Charlie Sheen allegedly jumped out of a dental chair last week, pulled his nitrous oxide mask off and grabbed the dental tech's breast ... so she claims in a new lawsuit -- claims that Charlie says are absurd.
Margarita Palestino alleges in her new lawsuit, Charlie came to the office last week for a procedure that required nitrous. As she put the mask on him, she says he ripped it off, jumped out of the chair and yelled, "I'm going to f***ing kill you!"
She says she continued trying to put the mask on, and this time he grabbed her left breast and pulled her scrubs, then grabbed her bra strap and tried pulling it down.
Palestino says Charlie came to the office "incoherent" and she says the dentist told her Charlie was high on crack cocaine ... something Charlie says is absurd.
She also says Charlie lunged at one of the dentists with a knife and then started stabbing the dental chair.
And Palestino says on their way out Charlie's assistant offered her $500 for her troubles.
As TMZ first reported ... the dentist has told cops Palestino is lying and nothing of the sort happened, and he accused her of blabbing that Charlie was a patient -- a violation of HIPAA.
Charlie's lawyer, Marty Singer, tells TMZ, "This is a ridiculous claim by an opportunist looking to make her 15 minutes of fame and my client is confident he will prevail in this absurd lawsuit."