From Harry Brearley’s gun barrels to the metal in modern dentistry, the Steel City’s fingerprints turn up in some deeply unglamorous places. Including, possibly, your jaw.
Have a look in your cutlery drawer. Somewhere in there, you’ll find a fork with SHEFFIELD stamped into the back of the handle. Most of us stopped noticing that years ago. It’s wallpaper. But that word on the fork is the tail end of a story that starts with a bloke trying to stop guns wearing out, and ends up somewhere he could never have predicted: inside people’s heads.
The accident at Brown Firth
In August 1913, Harry Brearley was working at the Brown Firth Research Laboratories, chasing a very specific and very boring problem. Gun barrels were eroding faster than the War Office would have liked, and someone needed an alloy that could take the heat. Brearley started fiddling with chromium content. The resulting cast, somewhere around 12.8 per cent chromium, was a dud for barrels.
What it did do was refuse to rust. It wouldn’t even stain.
The story of what happened next is told properly at Kelham Island Museum, and it’s worth the trip if you’ve somehow never been. The short version: Brearley took the idea to a cutler, the cutler told him it was nonsense, and then the first stainless knives and forks in the world were forged at Portland Works on Randall Street. There are people making blades in it today.
Sheffield being Sheffield, the discovery went out into the world and largely came back as other people’s money. But the more interesting inheritance was the habit of thinking about metal: what it does under load, how it behaves in a hostile environment, what happens at the point where two pieces of it meet.
Which brings us to teeth.
The rabbit that wouldn’t let go
In 1952, a Swedish researcher called Per-Ingvar Brånemark screwed a small titanium chamber into a rabbit’s leg bone so he could watch blood flow through a microscope. Standard stuff. Titanium was chosen because it was inert and convenient, and the chambers were expensive, so the plan was to take it back out afterwards.
He couldn’t. The bone had grown onto the metal and simply would not give it up.
Most people would have logged that as a ruined experiment and a wasted budget. Brånemark realised he’d found something nobody thought was possible, because the received wisdom at the time was that the body rejects foreign material. He called the phenomenon osseointegration, and if you want the proper account of how long it took the medical establishment to stop laughing at him, there’s a good history of it in the National Library of Medicine archive.
In 1965 he put titanium implants into a man named Gösta Larsson, who had them for the next forty years. Brånemark’s line about the whole business has aged well: nobody, he said, should die with their teeth sitting in a glass of water.
The bit that would interest a machinist
Think about the working conditions of a dental implant. It’s warm, it’s wet, it’s mildly corrosive, it’s crawling with bacteria, and it gets hammered by chewing forces thousands of times a day for the rest of your life.
It also has to be assembled by someone working through a hole the size of a Malteser, and how would you do that?
The obvious answer is a screw. The catch is that a screw needs an access channel straight down through the top of the crown, which then gets plugged with filling material. On a back molar, nobody cares. On a front tooth, well… you’ve got a screw in your mouth.
The alternative borrows a trick that any lathe operator in this city would recognise instantly: the taper fit, which is the principle behind what clinics now market as screwless dental implants. A Morse taper holds a drill bit in a machine tool using nothing but two matched cones and friction. Press them together hard enough and the surfaces effectively cold weld. It is not a free lunch, and any dentist worth their fee will say so. The profession has been going back and forth on this for years, which is what a real engineering trade-off looks like.
Full circle, more or less
Sheffield University’s School of Clinical Dentistry has been running implant research and training dentists in implantology for more than thirty years, on a course originally built in partnership with the company that grew directly out of Brånemark’s work.
So: a city that got rich on blades, then invented a metal that wouldn’t rust, then spent a century getting obsessive about joints and tolerances, now teaches people how to install replacement teeth.
Next time you pick up a Sheffield fork, give it a second’s thought.
