Featured Research

from universities, journals, and other organizations

Nature's Hardest Puzzle -- Researchers Closing In On Making Tooth Enamel

Date:
December 15, 1998
Source:
University Of Southern California
Summary:
Researchers at the University of Southern California's School of Dentistry are closing in on making tooth enamel, the hardest substance found in vertebrates. They have identified tiny spheres that regulate the formation and organization of tooth enamel by controlling the substance's crystalline growth.

Researchers at the University of Southern California's School of Dentistry are closing in on making tooth enamel, the hardest substance found in vertebrates. They have identified tiny spheres that regulate the formation and organization of tooth enamel by controlling the substance's crystalline growth.

Related Articles


Called nanospheres because they are only 20 nanometers in diameter, these structures are formed by a naturally occurring family of tooth-specific proteins known as amelogenins. These spheres are also a component of the synthetic amelogenin first cloned at the USC School of Dentistry's Center for Craniofacial Molecular Biology (CCMB) four years ago.

"More than 98% of tooth enamel consists of carbonated calcium hydroxy-apatite," says CCMB research professor A.G. Fincham, Ph.D. "Essentially, your teeth are made of rock."

For two decades, CCMB researchers have been studying tooth enamel with the goal of one day replacing mercury-based gold and silver fillings with restorations of man-made material identical or similar to natural tooth enamel. "Beyond that, the same principles that nature uses to make enamel might also be applied to create novel synthetic materials," Dr. Fincham says.

Tooth enamel begins to form in the human embryo when a specialized layer of cells, called ameloblasts, in the embryonic tooth bud secretes amelogenin proteins. The amelogenins self- assemble to form the extracellular matrix within which the inorganic crystals of mineral start to form. "The earliest enamel crystals form in extremely long, thin ribbons and are rather beautifully parallel," Fincham notes.

CCMB researchers first saw the spheres in 1994. "Magnified in an electron microscope, they looked like tiny ping pong balls among the long ribbons of crystal," Fincham reports.

A more powerful atomic force microscope recently revealed that the spheres are uniformly 18 to 20 nanometers in diameter. (A nanometer is a billionth of a meter, and a 20-nanometer- diameter sphere is roughly 1/500th the size of a red blood cell.)

Chemically, the mineral crystals in tooth enamel are a calcium hydroxy-apatite formed from calcium and phosphate ions, which are transported into the nanosphere matrix by ameloblast cells.

"At first," Fincham explains, "the elongated apatite crystals will grow solely on their end faces, becoming ever longer. With the nanospheres acting as spacers, these early crystals build a scaffold on which mature enamel can eventually form. After enzymes have broken down the amelogenin proteins, the crystals start to grow on all of their faces. They thicken, clump together and create mature enamel."

Apatite crystals grown in the lab by traditional methods are about 100 times smaller than the crystals nature makes. They grow haphazardly, and the resulting material is considerably weaker than natural enamel.

Four years ago, the CCMB researchers took the gene for an amelogenin protein from a mouse, placed it in a bacterial cell, and then used the bacterial reproductive process to produce an identical recombinant amelogenin protein. This recombinant amelogenin protein, which the researchers can now produce in quantity, has since been shown to self-assemble to make nanosphere structures identical to those seen in the mouse and other animals, including humans.

"The structure of the amelogenin enamel protein is virtually the same in all vertebrates, from wallabies to humans, suggesting it has a very specialized function," says Fincham. "That function is to spontaneously self-assemble into a matrix with nanospheres -- a matrix that controls the microarchitecture of the developing enamel, both the three-dimensional spacing between the initial mineral crystals and the later crystal growth."

Currently, CCMB researchers are growing apatite crystals within synthetic matrices made from recombinant amelogenin protein.

"We get very long, straight structures," Fincham reports. "The crystals grow only on their end faces, although the material is unremarkable. We can't make enamel yet, but we can see how nature does it. The nanospheres clearly have a capacity to regulate the way crystals grow."

Other researchers working on aspects of the enamel mineral/enamel protein project include: Janet Moradian-Oldak, Ph.D.; Maggie Zeichner-David, Ph.D.; Malcolm Snead, Ph.D.; Michael Paine, Ph.D.; Hai Bo Wen, Ph.D.; and Raji Ravindranath, Ph.D.


Story Source:

The above story is based on materials provided by University Of Southern California. Note: Materials may be edited for content and length.


Cite This Page:

University Of Southern California. "Nature's Hardest Puzzle -- Researchers Closing In On Making Tooth Enamel." ScienceDaily. ScienceDaily, 15 December 1998. <www.sciencedaily.com/releases/1998/12/981215080914.htm>.
University Of Southern California. (1998, December 15). Nature's Hardest Puzzle -- Researchers Closing In On Making Tooth Enamel. ScienceDaily. Retrieved October 24, 2014 from www.sciencedaily.com/releases/1998/12/981215080914.htm
University Of Southern California. "Nature's Hardest Puzzle -- Researchers Closing In On Making Tooth Enamel." ScienceDaily. www.sciencedaily.com/releases/1998/12/981215080914.htm (accessed October 24, 2014).

Share This



More Health & Medicine News

Friday, October 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Breakfast Debate: To Eat Or Not To Eat?

Breakfast Debate: To Eat Or Not To Eat?

Newsy (Oct. 23, 2014) Conflicting studies published in the same week re-ignited the debate over whether we should be eating breakfast. Video provided by Newsy
Powered by NewsLook.com
Ebola Fears Keep Guinea Hospitals Empty

Ebola Fears Keep Guinea Hospitals Empty

AP (Oct. 23, 2014) Fears of Ebola are keeping doctors and patients alike away from hospitals in the West African nation of Guinea. (Oct. 23) Video provided by AP
Powered by NewsLook.com
Despite Rising Death Toll, Many Survive Ebola

Despite Rising Death Toll, Many Survive Ebola

AP (Oct. 23, 2014) The family of a Dallas nurse infected with Ebola in the US says doctors can no longer detect the virus in her. Despite the mounting death toll in West Africa, there are survivors there too. (Oct. 23) Video provided by AP
Powered by NewsLook.com
Orthodontist Mom Jennifer Salzer on the Best Time for Braces

Orthodontist Mom Jennifer Salzer on the Best Time for Braces

Working Mother (Oct. 22, 2014) Is your child ready? Video provided by Working Mother
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins