MADISON, Wis. -

Dean physician shareholders voted Tuesday to approve a merger with SSM Health Care, according to officials from both organizations.

More than 97 percent of Dean shareholders voted in favor of the merger with the parent company of St. Mary’s Hospital, according to a news release.

The two companies signed an agreement in April under which Dean and its subsidiaries would become part of SSM Health Care. The deal still requires the approval of the Wisconsin Insurance Office of the Commissioner of Insurance and other regulatory agencies. Those decisions are expected by late summer.

The two companies have worked together for 100 years, but SSM Health Care President and CEO William P. Thompson said this process will streamline finances and decisions between the entities.

Dean Health System President and CEO Craig Samitt said this is a chance for his organization to serve patients on a larger scale by being connected to people throughout SSM’s network. Samitt added the focus will be low-cost, high-quality care.

Carl Vieth is a health systems expert at the University of Wisconsin-Madison, after years of work in the public health sector. Vieth said even though the two companies are calling it a merger, the process is an acquisition by definition.

Vieth said putting Dean under the same ownership as St. Mary’s could heighten health care competition in Madison and make it tougher for patients there to get referrals outside the system. He said the buyout probably won’t result in higher medical costs for people, but slightly higher premium costs are a possibility.

A transition team will begin working out the details of the integration plan.

The companies aren't releasing terms of the deal.