Heavy consumption of diet soda can damage teeth as badly as methamphetamine or crack cocaine, a new Kornberg School of Dentistry study contends. “You look at it side-to-side with ‘meth mouth’ or ‘coke mouth,’ it is startling to see the intensity and extent of damage more or less the same,” said Mohamed Bassiouny, a professor of restorative dentistry at Temple. Methamphetamine, crack cocaine and soda — sweetened or not — are all highly acidic and can cause similar dental problems, Bassiouny said.