system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How/why is it that teeth grinding or pressure points in your bite can cause gum recession?

I really don't get it - the surfaces are not touching each other.

I want to make sure my dentist isn't just giving me the hard upsell, because my finger is on the button and I may get the damn Invisaligns. 

Help me, dentists/orthodontists/periodontists!
gpt
Just retired after 42 years doing general dentistry. One mechanic of gum recession is when people grind their teeth at night the teeth flex a little like trees in the wind. Just at the gumline on a tooth is the CEJ - the cemento-enamel junction. It’s where the enamel of the tooth stops and the root begins. The fibers of the gum that seal the gum above the bone insert into the cementum layer of the root just below the CEJ. The attachment fibers that seal to the root help maintain the height of the gum at normal levels. Flexing of the tooth under grinding can make a V-shaped defect in the root at CEJ that looks like a bite was taken out of the root right at the edge of the enamel. Guess What:  the notch makes it impossible for attachment fibers to attach to the cementum on the root, and subsequently the gum has no place to sit on. The gum recedes and exposes a characteristic V-shaped notch called an abfraction lesion. Therefore: visible gum recession. Note:  this is a different mechanism of recession than the gum loss of Periodontal Disease, which is chronic infection caused by not cleaning well on a long-term basis. Now send me your Blue Cross number and birthdate.