Ultrastructure of tissue in intrabony and subperiosteal porous ceramic implants.

Porous ceramic (Al2O3) implants with pore size of 100--750 micron were placed intrabony in the maxilla and subperiosteally in the mandible of three adult monkeys. After observation periods of 10, 11 and 12 months, the animals were perfused with 1.7% glutaraldehyde and the jaws processed for electron microscopy. Tissue ingrowth into the pores was observed in all the specimens. The implant pores facing the host bone contained bone tissue to a depth of approximately 1 mm, while only unmineralized tissue was found in the implant part adjacent to the periosteum. The unmineralized tissue was of a fibrous nature with collagen fibers arranged in a lamellar fashion. Cells, often with extremely long and slender cellular processes, were seen between the lamellae. The cells had the cytoplasmic features typical of protein-producing cells. The mineralized tissue exhibited ordinary bone tissue structure with plate-like crystallites in a collagenous matrix. Some lacunae and canaliculi with osteocytes were observed, though they were scarce.

Further observations on the fine structure of cellular cementum from deciduous teeth of pigs.

Examination of microradiographs from the deciduous teeth of pigs revealed large lacunae or radiolucent zones close to the cemento-dentinal junction. Electron microscopic studies of the ground sections showed areas of irregularly shaped zones devoid of mineral and filled with collagen fibers. In the wide unmineralized zones, spherical clusters of crystallites were noted. Several cementum lacunae bordered by a broad rim of unmineralized collagen fibers were noted and some lacunae also contained zones of a moderately electron dense material. This material did not yield a diffraction pattern, while the mineralized part of the cementum gave the diffraction pattern typical of hydroxyapatite.

The effect of grinding of human dentine examined by X-ray diffraction, infrared spectroscopy, and electron microscopy.

Analysis of human dentine by infrared spectrophotometry suggests that ball-grinding may result in damage of the apatite crystallites. The present study includes further assessments of this effect by X-ray diffraction, infrared spectroscopy, and electron microscopy. Each of three coarse-ground dentine samples (Group I) was divided into three portions of 30 mg. One of these portions was ball-ground for approximately 1 min (Group II), the second portion for 6 min (Group III), and the third portion for 23 min (Group IV). The 002 reflection showed line broadening, most marked from Group II to III. Electron microscopy showed a gradual change in crystallite appearance with increased grinding, most pronounced from Group II to III. These observations indicate that by prolonged grinding a limit is approached where no further changes in the crystallites occur. Electron microscopy also indicated that fracture of the crystallites might have occurred. This was probably accompanied by strains in the lattice. The infrared spectra indicated that no breakdown of the apatite structure had occurred during the entire grinding.