In some ways, health insurance is like car insurance. Both are designed to protect you from the financial risk of repair associated with body damage.

But unlike a car insurance policy that comes with bumper-to-bumper protection, nongroup health insurance doesn't cover your grille. Dental insurance has always been a separate purchase from medical health insurance.

"A lot of this is a legacy in terms of historically how dental insurance came to be," says Marko Vujicic, chief economist and vice president of the American Dental Association's Health Policy Institute.

That tradition isn't the only thing affecting dental coverage. The Affordable Care Act and business considerations also play a role, as do consumers.

"People just don't seem to think dental care is as crucial to their overall health as what doctors might do," says Mark Pauly, professor of health-care management at the University of Pennsylvania's Wharton School. "I just think it's not a high-priority item for consumers."

But Vujicic believes emerging medical evidence linking oral health to whole-body health has the potential to change dental insurance's second-class-citizen status. There is new evidence he may be right.

In November, Independence Blue Cross introduced a platinum tier Personal Choice PPO Complete plan with adult dental and vision insurance wrapped into the monthly premium. It's an unusual plan because it includes adult dental care.

"We looked at it and said almost everyone buys dental anyway, so how do we start creating more attractive product bundles?" said Brian Lobley, Independence's senior vice president for marketing and consumer business.

Dental insurance, which tends to focus on covering preventive services, always has been viewed differently by insurance companies, Pauly says.

"Regular health insurance protects you from really high medical expenses," Pauly says. "Dental insurance, on the other hand, cuts out as the expenses get high."

Vujicic says health economists consider dental care apart from other medical insurance mainly because "there is a huge prevention factor" in dental care.

"In a sense, with proper prevention and oral hygiene, a lot of dental disease can be avoided," says Vujicic. That's also the case with numerous health conditions. But, in many cases, "you can do all the prevention you want, but there is still a risk out there that is beyond your control."

The ACA has helped and hindered dental insurance's joining the mainstream. The law mandates pediatric dental coverage as one of its 10 essential health benefits. Insurers selling individual or small-group plans on state or federally operated marketplaces must include dental benefits for children.

Vujicic says today, one out of three insurers on the marketplace embeds the pediatric benefit in its plan.

Adults in states that expanded Medicaid also receive some dental benefits. But most people buying health insurance through the marketplace must buy separate dental coverage, mainly because the law's designers want to keep the ACA "affordable."

"If this was going to be the Affordable Care Act, they had to be able to keep the premiums down," Pauly says. "So dental benefits was one of the things they decided to leave out."

Marketplace plans also must meet an "actuarial value," or a percentage of the total average costs covered by the plan. Dental and vision insurance do not count toward actuarial value.

"If they added dental or vision benefits on top of a package, it would boost the premium," Pauly says, "and you wouldn't be able to sell it to people who didn't have subsidies."

Most people buying insurance on the marketplace are price-sensitive, and that can make including dental benefits tricky.

Embedding dental would require Independence to raise the price of some plans by about $10 a month. And that still would cover only routine care.

Even though everything seems to point to dental benefits' remaining a stand-alone purchase, Lobley says Independence will track its PPO Complete plan to see how it performs this year and look for ways "we can get at a little bit of a price break" by bundling dental in its plans.

"All things remaining equal, we would like to have that one-stop-shopping product for people," he said. "Obviously, I can't guarantee you that that is the way it is going to go. But certainly it is the desire."

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This article was written in partnership with Kaiser Health News, an editorially independent program of the Kaiser Family Foundation.