Salivary proteins mediate greatest protection against dental erosion

Objectives: The aim is to investigate the effect of salivary ions and proteins on eroded enamel in a laboratory investigation.
Methods: 40 polished enamel specimens were prepared from extracted human teeth (Research ethics approval, Northampton REC, 14/EM/0183) and randomly assigned to 4 subgroups. 10 enamel samples per group were allocated to parotid, whole mouth, artificial saliva and water and immersed in the corresponding solution for 24 hours followed by a further 30 minutes prior to exposure to a 10-min erosion cycle in 80 ml of 0.3% pH 3.2, citric acid, agitated at room temperature, followed by 2-min water rinse. The 30 min immersion in the corresponding solution followed by the acid was repeated 5 times for all samples. Mean step height change from 5 randomly assigned points was measured using a non-contacting profilometer and Knoop microhardness measured at baseline (KHNb) and on the eroded surface of each sample (KHNe) and SMH change = (KHNb – KHNe) was calculated. Linear Regression model and Stata12.0 were used for the statistical analysis.
Results: Whole and parotid saliva produced significantly less step height (4.16±0.57 µm, 6.41±0.71 µm respectively) than artificial saliva (7.47±0.98µm) and these differences were statistically significant compared to water (10.89±0.98µm and p< 0.0001). Microhardness change, for whole mouth (224.11 ±29.29 KHN p<0.0001), parotid (208.16 ±50.20 KHN p<0.0001) and artificial saliva (194.0±19.75KHN p<0.002) was significantly greater than water (155.34±18.4 KHN). Whole mouth saliva had significantly greater microhardness change than artificial (p<0.012).
Conclusions: Saliva, containing proteins, appears to offer greater protection against dental erosion than artificial salvia and water. Whole mouth saliva provided less step height and greater hardness change than parotid saliva.