Smoking and dose-dependent early effects of nicotine on bone mechanical properties and histology

The objective was to study the effects of nicotine and cigarette smoke on mechanical properties of cortical bone. Experiments were conducted for 5 weeks with New Zealand White Rabbits. The first experiment of 18 rabbits studied the effect of nicotine levels delivered via a nicotine patch (5.25, 10.5, 21 ng/ml), measured by different mechanical tests, porosity, and composition. There was no significant difference between the control and the treatment groups.;The second experiment of 22 rabbits studied the effects of nicotine delivered via a nicotine patch (10.5 ng/ml) and via a smoking chamber on fracture toughness and porosity. The rabbits exposed to the smoke for 5 weeks had significantly lower fracture toughness values when compared to the different groups (exposed to smoke for 4 weeks group, nicotine group, and the control group). This suggests that other agents besides nicotine are responsible for the weakening of bone clinically seen in smokers.