PURPOSE: This study was to investigate how the crestal module design could affect the level of marginal bone stress around dental implant. MATERIALS AND METHODS: A submerged implant of 4.1 mm in diameter and 10 mm in length was selected as baseline model (Dentis Co., Daegu,Korea).A total of 5 experimental implants of different crestal modules were designed (Type I model : with microthread at the cervical 3 mm, Type II model : the same thread pattern as Type I but with a trans-gingival module, Type III model: the same thread pattern as the control model but with a trans-gingival module, Type IV model: one piece system with concave transgingival part, Type V model: equipped with beveled platform). Stress analysis was conducted with the use of axisy mmetric finite element modeling scheme. A force of 100 N was applied at 30 degrees from the implant axis. RESULTS: Stress analysis has shown no stress concentration around the marginal bone for the control model. As compared to the control model, the stress levels of 0.2 mm areas away from the recorded implant were slightly lower in Type I and Type IV models, but higher in Type II, Type III and Type V models. As compared to 15.09 MPa around for the control model, the stress levels were 14.78 MPa, 18.39 MPa, 21.11 MPa, 14.63 MPa, 17.88 MPa in the cases of Type I, II, III, IV and V models. CONCLUSION: From these results, the conclusion was drawn that the microthread and the concavity with either crestal or trans-gingival modules maybe used in standard size dental implants to reduce marginal bone stress.
Axis, Cervical Vertebra ; Dental Implants ; Implants, Experimental

PURPOSE: The purpose of this study was to investigate the influence of mobilization on bone-implant interface prior to osseointegration of fixtures. MATERIALS AND METHODS: The experimental implants (3.75 mm in diameter, 4.0 mm in length) were made of commercially pure (Grade IV) titanium, and were treated with RBM (MegaGen(R): Ca-P). The 80 implants (two in each tibia) were inserted into the monocortical tibias of 20 rabbits which each weighed more than 3.5 kg (Female, New Zealand White). According to the removal torque interval, the groups were divided into 10 groups, Group I (6 wks), Group II (4 days + 6 wks), Group III (4 days + 1 wk + 6 wks), Group IV (1 wk + 6 wks), Group V (1 wk + 1 wk + 6 wks), Group VI (2 wks + 6 wks), Group VII (2 wks+ 1 wk + 6 wk), Group VIII (3 wks + 6 wks), Group IX (3 wks + 1 wk + 6 wks) and Group X (10 wks). The control groups were Group I and X, the removal torque was measured at 6 wks and 10 wks with a digital torque gauge (Mark-10, USA). In the experimental groups, the removal torque was given once or twice before the final removal torque and the value was measured each time. After which, the implants were put back where they had been except the control groups. All the experimental groups were given a final healing time (6 wks) before the final removal torque test, in which values were compared with the control groups and the 1st and/or 2nd removal torque values in each experimental group. RESULTS: In the final removal torque tests, the removal torque value of Group X (10 wks) was higher than that of Group I (6 wks) in the control groups but not statistically different. There were no significant differences between the experimental groups and control groups (P>.05). In the first removal torque comparison, the experimental groups (4 days or 1 wk) values were significantly lower than the other experimental groups (2 wks or 3 wks). In the comparison of each experimental group according to healing time, the final removal torque value was significantly higher than the 1st torque test value. CONCLUSION: Once or twice mobilization of fixture prior to osseointegration did not deter the final bone to implant osseointegration, if sufficient healing time was given.
Implants, Experimental ; New Zealand ; Osseointegration ; Rabbits ; Tibia ; Titanium ; Torque

PURPOSE: The aim of this study was to investigate the effect of implant thread profile on the marginal bone stresses which develop during implant insertion. MATERIALS AND METHODS: Four experimental implants were created by placing four different thread systems on the body (4.1 mm x 10 mm) of the ITI standard implant. The thread types studied in this study included the buttress, v-shape, reverse buttress, and square shape threads. In order to examine the insertion stress generation, 3D dynamic finite element analysis was performed which simulated the insertion process of implants into a 1.2 mm thick cortical bone plate (containing 3.5 mm pilot hole) using a PC-based DEFORM 3D (ver 6.1, SFTC, Columbus, OH, USA) program. RESULTS: Insertion stresses higher than human cortical bone developed around the implants. The level of insertion stresses was much different depending on the thread. Stress level was lowest near the v-shape thread, and highest near the square shaped thread. Difference in the interfacial bone stress level was more noticeable near the valley than the tip of the threads. CONCLUSION: Among the four threads, the v-shape thread was turned out to minimize the insertion stress level and thereby create better conditions for implant osseointegration.
Bone Plates ; Finite Element Analysis ; Humans ; Implants, Experimental ; Osseointegration

