If there is one campaign that takes public pride in the integrity of its fund-raising practices, it is the presidential drive of Massachusetts Gov. Michael S. Dukakis (D), a reformer who has rejected political action committee gifts, turned down donations from lobbyists and limited contributions from state employes to a maximum of $100.

Just last month, however, dentists in Massachusetts received a "Dear Colleague" letter suggesting that contributions to Dukakis would be in order because his "support of organized dentistry throughout his years as governor has never wavered."

Raising money from dentists is probably tougher than pulling teeth, but in this case, Dukakis had a little extra leverage: two of the signers of the letter -- Walter Guralnick and Arnold Vetstein -- are members of the state Board of Registration and Dentistry, the agency that licenses and disciplines dentists; Guralnick, a leader of "Dentists for Dukakis," is the chairman of the board.

Asked about the letter, Robert Farmer, who is in charge of Dukakis fund-raising, said he was unaware of the ties of Guralnick and Vetstein. "That's an impropriety," Farmer said. "They shouldn't be sending out a fund-raising letter. Anybody who's on any board that has anything to do with regulation should not be raising money. I regret that."

Leslie Dach, a Dukakis spokesman, said, "It won't happen again." The campaign will ask all fund-raisers if they have any position in state government.