• The Journal of Korean Academy of Prosthodontics
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• v.41 no.4
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• pp.519-531
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• 2003

Statement of problem : Chronic implant screw loosening remains a problem in restorative practices. Some implant manufactureres have introduced abutment screws with treated material, surfaces and macrostructures in an effort to reduce potential loosening. Purpose : This study evaluated the materials and loading cycles on detorque value after dynamic continous fatigue test in the sinulated conditions of posterior single restoration. Material and method : Fourteen of each of the following abutment screws - titanium alloy, gold alloy, gold-tite, and titanium alloy modified - were used in test. SEM is used to verify macrostructures of each screws. $ZrO_2/Al_2O_3$ composite abutment was tightened on $4{\times}10.0mm$ titanium external implant at 30 Ncm. Cyclic loading machine delivered dynamic loading forces between 20 and 320N for 100,000, 200,000, 300,000, 500,000, and 1,000,000 cycles at frequencies 14Hz. Torque and detorque value after loading was measured. Results : All measued screws had different screw length and thread form. Titanium modified screw had greater detorque value than others before and after cyclic loadings(p<0.05). All abutment screws had no significant change in mean percentage of detorque value after loading to initial value after less than 500.000 cyclic loadings, but significant lower value after 1,000,000 cycles(p<0.05). Conclusion : Within limintations of this study all abutment screws may be loosend after about 1 year use. Annual check-up is nessasary to prevent screw loosening.

• Journal of Periodontal and Implant Science
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• v.42 no.6
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• pp.217-223
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• 2012

Purpose: Several parameters have been described for determining the success or failure of dental implants. The surface properties of transgingival implant components have had a great impact on the long-term success of dental implants. The purpose of this study was to compare the tendency of two periodontal pathogens to adhere to and colonize zirconia abutments and titanium alloys both in hard surfaces and soft tissues. Methods: Twelve patients participated in this study. Three months after implant placement, the abutments were connected. Five weeks following the abutment connections, the abutments were removed, probing depth measurements were recorded, and gingival biopsies were performed. The abutments and gingival biopsies taken from the buccal gingiva were analyzed using real-time polymerase chain reaction to compare the DNA copy numbers of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and total bacteria. The surface free energy of the abutments was calculated using the sessile water drop method before replacement. Data analyses used the Mann Whitney U-test, and P-values below 0.05 find statistical significance. Results: The present study showed no statistically significant differences between the DNA copy numbers of A. actinomycetemcomitans, P. gingivalis, and total bacteria for both the titanium and zirconia abutments and the biopsies taken from their buccal gingiva. The differences between the free surface energy of the abutments had no influence on the microbiological findings. Conclusions: Zirconia surfaces have comparable properties to titanium alloy surfaces and may be suitable and safe materials for the long-term success of dental implants.

• The korean journal of orthodontics
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• v.31 no.2 s.85
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• pp.173-185
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• 2001

The orthodontic osseointegrated titanium implant, a kind of intraoral skeletal anchorage can be an alternative to tooth-borne anchorage, in case that the conventional tooth-borne anchorage is not available or the anchorage is critical. This study was conducted to elucidate the effect of early loading on the osseointegration of the orthodontic titanium implant and the healing process of the impaired bone at the site of implant after removing it. In two adult beagle dogs24 osseointegrated titanium implants were inserted into the alveolar bone, with 12 implants placed in each dog. In dog1, 6 out of 12 implants were loaded with 200-300gm of force immediately after placing, and the remaining 6 implants were not loaded for 4weeks. In dog2, all 12 implants had healing period of 4weeks, and then were loaded with 200-300gm of force for another 4weeks. Following an observation period of 4 and 8 weeks, the animals were sacrificed. Then the implants and the surrounding bone of dog1 and dog2 were removed, respectively. Undecalcified sections along the long axis of implant were made and the degree of osseointegration was examined under the light microscope. The results were as follows. 1. In the histologic features of tissues around implants anchored in dog1, there was no difference between immediately loaded implants and unloaded implants. Immature woven bone was ingrowing into the thread spaces from the original compacta and in direct contact with the implant surface in part. 2. The premature loading just after 4weeks healing period did not halt the progress of the osseointegration between bone and implant surface. The woven bone around the implants was maturing into the lamellar bone which resembled the structure of the original compacta at the end of 8weeks observation period. 3. Most implants with the inflammed surrounding mucosa were lost or mobile. The mobile implants were encapsulated by fibrous connective tissue which separated the implant surface from the bone. 4. The impaired bone at the site of the implant failed to anchor was showing recovery without inflammatory reaction 2weeks after removing, with the immaure woven bone lined by active osteoblasts and osteoid. Based on the results of this study, the integration of this orthodontic implant seemed to be impaired by the inflammation of the tissue surrounding the Implant rather than by early loading on implant, and increased with time lapsed after placing the implant. The use of implant described in this report can be recommended as an orthodontic anchorage unit immediately after insertion under the careful control of orthodontic force applied and plaque.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.5
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• pp.386-395
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• 2011

