“…As stated above, this low pH also activates previously latent dentinal and salivary proteases, suggesting that bacterial biofilm is responsible for initiating dentinal destruction in the earlier stages of the root carious lesion, both by acid production that demineralizes dentin [ 10 , 21 , 30 ], and by direct dentin degradation [ 29 , 30 ]. Once dentin demineralization begins, and pH values are low enough to activate the zymogens, collagen breakdown is attributed to dentinal, salivary, bacterial, and neutrophil degradative activity [ 13 , 18 , 19 , 29 , 30 , 31 , 32 , 33 , 34 ]. Nevertheless, it has been reported that the bacterial contribution to dentinal degradation is much higher than that of dentinal and salivary degradative activity [ 13 , 21 , 29 , 30 ].…”