A dentists’ group is suing the state Health Department over what it calls illegal raids at dentists’ offices. The Rhode Island Dental Association filed a lawsuit Monday in Providence Superior Court against the Health Department’s Board of Examiners in Dentistry. The association represents more than 550 dentists. The association says Health Department officials have conducted illegal searches of dentists’ offices, illegally issued subpoenas, improperly seized patient records, and retaliated against dentists who tried to speak out against them. Health Department officials say they do not comment on pending litigation.