Ever noticed how most stars have perfect teeth? They weren't born that way, but not many people can make it in Hollywood without a 'million dollar' smile.

Dental veneers were actually invented in Hollywood. Back in 1928, studio execs hired a dentist named Charles Pincus to perfect some actors' teeth, according to The Atlantic. Dr. Pincus custom-made temporary tooth covers (the world's first veneers) and they were worn by many big stars of the day, from Shirley Temple to James Dean to Walt Disney himself.

With money rolling in and their faces on display, loads of modern-day celebs choose to invest in veneers and other dental cosmetic procedures. Most do this early on in their careers. At this point, it's probably hard for some of them to remember a time when they DIDN'T have perfect teeth.

Certain celebs changed their teeth after they'd already appeared onscreen - so unluckily for them, it's easy for us to see what they looked like before.

We've rounded up 15 before-and-after pics of stars who used to have crooked, gappy, or just plain different smiles than they have today. Read on to see just how much their new smiles changed how they look.

14 Zac Efron

He's a complex guy with constantly changing looks, so is it a surprise that Zac Efron used to have different teeth? Maybe not. According to an interview with Celebs Now, Zac's former girlfriend, Vanessa Hudgens, confirmed it: "I mean, he wasn’t the guy that he is today," she explained, when remembering their High School Musical days. "Like, he had a gap in his teeth! He was a whole different person." Agreed.

13 Tom Cruise

You might not recognize young Tom Cruise as pictured here, in a still from the movie, The Outsiders. He was just 21 when that movie came out and he had a completely different-looking mouth! It didn't take long for him to get braces and straighten out that whole situation, but you can kind of see that, to this day, his teeth aren't quite centered. Still a big improvement, though. In fact, he's known for his grin!

12 Hilary Duff

Hilary Duff claimed that her singing career was damaging her teeth because she would chip them on her microphone during concerts. The solution? Capping them with sturdy porcelain veneers. They've worked well most of the time since then, except for when one fell off on her wedding day. "Thank god I didn't swallow it," she confessed to Ellen DeGeneres. "Not good for a bride!"

11 Demi Lovato

Like Zac Efron, Demi Lovato was a Disney kid who started out with a gap. It turns out that closing it was Disney's choice. "I signed with Disney Channel when I got Camp Rock, and I had a gap between my two front teeth," she explained to Allure. "They were like, 'Would you be willing to fix it?' I wish today that I hadn't, because my gap was really cute."

RELATED: Everything Celebs Have Said About Demi Lovato (Good And Bad)

10 Nicolas Cage

Nic Cage's crooked teeth had a full overhaul. He ended up having two of them pulled without using anesthesia - by his own choice! He wanted to feel the pain of a non-numbed procedure, to better connect with a Vietnam war veteran he was about to play in the 1984 flick, Birdy. Now, he's got a set of porcelain veneers filling in the spaces left by his original - and crooked - teeth.

9 Cheryl Cole

Cheryl Cole is yet another celeb who redid her top teeth with some porcelain veneers. According to the Daily Mail, she used Invisalign braces to help get them perfectly straight, then got eight porcelain veneers to create her flawless smile. She admitted that she doesn't always wear her Invisalign retainer anymore, though. "I forget," she told Daily Mail. "I hope my dentist’s not reading this."

8 Gwen Stefani

It was 1986 when Gwen's career started taking off. This lady has been in the public eye for over 30 years, and you'd never guess how old she actually is now. Gwen's braces were part of her charm when she was, as the No Doubt song says, "Just A Girl." These days, she's got perfectly straight chompers, so the braces clearly did their job.

7 Niall Horan

Look at little baby Niall! Die-hard One Direction fans might remember how his teeth looked when he first auditioned on The X Factor. They kind of had a mind of their own. After hitting it big with the band, Niall had enough cash to drop on a new, straight smile. With perfectly flawless teeth and a thriving solo career, he's come a long way.

RELATED: The One Direction Guys All Have Stunning Girlfriends And Exes

6 Dakota Johnson

In an interview with Jimmy Fallon, Dakota explained that her gap actually closed on its own. She used to have a permanent retainer glued to the back of her teeth, but when her dentist removed it to help her with some pain, it inadvertently made her gap close. "I'm sad about my gap,” she joked to Jimmy, “so I'd really appreciate some privacy in this time."

5 Matthew Lewis

Talk about a transformation! Matthew Lewis played Neville Longbottom in the Harry Potter films and fit the part of a buck-toothed preteen when the franchise began. By the seventh movie, Matthew had fixed his naturally crooked teeth. "I thought were they going to recast me," he told Big Issue. Instead, the filmmakers had a creative solution. "I had to wear false teeth for a few years."

RELATED: What The Cast Of Harry Potter Has Been Up To Since Deathly Hallows

4 Kylie Jenner

Can you imagine Kylie Jenner getting work done on her teeth to look better? We know you can! This reality-TV-star-turned-billionaire-entrepreneur has different teeth now than she did before. It seems like she's spent money on transforming what's under her lips, as well as changing her actual lips. Her top teeth are currently even, likely thanks to some veneers, but we can't tell for sure...not until Kylie lets the world know.

3 David Beckham

David Beckham was cute with his original teeth! Victoria Beckham must have thought so, at least. He paid to adjust his crooked top set after hitting it big. His imperfect teeth run in the family, though. Both Brooklyn and Romeo Beckham have needed braces so far, and younger kids, Cruz and Harper, may be next in line for orthodontics.

2 Pete Davidson

Pete Davidson has had some memorable moments throughout his time as an SNL cast member. One was his surprise appearance on an April 2018 'Weekend Update' segment, when he announced out of nowhere, "I got new teeth!" It's a subtle difference between Pete's old and new smile, but he definitely lost that gap. Maybe he was preparing to look his best for his (eventually canceled) wedding to Ariana Grande?

1 Miley Cyrus

Miley's teeth are part of a long list of body parts she's changed over the years. Her hair is another - our girl has rocked blonde looks, bald looks, bang looks, and more. She's also got so many tattoos that she's lost count of them. Elle reports that she had braces on the backs of her front teeth ("lingual braces") to even them out during her time in the spotlight. Work it, Miley!

NEXT: 15 Singers' Transformations From Their First Vs. Latest Music Videos

Sources: TheAtlantic.com, CelebsNow.co.uk, BusinessInsider.sg, Medium.com, Allure.com, IMDB.com, CloserWeekly.com, BigIssue.com, DailyMail.co.uk, YouTube.com, Elle.com