I have a complicated question regarding acid etching. In dentistry, acid etching is used on tooth enamel, where the acid causes demineralization. This also occurs in dentin tissues, where we see hydroxyapatite demineralized via acid etching. However, in both cases (but more prominently in dentin), the organic collagen matrix is left undamaged. Why does and acid (32% phosphoric acid in this case) only affect the hard crystalline material and not the organic proteins?
Likewise, we can use acid etch on glassy-ceramic, where it eats away at the amorphous glassy matrix (SiO2). Conversely, it doesn't seem to eat away at the crystalline fillers (leucite, feldspar, etc.) inside the glassy matrix. Why? Unlike on dentin, where crystalline structures are quickly destroyed, here we see only the amorphous structure destroyed. The problem is further compounded when I think of zirconia oxide crowns, which are in a rigid crystalline structure but are said to be etch-resistant!
This is a very specific series of questions, but I haven't found any textbook or instructor that can adequately answer the question. I would love any and all input! Thank you!