The response of the fibroblast population in the periodontal ligament of rat incisors to altered eruption rates.

Abstract

The fibroblast population of the periodontal ligament (PDL) in impeded and unimpeded rat incisors was investigated. The material examined was limited to the functional compartment of the cementum‐bordering tooth‐related PDL (t‐PDL) located between 7 mm and 15 mm from the tooth origin. In five albino rats, weight 200g, the lower left incisor was left to erupt unrestrainedly for three weeks (900μ/day) and in five other rats, eruption of the incisors was imeded (450μm/day). The left mandibles were dissected and fixed: the incisors were demineralized, embedded in glycolmethacrylate, and cut into 2‐μ transverse sections. The sections were used to produce a three‐dimensional reconstruction of the PDL by means of computerized histomorphomety and to count the fibroblast population. The obtained data was combined, thus providing information on cell kinetics. The size of the tooth‐related PDL remained uniform along the impeded teeth, while in the unimpeded incisors it increased gradually in incisal direction, the total volumes estimated as 2.65 mm3 and 2.07 mm3, respectively. The calculated mean cell living space was 1,327 μm1 in the impeded teeth, rising in the unimpeded ones from 503μm3 to 858μm3 in the ineisal direction. The estimated total number of fibroblasts in the PDL of the impeded teeth was 2,000X103, the mean daily production rate amounting to 115x103 cells, while in the unimpeded incisors these numbers totaled 2,957x103 and 336x103 cells, respectively.