"Babyteeth" is guaranteed to get under your skin. This refreshingly original Australian indie about a terminally ill teen who falls in love with the wrong guy is designed to push all the buttons: It'll frustrate, delight, annoy and devastate. In other words, it's quite the journey. But it's one that mercifully avoids the trite sentimentality and emotional blackmail that have become clichés of the genre.

Eliza Scanlen stars as said teen, 16-year-old Milla Finlay, who is living with some kind of cancer. Her parents, Henry (Ben Mendelsohn) and Anna (Essie Davis), are well-off and loving, but it's not exactly happy times in the Finlay household all things considered.

Henry is an oblivious therapist whose default fix is plying his wife with drugs, which just means she's barely there. And Milla, meanwhile, is attempting to maintain a semblance of normalcy, attending her private school and music lessons, while also undergoing chemotherapy and knowing that she might not have much time left.

It's under these circumstances that Moses (Toby Wallace) comes crashing, literally, into Milla's life. He runs into her on a train platform and nearly pushes her onto the tracks. It's a deranged meet-cute, since Moses is not your typical movie teenager love interest. He is not some dreamy bad boy with a heart of gold. He is a rat-tailed, tattooed, 23-year-old drug addict and dealer.

Moses is high and red-eyed most of the time, essentially homeless, unreliable and, perhaps worst of all, unwilling and unable to change. And the first thing he does is ask her for money. But something about him snaps her out of a daze and she is improbably smitten.

Is it an act of teenage rebellion against her upper middle-class life? Is it out of genuine interest? Probably it's a bit of both and Milla invites him into her life immediately, much to the chagrin of her parents.

Moses adds an element of external chaos to their already internally chaotic lives. Milla is simply delighted by him. And in some ways, Henry and Anna seem to appreciate the distraction from the cancer. At least Moses is a tangible and somewhat manageable threat to their daughter. Besides, Moses does have a sweetness and an ability to surprise that makes you unable to hate him. It is a testament to Wallace's performance that you stay with him on this roller coaster.

"Babyteeth" is an assured and stimulating feature debut from director Shannon Murphy, who is working with a script by Rita Kalnejais. It is raw, funny and often uncomfortable.

Scanlen, who played another sickly teen, Beth March, in Greta Gerwig's "Little Women," is simply wonderful as Milla, a role that in the wrong hands could have been too precious or tragic or manic. Scanlen delicately balances strength, vulnerability and teenage yearning to create a truly memorable character. She was a bit underused in "Little Women," but this proves that she is no less worthy of her own spotlight.

And despite a rocky and overly quirky intro, Mendelsohn and Davis are equally superb as parents and partners trying to cling onto their daughter for as long as they can and drifting apart in the process. Henry has one moment with Moses that is sure to leave you in a puddle (the first of a few no doubt).

"Babyteeth," an IFC Films release, has not been rated by the Motion Picture Association of America. Running time: 117 minutes. Three stars out of four.