SMILING: Freddie Prinze Jr. (with 43% of the vote) and Britney Spears (29%) have the nation’s best smiles, according to a random sampling of 400 American teenagers, ages 14-20, conducted by BriteSmile teeth whitening system. Male runners up (in order) were Heath Ledger and ‘N Sync’s Justin Timberlake. Sarah Michelle Gellar and Beyonce Knowles followed Spears . . . GETTING HITCHED: Model-actress Andie MacDowell, 43, accepted an engagement ring last week from Rhett Hartzog, 43, an Atlanta jewelry businessman, whom she has known since grade school, says her father. Marion McBride said his daughter plans to marry in November in Asheville, N.C., where MacDowell lives. It will be her second marriage . . . REPLACING: Oscar-winning actor Tom Hanks, 45, and “L.A. Confidential” director Curtis Hanson, 56, have been elected to the board of governors of the Academy of Motion Picture Arts & Sciences. Hanks, a member of the actors’ branch, fills the vacancy left after the resignation of fellow best actor winner Gregory Peck, 85, who chose not to finish his three-year term . . . DIED: Educator and TV pioneer Dr. Frances R. Horwich, 93, revered by baby boomers as Miss Frances of “Ding Dong School,” passed away Wednesday, reports The New York Times. Her ’50s show, which she ran like a classroom, was the precursor of “Sesame Street” and “Mister Rogers’ Neighborhood.” Some lucky collectors still have their “Ding Dong School” finger-paint sets. Goodbye, Miss Frances, and thanks.