How do celebrities have such straight teeth?

Depends: Orthodontia (movement of their existing teeth into their ideal position) often with subsequent teeth whitening ---- or--- smile make-over (full mouth reconstruction) porcelain laminate veneers or porcelain full coverage crowns designed to look like a perfect set of teeth.

Cosmetic dentistry: Teeth are straightened , bleached, crowned filled, etc to get that great look. This involves time, expense and vanity, all qualities of stars.

They don't: These celebrities suffer with poor dental genes like the rest of the world, they just have the money to spend on cosmetic reconstruction. Under many crowns, veneers and bonding are crooked teeth. Many will not undergo orthodontics because of time and vanity. In the end, they act no better. There are a few who have had braces and i applaud them.

Braces or dentistry: Although for many celebs, their pearly smiles may be natural, many others have benefitted from orthodontic treatment. A quick internet search for celebrities and braces will reveal a number of them. Still others have new smiles from cosmetic dentistry (sometimes combined with preparatory orthodontics). In other words, they get those smiles just like you can.

Celebrity smiles: Thanks to excellent cosmetic dentistry. You too can have a Hollywood Smile, usually with a combination of Orthodontics and Prosthetic/Restorative Dentistry. Talk to both your General Dentist and a specialist Orthodontist.