| Summary: | There is a growing interest in the relative contribution of ions and proteins in acquired enamel pellicle (AEP) to protect against erosion and erosive tooth wear, but not enough is understood as yet. The effect of immersion of human enamel specimens in whole mouth saliva (WMS), artificial saliva (AS) and deionised water (DW) for three time periods [30 minutes (1), 60 minutes (2), 24 hour+30 minutes (3)] on erosion was assessed in vitro (n=90). Significantly less step height formation and greater surface microhardness change (SMHC) was observed for WMS3 [3.80 (0.59) μm and 249.4 (29.6) KHN respectively] compared with AS3 [6.34 (0.55) μm and 181.87 (20.48) KHN respectively] and DW3 [8.80 (1.28) μm and 148.82 (25.68) KHN respectively] (P<0.0001). The effect of AEP proteins was further investigated in vitro (n=80) after 24 hour immersion in either WMS, parotid saliva (PS), AS and DW followed by five or one cycles of erosion. WMS group had significantly (p<0.0001) less step height [4.16 (0.9) μm] than PS group [6.41 (0.3) μm] after five erosion cycles (p<0.0001). Concentration of total protein and mucin5b and albumin were higher in WMS derived AEP, compared with PS derived AEP and increased after 5 cycles, suggesting protection through physical barrier, diffusion barrier and lubrication. After one cycle erosion, there was a lower SMHC in specimens immersed in PS [85.19 (6.07) KHN (p<0.0001)], compared with those immersed in WMS [98.68 (8.5) KHN], suggesting protection through buffering and calcium homeostasis as PS AEP is richer in CA VI and statherin. Finally, same protein variables were also measured in in vivo film (F) and AEP (P) from eroded (E) and non-eroded (N) tooth surfaces in erosive wear patients (n=29). The total protein on EP [0.41mg/mL (0.03)] was significantly lower than that on NP [0.61 mg/mL (0.11) p< 0.05]. The amount of statherin was also significantly lower on EP [84.1 (221.8, 20.0) ng] compared to that from NP in the same subjects [97.1(755.6, 30.0) ng] (p=0.002). The overall findings in this thesis imply that proteins in AEP have a major contribution in protection against erosion and erosive tooth wear in vitro and in vivo.
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