3D printing shows its teeth

Few people would think of dentists as imaginative innovators. But their public image, clouded by long episodes of pain or boredom in the dentist’s chair, obscures the fact that many of them are enthusiastic developers of technology in the cause of healthy teeth and gums.

Take 3D printing – making solid objects by building up ultra-thin layers of material from a computer-controlled printer. “3D printing has recently captured the public imagination, but most 3D printers are churning out plastic junk,” says Andrew Dawood, who works in London’s Wimpole Street. “Dentists have been using 3D printing for 10 years, to make things that really can’t be made in any other way.”

In the basement of Dawood & Tanner, the practice that he runs with his wife Susan Tanner, are six 3D printers, making objects in various types of plastic, resin, plaster or metal. The main use of 3D printing in dentistry is to make precise models of patients’ faces, jaws and teeth, so as to plan procedures such as implants and oral and facial surgery.

The data for the printer usually come from a CT (computerised tomography) scanner, which uses low-dose X-rays to produce a 3D image in very thin slices. Software then transforms the CT slices into layers for a 3D printer to lay down.

“If we have an exact replica of the jaw, for example, it becomes far easier to plan the procedure, design implants and then practise before the patient comes in for surgery,” says Dawood.

Some patients have lost a lot of jaw bone through disease, accident or (in the case of one man) a gunshot to the face. The dentist may need to perform complex rebuilding in collaboration with medical surgeons – all helped by 3D modelling.

The CT images increasingly are supplemented by computer-aided design, with Dawood & Tanner adding its own bone replacements or implants to the scans, which can then be given physical form through 3D printing. Although conventional manufacturing still produces most implants, an increasing number are being printed, often using a very durable plastic called Peek that can be implanted into the jaw to replace lost bone. “Our experience with the use of technology to assist ‘extreme cases’ enables us to make straightforward treatment even more straightforward, and for many patients, to make possible what was once considered to be impossible,” says Dawood.

A 3D print of a skull and upper jaw

Patients for whom implant treatment used not to be feasible, because they did not have enough bone left in their jaw, can now be treated. New technology allows dentists to identify islands of bone into which implants can be placed, using minimally invasive techniques. “People who once might have been told they were untreatable or needed 18 months of carefully staged, arduous reconstructive surgery, are now being treated in hours or even minutes, usually receiving fixed replacement teeth on the day of treatment,” says Dawood.

When the implant work is more routine, life is made much easier for the patient by keeping surgery to a minimum. That means prefabricating replacement teeth to be fitted after a brief, digitally planned surgical procedure, using templates and bridgework formed through computer-aided design and 3D printing.

At the same time, the practice is starting to use its 3D technology in fields beyond dentistry. Two striking examples are gold-plated skulls obtained by scanning ancient Egyptian mummies in the British Museum and the Ashmolean in Oxford. The latter was a five-year-old child, scanned without unwrapping the mummy.

Through subsidiary companies, Digits2Widgets and Cavendish Imaging, Dawood & Tanner is moving into the art and design world too. One example is a sunglass frame designed by Ron Arad and printed in nylon as a single piece. Its most innovative feature is the hinge – the weakest feature of most frames – which is a series of slashes, like a shark’s gills, in the nylon where the stems meet the lens holders. The frame is made in the closed position. When the glasses are put on, they grip the head; when taken off, they close up naturally.

Other uses of the technology are far from being a distraction for the practice, because they lead to ideas that feed back into routine dentistry, Dawood says. “The real beneficiaries of our approach are our day-to-day patients.”

DNA’s ‘quadruple helix’ discovered

Sixty years after the discovery of the DNA double helix, Cambridge university researchers have shown that an alternative form of DNA – a “quadruple helix” – exists in some human cells. Quadruple helix structures, known as G-quadruplexes, form in regions of the genome that are rich in guanine, one of the four building blocks of DNA.

DNA’s four-stranded structure

G-quadruplexes were known to form from DNA in the test tube but were previously regarded as a curiosity. The Cambridge findings, published in Nature Chemistry, show that they occur in living cells – and particularly in cancer cells, an observation with clinical implications.

“The research indicates that quadruplexes are more likely to occur in genes of cells that are rapidly dividing, such as cancer cells,” says Shankar Balasubramanian, the project leader. “For us, it strongly supports a new paradigm to be investigated – using these four-stranded structures as targets for [cancer] treatments in the future.”

Many biological questions about the quadruple helix remain to be answered. “One thought is that these quadruplex structures might be a bit of a nuisance during DNA replication, like knots or tangles,” adds Balasubramanian. “Did they evolve for a function? It’s a philosophical question as to whether they are there by design or not – but they exist and nature has to deal with them.”

How can we avoid an asteroid strike?

Imagine an asteroid, just like the one that exterminated the dinosaurs 65 million years ago, heading for Earth and threatening to wipe out humanity. The need for technology to save us all if the worst comes to the worst is being taken increasingly seriously by space agencies.

The latest development is an appeal by the European Space Agency for research ideas to guide the development of a mission to test techniques for deflecting asteroids, scheduled for 2022. At this stage ESA is not looking for superheroes to undertake a Hollywood-style deflection, as in the movies Deep Impact and Armageddon. Rather, it wants scientists to send in concepts for ground- and space-based investigations that will improve our knowledge of high-speed collisions between man-made and natural objects in space.

The opportunity is a joint US-European mission with two spacecraft to a binary asteroid called Didymos. The 300kg US spacecraft, called Dart (for Double Asteroid Redirection Test), will smash into the smaller member of the Didymos pair. Its European partner Aim (Asteroid Impact Monitor) will observe the collision with the 150m rock from close up. The effects are more easily measured with a binary rather than a single asteroid.

There is considerable uncertainty about the best deflection technique to use if astronomers do spot an asteroid heading for Earth. A “hypervelocity impact” would hit with enough speed and energy to vaporise solid rock. Or a gentler approach could be taken, nudging the asteroid on to a new path that would not threaten Earth.

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