Biochemical and autoradiographical evidence that anterior mandibular displacement in the young growing rat does not stimulate cell proliferation or matrix formation at the mandibular condyle.

A removable bite plate was used to induce forward mandibular displacement in four-week-old rats for 10 h/day for 1, 3, 7, 11 and 14 days. The animals were killed and the condylar explants pulsed in vitro for 6 h with either [3H]-thymidine or [3H]-proline or 35SO(2-)4. The specific activity of radio-isotope incorporation was expressed as dis/min per microgram DNA, dis/min per mg protein and dis/min per microgram sulphated glycosaminoglycans (GAG). [3H]-thymidine autoradiography was also used in a 14-day experiment to establish a radioactive index (labelled cells per 1000 cells counted) for the anterior, middle and posterior regions of the condyle. There was no significant alteration in either cell proliferation (dis/min per microgram DNA and radioactive index) or matrix formation (dis/min per mg protein and dis/min per microgram GAG) at any point in the time scale.