SmileDirectClub Renews Legal Fight With Teeth-Aligning Rival

SmileDirectClub Inc., armed with a new patent, has renewed its legal fight with rival Candid Care Co.to protect its share of the expanding U.S. market for teeth-straightening products sold directly to consumers.

A previous patent for SmileDirectClub’s retail concept and the process by which it develops plastic aligners for customers was invalidated Monday by a federal judge in Delaware, who also tossed the company’s earlier infringement lawsuit against Candid Care. In his ruling, U.S. District Judge Colm Connolly called the patent an “abstract idea” that shouldn’t have been issued.

But on Tuesday, Nashville-based SmileDirectClub said the U.S. ...