Strengthening of bone-implant interface by the use of granule coatings on alumina ceramics.

Three different granule coatings (a granular alumina ceramic coating, a granular hydroxyapatite coating, and a polished granular hydroxyapatite coating) applied to alumina ceramic substrate were evaluated for their strengthening effects of the bone-implant interface in rabbit tibiae. For a comparison, noncoated alumina ceramics, and dense hydroxyapatite were assessed in the same way. The granular alumina ceramic coating, creating a bioinert, porous surface, was most effective due to a strong mechanical bond between the bone and implant. The interface strength was even higher than that of the dense hydroxyapatite. The granular hydroxyapatite coating, creating a bioactive, porous surface, was less effective than the granular alumina ceramic coating because of the brittleness of the hydroxyapatite granules, although it formed a direct and mechanical bond with bone tissue. The polished granular hydroxyapatite coating, creating a bioactive, smooth surface, was least effective because of the brittleness of the hydroxyapatite granules, though it presented an improved interface strength compared with that of the noncoated alumina ceramics due to a direct bond between the bone and hydroxyapatite granules.

A method for toxicological evaluation of biomaterials based on colony formation of V79 cells.

This report describes a method for cytotoxicity screening of biomaterials based on colony formation of V79 cells. For this test, two metals (titanium and nickel), two ceramics (alumina ceramic and tricalcium phosphate), and two types of polymeric material [high density polyethylene (HDP) and polyvinylchloride (PVC)] were used. Each metal and ceramic was cast into a disk and semidisk 49 mm in diameter and 1 to 2 mm thick. The HDP was molded into a petri dish and PVC was used as a thin film. The materials were sterilized by heating or with ethylene oxide and placed in plastic petri dishes, after which 8 ml cell suspension containing 100 cells were added to each dish. After 1 week, the colonies formed on the materials were fixed, stained, and then the number of colonies was counted. Titanium, alumina ceramic, and HDP showed no differences from the controls in terms of colonies. On the disks and the semidisks of nickel and tricalcium phosphate and on the thin disks of PVC, however, no colonies were detected. The V79 cells used in this experiment showed a rapid and logarithmically stable growth curve and such a high rate of colony formation as to form visible noticeable colonies, and were therefore suitable cells for screening test the cytotoxicity of biomaterials. Unlike other previously reported methods of in vitro cytotoxicity testing, this method permits assay of colonies formed from a single cell after proliferation directly on the materials. Moreover, the test with semidisks permits simple screening to assess the cytotoxicity is caused by either the chemical substances or the physical properties of the materials.(ABSTRACT TRUNCATED AT 250 WORDS)