In a 64-years-old patient, the maxillary dental implants were removed due to peri-implant inflammation and replaced with a upper full denture. The patient was satisfied with this treatment.
Bacteriological investigation was carried out for the necks and bodies of the removed implants and the remaining natural teeth. In all the areas examfined, bacterial flora was predominated by Streptococcus. The ratios of Streptococcus isolated from the natural teeth, the necks of the implants and bodies of the implants were 52.5,39.7 and 23.0% respectively. The ratios of Staphylococcus isolated from the natural teeth, the necks of the implants and the bodies of the implants were 3.4, 13.8 and 19.7% respectively, demonstrating high ratios of Staphylococcus in the implants.
These results suggested that since Staphylococcus have a severely pathogenic and phlogogenic action,the degree of inflammation at the implant-support may be estimable to a certain degree from the degree of multiplication of these bacteria, this may be usefull in the prediction of the prognosis.

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Linkow-blade implants are the most popular ones among the endosseous dental implants because of their efficiency and safety. However, we occasionaly experienced bone resorption during the long term observation. Stresses under masticating forces and other forces conduced to the bone resorption and the sinking of the implant body.
To elucidate this problem, we tried to examine how the stress distribution in the bone tissue changed according with its design of implant under the compressive force.
This time, we studied about two shapes of Linkow-blade implants, a wide use of endosseous implants designed by Dr. Linkow;one was so called“opened-type”whose feet were opened, and the other was so called“closed-type”whose feet were closed.
To find out the differences in the stress distribution of two cases, we used two methods of the photoelasticity test and the finite element method.
The result shows that the closed-type implant doesn't have so irregular stress distribution as opened-type.

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At the Harvard Meeting of 1978 the recommendation was obtained,“Only two kinds, Mandibular Subperiosteal Implant and Blade Vent Implant will be permissible provided they will be practiced based on adequate technology learned and judgment of good common sense and ethics of thought introduced”. However, there are many issues involved by Subperiosteal Implant as well. One of such issues will be the problem of initial fixation. In many cases Subperiosteal Implanting will be applied to Complete Edentulous cases and Multiple Teeth Deficiency cases which will difficult to cure throgh other methods of treatment. For that reason undercut will be less and no initial fixation of frames can be achieved. To cope with the situation there are various kinds of initial fixation countermeasures are reported. Hence, the author has classified and studied such countermeasures.
1. The method to use metallic screws
2. Combination use of Intraosseous Implanting to design stabilization.
3. Method for fixation in which remaining teeth will be utilized to connect frames.
4. Inner bone system.
5. Endosseous Subperiosteal Implant.
6. Method in which the bone undercut will be utilized.

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Materials compatible with the organization of the human body are being developed and clinical application of implants in places with missing teeth are progressing. In recent years, clinical reports and researches have been taking place rapidly.
As clinical applications progress, the complicated and closely connected reactions of the body to implants is becoming understood. For the body, an implant is a foreign material and for some unknown reasons, the results after the implant are sometimes not good. There are also some cases in which the implant must be removed due to complications of stress from the surgery.
The following is a report about a case in which I implanted a Linkow Blade in the mandibular molar,which caused sensory paralysis in the mentum, but received positive results.

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Since 10 years ago, I had continued to report the utility of the denture retainer applied the strong magnetic attraction between the ultra-minute Sm-Co magnet and the casting ferromagnetic alloys.
Here, I report the retainer of implant denture applied magnetic force, which I designed this time,and their good clinical results.
The main cause of failures of the implant denture was the effects of excess occlusal pressure against abutment implant.
Therefore, I designed the loose, not so close as traditional, connector of the abutment implant and denture applied the magnetic force, which devised the link to relieve the excess load.
It was proved that the implants were stiff and that the magnetic force could give adequate support and stability to the implant denture.

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We examined mobility of 8 bridges with the implant abutments by PERIOTEST^®. ITI implant is K type, and the bridge is one piece. The average PERIOTEST^® value of natural teeth before the bridge preparation is＋6.4 and that of implant is -2.4.The average value of the part of the implant abutment will increase ＋1.6 for one year after the bridge set from the result of the regression lines.

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[in Japanese]

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The application of Dental Implant to maxilla is difficult than to mandibule because of the smaller quantity of bone.
At this time, we applied I.T.I. F-type implants to maxillary tubercly and changed a loosened, conventional removable partial denture for the small implant Over Denture. The new removale partial denture fits to the patient tightly, and painlessly.
As a result, this female patient who had trouble with denture's trembling when eating, speaking and make-up has relieved the tension of orbicularis orismuscle.
The lips of the patient regained the natural swelling which make her look younger.

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It has been twenty years since blade vent implants were developed. This type of implants have been widely employed, and the number of clinical data on such implants exceeds that of any other kind of implants. Conducting a survey on the situation concerning implants is meaningful because it provides us with much information which are useful in seeking ways for the betterment of implants.
In May 1988 my colleagues and I sent out a questionair to the members of our study group to obtain data concerning endosseous implants which had existed in the bones of the patients for three years or more. The questionair was returned to us along with panorama X-rays taken before, during and after the insertion of the implants concerned.We were able to get data on 200 cases, involving 363 implants, and we examined these data, focusing especially on the mode that implants are used and both patients and dentists opinions on implants. This essey introduces some interesting points found through the study.

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Disuse mandibular osteoporosis caused by chronic marginal periodontitis were reported here. And these osteoporosis could be classified into 4 types such as speckled or spotty, linear bands, generalized or diffused, and geographic or combination type.
Chronic periodontitis can make changes or cementum and periodontal ligament, morphologically and functionally. And then the phygiological stimulation such as mastiocatory forces would not be transfered to mandibules.
The disuse osteopososis would be observed in many cases, when the mandibular bodies could not be stimulated by these forces for a long time. In most cases reported here, the cancellous tissues of the mandibules were so porous that periodontal probe could be inserted into the tissue. We are focussing the examination of the mandibular body as well as alveolar bone when chronic marginal periodontitis is diagnosed.

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The purpose of the present study is to evaluate the clinical usage of zirconia ceramics dental implant,and to evaluate the mechanical strength of zirconia ceramics implant prior to its clinical application. It was originally designed type A as a mold of blade,and it was analysed by finite element method. Then developed type B and consequently type C which showed favorable property compareing proceding type. Characteristic shape of type C having two vent located underneath the two heads and concaved contour of wing. Beside, compression and bending test made on this type C dental implant showed most desirable result. Histological examination also showed that the dental implant was attached with bone,partially surrounded with thin fibrous connective tissues without any sign of bone resorption. The result obtained in the present study is that the type C dental implant is positively suggested and concerned application for clinical use.

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Local examination before operation, besides checking general condition, is crucial for implant surgery.Information obtained from the existing ways of examination such as inspection, palpation, examination of study casts, and X-ray examination(general filming of dental film and occlusal method and tomography such as orthopantomography)has provided merely superficial two-dimensional pictures and has been difficult to give a three-dimensional view of floor of nasal cavity, floor of maxillary sinus, mandibular canal and mental foramen.
A biggest advantage of the X-ray computed tomography(XCT)over conventional X-ray filming resides in the capability of imaging minute differences in coefficient of X-ray absorption. This also makes it possible to obtain desired sections by means of computerized multiplanar reformation that should be very helpful for the three-dimensional view of inner structure of bone and the examination of bone density.
This time, I performed an XCT examination prior to operation of endosseous implant in addition to the existing local examination before operation.With this examination, I was able to safely perform the operation by analyzing a possibility of endosseous implant and also by producing split casts from the pictures obtained to determine the type and location of insertion of endosseous implant as well location and orientation of implant post.
Now let me report on this case in detail.

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Denture is constructed for esthetics and masticatory function after the loss of teeth. To obtain good retention and stability, various methods have been introduced. However in clinic, general practitioners encounter many denture cases that are very poor in retention and stability.
For this reason, the button dentures with intra mucosal inserts have been studied by many implantologists since Dahl introduced it in dental clinic in 1943.But there are few articles about the technique itself and almost no report which studied the change of size and depth of the button hole.
In this article, the author measured the dimension of the button holes of maxillary mucosa of the patient who had worn a button denture successfully for 8 years, and the following conclusions were obtained;
1. Button denture must have good occlusal stability.
2. There were no progressive mucosal inflammation and the inside of button holes were kept clean.
3. The depth of the botton hole was not changed from 5 to 8 years postoperatively.
4. There was no changed in diameter of the button holes in premolar region.
5. The diameter of the button holes became a little larger mesiodistally in the molar region.
6. The author believes that the button denture reported in this paper will keep pretty good stability and masticatory function for several more years.

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The purpose of this study was to evaluate mucous membrane irritation of biomaterials;pure titanium plasma-sprayed with hydroxyapatite-alumina(HA), gutta percha(GP) as negative control and polyvinyl chloride(PVC) as positive control using 50 golden hamsters. Each sample was fabricated into a shape of a disk of 5 mm in diameter and 0.5 mm in thickness, then fixed on hamster cheek pouch by suturing. The animals were sacrificed at the end of the 14-day test period. The pouches were everted and examined grossly for inflammation and ulcer. The samples were preserved in situ on the pouches at a rate of 42%. The pouches were dissected out, then 4 μm paraffin-embedded histologic sections were prepared to observe histopathologic features. Irritation score was higher in PVC group than in HA group and GP group. There was not large difference between HA group and GP group. It was suggested that HA would not promote irritant response to oral mucosa.
From the results, this mucous membrane irritation test using hamster's pouch is considered to be very useful to assess biomaterials in our field.

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