PURPOSE: The aim of present investigation was to find out the influence of several times iatrogenic mobilization in the initial stage of implant installation on bone-implant osteointegration. MATERIALS AND METHODS: The experimental implants (3.75 mm in diameter, 8.0 mm in length) were made of commercially pure (Grade IV) titanium, and were treated with RBM (MegaGen(R): Ca-P) on lower 4.0 mm part. Only lower part of implant was inserted to bone and the implants were nonsubmerged. The 130 implants (two in each tibia) were inserted into the monocortical tibias of 33 rabbits which each weighed more than 3.5 kg (Female, New Zealand White). According to the removal torque interval, the groups were divided into 13 groups, group I (1 day), group II (1 day + 2 days), group III (1 day + 2 days + 3 days), group IV (1 day + 2 days + 3 days + 4 days), group V (2 days), group VI (2 days + 4 days), group VII (2 days + 4 days + 6 days), group VIII (2 days + 4 days + 6 days + 8 days), group IX (4 days), group X (4 days + 7 days), group XI (4 days + 7 days + 10 days), group XII (4 days + 7 days + 10 days + 14 days) and control group. In the control group, the removal torque was measured at 8 weeks with a digital torque gauge (Mark-10, USA). In the experimental groups, the removal torque was given once, twice, three times or four times by experiment design before the final removal torque and the value was measured each time. The implants were then screwed back to their original positions. All the experimental groups were given a final healing time of 8 weeks after placement, in which values were compared with the control groups and the 1st, 2nd, 3rd or 4th removal torque values in each experimental group. RESULTS: In comparison of the final removal torque tests among experimental groups, the removal torque value of experimental groups except group XII were not statistically different that of control group. And the values of group I and II were significantly higher than the values of group VI, VIII, X, XI, and XII. In addition, the values of group III, IV, and V were significantly higher than group XI and XII. In comparison of the removal torque in the each experimental group, the final removal torque were significantly higher in all groups except group VIII, X, XI, and XII. CONCLUSION: If sufficient healing time was allowed, a few mobilization of fixture at the very early stage after the implant placement in the rabbits didn't interrupt the final bone to implant osseointegration.
Dental Implants ; Implants, Experimental ; New Zealand ; Osseointegration ; Rabbits ; Tibia ; Titanium ; Torque

implants were supplied by KJ Meditech (Korea). One is an external hexa system (External type) and the other is an internal system with threads (Internal type). The implants were pasted with beads using polyvinylalcohol solution as a binder, and then sintered at 1250 degree C for 2 hours in vacuum of 10(-5) torr. The resulting porous structure was 400-500 micrometer thick and consisted of three to four bead layers bonded to each other and the implant. The pore size was in the range of 50-150 micrometer and the porosity was 30-40 percent in volume. The aim of this study was to evaluate the osseointegration of the newly developed dental implant. The experimental implants (n=16) were inserted in the unilateral femur of 4 mongrel dogs. All animals were killed at 8 weeks after implantation, and samples were harvested for hitological examination. All bead coated porous implants were successfully osseointegrated with peripheral bone. The average bone-implant contact ratios were 84.6 percent (External type) and 81.5 percent (Internal type). In the modified Goldner's trichrome staining, new generated mature bones were observed at the implant interface at 8 weeks after implantation. Although, further studies are required, we could conclude that the newly developed vacuum sintered Ti-6Al-4V bead coating implant was strong enough to resist the implant insertion force, and it was easily osseointegrated with peripheral bone.]]>
Alveolar Bone Loss ; Animals ; Dental Implants ; Dogs ; Electrodes ; Femur ; Implants, Experimental ; Osseointegration ; Plasma ; Porosity ; Titanium ; Vacuum

To evaluate the biological safety of collagen-based bone repairing material, we implanted the sample or reference substance into rats, and observed relative signs, including the specific inspection targets in animals, blood examination, analysis of immune organ, the pathological examination of organs and tissues, NK cell killing activity assay, lymphocyte group analysis, serum IL-1, IL-6, TNF-alpha detection, detection of immune globulin. Meanwhile, we set control group, sham group, and immunosuppression group. The final results showed that there was no abnormal mental state before and after the experiment. Compared with the control group, the tested group indicated no significant difference in blood test, immune organ analysis, the pathological examination of organs and tissues, NK cell killing activity assay, lymphocyte subset analysis serum IL-1, IL-6, TNF-alphadetection, and detection of immune globulin. Collagen-based bone repairing material produced a slight and transient stimulation on the rats, but created no significant inflammatory responses.
Absorbable Implants ; Animals ; Bone Matrix ; physiology ; transplantation ; Bone Regeneration ; Bone Substitutes ; Collagen ; chemistry ; Implants, Experimental ; Materials Testing ; Prostheses and Implants ; Rats

In this study the poly(vinyl alcohol)(PVA) hydrogel elastomer was prepared by freezing-thawing method. The influences of percentage of poly (vinyl alcohol) in hydrogel, pH of solution and swelling temperature upon the swelling characteristic of PVA-hydrogel prosthetic nucleus material were studied. Its micropores were observed using SEM, and the swelling dynamics was further discussed. The experimental results showed that the poly (vinyl alcohol) hydrogel was a kind of network with a lot of micropores, the pore size was related with the PVA content. The maximum swelling ratio decreases when the percentage of PVA in hydrogel, the pH of solution and the swelling temperature were enhanced. The swelling process was described by the equation of swelling dynamics equation. The swelling rate was greatly influenced by the PVA content, the pH of solution and the dimension of hydrogel sample.
Biocompatible Materials ; chemistry ; Hydrogels ; Hydrogen-Ion Concentration ; Implants, Experimental ; Intervertebral Disc ; Polyvinyl Alcohol ; chemistry ; Prostheses and Implants ; standards

