The distribution of multinucleated giant cells (MGCs) and osteoclasts after intraosseous implantation of synthetic hydroxyapatite (HA) was studied using light microscope and histomorphometry. HA dried at 200℃(2 HA) and HA sintered at 1,250℃ (12HA )were used in this study. Light microscopically, MGCs in response to 2 HA showed a ruffled border-like structure at the interface between 2 HA and MGCs,but MGCs in response to 12 HA did not. The amount of new bone formation after intraosseous implantation of 2 HA was similar to that after intraosseous implantation of 12 HA. However, MGC count in response to 2 HA was higher than in respose to 12 HA, especially 2～ 6 weeks after intraosseous implantation of HA. Moreover, osteoclast count on new osseous tissue without HA implantation was apparently higher than after implantation of 2 HA or 12 HA. These results suggest that MGCs responding to HA do not effect new bone formation around the intraosseous implanted HA. New osseous tissue remodeling,after implantation of HA, is either on a low level or delayed when compared with tissue not HA implantated.

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Some biomaterials including implants have been widely used in dentistry and oral surgery.They work well in many (but not all) cases. The purpose of this study is to reexamine unfavorable cases and to show a concept in dealing with the clinical use of implants. We observed 5 unfavorable cases to which were applied various systems. The patients consisted of three males and two females, 43 to 78 years old. Their chief complaints were painful swelling, abnormal sensation,and mastication difficulty. Clinical symptoms disappeared after the removal of implants. These cases indicated that the success of implantation would depend on the preoperative evaluation of a patient, surgical procedure, postoperative care and etc.

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Implants have come to be extensively applied to general dental treatment since L.I.LINKOW introduced the blade implant method in 1968. Since then, various other types of implants were developed in many places around the world, but the blade method is most commonly used even today. It is believed that this is because the implant using the blade method can demonstrate strong support to mastication. However, this method still leaves room for debate as to the best bent angle or the outer shape of the blade.
Therefore we designed four single-headed implants with various bents and outer shapes on a blade of 20 mm in length, 7 mm in height and 1 mm in thickness which was made of a material like titanium alloy with the Young's modulus of 2,700 kg/mm² and the Poisson's ratio of 0.3. Then we planted each of the seven implants on a material similar to human cancellous bone with the Young's modulus of 2,500 kg/mm² and the Poisson's ratio of 0.2, and measured the stress when the vertical pressure of 50 kg was given on top of the head of each implant. Then we analyzed the stress three-dimensionally using CAD/COM.
The results are as follows:
1. Irrespective of implant types, the sites where the stress concentrates most in and around the implant are surrounding and partially in the head and neck.
2. The stress in the upper part of the shoulder is extremely less-concentrated in the tapered form shoulder than in the horizontal one.

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We took many implant measurements and natural teeth mobility with PERIO TEST measuring device.We had some interesting results for each implant group.Those results were as follows;
1. Cases of bioactive implant with SUMICIKON The average PERIO TEST value was climbing in the primary movable stage from immediate post operation to 60 days later. Then the average value gradually decreased until it was smaller than the periodontal tendency value before the operation.
This phenomenon was becoming“Bio-integrate”.
2. Cases of Ordinary blade-vent implant with Shape memory implant.
Immediate post operation and 1 day post operation, the average value was declining for shape memory function.
At first movable stage (14 days post operation), the average value ascended more than SUMICIKON's, and 21 days post operation it returned to the level 7 days post operation and then declined again. More than 21 days post operation the convalescence was satisfactory.

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The quantity of exudation from peri-implant sulcus was measured by Brill's method using Periotron Economy^® apparatus. Implants were 2 part-hollow screws of Bonefit^®. In some cases,Periotron values were very high (40～60) at first (after implantation), but dropped below 10 as time passed. In other cases values were always below 10. In non-functioning conditions of 11 cases over 90 days after implantation, the values of 9 cases were below 10 and the value of only one case was over 20. No inflammation of the peri-implant mucose was observed in the above cases. In functioning conditions of 17 cases, the values were below 10 in 11 cases and over 20 in 2 cases respectively. Thus, Periotron values of most cases were below 20 in functioning conditions as well as in non-functioning states.

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In atrophied edentulous mandible cases, conventional denture systems present many treatment problems and difficulties. Although subperiosteal implants are very good procedures for these patients, some problems have been found in the conventionally designed subperiosteal implants. The tripodial subperiosteal implant (TSI) developed by Linkow is very effective and safe for the treatment of such cases. But the material nature and procedure to fit it to the mandibular surface should be improved to provide desirable results. Therefore,we used pure Titanium instead of Co-Cr-Mo alloy and divided the frame into 2 parts and 1 endosseous blade.
They were connected together with a mesostructure bur and held by 4-Meta resin. We named it modified TSI. It was adopted clinically and there were no disturbances of speech or mastication about 10 months after completion of dental implantation.

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Recently, artificial organs have been made impressive progress in the medical profession. The same is true of the dental profession, where diverse dental implant materials, centered on ceramics, have been designed. These have been highly rated by clinicians for their stability and resistance to occlusional force.
The stability of these implants, however, depends greatly on how well the occlusional forces of the structures on the implants and plaques are controlled. The first step for setting up the upper structures is to obtain precise impressions.This article presents a rational method for obtaining impressions,centered on agar/alginate composites, and introduces a newly developed bioceramic material characterized by precision and firmness for dental implantation. We will also discuss preparation for this material and measured values for its precision and strength.

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The implant often used by dentists as a substitute for lost teeth takes on,when subjected to heating,a color, which is considerably different from that seen in untreated or normal specimens.Unless dentists pay attention to this fact, it may lead to grave blunders when special cases are encountered. We observed one such case and obtained results therefrom, which are summarized below.
1. The metal constituting the implant changes appearance when heated.
2. An oxide membrane, white in color, consisting of TiO₂ and covering the surface of the metal substrate is formed through cremation.
3. As far as can be determined from color changes of the oxide membrane covering the implant body, the cadaver was subjected to cremation at 800～850℃ for 60～180 minutes.

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[in Japanese]

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