Fibers used in bullet-proof vests quadruple toughness of dental composites

Dec 06, 2006
Composite Bridge
Fiber-reinforced composites are so strong that dental bridges made with them can be attached with less invasive techniques to adjacent teeth. Credit: UC San Diego

Vistasp Karbhari, a professor of structural engineering at UC San Diego, has developed fiber-reinforced polymer composites as strong, lightweight materials for aerospace, automotive, civil and marine applications, so he thought, "If they work so well in highway bridges, why not dental bridges?"

In a paper scheduled for publication in Dental Materials, Karbhari and Howard Strassler, a professor and director of Operative Dentistry at the University of Maryland Dental School, report the results of detailed engineering tests on dental composites containing glass fibers as well as the type of polyethylene fibers used in bullet-proof vests.

Karbhari and Strassler found that the toughness of fiber-reinforced dental materials depends on the type and orientation of the fiber used. Their report, available at the Dental Materials website, shows that braided polyethylene fibers performed the best, boosting toughness by up to 433 percent compared to the composite alone.

Many of the strength and durability tests reported in the paper are not currently required by the U.S. Food and Drug Administration (FDA), which regulates dental composites as class II prescription devices. The agency requires eight minimum tests plus biocompatibility tests to ensure that dental composites are safe and nontoxic.

“Fiber-reinforced composites are now widely used in the aerospace and automotive industries and the experience we’ve gained in these applications can be applied in a more rigorous way in dentistry and medicine to tailor performance to exacting requirements,” said Karbhari. Dentists began using particle filled composites 10 years ago as an alternative to ceramics and mercury-containing metal amalgams. Strassler selected three commercially available fiber-reinforced composites for analysis.

Dental composites made with glass or polyethylene fibers are sold as pliable ribbons that dentists mold into the required shape and then harden with curing lights. “Many reinforcing fibers can add strength and toughness to dental composites,” Karbhari said, “but if they are improperly aligned they could actually accelerate damage to existing teeth.”

“What’s been missing until now is a rigorous, reproducible way to test the durability and resistance to breakage for these materials,” Strassler said. “Makers of fiber-reinforced dental composites need a much better understanding of how their products actually perform as part of a restoration, crown, or bridge, and this study provides an analytical standard with which all composites should be evaluated in the future.”

The three products tested were a 3-millimeter-wide ribbon of unidirectional glass fibers, a 3-millimeter-wide ribbon of polyethylene fibers woven in a figure-8 stop-stitch leno-weave, and a 4-millimeter wide ribbon of polyethylene fibers woven in a biaxial braid. The resistance to breakage and various measures of toughness of the three preparations were compared to the dental composite alone.

“All three fiber fabrics dramatically increased the durability and strength of the dental composite, but the polyethylene fibers braided in a biaxial ribbon performed best,” said Karbhari. “The tests required by the FDA indicate that fiber-reinforced composites are safe, but those tests are only partially informative. Our analyses show that we can optimize these materials to match and improve performance of teeth, for greater durability, toughness, and resistance to breakage.”

Source: University of California - San Diego

Explore further: A refined approach to proteins at low resolution

add to favorites email to friend print save as pdf

Related Stories

Indonesia to ratify ASEAN haze agreement

58 minutes ago

Indonesia's parliament on Tuesday voted to ratify a regional agreement on cross-border haze as fires ripped through forests in the west of the country, choking neighbouring Singapore with hazardous smog.

White House backs use of body cameras by police

3 hours ago

Requiring police officers to wear body cameras is one potential solution for bridging deep mistrust between law enforcement and the public, the White House said, weighing in on a national debate sparked by the shooting of ...

Recommended for you

A refined approach to proteins at low resolution

10 hours ago

Membrane proteins and large protein complexes are notoriously difficult to study with X-ray crystallography, not least because they are often very difficult, if not impossible, to crystallize, but also because ...

Base-pairing protects DNA from UV damage

13 hours ago

Ludwig Maximilian University of Munich researchers have discovered a further function of the base-pairing that holds the two strands of the DNA double helix together: it plays a crucial role in protecting ...

Smartgels are thicker than water

13 hours ago

Transforming substances from liquids into gels plays an important role across many industries, including cosmetics, medicine, and energy. But the transformation process, called gelation, where manufacturers ...

Separation of para and ortho water

Sep 18, 2014

(Phys.org) —Not all water is equal—at least not at the molecular level. There are two versions of the water molecule, para and ortho water, in which the spin states of the hydrogen nuclei are different. ...

User comments : 0