Effect of Saliva on Dental Erosion

Method: 90 specimens were prepared from extracted human teeth and were randomly assigned to 3 experimental groups, 30 samples per group: natural saliva (NS), artificial saliva (AS) and distilled water (DW). Within each group samples were then randomly allocated to 3 subgroups: 30 minutes immersion in solution (1), 60 min immersion (2) and 24 hours immersion followed by a further 30 minutes (3) prior to exposure to a 10-min erosion cycle. The erosion cycle consisted of 80 ml 0.3% citric acid, pH=3.2, at 22°C±1, followed by 2-min water rinse which was repeated 5 times. Step height change was measured using a non-contacting profilometer. Knoop microhardness was measured at baseline (KHNb) and for the eroded surface of each sample (KHNe) and % SMH change = (KHNb – KHNe) calculated. Two-ways ANOVA and Bonferroni tests were used for the statistical analysis. 

Result: The NS and AS groups had significantly less enamel loss for all three immersion times (NS1: 6.33 µm; NS2: 5.91 µm; NS3: 3.80 µm) (AS1: 6.02 µm; AS2: 6.72 µm; AS3: 6.34 µm) compared with DW groups (DW1: 8.61 µm; DW2: 8.24 µm; DW3: 8.80 µm) (P<0.0001). When comparing NS with AS, there was only a significant difference between groups AS3 and NS3 (p < 0.0001). 

A significantly greater % SMH change was observed for group NS3 (249.4±29.6KHN) compared with AS3 (181.3±31.0) and DW3 (167.1±30.3) p<0.0001). Within subgroups, only NS3 showed significantly less enamel loss and greater % SMH change than NS1 and NS2 (P<0.0001). 

Conclusion: Natural saliva provided better protection against enamel loss compared with artificial saliva and water leaving a softened layer in place.