Akiyoshi Yamagami

Electron Microscopic Study of the Cytotoxicity of Cadmium and Mercury In Vitro

The cells treated with cadmium chloride showed severe changes: ribosomes disappeared, mitochondria showed various degrees of destruction, and the endoplasmic reticulum had a swollen and beadlike appearance. In cells treated with mercuric chloride, ribosomes increased in their density and rosette-like polysomes were predominantly observed. The effects of these two metallic ions were discussed.

In Vitro Studies of Cellular Responses to Heat and Vibration in Cavity Preparation

Fibroblasts in tissue culture responded to heat and vibration induced by dental drilling at varying speeds. The in vitro findings suggest that pulpal responses are more likely caused by severance of odontoblastic processes than by the factors studied.

The Effect of Surface Roughness Difference on Bone Integration of Anodic Oxidized Ti Alloy Implants

At present, immediate loading of dental implants is of great interest. The key of this issue is how quickly implant can acquire firm fixation in the jaw bone, and how quickly the superstructure can be fabricated. In order to achieve these, it is necessary a large surface area of the implant and to promote early contact of the surrounding bone which can bear the load. In addition to this, anodic oxidization was carried out to prevent ion elution from titanium and titanium alloy in the body. The experiment was conducted with cylindrical Ti alloy test pieces of 4 different surface roughnesses (Ra=1.1μm, 1.2μm, 2.7μm, 4,7μm). These test pieces were treated by sandblasting and anodization, and implanted into the diaphysis of the femur of New Zealand white rabbits. Six weeks later, shear loading tests and histological examination were carried out. Strong interfacial bonding strength and active new bone formation were confirmed in the peripheral area of the test pieces having a surface roughness of Ra=2.7μm and 4,7μm. Judging from the stable fixation against the shear loading in the bone tissue seen in group C(Ra=2.7μm), it was

Studies on a Porous Alumina Dental Implant Reinforced with Single-Crystal Alumina: Animal Experiments and Human Clinical Applications

A new type of porous alumina dental implant has been designed. A biological seal is provided by single-crystal alumina on its cervical portion, and fixation capability in bone is provided by a porous alumina layer with anaverage interconnecting pore size of approximately 130 μm. The mandibular premolar and molar extraction sites of 15 male rhesus monkeys (3 to 6 years old) were used in the animal experiments. All the implants and superstructures that were not retained by attachment to proximate teeth participated in functional occlusion at all times except during the first two to four weeks. After four, six, and eight months, histological examinations, including light microscopy (LM), scanning electron microscopy (SEM), and electron probe microanalysis (EPM), were conducted. The surrounding gingival tissue strongly adhered to the single-crystal alumina on the cervical portion of the implant, and prolific bone ingrowth was observed within the porous network of the root component. The human clinical evaluations showed a high success rate of 94% in 45 cases. Long-term clinical cases were included, the longest implant having survived for eight years in free-standing form. These cases included 23 free-standing cases and 22 bridge cases; 3 of these failed in the first stage of human clinical trials.