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In the mouths of babes: no more cavities?

The next time your dentist finds a cavity in your mouth and pulls out a squealing drill, you can blame it all on your mother.

Using a sophisticated technique called DNA fingerprinting, dental researcher Page Caufield has demonstrated that mothers serve as the source of the major cavity-causing bacteria in their children. Caufield, of the University of Albama School of Dentistry in Birmingham, also discovered that these bacteria infect children only during the 12 months following the eruption of baby teeth -- a period he calls the "window of infectivity." if scientists could find a way to stave off infection during this critical time, they might prevent 95 percent of all cavities, he suggests.

The decay-causing bacteria, Streptococcus mutans, is spread through saliva, explains Caufield, who has submitted his research report to several scientific journals. While kissing would be the most direct means of transmission, he emphasizes that it's not the only means. "Saliva is ubiquitous," he says. "It can be spread simply by talking."

In his study, Caufield tracked 46 mother-child pairs from the infant's birth up to age 5. He deliberately selected women who harbored three times the normal level of S. mutans. All participants drank from the same fluoridated water supply.

Every three months, Caufield examined each child's saliva. If S. mutans showed up, he compared swatches of its DNA with swatches taken from the mother's S. mutans to find out whether she was the source of the infection. Almost all the swatches matched up, he says.

Although earlier studies suggested that mothers play a significant role in spreading S. mutans to their children, Caufield says his is the first to show that the mother is the principal source. He credits that discovery to the accuracy of DNA fingerprinting. "Caufield's method of identifying the strains with fingerprinting is at the forefront of the technology that's available," observes Ronald J. Gibbons of the Forsyth Dental Center in Boston.

During the five-year study period, 38 of the 46 children acquired S. mutans -- in each case between 19 and 31 months of age, Caufield says. The eight children who remained uninfected showed no cavities at age 5, whereas cavities developed in nine (24 percent) of the infected children. Caufield speculates that this percentage would have been higher if not for the use of fluoridated water and good oral hygiene.

The complex ecosystem inside the human mouth -- where about 200 species of bacteria establish residency -- causes the window of infectivity to open and shut, he says. S. mutans requires a hard surface to colonize, so it cannot gain a foothold in the mouth until the teenth emerge. But if the bacterium enters the ecosystem after the teeth have already been colonized by other species of bacteria, it won't have room to settle down. The window of infectivity has closed.

Caufield says he isn't sure how eight of the toddlers managed to escape infection, but he mentions that four of them underwent extended separations from their mothers at some point during the window of infectivity, while none of the infected children experienced lengthy maternal separations at that time.

This observation provided him with a theory to explain why only a child's mother could transmit S. mutans. During pregnancy, every child receives antibodies programmed to behave like the mother's, so that bacteria passed from mother to child are treated as friendly, while anyone else's bacteria are recognized as alien and destroyed.

Other dental researchers express interest in Caufield's findings but remain cautious about drawing firm conclusions. "It's a study involving a couple dozen people, and it would be nice to see it involve a couple hundred people," Gibbons says. Adds Johannes Van Houte of the Forsyth Dental Center, "If it is correct, then it is a major step forward."
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Title Annotation:infecting bacteria may come from child's mother
Author:Stroh, M.
Publication:Science News
Date:Feb 1, 1992
Previous Article:Alcoholism: nurture may often outdo nature.
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