Immunohistochemical Localization of Osteoclastogenic Cell Mediators in Feline Tooth Resorption and Healthy Teeth

Introduction In addition to periodontal disease and chronic gingivostomatitis, tooth resorption (previously termed feline odontoclastic resorptive lesions, FORL) are among the most common and frustrating diagnostic findings in feline dentistry. Reported prevalence rates of tooth resorption range from about 30 to 70 %, depending on the composition of the population examined and on the diagnostic tools used to establish the diagnosis of tooth resorption. The prevalence increases with age. Tooth resorption is associated with pain, gingivitis, ankylosis, and impairment of the periodontal ligament (PDL). Eventually, tooth resorption leads to crown and often root loss. To date, extraction of affected teeth is the treatment of choice. Tooth resorption appears as defects in cervical enamel, dentin, and cementum. The resorption of these tooth substances is not due to carious decay but results from odontoclastic activity. Odontoclasts are tartrate-resistant, acid phosphatase (TRAP)-positive, multinucleated giant cells that fulfill the same function in dental tissues as osteoclasts in bone tissue. Summary: Tooth resorption is among the most common and most challenging problems in feline dentistry. It is a progressive disease eventually leading to tooth loss and often root replacement. The etiology of tooth resorption remains obscure and to date no effective therapeutic approach is known. The present study is aimed at assessing the reliability of radiographic imaging and addressing the possible involvement of receptor activator of NFΚB (RANK), its ligand (RANKL), and osteoprotegerin (OPG) in the process of tooth resorption. Teeth from 8 cats were investigated by means of radiographs and paraffin sections followed by immunolabeling. Six cats were diagnosed with tooth resorption based on histopathologic and radiographic findings. Samples were classified according to a four-stage diagnostic system. Radiologic assessment of tooth resorption correlated very strongly with histopathologic findings. Tooth resorption was accompanied by a strong staining with all three antibodies used, especially with anti-RANK and antiRANKL antibodies. The presence of OPG and RANKL at the resorption site is indicative of repair attempts by fibroblasts and stromal cells. These findings should be extended by further investigations in order to elucidate the pathophysiologic processes underlying tooth resorption that might lead to prophylactic and/or therapeutic measures. J Vet Dent 27(2); 75 83, 2010 David Senn, Dr med vet; Peter Schwalder, Dr med vet; Philippe Roux, Dr med vet; Dieter D. Bosshardt, PhD; Michael H. Stoffel; Dr Med vet