Effect of gels containing chlorhexidine or epigallocatechin-3-gallate on the protein composition of the acquired enamel pellicle

Objective: This study evaluated changes in protein profile of the acquired enamel pellicle (AEP) formed in vivo, after application of gels containing chlorhexidine or EGCG and further challenge with citric acid. Design: AEP was formed in 9 volunteers for 2 h and then treated with one of the following gels: placebo, 400 mu M EGCG or 0.012% chlorhexidine. A thin layer of gel was applied and after 1 min the excess was removed. One hour after gel application, the AEP was collected from the buccal surface (upper and lower jaw) of one of the sides with filter paper dipped in 3% citric acid. On the other side, erosive challenge was performed through gentle application of 1% citric acid (pH 2.5) for 20 s (using a pipette) followed by washing with deionized water. The AEP was collected as mentioned before. Proteomic analysis was performed through liquid chromatographyelectrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The MS/MS spectra obtained were compared with human protein databases (SWISS-PROT). Label-free quantitation was done using the PLGS software. Results: In total, 223 proteins were identified. After treatment with EGCG and CHX gels, proteins with potential functions to protect against caries and erosion such as PRPs, calcium-bind proteins and Statherin were increased. When EGCG and CHX-treated AEPs were challenged with citric acid, there was increase in cystatins and Profilin1. Conclusion: CHX- and EGCG-treated AEPs, submitted to challenge with citric acid or not, had remarkable changes in their proteomic profiles.