Oral nitric oxide during plaque deposition

Background Nitric oxide (NO) is one of the most powerful antibacterial compounds. We investigated if NO oral production increases during dental plaque deposition. Materials and methods Oral NO and salivary nitrite were measured in 31 healthy subjects – 11 smokers and 20 nonsmokers – with natural healthy teeth, in the morning after tooth cleaning (baseline), after withdrawal of oral hygiene for 24 h and again after tooth cleaning. Results NO and nitrite were significantly higher during plaque deposition than with clean teeth: mean NO values ± SEM were 44·3 ± 4·9 parts per billion (ppb) at baseline, 58·8 ± 3·7 ppb with plaque and 43·6 ± 3·7 ppb after tooth cleaning, P < 0·05; nitrite values were 32·9 ± 5·5 µm at baseline, 66·4 ± 8·2 with plaque and 37·5 ± 5·5 after tooth cleaning, P < 0·01. During plaque deposition, oral NO was significantly directly related to salivary nitrite (r = 0·497, P = 0·002) and so were their respective changes after tooth cleaning (r = 0·577, P < 0·001). Smokers had significantly lower oral NO than nonsmokers, with both clean and dirty teeth (P < 0·001), and higher bacteria counts in the plaque (38·6 ± 11·5 vs. 19·9 ± 2·3, P = 0·046). Conclusions Oral NO production increases during de novo deposition of dental plaque. NO might be an early host defence mechanism against bacterial proliferation in the plaque. Such a mechanism is inhibited by cigarette smoking.