Carrageenan-induced inflammation and its effects on mitotic activity and keratinization of gingival epithelium. A histologic and autoradiographic study.

This study was undertaken in order to: evaluate the cell population in carrageenan-induced inflammation and investigate the extent to which this inflammation modified mitotic activity, and keratinization of the sulcular epithelium induced by daily prophylaxes in monkeys. Normal-keratinized oral gingival epithelium was also evaluated for these processes in the same gingival specimens. Each of three adult Rhesus monkeys received a thorough prophylaxis 1 week prior to the experiment. Over the 10-week experimental period, each monkey received daily rubber cup prophylaxes. In addition, during the last 10 days, daily gingival injections of a 1% carrageenan saline solution and normal saline solution were given. One hour prior to sacrifice, each monkey received an intravenous injection of tritiated thymidine, 1 microCi/gram of body weight. After sacrifice and tissue processing, the histologic sections were evaluated. It was found that the carrageenan solution injected into gingival tissues produced an acute inflammatory response consisting of polymorphonuclear leukocytes PMNs (61.3%), lymphocytes (5.2%), monocytes/macrophages (23.5%), plasma cells (2.0%) and unidentified cells (3.8%). An Inflammatory Index and a Mitotic Activity Index were determined, and keratin length and widths were measured. Data were analyzed statistically using analysis of variance. Pairwise comparisons were also made using Scheffe's method of multiple comparisons. The study showed that: carrageenan solutions injected into gingival tissues elicited an acute inflammation; acute inflammation present in gingival connective tissue stimulated an increase in mitotic activity in subjacent gingival epithelium; acute inflammation within gingival tissues did not modify the induced-keratinized sulcular epithelium, or the normally-keratinized oral gingival epithelium; and acute inflammation may not necessarily affect tissue keratinization, if bacterial plaque is removed daily.