Thousands of Massachusetts patients were victimized through deceptive advertising by Aspen Dental, according to a lawsuit filed against the dental chain on Thursday by Attorney General Maura Healey.

Healey alleges that Aspen Dental falsely advertised “free” dental services to patients in violation of state consumer protection laws and a settlement the company reached in 2014 with attorney general’s office to resolve similar complaints. “Aspen Dental took advantage of vulnerable consumers in need of dental care and used misleading advertising to lure them into their offices under false pretenses,” Healey said in a statement. “We’re suing this company for violating both state law and its earlier promises not to engage in precisely these illegal practices, and we’re seeking restitution for patients harmed by this misconduct.”

In the Suffolk Superior Court complaint, Healey accused the company of charging patients, including those seeking emergency care, for services it advertised as free, without disclosing limitations to that policy. The company also trained scheduling center employees not to advise potential patients of certain fees associated with emergency appointments, and “deceptively advertised” the price of dentures and the existence of money-back guarantees, according to the allegations. Aspen Dental operates more than 25 offices in Massachusetts.