Abstract
To decide the application of hydroxyapatite to periodontal therapy, following fundamental studies on hydroxyapatite were performed.
Materials used were six kinds of hydroxyapatites of which firing temperature were 900°C (LT) and 1, 400°C (HT), and diameter were less than 100μm (size S), 200-300μm (size M) and 500-1, 000μm (size L).
To investigate the surface ultrastructure of the hydroxyapatites with different firing temperature, LT-size M and HT-size M were coated with gold and observed scanning electron microscopically.
Dissolving each hydroxyapatite in pure water and 0.1% hydrochloric acid, specific electron conductivity test was carried out to compare the solubilities.
Each hydroxyapatite was implanted in M. rectus femoris of rats, and in artificial bone defect cavity (measuring 1×3×1mm) on maxillas and mandibles of dogs. These animals were sacrified two or four weeks after implantation. Then tissue response against hydroxyapatite and osteogenic activity of hydroxyapatite were examined histopathologically.
The results obtained were as follows.
1) On scanning electron microscope, LT showed fine granular surface, but on the other hand, HT showed smooth surface.
2) Specific electron conductivity test presented higher solubilities in LT than HT.
3) At two and four weeks after implantation in muscles, all hydroxyapatites were enclosed with fibrous capsules involving foreign body giant cells and isolated from surrounding muscular tissues.
4) At two weeks after implantation in artificial bone defect cavity, foreign body response was not seen. Bone repairs in both case-LT and case-HT were more delayed than in control case, but that in case-LT was more prompt. Osteblastic cells coexisted with fibrobrasts in the connective tissue filling the artificial bone defect cavity and were in immediate contact with hydroxyapatite.
At four weeks after implantation, bone repairs had almost already completed in control and all hydroxyapatite.
At two and four weeks, there was no foreign body response and inflammatory cell infiltration.
Considering above results, hydroxyapatites were non-inflammatory and non-stimulative, and had good tissue tolerance and some kind of osteogenic activity.
