What can bad dental hygiene lead to?

For example, not flossing or only brushing teeth in mornings. Please answer, list even the extreme cases. I'm trying to reason with someone who doesn't care much about dental hygiene Thanks!
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DEATH. that's pretty much the most extreame prognosis. the infection surrounding an abscess can escalate rapidly, killing a verile, physically fit person in a matter of days without medical intervention. Forensic science has determined oral infection as the cause of death for a number of Egyptian pharos/princes, and, even today, some idiots die from it because they were too stubborn to go to the ER after it got really bad.
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