Proteins from whole mouth saliva mediate greater protection against severe erosive tooth wear than proteins from parotid saliva using an in vitro model

Abstract

Objectivesto investigate how the composition of the acquired enamel pellicle (AEP) affected a laboratory model of erosive tooth wear (ETW) on human enamel by comparing whole mouth saliva (WMS) to parotid saliva (PS). Methods60 enamel specimens were prepared from extracted human teeth and were randomly assigned to 4 experimental groups: WMS (n = 20), PS (n = 20), artificial saliva (AS, n = 10) and deionised water (DW, n = 10). Following incubation, a subset of WMS (n = 5) and PS (n = 5) groups were used to collect the AEP before the erosive challenge. The rest of the blocks, had their AEP collected after five cycles of acid, wash and saliva and were then assessed for mean step height changes using a non-contacting profilometer (n = 10 each). AEP samples were collected from the enamel specimens by rubbing with filter papers soaked in sodium dodecyl sulfate. Total protein in AEP was quantified using BCA assay, individual protein components of AEP were separated and analysed using SDS-PAGE and western blot for [mucin 5b, albumin, carbonic anhydrase VI (CA VI), statherin]. Specific antibody binding was quantified using purified protein standards of known concentration. Samples of AEP were also analysed by LC/MS/MS sequencing. ResultsWMS group had significantly (p < 0.0001) less acid-induced erosion (step height [4.16 (0.9) μm]) than PS group [6.41 (0.3) μm]. The amount of total protein, mucin 5b and albumin were more dominant in WMS pellicles than PS (p < 0.0001) whereas CA VI and statherin were dominant in PS pellicles (p < 0.0001). ConclusionThe composition of the acquired enamel pellicle influences the degree of protection from acid attack, possibly by altering the mechanism of protection. The in-vitro model used in this study was severe enough to cause tissue loss as opposed to just softening of the surface structure. AEP from WMS was more protective than that of PS, and its likely mechanisms of protection seem to be as a physical barrier rather than stabilising the crystal structure. SignificanceThe protective salivary proteins against in-vitro erosion models differ from in-vivo studies. Therfore, it can be recommended that in-vitro laboratory models of ETW need to be assessed carefully to represent the clinical environment more closely.