This study was undertaken to investigate the effect of the direct current stimulation on surrounding tissue of the intra-osseous implant in dogs. The implant material was composed of a peripheral hydroxyapatite layer and a center metal core used as an electrode. After embedding the implant on the mandibular edentulous ridge of the dog, a constant direct current, 10μA and 1.55V, was applied for a successive 14 days and 28 days.

Histopathologic findings were as follows:

1. When the bone marrow was stimulated electrically with a constant direct current for 14 days or more, bone formation around the implant accelerated.

2. There was a different histological reaction surrounding tissues between the cathode and anode sites. Around the cathode, bone formation on the surface of the implant was remarkable, but around the anode, bone formation on the surface of the implant was poor.

3. The electrical stimulation, with a newly developed power unit and electrode, accelerated new bone formation in the surrounding tissue of the intra-osseous implant.