On August 15, 1848, the first U.S. patent for a dental chair with adjustable elevation and tilt of the seat and back was issued to M.W. Hanchett of New York. 

He attached a neck extension to a four-legged chair. Further, the chair included a footrest with adjustable elevation.

Since, then dental chair has evolved considerably. However, some recent discoveries have revealed that dental techniques today are pretty similar to the techniques used over 14,000 years ago. The only difference is that then the tools made out of chipped rocks rather than metal.

Sources: TodayInSci

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