From Marketing Land via Sesame Communications:
Google spend grew 24 percent year-over-year with a 13 percent increase in click volume and CPCs rising by 10 percent…
Interestingly, this marked the first quarter that smartphone paid click share surpassed tablets. Tablet share remained flat at 18 percent, while smartphones saw click share rise from 14 percent in 2013 to 19 percent in Q2 2014.
These numbers are for overall activity not just dental. My sense is that dental shoppers are more interested in a personal referral and less likely to click an ad. However it would be nice to get some actual research that lets us know one way or the other.