humanoid practice robot with a complete set of pearly white teeth.

Japan Expo Showcases Latest Humanoid RobotsA robot math whiz breezes through a Rubik's Cube, using metal hands to twist and turn the colorful toy.

A panda robot uses sensors to detect when people are laughing, and joins in.

A dentistry student peers into the mouth of a new patient — a humanoid practice robot with a complete set of pearly white teeth
Japan showed off its cutting-edge robots Wednesday at the country's largest robotics convention, a dazzling display of the technologies that make it a world leader in both service and industrial robotics.

The dental training robot, dubbed Simroid for "simulator humanoid," has realistic skin, eyes, and a mouth fitted with replica teeth that trainees practice drilling on.

A sensor fitted where the nerve endings would be raises the alert when dental students drill too close — triggering a yelp from the robot.

"Ow, that hurt!" a female robot squeaked, narrowing her eyes as a young dentist drilled on her replica teeth. "Now, I'm OK," she said as the dentist eased off.

"Our aim is to train dentists to worry about whether patients are comfortable, and not just focus on technical expertise," said Dr. Naotake Shibui of the Nippon Dental University in Tokyo, who collaborated with technicians at Kokoro Co. to develop the robot.

Researchers are still ironing out a few kinks — including perfecting a function that lets novices inject anesthetic into robot gums — before working on commercialization plans, Shibui said. He said a prototype has been used at the university since September.

Across the hall, Kawasaki Heavy Industries' Mr. Cube robot used built-in color sensors and a pair of dexterous hands to solve a Rubik's Cube, then raised the completed puzzle in glee to show off to spectators.

Mr. Cube is no match for his human counterparts, taking up to five minutes to solve a typical puzzle while the human world record is 9.77 seconds.

Still, the sensors' ability to quickly detect and differentiate between colors is a breakthrough in industrial robotics, said Kawasaki engineer Masafumi Wada.

"We hope to employ this technology to robots working in factories, so they can distinguish parts by color, as well as size and shape," Wada said. "That would make production lines much more versatile," he said.

The main focus of the 2007 International Robot Exhibition, which kicked off Wednesday in Tokyo, is on industrial robots like Mr. Cube.

Japan is an industrial robot powerhouse, with over 370,000 in use in 2005 — about 40 percent of the global total and 32 robots for every 1,000 Japanese manufacturing employees — according to a recent report by Macquarie Bank.

But Japan has also led the way in personal robots, with big players like Honda Corp. and Sony Corp. to little-known startups launching robotic companions for the home.

Waseda University's furry, panda-shaped Tocco-chan robot, for example, is designed to relieve stress by helping people laugh.

A Web camera connects to software that scans a person's face for smiles — and when it detects one, the robot joins in by giggling and wiggling its arms and legs.

"We all know laughing is good for your health. This robot helps you laugh, by laughing together with you," said Waseda research student Saiko Hirano, who developed Tocco-chan.

"I wanted to design a robot that helps people," she said. "But mostly, this robot is the product of a wild imagination."