Many cross arch prothesis cases had a lot of tooth loss with implantation. When an implant was selected the method of dental anatomical view was used. Another method that measures many natural teeth and implants by Periotest^® was investigated and a new implant selecting concept of key tooth was developed.
The results were as follows:
1. Natural tooth (Key tooth)
1) Natural canine: 1.69 (n=341×4=1364, S.D.=3.99)
2) Natural molar teeth: 6.93 (n=132×16=2112,S.D.=0.87)
2. Implant (n=266)
1) Blade vent implant: 11.22 (n=11, S.D.=4.52)
2) Sumicikon^®:6.00(n=42, S.D.=0.94)
3) Bonefit^®:0.36(n=205, S.D.=0.66)
From just PT values result of Key tooth selecting method,
1. Blade vent implant value is higher than both part of natural tooth PT value. If Blade vent implant was chosen care of periodontal factor,connecting natural teeth, should be taken.
2. Data of natural posterior teeth approximated Sumicikon's by natural tooth connecting. Sumicikon^® should be selected in posterior key tooth loss cases.
3. Data of natural incisal teeth approximated to Bonefit's. Posterial part should be selected for Bonefit^® of free-standing type. Bonefit^® should be selected in incisal key tooth loss and incisal key tooth loss cases. This material should be free-standing in posterior cases.
This method was used in many clinical cases.Good results were obtained, especially protheses that underwent periodontal maintenance by objective periodontal data.

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The purpose of this investigation was to clarify how bone resorption proceeded with the passage of time after bone was grafted to the maxillary sinus floor. Six cases (9 sinuses) underwent bone grafting to the maxillary sinus floor. Panoramic radiographs were taken of all cases preoperatively and at postoperative 1, 3, and 6 months. Measurements were taken of bone height from the alveolar crest to the original or new sinus floor in three regions (extended parts from the infraorbital canal, posterior surface of the zygomatic process, and maxillary tubercle) on the X-ray. For correction of magnification on the X-ray, the linear distances defined from anatomical landmarks were also measured, and the ratios of the bone heights to the linear measurements were calculated. The results were as follows
The ratios indicated that statistically significant decreases took place over 3 to 6 months after grafting to the extended part from the infraorbital canal, over 1 to 6 months after grafting on the extended part from the posterior surface of the zygomatic process, and over 1 to 3 months after grafting on the extended part from the maxillary tubercle. The decreases of ratios in the three areas from 3 to 6 months after grafting were slight as compared with the decreases from 1 to 3 months after grafting.But at the same time, the ratios, when computed on the preoperative and postoperative panoramic radiographs based on the bone height from alveolar crest to the original sinus floor in the three areas,almost never changed in any of the cases.
The findings suggested that resorption of grafted bone arose during the 3-month period after grafting in the first and second molar and maxillary tuberosity regions. In addition, bone resorption took place slightly over 3 to 6 months after grafting in the second premolar and the second molar regions.

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The composite of bone morphogenetic protein (BMP) and collagen fibers was inserted beneath the calvarial periosteum of 18-month-old rats. Each composite was removed by block resection together with a cranial bone at 1, 2, and 3 weeks after implantation, and evaluated as an onlay graft substitute in a calvarial model by histopathological observations. In BMP/collagen, osteoblast differentiation occurred in the proliferating mesenchymal tissue at 1 week, and bone formation proceeded extensively at 2 weeks. At 3 weeks, the BMP composite was almost replaced by new bone and the bone marrow, and the augmented bone was firmly connected with original bone. However, in collagen alone, neither cartilage nor bone formation was found. These results suggested that the composite of BMP and collagen was an effective absorbable material with osteoinductivity as an onlay graft substitute, and may be clinically applicable to biological bone reconstruction in aged patients.

