A histopathological study of the role of periodontal ligament tissue in root resorption in the rat

Whether periodontal ligament (PDL) tissue is capable of inducing root resor ption was examined. The distal root of the rat molar was sectioned at the f urcation and the PDL tissue removed from the root (non-PDL group, n = 40). The distal root with the PDL intact was also prepared (PDL-intact group, n = 40). The roots were transplanted into the dorsal skin of the rat. On the ist, 3rd, 5th, 7th, 10th, 14th, 21st or 28th day after transplantation, the roots were removed together with surrounding dorsal subcutaneous ti!;sue a nd were fixed, demineralized and embedded in paraffin. Serial sections from each block were stained with haematoxylin and eosin or by the tartrate-res istant acid phosphatase (TRAP) method to observe root-resorbing cell format ion. Cyclo-oxygenase-2 (COX2) was also detected immunohistologically to exa mine prostaglandin E-2 production. On the 7th day after transplantation, mu ltinucleated root-resorbing cells with TRAP were observed in the PDL-intact group. The number of TRAP-positive cells peaked on the 10th day after tran splantation. COX2-positive cells were observed in PDL during the early expe rimental stages. No root resorption was seen in the non-PDL group. These re sults suggest that PDL tissue is involved in the formation of root-resorbin g cells and root resorption. (C) 2001 Elsevier Science Ltd. All rights rese rved.