“Nothing is more memorable, for better or worse, than a trip to the dentist.” Los Algodones, Mexico—known as Molar City—attracts scores of Americans from across the border seeking cheaper dental work. And Michael Luo on why shootings like the one yesterday in Manhattan remain so hard to prevent. Plus:

• Training cops to be like U.F.C. fighters
• Adam Gopnik remembers the satirist Tom Lehrer
• You have some questions about the W.N.B.A.?

Burkhard Bilger
A staff writer at The New Yorker since 2001.

“Show me your teeth and I will tell you who you are,” Georges Cuvier, the eighteenth-century French naturalist and paleontologist, is said to have remarked. Teeth are the most durable bits our ancestors left behind—miniature records of how and where they lived and ate, and of how their bodies were shaped. But that was before modern dentistry. These days, we do our best to erase the stories teeth tell. Three out of four American teen-agers straighten their teeth with braces, while more and more adults are replacing them with artificial implants, crowns, and veneers. In a country obsessed with identity and being “seen,” our smiles are all starting to look alike.

If we can afford it, that is. In any given year, more than half of Americans never see a dentist. Health insurance won’t cover their tooth problems—even ones that could be life-threatening—and dental insurance is small comfort: the more serious the condition, the less likely it is to be covered. Some dentists and orthodontists are part of the problem—raising costs by pushing cosmetic choices as medical necessities. But most are trapped in a system they didn’t create and wouldn’t choose. Three-quarters of American dentists have been verbally abused by their patients, according to one survey, and nearly half have been physically assaulted.

No wonder an alternative has sprung up across the border. Los Algodones, Mexico—A.K.A. Molar City—may have more dentists per capita than any place in the world: well over a thousand in a town of fifty-five hundred. Every year, more than a million Americans walk or drive there, fleeing the high cost of dental work in the U.S. A root canal in Molar City may cost less than one-fifth of what it would in Yuma, Arizona, ten minutes away.

I visited Molar City for a piece in this week’s issue. Dentistry tends to be a no-fly zone for journalists—who wants to relive those moments in print? But wherever I went in town, people couldn’t wait to talk about their teeth. Nothing is more memorable, for better or worse, than a trip to the dentist. From Louis XIV to the latest celebrity with a bad veneer job, everyone has a horror story to tell. But the opposite is also true. If dentists are willing to endure so much abuse, it’s because no one is more grateful, more profoundly relieved, than a patient whose pain has been taken away.

Kash Patel, the F.B.I. director, has said that he wants to get mixed-martial-arts fighters to train his field agents. But a version of this is already happening, with law-enforcement agencies embracing Brazilian jiu-jitsu. Sam Eagan reports »

A gunman carrying an assault rifle killed four people in a Manhattan skyscraper yesterday, before taking his own life. He was reportedly targeting offices of the National Football League, and left behind a note asking that his brain be studied for signs of chronic traumatic encephalopathy, or C.T.E.—a brain disease that can develop after repeated hits to the head.

Why are incidents like this still so hard to prevent? “We’re in that phase after every mass shooting when a portrait of the shooter starts to cohere and the assigning of blame begins,” Michael Luo, an executive editor at The New Yorker, told us. He pointed to reporting by ABC News and the Wall Street Journal which suggested that the suspect had, in recent years, been the subject of at least one “mental-health crisis hold” in Nevada.