This study investigated the influence of nicotine on bone density around titanium implants inserted in rabbits. Thirty-two New Zealand rabbits were included. After anesthesia, the tibiae surfaces were exposed and two screw-shaped, commercially available, pure titanium implants of 7.0 mm in length and 3.75 mm in diameter were placed bilaterally. A total of 128 implants were inserted: 64 blasted with Al2O3 particles (group 1) and 64 with a machined surface finish (group 2). The animals were randomly assigned to one of four treatment subgroups, and daily subcutaneous injections of nicotine were administered. After 42 days, the animals were killed and undecalcified sections were prepared. The bone density was measured in the cortical passage of the implant. Statistical analysis (two-way analysis of variance) revealed no significant difference neither regarding the effect of nicotine nor the effect of surface design on bone density around the implants (P > 0.05). Within the limits of the present study, it can be assumed that daily nicotine administration may not statistically influence bone density around titanium implants.
Local and systemic factors, which may impair bone healing or may interfere with the maintenance of osseointegration, have been described to affect the success rate of osseointegrated implants. 1 Smoking is one of the factors often discussed in relation to implant failure. 1-5 It is well recognized that cigarette smoking is associated with impaired wound healing after surgical treatment in the oral cavity, 6 reduced bone height, 7 increased bone loss rate, 8 increased resorption of the alveolar ridge, 7 higher incidence of periodontitis, 9 and type IV bone. 10 In addition, smoking has been found to be an important factor in periimplant soft tissue changes. 11
Nicotine is one of the 2000 potentially toxic substances in tobacco smoke. Nicotine and its metabolite cotinine have been found in the saliva and gingival crevicular fluid of smokers. 12In vitro studies have shown that nicotine can inhibit neutrophil/monocyte defensive functions, 13 potentiate lipopolysaccharide-stimulated human peripheral blood monocyte secretion of PGE2, 14 and have direct adverse effects on various functions of the periodontal cells. 15In vivo, it has been reported that nicotine administration may enhance the effects of the local components of periodontitis. 16,17 In an experimental study in rats, in which subperiosteal bone formation was stimulated, Boyne and Herford 18 found that animals exposed to cigarette smoke produced less bone than the control animals. Rats that were not exposed to cigarette smoke and received 1.0 mg of nicotine exhibited 35% less bone growth than those exposed to smoke and 50% less bone growth than the control group. Recently, we have reported that nicotine by itself may not be responsible for the decreased success rates reported for osseointegrated implants placed in smokers. 19 Because cigarette consumption has also been associated with poor bone quality, 10 the purpose of the present study was to investigate the effects of daily nicotine administration on bone density around titanium implants with different surface designs inserted in the tibiae of rabbits.