An index was established for the laser apparatuses selection for appropriate laser treatment in the clinic. In this experiment, rat skins were incised using CO₂ and Nd:YAG lasers, and histopathological examination of each healing process was performed. After CO₂ laser treatment, the margin showed coagulation necrosis with carbonization immediately after incision. A few days later, mild epithelial cell proliferation and inflammatory cell infiltration in subcutaneous tissue and dermis were observed. Thereafter, inflammatory changes diminished gradually, and granulation tissue, consisting of fibroblasts and neovascularization, was seen in subcutaneous tissue. Five and 6 days later, epithelial regeneration and necrosis tissue absorption had almost been completed, respectively. On the other hand, after Nd:YAG laser treatment, histological changes were similar to those after CO₂ laser treatment. However, necrosis was greater than that after CO₂ laser treatment, and inflammatory cell infiltration, chiefly neutrophils, were present in all specimens 0.5 days later. Although granulation tissue formation and necrosis absorption occurred, reepithelialization tended to be delayed in contrast to that after CO₂ laser treatment. These findings suggested that the CO₂ laser was more suitable to incise the skin or other tissues with the cornification stratified flattened epithelium than the Nd:YAG laser.

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Recently, Finite Element Analysis (FEA) has been often used to study the deformation of osseointegrated implant because its displacement increases in proportion to load increase. In this study, the reliability and problems of FEA were investigated by comparing the measured values in dogs and the analyzed values of FEA. It was revealed that analyzed values were reliable when fixture was supported only by compact bone around the upper region of the fixture. However, it seemed problematic to analyze when the fixture was supported only by compact bone beside the fixture. Therefore, it was very important to choose suitable initial conditions especially when the fixture was supported in an unusual compact bone state.

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The purpose of this study was to compare removal torque of osseointegrated implants in three types of vascularized bone.
Scapula, iliac crests, and fibula were used as samples from five formaline-fixed cadavers, and the removal torque of implants was measured with torque gauge meter (Tohnichi 15 BTG-N). In addition, the thickness of cortical bone and total bone were measured. As a result, the fibula had the strongest removal torque of implant, and the thickest cortical bone among the three bone flaps. There was a correlation between the removal torque and the thickness of cortical bone, though there was no significant correlation between removal torque and the thickness of total bone.
These results suggested that the fibula has the strongest initial fixed strength for osseointegrated implants.

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The purpose of this study was to observe tissue reactions to two chitosan films containing synthesized hydroxyapatite(HA) or bovine bone powder (BB). Each film was implanted under the periosteum of rabbit tibiae, and submitted to histopathological examination at 4 and 12 weeks after operation. At 4 weeks after implantation, granulation tissue with inflammatory cell infiltration around the films were observed in both groups. Granulation tissues in BB-containing films were more mature than that of the others, because inflammatory reactions were minimum in BB-containing films. In osseous tissue, fibrous bone had proliferated from cortical bones and invaded granulation tissue formed by chitosan films. At 12 weeks after implantation, BB-containing films was already absorbed,and new cortical bone was formed in implanted sites. On the other hand, in synthesized HA-containing films, apatite components encapsulated by fibrous connective tissue were still present, and numerous fibrous bones penetrated into this connective tissue. These findings suggested that apatite containing chitosan films showed good absorbency under the periosteum of rabbits tibiae. In addition, granulation tissue and fibrous connective tissue as well as HA seemed to play significant roles in osteoconduction.

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Bone is composed of calcium, phosphorous, magnesium, and silicon. Therefore, it is most desirable that bone filling material include these elements. It is possible to replace bone filling material for bones. Furthermore, other properties must be regarded as essential, including setting time and pH value.
In the present study, the relationship of various amounts of added CaO and CaSiO₃ to the setting time and pH value were observed. The results were as follows:Increasing CaO and CaSiO₃ volume resulted in shortened setting time. Increasing CaO and CaSiO₃ volume resulted in a higher pH value. The findings indicated that C 4560 is optimum for preparation of bone filling material.

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Forty-three endosseous dental implants of 26 patients, 4 three-dimensional, 14 blades, 14 root-hollows, and 11 root-solids, were removed due to various reasons. Clinical observation indicated that osseointegrated implants with severe bone loss did not necessarily show any mobility in jaw bones, and that the removal of three-dimensional and blade implants often resulted in big bone loss because of their large root structure. Thirty-seven of the implants were histologically examined, and 6 implants without any surrounding tissue were excluded from the histological observation. Histologic sections indicated that the three-dimensional and the root-hollow implants often showed the presence of granulation tissue with stratified flattened epithelium in the complicated root-structure. Consequently, based on our observations and the review of literature, the root-type implant might be preferable because of its high predictability and easy removal.

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It has been reported that cigarette smoking may have negative effects on osseointegrated implants, but detailed investigations have not been made on many cases. The purpose of this study was to compare the long-term results of implants between a smoking group and a nonsmoking group. One hundred thirteen patients who had received Brånemark implants and had undergone prosthetic treatment between August 1990 and February 1996 at the Department of Oral Surgery, Nagoya University School of Medicine or hospitals affiliated with that Department were investigated.
The relation between failure rates and smoking habits was studied. The overall failure rate was 5.45%. It was found that a significantly greater percentage of failures occurred in smokers (7.14%) than in nonsmokers (3.56%). Failure rates were higher in smokers than in nonsmokers, even for longer fixtures which have generally good predictability. Further, the failure rates of the implants with one or more years of follow-up period were higher in smokers than in nonsmokers.

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