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• 1994

In cementless total hip arthroplasty(THA), an initial stability of the femoral component is mandatory to achieve bony ingrowth and secondary long term fixation. Bone ingrowth depends strongly on relative micromotion and stress distributions at the interface. Primary stability of the femoral component can be obtained by minimizing the magnitude of relative micromotions at bone-prosthesis interface, Hence an accurate evaluation of interface behavior and stress/strain fields in the bone implant system may be relevant for better understanding of clinical situations and improving THA design. However, complete evaluation of load transfer in the bone remains difficult to assess experimentally, Hence, recently finite element method (FEM) was introduced in orthopaedic research field to fill the gap due to its unique capacity to evaluate stress in structure of complex shape, loading and material behavior. The authors developed the 3-dimensional numerical finite element model which is composed of totally 1179 elements off and 8 node blick. We also analyzed the micromotions at the bone-stem interface and mechanical behavior of existing bone prosthesis for a loading condition simulating the single leg stance. The result indicates that the values of relative motion for this well fit Multilock stem were $150{\mu}m$ in maximum, $82{\mu}m$ in minimum, and the largest relative motion developed in medial region of proximal femur with anterior-posterior direction. The proximal region of the bone was much larger in motion than the distal region and the stress pattern shows high stress concentration on the cortex near the tip of the stem. These findings indicates that the loading in the proximal femoral bone in the early postoperative situation can produce micromotions on the interface and clinically cementless TEA patient should not be allowed weight bearing strictly early in the postoperative period.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.1
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• pp.43-66
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• 1997

Dental implant may be immediately placed in postextraction socket which has alveolar bone defect. The purpose of this study was to compare the bone regeneration and bone quality around defects adjacent to implants that were placed into extraction sockets according to EFEB, GTAM barrier and GTAM barrier with DFDB. Mandibular P2, P3 and P4 were extracted bilaterally in dogs, and buccal defects were created about 4mm in depth and 3.3mm in width. Screwed pure titanium implants, 3.8mm in diameter and 10mm in length, were placed into the extraction sockets. The experimental groups were divided into four groups : the G group was covered with a GTAM barrier on the defective area, the D+G group was filled with DFEB and covered with a GTAM barrier, the D group was filled with DFDB only and the control group was sutured without any special treatment on the defective area. The experimental animals were killed after 12 weeks and specimens were prepared for light microscopic evaluation and fluorescent dyes were administered daily for 2 weeks after implantation, and injected on the 4th and 11th week for fluorescent microscopic examination to observe new bone formation and bone remodeling. The new Bone height of the buccal defect was measured and compared with the another for bone gain and the removal torque for the implant was measured for the comparison of bone density and bone-implant osseointegration. Results obtained were as follows : 1. Experimental groups showed bone regeneration in oder from D+G, G, D group and control. D+G and G group was significantly from D group and control(P<0.01). 2. In the defective area of control the regenerated alveolar bone showed poorly developed lamellated structure and fibrous tissue intervention into the bone-implant interface but the others showed well developed lamellated structure and osseointegration. 3. All implant groups showed no significaant difference in the removal torque for implant(P>0.05) These results suggest that immediate implants placed in defective sockets were successfully osseointegrated and utilizing placed in defective sockets were successfully osseointegrated and utilizing not only the combination of GTAM and DFDB but also only the GTAM was favorable for the predictable regeneration of the defective area.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.3
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• pp.255-265
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• 2009

Recently many studies have been published on application of immediate loaded implants. However, the immediate loading protocol has not been well documented. The purpose of the present study was to evaluate the stress distribution between bone-implant interfaces and the effect of implant length in the anterior maxilla using 3 dimensional finite element analyses. The diameter 4.0 mm threaded type implants with different length(8.5 mm, 10.0 mm, 11.5 mm, 13.0 mm, 15.0 mm) were used in this study. The bone quality of anterior maxillary bone block was assumed to D3 bone. Bone-implant interfaces of immediately loaded implant were constructed using a contact element for simulating the non osseointegration status. For simplification of all the processing procedures, all of the material assumed to be homogenous, isotropic, and linearly elastic. The 178 N of static force was applied on the middle of the palatoincisal line angle of the abutment with $120^{\circ}$ angle to the long axis of abutment. Maximum von Mises stress were concentrated on the labial cortical bone of the implant neck area, especially at the cortical-cancellous bone interfaces. Compared the different length, highest peak stress value was observed at the 8.5 mm implants and the results indicated a tendency towards favorable stress distribution on the bone, when the length was increased. Presence of cortical bone was very important to immediate loading, and it appears that implants of a length more than 13 mm are preferable for immediate loading at the anterior maxilla.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.1
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• pp.31-42
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• 2007

The purpose of this study was to compare the stress distribution according to the splinting condition and non-splinting conditions on the finite element models of the two units implant prostheses. The finite element model was designed with the parallel placement of two fixtures ($4.0mm{\times}11.5mm$) on the mandibular 1st and 2nd molars. A cemented abutment and gold screw were used for superstructures. A FEA models assumed a state of optimal osseointegration, as the bone quality, inner cancellous bone and outer 2 mm compact bone was designed. This concluded that the cortical and trabecular bone were assumed to be perfectly bonded to the implant. Splinting condition had 2 mm contact surface and non-splinting condition had $8{\mu}m$ gap between two implant prosthesis. Two group (Splinting and non-splinting) were loaded with 200 N magnitude in vertical axis direction and were divided with subdivision group. Subdivision group was composed of three loading point; Center of central fossa, the 2 mm and 4 mm buccal offset point from the central fossa. Von Mises stress value were recorded and compared in the fixture-bone interface and bucco-lingual sections. The results were as follows; 1. In the vertical loading condition of central fossa, splinting condition had shown a different von Mises stress pattern compared to the non-splinting condition, while the maximum von Mises stress was similar. 2. Stresses around abutment screw were more concentrated in the splinting condition than the non-splinting condition. As the distance from central fossa increased, the stress concentration increased around abutment screw. 3. The magnitude of the stress in the cortical bone, fixture, abutment and gold screw were greater with the 4 mm buccal offset loading of the vertical axis than with the central loading.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.5
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• pp.594-605
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• 2006

