Delta Dental Insurance Company is part of a San Francisco-based holding company along with its parent company, Delta Dental of California. Affiliated companies within the holding company system are also part of the larger Delta Dental Plans Association (DDPA), based in Oak Brook, Ill. DDPA consists of 39 Delta Dental member companies licensed in all 50 states. The association collectively covers about 46 million of the 159 million people nationwide with private dental insurance, making it by far the largest national system of dental plans.