A circle drawn on the I-35 corridor buys empty Hill Country
Radius targeting assumes people are distributed evenly around you, and in Central Texas they are not.
Population here strings out along a north to south line. Round Rock, Pflugerville and Georgetown sit above the city, Kyle, Buda and San Marcos below it. Head west and density drops away quickly through Bee Cave and Dripping Springs into the Hill Country.
Any circle wide enough to reach the towns you want will also cover a large area of land where nobody is searching for a dentist and a wedge where people are searching but would never make the drive. You pay full price for both.
Target by named city, county or ZIP code instead. Build the list from the places your patients actually come from, then add the ones you want more of, and leave the rest out until the account has data to argue otherwise.
Set the location option to people in your targeted places rather than people showing interest in them. Without that setting you buy clicks from anyone reading about the city, which in a place people visit constantly is a real and invisible cost.