Orthodontic tooth movement in the prednisolone-treated rat

Adverse effects of corticosteroids on bone metabolism raise concerns as to whether steroid treatment may influence orthodontic movement. This study examined the effect of prednisolone on orthodontic movement using an established rat model. The corticosteroid treated group (N = 6) was administered prednisolone (1 mg/kg) daily, for a 12-day induction period; the control group (N = 6) received equivalent volumes of saline. On day 12, an orthodontic appliance was placed which exerted 30 g of mesial force to the maxillary first molar. Animals were sacrificed on day 24 and tooth movement was measured. Sagittal sections of the molars were stained with haematoxylin and eosin, and for tartrate-resistant acid phosphatase (TRAP) activity. While there were no significant differences in the magnitude of tooth movement between the 2 groups, steroid-treated rats displayed significantly less root resorption on the compression side and fewer TRAP-positive cells within the PDL space on the same side. This suggests steroid treatment suppressed elastic activity

Lathyrism and the half-life of collagen

Maturation of collagen in the periodontal ligament has often been designated as the cause of tooth eruption. The fact that collagen has a high turnover rate provided some sort of proof of this hypothesis. It is well known that lathyrogens decrease eruption rate. Experiments were performed, using Wistar rats, which looked into the relationship between collagen turnover and lathyrism. The collagen turnover was established in teeth not erupting after the administration of lathyrogens. These results were compared to those obtained after having stopped eruption by the placement of a goldcrown on the lower incisors. It was found that lathyrism, and therefore collagen maturation, did not influence turnover rate. Thus the supposition, that collagen is responsible for tooth eruption, becomes doubtful