['This study was carried out to investigate the effects of insulin-like growth factor-II (IGF-II) and basic fibroblast growth factor (bFGF) on osteoprotegerin (OPG) secretion of periodontal ligament cells (PDLCs).', 'Healthy human premolars extracted for orthodontic reasons from 12-14 years old donators were obtained, and periodontal tissues were collected and cultured to obtain PDL cells. Primary or first passage PDLCs were cloned by means of limited dilutions. PDLCs with osteoblastic phenotypes were characterized as follows: Alkaline phosphatase activity, collagen III production and bone-like nodules formation. IGF-II and bFGF were added into culture media and their effects on PDLCs proliferation and OPG secretion were observed. The OPG concentrations in cell culture supernatants were detected by sandwich ELISA. Living cell numbers were demonstrated by MTT test. The average levels of OPG secretion by a single cell were calculated by dividing OPG concentration with MTT-test result.', 'Both IGF-II and bFGF upregulated the mtt values (P < 0.05), but ICF-II downregulated the opg/mtt values (P < 0.05), whereas bFGF had no significant effect on opg/mtt values (P > 0.05).'] Do [ Insulin-like growth factor-II and basic fibroblast growth factor affect periodontal ligament cells expressing osteoprotegerin in vitro ]?