When twins Lincoln and Nolan Potts were born in November, their heads were perfectly shaped.

By April, it was clear that weeks of lying in cribs and strollers had caused a condition known as flat head syndrome. They’d each require a specially fitted helmet to reshape their skulls over a critical 14-week growth period.

Gillette Children’s Specialty Healthcare in St. Paul, quickly got to work. Nolan was first. They scanned his head and e-mailed the images to a specialty carving company in Florida. But it took over a week for the modeled head to arrive back in St. Paul so work could begin vacuum-molding his customized “CranioCap.”

A month later, it was Lincoln’s turn. This time, the process took only five hours — three hours to make the replica of his head and two to make the CranioCap. The change was due to a new $225,000 refrigerator-sized 3-D printer that the hospital bought from Eden Prairie-based Stratasys in May.

The printing technology that duplicates images from real MRIs and scans “is awesome,” said mom Rebecca Potts, who first heard about 3-D printing on the TV drama “Grey’s ­Anatomy.”

While successes in the 3-D printing of human tissues and transplantable organs are still far away, Stratasys and other industrial companies have made headway introducing 3-D printing technology into the medical realm.

“In terms of Stratasys, we are more focused on non-tissue related printing. Most of our focus is on the printing of polymers” for ­various medical purposes, said R. Scott Rader, the general manager of Stratasys Medical Solutions division.

Its machines now make the head molds so CranioCaps can be formed. They build ­orthotics, prosthetics and even organ models used by medical students and doctors practicing for difficult surgeries.

The medical device field represents an undisclosed but slim segment of Stratasys’ total revenue, which topped $770 million last year. But medical sales are growing steadily amid expanding health care applications that didn’t exist four years ago, CEO David Reis recently told analysts during a conference call earlier this year.

Stifel stock analyst Patrick Newton forecasts the entire 3-D printing industry will reach $50 billion in a decade. He thinks medical/dental applications alone “could be a $10 billion 3-D printing opportunity long term,” Newton said.

For Gillette and other health care providers, the advances mean faster treatment, often in time critical periods. Gillette treats 1,100 babies with its formfitting CranioCaps each year.

Burgeoning partnerships with medical nonprofits plus hospitals like Gillette have gone global. “3-D printing as a technology has a huge role to play in the [global medical] arena,” Rader said. “What I found exciting in 3-D printing is that we can create new products that we could not do before. We [can] improve the delivery of health care.”

Though still developing, Stratasys is positioning itself to be a leader.

“With increasing use of Stratasys’ FDM technology in [prosthetics] and of Stratasys’ PolyJet technology that uses multi-materials and multi-colors, our leadership in the health care industry is clear,” Rader said.

Stratasys printers are now regularly used by doctors to make custom orthotics that relieve foot pain and customized leg and arm braces.

In Florida, Limbitless uses Stratasys machines to make prosthetic arms for children. This spring, the nonprofit surprised one little boy with a new “Iron Man” bionic arm that was presented by movie “Iron Man” Robert Downey Jr.

Stratasys’ first arm work was done in 2012 when it printed arm braces for a 3-year-old girl with a rare muscular condition who was a client of Minneapolis-based MagicArms.

One Argentinan surgeon 3-D printed a titanium skull implant for a patient with a large break. University of Michigan professors 3-D printed splints for a toddler’s collapsed airway that were not only custom fitted but would biodegrade after three years. Doctors at Wake Forest School of Medicine in North Carolina are working to 3-D print skin cells for burn patients.

Stratasys introduces 10 to 20 new products a year and keeps evolving. While the company has had trouble with its small and consumer-oriented MakerBot 3-D printers sold in Home Depot and other stores, its large industrial models are very well received by auto and plane makers and now by medical experts.

Financial analysts warn that happy patients and big headlines about new medical applications for the technology don’t always spell instant riches for such 3-D printing firms as Stratasys.

Heightened competition, huge R&D costs and overinflated stocks have swarmed the industry, Newton, the Stifel stock analyst, warned in a note to clients. But even he called the industry “revolutionary” and ticked off numerous 3-D printing breakthroughs.

Stratasys is selling 3-D printers to hospitals and clinics and partnering with teaching hospitals in Minnesota and Florida, as well as in Malaysia, Japan and Australia to build lifelike models of kidneys, tracheas, hip bones and even artery-webbed lungs. Some models are printed complete with simulated “tumors,” which medical students learn to surgically remove.

In Japan, Stratasys’ Fasotec unit is using 3-D printing to make “biotextured wet lungs” that squish “blood” when cut. Medical students at Jikei University Hospital in Tokyo performed “lung surgery” on several models this spring.

“We can print out [simulated] organs with the right textures, the right colors and the exact look of the patient’s,” Rader said. “We can print the organ so that it even has the same pathology as what you are trying to [surgically correct]. It’s just amazing. I just visited Australia, where a professor has made an entire [simulated] cadaver using our technology.”

The technology, akin to an inkjet printer, once dispensed just one type of molten plastic into specific shapes. Newer models “print” alternating layers of silicone, nylon, rubbers, foams or other plastics in varying colors, thicknesses, strengths and flexibilities. That has benefited the medical device industry, Rader said.

Partnership with the U

A few years ago, Stratasys partnered with the University of Minnesota Medical School. The school had bought its first 3-D printer several years ago to replicate patient hip bones and skulls.

Today, it owns three large Stratasys machines and uses them and other molding techniques to make kidneys that are so realistic they teach medical students how to remove kidney stones or work with the specific anatomy of a pre-surgical patient.

“We have taken these models to hospitals and military medical training facilities and to nursing [schools]. They love it and they want them,” said Dr. Robert Sweet, a University of Minnesota urologist and director of the medical school’s simulation programs.

Sweet proudly displayed several simulation laboratories and scores of models just an hour before hopping on a plane with 15 kidney replicas headed to surgeons in training at Long Island Jewish Medical Center. “We don’t typically use cadavers for scope training, so these are great solutions for being able to teach the kidney stone stuff,” he said.

Impressed by the organ replicas, the U partnered with Stratasys to win a Department of Defense grant contract to make head, tongue and trachea models that were realistic enough to train Army doctors and first responders to intubate patients in combat or on the street.

That project — which used 3-D printed parts plus silicone molds, hand painting and water tight sealants, were such a success — the simulated tracheas will soon be commercialized and sold on the open market, Sweet said.

Last year, the Defense Department tapped the university and Stratasys again, this time to conduct an entire “modular manikin project.”

Inside the U’s simulated technologies lab in Minneapolis, operations director Troy Reihsen patted the shoulder of a “half man” lying on a lab table. The manikin had a 3-D-printed heart, skull, tongue, renal arteries and arm and hand bones.

“It took a year to make this,” Reihsen said.

A towering Stratasys machine in the medical school basement printed out the manikin’s skull, spine and rib cage, plus the molds used to make a realistic airway. Separate silicone molds gave the manikin its face, neck skin, teeth and squishy tongue. Tiny electrical sensors dotted the innards, which allowed medical students and their guiding physicians to track by computer every probe or cut by a scalpel.

“Right now, there are many, many steps in making the manikin,” said Reihsen, who admits to waiting for the day when all facets of a human organ or body can simply be 3-D printed, down to the smallest vein and most realistic skin materials.

“If we got to that point, we could get to this [surgically realistic manikin] in days rather than months or years,” he said. “We’ll get there. But we are not there yet.”