"When you're smiling/the whole world smiles with you" are lyrics from a 1928 song that's never lost its popularity. It was even sung by Helena Bonham Carter as Princess Margaret in Season 3 of "The Crown."

Smiles are good for your physical and mental health, no matter what your age. Unfortunately, they're increasingly difficult for many older people.

A study in the journal Health Affairs found that 50% of older adults lack dental insurance, and in 2018 nearly half received no dental care. Put another way, for 1 in 20 people, being old enough to sign up for Medicare is associated with loss of all their teeth.

That increases the risk of poor nutrition, cognitive impairment, and decreased quality of life.

It's never too early — or too late — to take care of your teeth. And if the cost of dental care is an impediment, it's more important than ever.

Brushing and flossing twice a day are steps one and two.

Upgrading your diet is essential as well. High-calcium foods neutralize acid that harms enamel and can help add minerals back into tooth surfaces.

Dairy products (low- or no-fat) are a great calcium source; so are soybeans, broccoli rabe, kale, and other leafy greens.

Drink plenty of water to help boost saliva levels — saliva helps gets calcium to your teeth.

And ditch sugary foods. Sugar feeds bacteria that damage tooth enamel.