The pathologic alterations occurring in the gingival tissues of humans immediately following the beginning of plaque accumulation have not heen elucidated previously. Seven males, 22--31 years of age, free of clinical manifestations of dental and periodontal disease, and exhibiting a Plaque Index score of zero for the previous 28 days served as subjects. Plaque control measures were discontinued for 8 days and biopsies were taken from the buccal marginal gingiva of the first premolars on days 0, 2, 4, and 8. Paraffin- and Epon-embedded section, treated with a variety of histochemical stains were analyzed microscopically and cell counts were done on 1-micron Epon section. At 2 and 4 days following the beginning of plaque accumulation, the vessels subjacent to the juctional epithelium exhibited vasculitis and alterations in the perivascular collagen. There was a statistically significant increase in the number of neutrophils residing in the junctional epithelium. By the end of the 8-day period, the number of small mononuclear cells, mostly lymphocytes, in the connective tissues had increased by 3-fold and the area of collagen fiber alteration by 4-fold. In addition, the number of fibroblasts per unit area of connective tissue decreased significantly. Thus, within the period of 8 days following the beginning of plaque accumulation, an early lesion exhibiting many features characteristic of delayed hypersensitivity develops.

A TEM study was made of the response to synthetic hydroxyapatite prepared in powder form and implanted for 6 and 12 months respectively in infrabony lesions in 2 adult patients with chronic periodontitis and tooth mobility. Round or oval‐shaped crystal aggregates, ranging in diameter from 1 to 20 μm, were surrounded by connective tissue free of inflammatory cells. The aggregates were made up of loosely‐packed individual synthetic hydroxyapatite crystals, with a mean diameter of 128.12±14.57 nm, separated by an amorphous matrix containing few collagen fibrils. In the 6‐month implants small apatite crystals, of a size similar to those found in adjacent alveolar bone and giving similar diffraction patterns, appeared in the center of the aggregates between the relatively large crystals of synthetic hydroxyapatite. These new apatite crystals filled the amorphous matrix progressively from the center to the periphery of the aggregate. The latter was surrounded either by fibroblasts or by osteoblasts and osteoid tissue. In the 12‐month samples a calcified collagenous bone matrix enveloped the crystal aggregates. Typical osteoclasts, lacking a brush border, were evident around certain aggregates. Some osteoclasts contained large vacuoles filled with synthetic hydroxyapatite crystals.

No abstract