ABSTRACT
<p><b>OBJECTIVE</b>To study mRNA expression of receptor activator nuclear factor kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG) in peri-implant tissue during unloading period.</p><p><b>METHODS</b>An animal model of dental implant was established in 6 male Beagle dogs of 1-2 years old. Bone remodeling was tested at 3, 7, 15, 30, 60 and 90 days since the placement of implants. RANKL and OPG mRNA expression were quantified by real-time polymerase chain reaction (PCR). Then mandibular bones were taken out and the morphological changes were observed by X-ray, bone tissue was tested by immunohistochemistry stain.</p><p><b>RESULTS</b>The most prominent period of bone remodeling occurred at 7th day after the placement of implants. The expression of RANKL and OPG increased in a time-dependent manner in both soft and hard tissue. After 7 days they gradually decreased.</p><p><b>CONCLUSION</b>RANKL and OPG can express in soft tissue, and the changing tendency is consistent with the change of bone remodeling, it indicates that RANKL and OPG play an important role in the bone remodeling.</p>