Dentists need to take a closer look at potential hazards of exposing patients to zinc

Dentists need to take a closer look at potential hazards of exposing patients to zinc, a common ingredient of many dental products, according to a report by Amar Patel, DDS, resident and colleagues at the University of Maryland Dental School in the March/April 2011 issue of the journal General Dentistry.

Small amounts of the element zinc are essential to the proper functioning of nearly every body system, but too much can be toxic. Some patients develop neurological problems from zinc. Toxicity from zinc also can be manifested as nausea, stomachache, and mouth irritation.

The authors reviewed and analyzed a wide range of information now available to dentists and physicians on the use of zinc in dentistry. Many dental patients are regularly exposed to zinc from certain restorative materials, mouthwashes, toothpastes and denture adhesives.

"Dentists are suddenly hungry for more information on zinc," says co-author Nasir Bashirelahi, PhD, a professor with the School. "It is used in dental products abundantly, especially denture adhesives or pastes."

Growing concern with denture adhesives may tip the decisions of some patients away from getting fitted with dentures, which may require perpetual pasting to the gums, to opting for dental implants instead, typically a more expensive choice, says Bashirelahi.

In the paper "What Every Dentist Should Know About Zinc," Patel writes, "Of direct concern to dental professionals ... has been the recent discovery of neurologic disorders resulting from excessive use of denture adhesives, having high leachable zinc contents which can cause copper deficiencies."

They explain that the link of excessive zinc intake has been related to copper insufficiency due to the competition in absorption patterns for the two metals in the gastrointestinal tract. Several studies, according to the review paper, link copper deficient anemia and neutropenia with an increase of zinc intake. (Neutropenia is a blood disorder of abnormally low counts of neutrophils, important white blood cells.)

"Suddenly this issue is very important for the dental profession, with many practical applications," said Bashirelahi, who knows of at least one manufacturer that has added a consumer warning label on a product. And the authors also urge dentists to thoroughly understand the relationship among zinc, health, and dental products because of "legal ramifications." Presently there are zinc-free adhesives in the market.

Bashirelahi lectures in continuing education classes on dentistry where the topic raises eyebrows. He says, "People are living longer these days and want to stay healthy for as long as possible."

Zinc plays an important role in human physiology. It is involved in the proper functioning of the immune system, cellular growth, cell division and normal cell death (a replacement system). The element also plays a key patho-physiological role in major neurological disorders as well as diabetes. Zinc deficiency is a worldwide problem, whereas excessive dietary intake of zinc is relatively rare.

Bashirelahi, a molecular endocrinologist, says that among the principal roles of zinc is proper function of the pancreatic system. Another zinc-dependent process is spermatogenesis, as zinc is important for testosterone metabolism.