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In this study, histological and in situ hybridization methods were applied to investigate ectopic hard tissue formation induced by bone morphogenetic protein (BMP)-collagen composites. The BMP-collagen composites were implanted into dorsal subcutaneous tissue of mice, and examined at 3 days,1 week, and 2 weeks after implantation. Formation of cartilage-like tissue mainly composed of ovoid chondrocyte-like cells was observed at 3 days after implantation. Maturation of the cartilage-like tissue and presence of a number of hypertrophic chondrocyte-like cells were observed at 1 week after implantation. Bone-like tissue formation occurred at 2 weeks after implantation. The localization of type Ⅰ and Ⅱ collagen mRNAs was examined during the ectopic hard tissue formation by the composites and compared with that of endochondral ossification in tibial growth plate of mice. In the ectopic hard tissue, both type Ⅰ and Ⅱ collagen mRNAs were detected in chondrocytelike cells and hypertrophic chondrocyte-like cells. Whereas in the chondrocytes and hypertrophic chondrocytes of the tibial growth plate, only type Ⅱ collagen mRNA was detected. These results indicated that ectopic hard tissue formation induced through this process was histologically similar to normal endochondral ossification, but different from it in aspects of expression pattern of type Ⅰ and Ⅱ collagen genes. It was suggested that the chondrocyte-like cells in the ectopic cartilage-like tissue have both characters of chondrocytes and osteoblasts.

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Implant therapy at the site of missing teeth associated with periodontitis or any other disease may be difficult due to the loss of alveolar bone. Alveolar ridge augmentation has been attempted in such cases from an esthetic and functional point of view. This study was conducted to investigate the effectiveness of Hydroxyapatite-coated Implant conducting ridge augmentation using the guided bone regeneration technic (GBR). Three months after extraction of the lower P 1, P 2, P 3, and P 4 of mongrel dogs, Hydroxyapatite-coated Implant covered with polytetrafluoroethylene (PTFE) membrane was placed on the artifical bone defects on the buccal side of extraction sites.
There was no inflammation during this study.
Specimens were removed and examined by light microscopy three months later.
Histological evaluation of specimens showed bone formation in the right upper mesh zone of Implant. About 60.7 kg/cm² was required to transect osseointegrated bones.
These findings suggested that Hydroxyapatitecoated Implant covered with PTFE membrane may be useful for implantation in the site of bone resorption.

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Clinical evaluation was performed using commercial titanium 2-piece implants (IAT Fit Ⅱ®, ISHIFUKU Co.)whose fixture was treated by wire-type electric discharge machining.
One hundred ten fixtures were implanted in 32 patients between 1995 and 1997. One fixture was sleeping and 43 were super structures. Achievement of osseointegration was clinically evaluated for 109 fixtures. One fixture of the mandible failed without osseointegration. Therefore, the survival rate for the fixtures was 100.0% for maxillary and 99.0% for mandible during the follow-up period. These findings indicated the IAT Fit Ⅱ was highly biocompatible and clinically useful. Evaluation of maintenance of osseointegration with function will be continued in the future.

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The Guided Bone Regeneration Technique (GBR) to place a Gore-Tex^TM Augmentation Material (GTAM) in a patient with insufficient remaining bone height of the maxilla was used at the time of placing a blade type implant. In the second surgery, the GTAM was removed and observed under an optical microscope and a scanning electron microscope. The findings were as follows:
1. Even though bacteria were present on the mucoperiosteum side of the outer portion (OP) of the GTAM adjacent to the tooth and implant head, the GBR was effective, provided that no bacteria intruded into other portions.
2. When bacteria intruded into the OP adjacent to the tooth and implant head, the mucoperiosteum side of the inner portion (IP) covering the defective portion with insufficient remaining bone height, an intertubercular gap, and the alveolar bone side of the IP, the GBR had no effect.
From this, it could be suggested that the GBR is applicable if the infection of bacteria can be blocked on the mucoperiosteum side of the OP of the GTAM placed in a portion with insufficient remaining bone height of the maxilla for supporting the implant.

