If parents needed one more reason to quit smoking, a new study may provide it. Secondhand smoke, according to Japanese researchers, may discolor children’s gums.

Some past research has linked secondhand smoke to cavities and gum disease. The new findings, say the study authors, suggest a “third effect” on children’s oral health: brownish or black pigmentation of the gums.

Their study of 59 children at one Japanese dental clinic found that the majority - about three-quarters - had some darkening of the gums.

Most of the children also had at least one parent who smoked, and they were more likely than their peers to have discoloration in spots along the gum line or across the whole area.

Of that group, about 70 percent had a parent who smoked, versus 35 percent of children with no gum darkening, according to findings published in the journal Pediatrics.

Factors other than passive smoke do contribute to dark pigmentation of the gums, said Dr. Takashi Hanioka of Fukuoka Dental College, the study’s lead author. For example, dark pigmentation varies according to ethnicity, with about one-third of people in Asian populations having darkened gums.

But the current findings suggest that parents’ smoking leads to gum discoloration in some cases, according to Hanioka. And since it’s an effect parents can plainly see, the researcher told Reuters Health, it may encourage them to kick the smoking habit.

Gum darkening does seem to go away in some cases, according to Hanioka. It is less common among teenagers than younger children, the researcher noted, which suggests that the normal buildup of a protein called keratin over the gums can “hide” the pigmentation seen at an earlier age.

In addition, Hanioka pointed out, a Swedish study of smokers, whose gums can also be discolored by the habit, found that gum darkening tended to fade in the years after a smoker quit.

SOURCE: Pediatrics, August 2005.