On a warm Friday evening in Houston, Texas, 62-year-old Michael Carter believed the hardest part of his dental appointment was already over.

Earlier that afternoon, his dentist had removed a severely decayed lower molar. The extraction had been difficult because the tooth had fractured below the gumline, but after several stitches and nearly an hour in the dental chair, Michael was sent home with standard instructions.

"Keep pressure on the gauze, avoid drinking through a straw, don't spit, and call us if the bleeding doesn't stop."