To illustrate the importance of pay-per-click, PPC visitors are 50 percent more likely to purchase a product than organic visitors, according to data from Unbounce. And 41 percent of clicks go towards the first three ad positions.
Source: How to Implement Pay-Per-Click the Right Way
Two take aways from the linked article. The average cost of a PPC click in healthcare is $2.62. You will be best served by a specialist in your market. Check with my friends at TNT Dental for some specific dental marketing expertise.