A magazine ad for Playtex tampons that says "Playtex protects better" was called "dangerous and misleading" yesterday by the Ralph Nader-founded Health Research Group.

The ad says "consumer tests" showed that both Super and Regular Playtex "provided better absorbency and better protection" than other tampons.

It says nothing about a possible link between high-absorbency tampons and toxic shock syndrome (TSS), although a statement that the government ordered placed in every tampon package tells users: "You can possibly reduce the risk of getting TSS . . . by using tampons with the minimum absorbency." The statement was ordered by the Food and Drug Administration as a result of the toxic shock outbreak of 1980-81.

The Health Research Group asked Playtex to withdraw its ad "immediately," and asked the Federal Trade Commission and the FDA to act to halt the ad campaign because it may cause "death and injury to many American women."

There are still about 500 cases of toxic shock syndrome a year, according to doctors' reports, and possibly as many as 8,800 cases, by some estimates. At least three of every 100 cases are fatal. Eighty-five percent of all cases occur in menstruating women, mainly tampon users.

Last year the National Academy of Science's Institute of Medicine urged women to minimize use of "super," or high-absorbency, tampons.

Walter Bregman, president of Playtex U.S., yesterday called the absorbency issue "unresolved." He called Playtex "a responsible advertiser and marketer" whose tampon advertising is neither misleading nor improper.