This study evaluated the effect of smoke exposure on the expression of genes related to bone metabolism in implants coated with nanohydroxyapatite (NHA). A total of 36 rats were exposed to cigarette smoke for 60 days. The animals were allocated into three groups: machined implants (MAC), dual acid-etched implants (DAE), and NHA-coated implants (NHA). Implants were installed in the left tibia of the rats after 30 days of smoke exposure. The implants were retrieved 7 and 30 days after implantation, and the adjacent bone analyzed using a real-time polymerase chain reaction for gene expression of alkaline phosphatase (ALP), osteopontin (OPN), receptor activator of the nuclear factor kappa ligand (RANKL), osteoprotegerin (OPG), the RANKL/OPG ratio, osteocalcin (OCN) and runt-related transcription factor 2 (Runx2). After 7 days, Runx2, OPN and OPG expression demonstrated significantly higher levels for the NHA surface treatment relative to DAE and MAC surfaces. NHA presented the lowest RANKL and RANKL/OPG levels. After 30 days, NHA-coated implants showed significantly higher levels of Runx2, ALP, OPN, OPG, OC, RANKL and RANKL/OPG relative to DAE and MAC implants. The results indicated a greater osteogenic and high osteoclastic activity around NHA implants, in comparison to DAE and MAC implants.
Keywords: animal study; dental implant; gene expression; implant surface; nanohydroxyapatite; smoking.