Mr. Pender, age 75, calls the dental office with a dental emergency. He has fractured tooth 4-6. Upon clinical examination, gingival recession, cervical abrasion and numerous root caries are observeWhile reviewing the medical history, Mary, the dental assistant records medical conditions of rheumatoid arthritis and diabetes. During Mr. Pender's oral hygiene instruction, Mary stresses the importance of tooth brushing to remove NON-acid-producing bacterial deposits from the tooth surface.
These deposits attach to the naturally occurring colourless film called ?