82 Theories and techniques of oral implantology

was placed so that it was in occlusion when the jaws were closed.

After the implant had been in place for more than 115 weeks without event, the dog was sacrificed. The Vitallium screw was carefully removed with a screwdriver. The screw was bent at about a 15-degree angle because of occlusal forces; otherwise it appeared exactly as it did prior to its insertion. Histologic sections of the hard and soft tissues surrounding the implant were prepared (Fig. 4-2) .

The following reports the histologic findings of the Department of Pathology* :

Large celloidin sections were made through a block, which included the region in which the screw had been placed as well as a considerable amount of surrounding tissues. After decalcification with nitric acid and embedding in celloidin, sections from multiple levels were stained with H (hematoxylin) and E (eosin). At the buccal margin there were a few downward projections of fibrous tissue containing numerous blood vessels of capillary size. The tissue was rather rich in collagen and there was a moderate amount of lymphocytic infiltration. This reaction extended only a short distance from the margin of the screw. Beneath this rather narrow zone there was a region where the margin of the tissue abutting the screw was composed of very dense collagenous connective tissue. The bone had been reshaped so that it fitted exactly against the margin of the screw and there was no evidence of disintegration

*Strock, A. E., and Strock, M. S.: Method of reinforcement for pulpless anterior teeth, J. Oral Surg., July, 1943.

Fig. 4-1. A soft tissue specimen around the base of a crown covering an implant has been removed for biopsy (arrow). A full ring of tissue was taken from the marginal gingiva to the gingival attachment.

of the bone or of lymphocytic infiltration in the part where the screw passed through the bony framework. The point of the screw had pushed forward the antral lining but had not perforated it. The lesion was covered with a moderately thick layer of connective tissue. Fine strands of connective tissue lined the screw tract. Occasional pigment cells were seen.

On the whole, the histological study of this material indicates an extraordinary lack of re-

Fig. 4-2. A, A longitudinal section from the bone block of a dog. Bone has filled in around the implant, clearly outlining the site. B, A cross section from the same bone block shows that the bone is dense. The soft tissue encircling the site is a thick collagenous connective tissue. (Courtesy A. E. Strock.)