Could use expert help with why meth-heads teeth fall out?

Dental neglect: Meth mouth is seen in people who abuse the drug methamphetamine over a long period of time. The cause of it is unknown, but it leads to severe dental decay and loss of teeth. Many suspect it may be due to severe dry mouth, leaving an environment where bacteria thrive. These patients tend to ignore their oral hygiene, allowing the bacteria to attack tooth structure. Also, they tend to grind a lot.