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Clinical examination of Osteo-Loc Implant (OL), a blade type, applied in our clinic for more than 3 years, is discussed in this article. Materials and Methods: The OL has been applied to 51 cases for more than 3 years postoperatively, and a total of 108 OLs were used. Among them, 71 OLs in 33 cases were observed in this study. These OLs were evaluated according to the method reported by Abe et al., and postoperative shrinkage was also studied.
The formation of deep pockets around the OL was clearly found in g OLs, moderate in 37 OLs and only slight in 25 OLs. As for comparison of the inflammation around the OL with that of other gingiva, 48 OLs were good, and 23 OLs were the same as other gingiva. The mobility of the OL was not remarkable in 62 OLs, moderate in 8, and severe in only one. Slight or no cup state resorption of alveolar bone around the OL was found in 56 OLs. One-third or less of its body length in 9 OLs and two-thirds of it in 6. The results were comprehensively assessed, and were categorized into four grades (Grade 1-4). Sixty OLs were grade 1 (excellent), 4 were grade 2 (good), 7 were grade 3 (fair), but there were no cases in grade 4 (poor). As for shrinkage, no removal of articulating paper was observed in 55 OLs, removal of paper by pulling it strongly in 6 OLs, and easy removal there of in 10 OLs.
In 47 OLs, no complicated systemic diseases were found, but some systemic diseases were found in 24 of them.
As for satisfaction, patients with 15 of the OLs expressed dissatisfaction, but patients with 56 of the OLs did not desire to have the OLs removed.
Discussion:In the cases of maxillary subperiosteal implants, the comprehensive evaluation with grades 1 and 2 was observed in 83.3% as the author previously reported. In the cases of the OLs, it was seen in 90.1%. Shrinkage was found in 14.1% of the OLs. Although specific attention should be given to shrinkage in the OLs, overall the results received from grades 1 and 2 were extremely positive.

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The maxillary molar region is often a problem area for the insertion of the endosseous implants. Sinus lift is a surgical procedure to create the space for the implants by increasing the alveolar height by raising the maxillary sinus floor. As the graft materials, hydroxyapatite(HA), β-tricalcium phosphate (TCP), frozen bone particles, dried demineralized bone patrticles, and so on have been used. However, the reports regarding histological studies on sinus-lift grafts are very few.
This study was undertaken to histologically evaluate the postoperative states of four cases of sinus lift performed with resorbable bone graft material, Augmen^®, which is composed of TCP.
The results were as follows:　While three of the four cases showed sufficient bone formation as well as connective tissue around the TCP particles, in one case, most of the areas around the particles were occupied by the connective tissue and the area of bone formation was very small. In all cases, the degree of chronic inflammatory infiltrate into the connective tissue was minimal.
These results provide useful information about applying sinus lift to patients.

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Recently, various reconstructive surgical techniques have been developed, including use of cutaneous flaps, myocutaneous flaps, and free tissue transplantations using microvascular anastomoses. Due to the progress in these reconstructive methods, ablative surgery can be applied in the case of advanced oral cancer in which the defect is too extensive to be reconstructed with local flaps. These reconstructive tissues greatly contribute to recovery of postoperative ugly or and functional disorders, including swallowing and pronunciation. However, these tissues sometimes prevent the wearing of dentures. In such cases, osseointegrated implant rehabilitation is an accepted and widespread treatment modality.
Three oral cancer patients who were treated with osseointegrated implants following ablative surgery and reconstructive surgery were reported, and our method for surgical reconstructive soft tissue management was presented.

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The guided bone regeneration (GBR) technique has been used to promote the formation of new bone around endosteal implants that are exposed because of an insufficient amount of the alveolar bone, endosteal implants inserted in extraction sockets, or after the removal of endosteal implants.
A 58-year-old female was first examined in November 1982. In December, a BIOCERAM plate implant was placed in the mandibular left molar region and a bridge was seated. She had worn the implant for 14 years. In November 1996, the implant was removed because of surrounding bone resorption and replaced with three root form implants. At that time, an extensive bone defect was noted around the newly-placed implant in the mandibular left second premolar region. To promote the formation of new bone in the area of exposure, the GBR technique was performed using a GTAM (Gore-Tex tissue augmentation material) membrane, autogenous bone dust harvested with an osseous collection filter, and resorbable hydroxyapatite. As the patient was 72 years old, the formation of new bone required more time than that in younger patients. After 1 year, the GTAM membrane was removed during secondary implant surgery. In December 1997, the superstructure was seated.
There was no exposure of the membrane after primary surgery. The presence of sufficient newly-formed bone-like tissue around the exposed implant was confirmed by inspection and palpation. CT number and 3DCT in computed tomography revealed newly-formed bone in the defect around the replaced implant.
The GBR technique using autogenous bone dust, resorbable hydroxyapatite, and a GTAM membrane is effective for promoting the formation of new bone.

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