PURPOSE: The purpose of this study is to analyze the change in re-osseointegration over time and bone reaction at the interface between implant fixture and the surface of the bone, after destroying re-osseointegration by distorting the bone-implant interface artificially. MATERIAL AND METHODS: Experimental implant fixtures (cp titanium, small ef, Cyrillic3.75 mm x 4 mm) which didn't have surface treatment were produced. Two or three fixtures were implanted on both tibias of twelve female rabbits (New Zealand white, more than 3.5 kg). Then after six weeks, removal torque (RT) was measured and the results were recorded as the first measurement values. The fixtures were submerged again to get reosseointegration between the bone and fixture. To identify the change in re-osseointegration of submerged fixtures over time, six groups had the healing time for four days (group I), one week (group II), two weeks (group III), three weeks (group IV), four weeks (group V) and five weeks (group VI), and then the secondary removal torque was measured for each group. To identify the bone formation under fluorescent light, tetracycline (15 mg/kg, IM) were treated on the rabbits of each group. After the second measurement, the rabbits were sacrificed, and 16 slides were made, two or three for each group. The slides were observed under the fluorescent light with light microscope. To find out the change in the secondary removal torque over the primary removal torque in progress of time, the averages of the increase rate of the primary and secondary torque removal force were calculated. Then, to find out if there were any critical differences between the primary removal torque and the secondary removal torque in each group and among the groups, the results were analyzed statistically by paired t-test, one-way ANOVA, and Duncan's Multiple Range Test. RESULTS: In group I and II, secondary removal torque decreased, especially in group I. In group III, IV, V, and VI, secondary removal torque increased critically. Comparing the differences among the groups, the critical difference was shown between group I, II and group III, IV, V, VI. Mineralization at the interface between the bone and implant fixture was identified from the first week, and bone formation was shown more clearly from the second week. CONCLUSION: If the implant fixture remains unforced for a certain period of time after the fixture has had iatrogenic mobility, re-osseointegration occurs at the surface of the fixture, and for tibias of rabbits, higher re-osseointegration was obtained within two weeks.
Female ; Humans ; Implants, Experimental ; Light ; Osseointegration ; Osteogenesis ; Rabbits ; Tetracycline ; Tibia ; Titanium ; Torque

OBJECTIVETo observe bone ingrowth of artificial femur which three dimensions (3-D) porous Ti combined bone morphogenetic proteins (BMPs) integrating on the prostheses surface in dogs.

METHODSThe prostheses integrated 3-D porous Ti on the surface, which combined BMPs directly or through FG, were implanted canine. And fluorescent labeling was done at 2, 5 weeks after that, and then the prostheses with femurs were taken out in 3, 6 weeks after operation. These specimens were treated, then observed through microscopy.

RESULTSAt 3 weeks, bone growing 1/2 of full thickness in 3-D porous Ti, but bone growing full thickness in 3-D porous Ti at 6 weeks. Bone formation was obviously higher at 6 weeks than at 3 weeks.

CONCLUSIONThe prostheses modified 3-D porous Ti can accelerate osteogenesis and improve bone formation so that mechanical interlock and integration can be come true.

Animals ; Bone Morphogenetic Proteins ; Bone Substitutes ; Coated Materials, Biocompatible ; Dogs ; Female ; Implants, Experimental ; Male ; Porosity ; Titanium

OBJECTIVETo observe the histocompatibility of a polypropylene matrix implanted subcutaneously for potential hair follicle transplantation in rabbits.

METHODSThe polypropylene matrix for harboring the hair follicles was prepared and implanted subcutaneously at the neck of 5 New Zealand white rabbits by means of hair follicle unit transplantation. At 1 week after the transplantation and then on a monthly basis in the following 6 months, full-thickness skin tissues were sampled at the site of grafting to evaluate the histocompatibility of the matrix material using HE staining and scanning electron microscopy.

RESULTSAt 1 week after implantation of the matrix material, a small number of inflammatory cells and lymphocytic infiltration were observed around the graft, with mild hyperemia in the proliferative capillaries and mild inflammatory responses. In the following 6 months, the inflammatory cells and lymphocytes around the graft decreased obviously or even disappeared, and such graft rejection responses as tissue lysis and necrosis were not observed. A large quantity of collagen fibers were found to encapsulate the polypropylene material.

CONCLUSIONPolypropylene matrix graft has good histocompatibility with the rabbit subcutaneous tissue without producing obvious graft rejection responses, suggesting its feasibility for further experiments of hair follicle transplantation.

Animals ; Biocompatible Materials ; Female ; Hair Follicle ; transplantation ; Implants, Experimental ; Male ; Polypropylenes ; Rabbits