Introduction: Osteoporosis is a major health problem in the elderly that involves changes in the properties of bone as well as impaired bone healing around a titanium implant in both humans and animals. This study examined effect of low intensity pulsed ultrasound (LIPUS) on the bone healing process around a titanium implant in osteoporosis-induced rats. Materials and Methods: Sixteen rats were divided into two groups. A control group with osteoporosis induced by removing both ovaries and an experimental group of rats that were applied with LIPUS after osteoporosis had been induced. A screw type titanium implant (diameter, 2.0 mm: length, 3.5 mm, Cowell-Medi, KOREA) was placed into the tibias of 16 rats. The control and experimental group contained 8 rats each. The rats were sacrificed at 1, 2, 4, and 8 weeks after implantation to examine the histopathology and immunochemistry. Results: The histopathology examination revealed earlier new bone formation in the experimental group than the control group. In particular, at 1 week after implantation, more new bone matrix and collagen were observed around the implant of the experimental group compared to the control group. Immunochemistry analysis showed that the level of OPG expression of the experimental group was higher in the early stages than in the control group. After 8 weeks, the levels of OPG expression were similar in both groups. The expression level of receptor activator of nuclear factor kB ligand (RANKL) was stronger in the experimental group than the control group. After 4 weeks, the level of RANKL expression was similar in both groups. Conclusion: These results suggest that the application of LIPUS to implantation can promote bone healing around titanium in osteoporosis animals.

• Journal of Periodontal and Implant Science
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• v.35 no.4
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• pp.851-861
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• 2005

The nature of the implant surface can directly influence cellular response, ultimately affecting the rate and quality of new bone tissue formation. The aim of this in vitro study was to investigate if human osteoblast-like cells, Saos-2, would respond differently when plated on disks of magnesium titanate and machined titanium. Magnesium titanate disks were prepared using Micro Arc Oxidation(MAO) methods. Control samples were machined commercially pure titanium disks. The cell adhesion, proliferation and differentiation were evaluated by measuring cell number, and alkaline phosphatase(ALPase) activity at 1 day and 6 day after plating on the titanium disks. Measurement of cell number and ALPase activity in Saos-2 cells at 1 day did not demonstrate any difference between machined titanium and magnesium titanate. When compared to machined titanium disks, the number of cells was reduced on the magnesium titanate disks at 6 day, while ALPase activity was more pronounced on the magnesium titanate. Enhanced differentiation of cells grown on magnesium titanate samples was indicated by decreased cell proliferation and increased ALPase activity.

• The korean journal of orthodontics
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• v.47 no.4
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• pp.229-237
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• 2017

Objective: The aim of this study was to compare the initial stability as insertion and removal torque and the clinical applicability of novel orthodontic zirconia micro-implants made using a powder injection molding (PIM) technique with those parameters in conventional titanium micro-implants. Methods: Sixty zirconia and 60 titanium micro-implants of similar design (diameter, 1.6 mm; length, 8.0 mm) were inserted perpendicularly in solid polyurethane foam with varying densities of 20 pounds per cubic foot (pcf), 30 pcf, and 40 pcf. Primary stability was measured as maximum insertion torque (MIT) and maximum removal torque (MRT). To investigate clinical applicability, compressive and tensile forces were recorded at 0.01, 0.02, and 0.03 mm displacement of the implants at angles of $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$, and $40^{\circ}$. The biocompatibility of zirconia micro-implants was assessed via an experimental animal study. Results: There were no statistically significant differences between zirconia micro-implants and titanium alloy implants with regard to MIT, MRT, or the amount of movement in the angulated lateral displacement test. As angulation increased, the mean compressive and tensile forces required to displace both types of micro-implants increased substantially at all distances. The average bone-to-implant contact ratio of prototype zirconia micro-implants was $56.88{\pm}6.72%$. Conclusions: Zirconia micro-implants showed initial stability and clinical applicability for diverse orthodontic treatments comparable to that of titanium micro-implants under compressive and tensile forces.

