WASHINGTON (AP) — Many working-age people assume that Medicare covers just about every kind of health care that an older person may need.

It doesn't.

Some of the biggest gaps involve dental, vision and hearing services. Medicare does not cover dental cleanings or root canals. It doesn't cover everyday eyeglasses and contact lenses. It doesn't cover hearing aids.

Now Democrats are trying to make those benefits a standard part of Medicare under massive, multifaceted legislation expected later this year to advance President Joe Biden's ambitious domestic agenda.

Many consider such as expansion of the program overdue. But that doesn't mean it will be easy.

WHAT ARE THE PROSPECTS?

Sen. Bernie Sanders, I-Vt., and other progressives are leading the push for dental, vision and hearing coverage. Their goal is to provide a comprehensive benefit available to as many Medicare recipients as possible without delays such as an extended phase-in period.

But adding more benefits to Medicare is expensive, and the idea will have to compete with other priorities on Democrats' health care wish list.

Republicans are expected to unite in opposition to the far-reaching Biden agenda legislation into which Medicare benefits would get spliced. Democrats would have to pass the bill under special budget rules allowing a simple majority to clear the Senate.

“It's way too soon to handicap the odds,” said Tricia Neuman, a Medicare expert with the nonpartisan Kaiser Family Foundation.

HOW WOULD THE NEW BENEFITS BE PROVIDED?

The simplest approach seems to involve making dental, vision and hearing coverage a component of Medicare Part B, which pays for outpatient care.

Part B is voluntary, but the vast majority of Medicare's more than 60 million beneficiaries sign up. There's a premium, and most people now pay $148.50 a month. While not cheap, that's actually considered a good deal because taxpayers cover 75% of the overall cost of the insurance. Premiums would be expected to rise with richer benefits, but the cost would be spread broadly.

On a side note, most people with private Medicare Advantage plans now have some level of dental coverage, but that can vary greatly. If dental, vision and hearing benefits were standard under Part B, the Medicare Advantage plans would have to provide them as well.

WHAT KINDS OF SERVICES WOULD BE COVERED?

Though details will take a while to flesh out, comprehensive dental coverage would include regular preventive care such as cleanings and X-rays, minor work such as fillings, and major work including root canals, crowns and dentures.

Vision coverage would include eyeglasses and contacts, plus the needed exams and fittings. Hearing coverage would include hearing aids and their maintenance, as well as audiology services.

HOW MUCH WOULD THIS ALL COST?

Again, that's unclear because key details such as the scope of benefits and cost sharing by Medicare beneficiaries haven't been determined.

But a 2019 bill from House Speaker Nancy Pelosi, D-Calif., carried a price tag of almost $360 billion over 10 years.

Of that, $238 billion would have paid for dental care, $30 billion would have paid for vision care, and $89 billion would have paid for hearing services, the Congressional Budget Office estimated.

The coverage expansion was part of broader legislation that would have empowered Medicare to negotiate prescription drug prices. Some of the savings from drug costs would have been plowed back into the program.

Pelosi's bill passed the House, but went nowhere in the Senate. Democrats are still using its approach as a template.

WHAT'S THE NEED?

Dental, vision and hearing are considered integral to good health.

An older person with hearing problems who cannot afford hearing aids may find herself in a deepening state of isolation that can exacerbate depression. Dental infections can spread through the bloodstream to other parts of the body.

But a 2019 Kaiser Foundation report found that nearly 2 out of 3 Medicare recipients had no dental coverage, and nearly half had not seen a dentist in the past year. About 1 in 7 had lost all their teeth.

Black and Hispanic enrollees were far less likely to have visited a dentist in the past year.

“It is obviously a big, gaping hole in the Medicare program,” said David Certner, legislative director for AARP.

WHY DOESN'T MEDICARE COVER DENTAL, VISION AND HEARING?

Experts say the reason probably dates back to 1965, when the program was created.

It was modeled after the kinds of private health insurance that were then most commonly available. And those were built around hospitalization and visits to the doctor's office.

Another big gap in coverage — retail pharmacy prescription drugs — wasn't addressed until 2003.

WHAT ELSE ISN'T COVERED BY MEDICARE?

Long-term care.