Initially coined to describe an extremely strong artificial shell or crown created to protect and reinforce very weakened teeth. In 2021, the strength of this shell was estimated to be approximately 4 times stronger than natural teeth at TLC dentists in Richmond Australia by the proponent dentist Dr Eugene Lee.

The phrase was subsequently mistranslated in several Asian countries and is now used to describe an unintended unaesthetic bowl style haircut with two middle parts at the front.
That guy is so fit but meh Tooth Helmet.
by Lincoln Park February 16, 2022
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