COLLAGEN-SYNTHESIS FROM HUMAN PDL CELLS FOLLOWING ORTHODONTIC TOOTH MOVEMENT

The dynamic remodelling processes in the periodontal ligament (PDL) ac count for the reaction of PDL cells to different orthodontic force sim ulations. These occur mostly by degradation and synthesis of collagen types I, III, V, VI, XII and XIV. The purpose of this study was to qua ntify specific collagen types in the PDL from zones of tension and com pression of experimental teeth. Such changes could then be correlated with the processes of orthodontic-stimulated tissue breakdown. Maxilla ry and mandibular premolars of three females and one male patient were orthodontically moved with a box loop for a total of 14 days, prior t o tooth extraction. Teeth from the contralateral side of either the ma xilla or the mandible served as the untreated controls. A total of sev en experimental and seven control teeth were used in this investigatio n. PDL fibroblasts from the cervical third of the roots corresponding to the compression and tension zones of the experimental and control t eeth, respectively, were scraped and cultured in vitro at 37 degrees C in a humidified incubator with 5 per cent CO2/95 per cent air. Collag en synthesis of types I, III, V and VI was quantified by using an ELIS A. Application of orthodontic forces in the experimental teeth showed a significant increase (P < 0.05) of the synthesis of all collagen typ es in the compression as opposed to the tension zones. Collagen synthe sis on the compression zone of experimental teeth was not significantl y different in the mandible when compared with those of the maxilla. I n addition, the proportional distribution of different types of collag en was also not significantly different in the PDL fibroblasts from ei ther zone of experimental teeth of either the maxilla or the mandible. Collagen metabolism in response to orthodontic stimulation appears to be higher in the compression zones and lower in the tension zones. Co ntrary to what is traditionally assumed in the literature, such findin gs indicate that in addition to bone resorption, tissue remodelling is very active in zones of compression following the disappearance of th e hyalinized areas. These findings constitute a model for future studi es on collagen metabolism during orthodontic-stimulated tooth movement .