Role of T cells in the pathogenesis of periapical lesions. A preliminary report.

The pulps of mandibular molars of 15 athymic and 15 conventional rats were surgically exposed and left open to their oral flora. Each group was divided into three subgroups of five animals each. The rats were killed after their pulps were exposed for 2, 4, or 8 weeks. After fixing, decalcifying, and embedding, the specimens were sectioned and stained with hemotoxylin and eosin. They were then examined under a microscopic grid and quantified by percentages of surface areas of bone, connective tissue, bone marrow, intrabony spaces, periapical lesions, and numbers of osteoclasts, with the use of a DataVoice computerized data collection and analysis system. Statistical analysis showed no significant difference between periapical tissue responses of the conventional and athymic groups. The results indicate that the pathogenesis of periapical lesions is a multifactorial phenomenon and is not totally dependent on the presence of T-cell lymphocytes.