Composition and metabolism of the extracellular matrix in the periodontal ligament of impeded and unimpeded rat incisors.

Potential differences were studied in the composition and metabolism of the connective tissue components (collagen, non-collagenous proteins and glycosaminoglycans) of the periodontal ligament (PDL) as a result of alterations in the rate of eruption. The amount of collagen, glycosaminoglycan (GAG) or the water content of the tissue was the same in the unimpeded and impeded situation. The only difference was in the amount of structural non-collagenous proteins: 33 per cent increase in the unimpeded PDL. The rate of turnover of insoluble collagen, structural non-collagenous proteins and the sulphated GAG, studied in vivo by administration of [3H]-proline or [35S]-sulphate, did not differ significantly in both situations: their extremely short half-lives were respectively 9.7, 3.5 and 1.7 days. Increase in the rate of eruption and hence in the remodelling process does not result in alterations in the metabolic activity of the PDL components. Their metabolism is probably already at maximal rate and may permit the more rapid rate of eruption when the opposing force of the antagonists is diminished during the non-occlusional state of the incisors.