Saliva and salivary pellicle composition and proteomic profile in smokers vs. non-smokers and its effect on dental erosion.
OBJECTIVE: To analyse the salivary composition and proteomic profile of saliva and the salivary pellicle in smokers compared to non-smokers, and to examine potential differences in the erosion-protective capacity of the salivary pellicle. METHODS: Twenty-five smokers and 25 non-smokers were included. Unstimulated and stimulated saliva samples were analysed regarding flow rate, pH, buffer capacity, calcium, phosphate, fluoride, and protein content. Saliva and salivary pellicle samples were analysed by data-independent acquisition mass spectrometry (DIA-MS) for proteome profiling. In an in situ experiment, intraoral splints were loaded with bovine enamel and dentine specimens for 120 min. Pellicle-covered specimens were extraorally eroded (HCl, pH 2.3, 60 s). Calcium release was determined photometrically and compared to pellicle-free controls. RESULTS: Except for phosphate in stimulated saliva (padj.=0.003), salivary parameters were not significantly different between smokers and non-smokers. Proteome profiling detected 1759±154 proteins (cumulative 1963) in saliva, and 4262±362 proteins (cumulative 4625) in the salivary pellicle. The relative abundances of 282 (unstimulated saliva), 338 (stimulated saliva), and 4 (salivary pellicle) protein groups differed significantly between smokers and non-smokers. Functional enrichment analysis of differentially abundant human proteins revealed biological processes such as coagulation, immune response, and carcinogenic reactive oxygen species processes to be impacted by smoking. The salivary pellicle had a significant erosion-protective effect in enamel compared to the control (41.4 ± 6.3 nmol/mm2), but no differences between smokers (33.2 ± 10.6 nmol/mm2, padj.=0.001) and non-smokers (32.7 ± 8.6 nmol/mm2, padj.=0.001) were found. CONCLUSION: The proteomic profiles of both unstimulated and stimulated saliva and the salivary pellicle differ between smokers and non-smokers. CLINICAL SIGNIFICANCE: Despite the different proteomic profiles indicating a significant impact of smoking on the oral cavity, the erosion-protective capacity of the salivary pellicle of smokers and non-smokers does not differ.