Oregon Insurance Commissioner Laura Cali on Monday approved the sale of a majority stake in Redmond-based Advantage Dental to a Massachusetts firm.

Advantage President Mike Shirtcliff announced the deal with DentaQuest in January. The purchase price has not been disclosed, but according to Cali’s order, DentaQuest will receive 80 percent of the Advantage holding company in an all-cash transaction. The deal may close in two months, according to Cali’s order. DentaQuest’s acquisition is not expected to affect Advantage Dental’s structure or operations.

Advantage, which has about 400 employees, is the largest provider of dental services to Oregon Health Plan members with about 340,000 plan members in its network. Oregon Health Plan is the state’s Medicaid program. Like Advantage, DentaQuest specializes in serving people covered by Medicaid, but it’s much larger with a presence in 30 states.

Advantage administers insurance benefits on behalf of about 300 dentists, who also own shares in the company, and it operates 40 of its own dental clinics. In announcing the deal with DentaQuest in January, Shirtcliff said it would provide capital to further Advantage’s expansion and allow about 100 retirement-age dentists to sell their shares in the company.