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Monday, March 14, 2005; Page A10

Lip Piercings and Gum Woes

Decorative studs, rings and other lip piercings can seriously damage gums and increase the risk of infections, tooth sensitivity and tooth loss, a new study suggests.

Ohio State University researchers recruited 29 young adults with lower lip piercings and 29 without the popular accessories and looked for evidence of gingival recession -- retraction of the gums that can expose the tooth roots -- around the bottom front teeth. Each group had 15 female and 14 male members with an average age of 22.

Only two of the non-pierced participants had receding gums, while 12 pierced participants suffered from the syndrome, Dimitris Tatakis and his colleagues reported in Baltimore last week at the International Association for Dental Research. The longer the piercing has been in place, the greater the chance of gum problems.

A number of case reports from dentists in recent years have documented individual patients with lip piercings whose gums were receding as though from chronic trauma. (Tongue piercings have been associated with similar problems on the inner-gum surfaces.) But the Ohio study is the first to compare the incidence of the syndrome among groups of people with and without piercings. It adds to the evidence that the ornaments are causing the problems.

The culprit seems to be the constant rubbing of the metal rings or stud backings against the gums, which sends the delicate tissues into retreat.

The syndrome can be reversed, other dentists and periodontists have reported, but the process can be expensive and painful. Typically it involves the permanent removal of the piercing, thorough scraping of the tooth roots and a transplant of soft tissue from the roof of the mouth to replace the lost tissue.

Earrings, anyone?

-- Rick Weiss

The Oil-Additive Secret

Despite the rivers of lubricant poured into engine blocks every day, just how the additives in modern automotive oils work to decrease friction in the heat and pressure of internal combustion is something of a mystery.

A team of chemists and mathematicians at the University of Western Ontario, however, has come up with a theory that appears to explain not only how additives work -- but why they sometimes don't.

The most common anti-wear additives are complicated compounds containing zinc and phosphate. Martin H. Muser and his colleagues used computer simulations, not laboratory experiments, to deduce what happens at a molecular level when a film of oil containing additives is compressed between two hot, hard surfaces.

Their conclusion is that as the pressure rises, the molecules of zinc-phosphate dissolved in the oil form cross-links with each other. More are formed as the pressure increases, until at pressures achieved in engines made of steel alloys the compounds form a semi-solid molecular mesh. The mesh is capable of bending and stretching between the steel surfaces, keeping them from wearing each other down.

When the pressure drops, only some of the cross-links undo themselves. Most remain. This gives the oil a "memory" of its harshest conditions and helps it return more easily to full lubricating capacity.

The findings, reported last week in the journal Science, also explain why zinc-phosphate additives can damage aluminum engines. The cross-linked mesh can become harder than aluminum and abrade surfaces rather than protect them.

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