Why do they people who are addicted to heroine and cocaine lose their teeth?

Bad for Mouth: Drugs, especially methamphetamine cause "meth-mouth" with rotted, decayed, fractured teeth. Either the drugs dry the mouth, or cause grinding, also poor nutrition and poor oral hygiene with drug use can cause the dental issues.

Meth: People who are addicted to drugs often include meth amongst the drugs they use. The chemicals in meth destroy the teeth. You can imagine what it amaze it also does to the rest of the body.

Teeth loss: Substances that elevate norepinephrine levels cause narrowing of blood vessels, and when salivary vessels are affected, there is decrease saliva, leading to dryness & susceptibility to infection.