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An invention that’s helped millions, but which no one really likes, was patented in 1875 — the electric dental drill. Those who dread the device should consider the primitive state of dental technology before George Green of Kalamazoo, Michigan, was granted his patent. Today, the whine of the dental drill — and that of the patient — is heard less often. Americans are flossing more and generally taking better care of their teeth. As a result, the nation’s dentists are spending more time treating gum disease and poor tooth arrangement than in filling cavities. There are about 196,000 dentists in the U.S. Our annual tab for visiting their offices is more than $38 billion, not covered by insurance.

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