A fast-growing Nashville healthcare company faces a class action lawsuit that attempts to halt its meteoric rise.

SmileDirectClub has faced the ire of dentists and orthodontists in its short 5-year history. Now, some of them are alleging the company is committing fraud and misleading customers.

The lawsuit filed in federal court in Nashville on Wednesday accuses SmileDirectClub of sidestepping FDA approval for its 3-D printing of retainers at a Tennessee facility. The orthodontists also say the company’s marketing materials are misleading since the doctors who oversee the process are based in Costa Rica, not the U.S. That’s led to accusations that SmileDirect is operating illegally, violating state-based licensing laws. 

The American Dental Association tried to stop SmileDirect from selling its products earlier this year but was denied an injunction by the FDA.

The company has — itself — been rather litigious, frequently suing critics who question its popular product, including a journalist.

SmileDirectClub continues to disrupt the dental industry, with its most recent growth falling outside the U.S. The company expanded to the U.K. in August.

SmileDirectClub became a public company this month. A spokesperson says the company is not commenting on the class action suit because it’s still in a quiet period following the IPO, which raised $1.3 billion and valued the company at $10 billion.