• Imaging Science in Dentistry
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• v.51 no.1
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• pp.1-7
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• 2021

Purpose: The aim of this study was to assess artifacts generated in cone-beam computed tomography (CBCT) of 3 types of dental implants using 3 metal artifact reduction (MAR) algorithm conditions (pre-acquisition MAR, post-acquisition MAR, and no MAR), and 2 peak kilovoltage (kVp) settings. Materials and Methods: Titanium-zirconium, titanium, and zirconium alloy implants were placed in a dry mandible. CBCT images were acquired using 84 and 90 kVp and at normal resolution for all 3 MAR conditions. The images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the intensity of artifacts for each combination of material and settings. A 3-factor analysis of variance model with up to 3-way interactions was used to determine whether there was a statistically significant difference in the mean intensity of artifacts associated with each factor. Results: The analysis of all 3 MAR conditions showed that using no MAR resulted in substantially more severe artifacts than either of the 2 MAR algorithms for the 3 implant materials; however, there were no significant differences between pre- and post-acquisition MAR. The 90 kVp setting generated less intense artifacts on average than the 84 kVp setting. The titanium-zirconium alloy generated significantly less intense artifacts than zirconium. Titanium generated artifacts at an intermediate level relative to the other 2 implant materials, but was not statistically significantly different from either. Conclusion: This in vitro study suggests that artifacts can be minimized by using a titanium-zirconium alloy at the 90 kVp setting, with either MAR setting.

• Toxicological Research
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• v.20 no.1
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• pp.13-20
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• 2004

The purpose of this study is to compare the biocompatibility of commercial purity Ti, Ti-6AI-4V and Ti-6AI-7Nb alloy specimens with and without surface treatment in mouse abdominal connective tissue in vivo. Each metal was implanted into specific abdominal subdermal tissue site of female mouse. After 4 weeks, the implants were removed and abdominal tissues were fixed, dehydrated and embedded in glycol methacrylate resin. And the tissues were histologically prepared for microscopical evaluation. It was characterized by the presence of connective tissue with fibrous capsule surrounding the implant. The fibrous tissue surrounding the implant was studied to determine the biocompatibility of implanted metals. The average thickness of the fibrous capsule formed around the implant was much thinner for the hydrogen peroxide added hydrochloric acid solution-treated specimen than for the others. The results of this evaluation indicate that modification of the surface properties of titanium and titanium alloy implants changes the biological properties in the abdominal connective tissue. In conclusion, these observations suggest that the proper surface treatment performed in the study is effective for the improvement of biocompatibility.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.2
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• pp.255-264
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• 1997

The conventional osseointegration protocol calls for waiting up to 12 months for ossification of an extraction socket to heal before placing an endosseous implant. In this study, the possibility of placing a pure titanium implant directly into an extraction socket immediately after extraction was investigated. And the marginal bone loss of immediate nonsubmerged and submerged endosseous dental implants placed into extraction sockets was also compared. Pure titanium Nobelpharma Branemark implants and solid screw type ITI implants were placed into premolar extraction sockets of two adult dogs and allowed to heal for a period of 3 months, followed by functional loading of the implant. Radiographic examination was performed before implantation, immediately after implantation and 3, 6, 9, 12 months after implantation. The results obtained were as follows : 1. Immediately placed nonsubmerged ITI implants and submerged Branemark implants showed favorable radiographic osseointegration status and there were minimum marginal bone loss. 2. There were no significant differences in radiographic finding of osseointegration between conventional and immediate implantation. 3. Gingival tissue around implants showed more inflammatory signs than that of adjacent natural teeth. This study suggest that pure titanium Branemark implants and submerged ITI implants have the potential to integrate when placed immediatly after extraction of the teeth and warrants further investigation.

• The Journal of the Korean dental association
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• v.52 no.9
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• pp.541-549
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• 2014

The restorative treatment using titanium implants has become a standard procedures in everyday clinical practice. However, there are several concerns about the use of titanium as a materials. Above all, the grayish metal color provokes esthetic problems when the soft tissue around the implants is not optimal. Recently, zirconia has been emerging as an alternative to titanium due to its white color and superior physicochemical properties. In this paper, the current findings about zirconia implants was reviewed based on the results from animal and clinical experiments. In addition, the immediate implantation protocols using the natural tooth form zirconia implants was introduced as a novel procedures and future perspectives were discussed.