Biomimetic Effect of Saliva on Human Tooth Enamel: A Scanning Electron Microscopic Study

Introduction: Due to the presence of ion reservoir, saliva may facilitate enamel remineralization and neutralize pH of acidic beverage leads to prevent enamel demineralization. Saliva substitute/artificial saliva has been developed in subsequent years and may differ in physical properties, function, or pH level from 5.0 to 7.3. Objectives: To evaluate the biomimetic effect of saliva (neutralization) on tooth enamel exposed to carbonated beverage (pH 2.44) and to observe therapeutic capability (remineralization) of artificial saliva over previously eroded (grade 3 and grade 5) enamel surface. Methods: After scanning with electron microscope (SEM-EDX), nondemineralized crown samples (n = 40) were randomly grouped into two. Samples (50%) were flushed all around to carbonated beverage with collected natural saliva bathing simultaneously (experimental group, n = 20), and the rest flushed to beverage only without saliva bathing simultaneously (control group, n = 20). Flushing action was performed for 3 min by a customized digital automatic flusher for 30 times for each sample. Samples (n = 40) were further scanned under SEM-EDX to evaluate the demineralization grade and concentration of Ca, P, O, and C elements of crown samples to find out the neutralization effect of saliva. In the second phase, already demineralized crown samples (n = 30) were randomly treated with artificial saliva having two different pH (7 or 6.8, experimental groups) and distilled water (control group) for 15 min 3 times daily for 30 days. The remineralization score of experimental samples was graded, and therapeutic capability was established. Results: Samples, when exposed to a carbonated beverage with saliva bathing simultaneously, showed low level of demineralization (mean 2.9 ± 0.3) than the control (without saliva) (mean 4.8 ± 0.3) (p = 0.01) which indicated neutralization (bioimimetic) effect of natural saliva. All (100%) of demineralized samples treated with both artificial saliva (pH 7 or pH 6.8) showed significant remineralization (p = 0.01), thus revealed biomimetic capacity. SEM-EDX analysis showed initial (before beverage exposure) concentrations of calcium, phosphorus, oxygen, and carbon elements of crown samples were 32.48%, 31.5%, 28.3%, and 5.5%, respectively. The calcium (Ca) (9.7%) and phosphorous (P) (18.5%) values were more decreased after beverage exposure without saliva bathing simultaneously compared to after beverage exposure with saliva bathing simultaneously. The concentration of oxygen (54.4%) and carbon (15.5%) were more increased after beverage exposure without saliva bathing simultaneously compared to after beverage exposure with saliva bathing simultaneously. Though the concentration of calcium (38.5%) of the crown sample was increased after treatment with artificial saliva (pH 7), but the phosphorus (18.5%) concentration of the crown sample was not increased. Conclusion: Within the context of the present study, both natural and artificial saliva showed significant biomimetic effects with respect to neutralization and remineralization.