These devices are classified by FDA as class 1 devices that do require 510k clearance. Check out the FDA's classification page for these following
this link.
Here is the FDA definition (to make sure what I'm referencing is what you are describing): A dental handpiece and accessories is an AC-powered, water-powered, air-powered, or belt-driven, hand-held device that may include a foot controller for regulation of speed and direction of rotation or a contra-angle attachment for difficult to reach areas intended to prepare dental cavities for restorations, such as fillings, and for cleaning teeth.
You can see a large number of these products cleared by FDA if you search the
FDA 510k database with product code
EGS. (This will be very helpful if you decide to seek clearance to market these as clearance is based on finding a substantially equivalent product already cleared by FDA). Also try clicking the "Registration & Listing" link in their database to search for other manufacturers listed with devices classified as product code EGS.
See
this link for information on how to market such a device.