Final answer:
Coronal polishing is not used before acid etching but is essential for removing biofilm and stains as part of oral prophylaxis.
Explanation:
Coronal polishing is NOT used before acid etching. It is utilized to remove biofilm and stains and as an oral prophylaxis (prophy). Therefore, the correct answer is 'All of the above'. Coronal polishing involves using abrasives like dental polishing agents to remove stains from teeth surfaces.
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