Influence of high + Gz environment on receptor activator of nuclear factor κB ligand and osteoprotegerin mRNA expression in the peri-implant bone tissue

Objective To investigate the influence of high + Gz environment on receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG) messenger RNA (mRNA) expression in the peri-implant bone tissue by an animal model. Methods Thirty New Zealand white rabbits were randomly and averagely divided into 3 control groups and 3 experimental groups corresponding to the investigation for 3 weeks, 5 weeks and 12 weeks respectively. Rabbits′ mandible incisors of both sides were extracted and implanted with 1 implant in each socket immediately. After 1 week of rest, the experimental rabbits were exposed to high + Gz environment 3 times a week (Monday, Wednesday, Friday), The exposure scheme choose the + Gz profile with 4~9 G for 10~45 s with 1 G/s onset rate and with the intervals of 1 min. The rabbits of control groups were not exposed to + Gz environment and normally fed. One control group and one experimental group rabbits were respectively sacrificed at the 3rd week (+ Gz exposure for 2 weeks), 5th week (+ Gz exposure for 4 weeks) and 12th week (+ Gz exposure for 4 weeks and normal feeding for 7 weeks) after the implanting surgery. The specimens were obtained to find the mRNA expression of RANKL and OPG by real-time polymerase chain reaction (RT-PCR) examination. Results The mRNA expression of RANKL and OPG were the highest 3 weeks after the surgery in both groups, and then decreased gradually. The RANKL mRNA expression and the RANKL/OPG ratio of the experimental group were significantly higher than those of the control group 3 weeks after the surgery (P<0.05). Five weeks after the surgery, the OPG mRNA expression of the experimental group was significantly lower than that of the control group (P<0.05), but the RANKL mRNA expression and RANKL/OPG ratio were still higher than that of control group (P<0.05). Twelve weeks after the surgery, the differences on RANKL and OPG mRNA expressions was not obvious between two groups. Conclusions High + Gz exposure could increase the expression of RANKL, raise RANKL/OPG ratio and promote bone resorption, but may be not conducive to implant bone bonding. Key words: Acceleration; Rabbits; Dental implant; Receptor activator of nuclear factor-kappa B ligand; Osteoprotegerin