Statement of problem: Modification of titanium implant surface has potential to ensure clinically favorable performance that several surface modification technologies have been introduced. Among the methods. anodizing method and sol-gel hydroxyapatite coating method have gained much interest due to its roughness and chemical composition of the coating layer, but more of its biocompatibility result is required. Purpose : The purpose of this study was to compare bone-implant interface shear strength of four different surface treated implants as time elapsed. Resonance frequency analysis(RFA) and removal torque measurement methods were employed to measure implant stability at one week and six week after implantation. Material and method: A total of 80 screw-shaped implant [20 machined, 20 resorbable media blasted(RBM), 20 anodized, and 20 anodized+hydroxyapatite sol-gel coated] were prepared, and one of each group was implanted in the tibia of a New Zealand white rabbit that total 20 of them were used. In order to test the implant stability and implant-tissue interface contact changing in the bone bed, each 10 rabbit were sacrificed 1 week and 6 week later while resonance frequency and removal torque were measured. One-way analysis of variance and the Tukey test were used for statistical analysis. Results : The results were as follows. 1. There was no statistically significant difference of implant stability quotients(ISQ) value in RFA between individual groups after 1 week of implantation and 6 weeks(p>0.05). But, there was statistically significant increase of ISQ value in 6 weeks group compared to 1 week group(p<0.05). 2. There was no statistically significant difference in removal torque analysis between individual groups after 1 week of implantation and 6 weeks(p>0.05). but there was statistically significant increase in all 4 groups after 6 weeks compared to 1 week later(p<0.05). 3. There was no statistically significant difference in removal torque analysis between anodized group and HA coating after anodic oxidation 6 weeks later(p>0.05), but significant difference was appeared in both groups compared to RBM group and smooth-machined group(p<0.05). Conclusions : It can be suggested that changes in surface characteristics affect bone reactions. Anodized and anodized+hydroxyapatite sol-gel coating showed significantly improved bone tissue response to implants, but further study on the effect of hydroxyapatite dissolution is needed.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.1
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• pp.9-14
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• 2001

With the object of providing a temporary artificial periodonal ligament-like membrane around the dental implant, 10 Branemark type implants were coated with commercially available chitosan(Fluka Co., Buchs, Switzerland) which has a molecular weight of 70,000 and 80% deacetylation degree. Once this bioactive hydrophillic polymer(chitosan) contacts with blood or wound fluids, it becomes swollen and penetrates into the adjacent cancellous bone. Thus the interface between implant and surrounding bone is completely filled with chitosan. This tight junction in early healing phase enhances primary stability. The chitosan coated dental implants were implanted into the fresh patella bones from porcine knees, since the thickness of cortical bone is relatively even and their cancellous structure is homogenous. To test the shock absorbing effect, 1mm delta-rogette strain gage was installed behind the implant. The results showed 1. The principal strain peak value directed to the impact of coated implant was 0.064 0.018(p<0.05) and that of uncoated implant was 0.095(0.032 p<0.05). 2. The peak time delay of coated implant was 0.056sec(0.011 p<0.05) and that of uncoated implant was 0.024sec(0.009 p<0.05). It can be reasoned from this results that the chitosan coating has a shock absorbing effect comparable with a temporary artificial periodontal ligament.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.133-136
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• 1996

We investigated how hydroxyapatite (HA) coating onto a porous super stainless steel (S.S.S, 22Cr-20Ni-6Mo-0.25N) affects bone ingrowth in a dog transcortical femoral model. Implants were histologically evaluated after 4 and 48 weeks of implantation, and the bone bonding strength at the bone/implant interface was examined by employing the pull-out test. The direct osseous tissue bonding onto the HA-coated S.S.S was observed, but the uncoated stainless steels had thin fibrous tissue layers. The mean interface strength of the HA-coated S.S.S was 1.5 and 2.5 times greater than those of the S.S.S and the 316L SS after one year of implantation, respectively. In preliminary studies, no toxic responce was observed from a cytotoxicity test of the S.S.S, having similar corrosion resistance to titanium. Our results suggest that early osteoconductive nature of HA coating may induce long term osteointegration for a bioinert substrate.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.117-122
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• 2007

The novel implant system was developed using osseo-integration technology which enable amputee to overcome skin troubles in use of previous socket system and was evaluated in view of biomechanics, radiology, histology, and pathology. The osseo-integrated implants were designed and manufactured using CT image of canine's tibia and were applied to laboratory animals (canines). The follow-up studies were performed for 24 months with 10 canines. In radiology examination, we found that the relative low strain distribution caused medial and posterior bone resorption and then we verified them by biomechanical testing. In histological approach, the complete osseo-integration was observed through the activity of osteoblast cells around bone-implant interface and the radial outer region of bone due to peristeum reaction. Lastly in pathological aspect, the evidence of superficial infection was detected but that of deep infection was not. Therefore it is thought that infection problem will be overcome by immunity of body and good hygiene.