When a consumer does a search for local businesses, the Google Places/Maps results start with the city center (what Google calls the centroid) and lists results moving outward from there. So, the closer to the centroid a business is located, the better chance it has of being shown in the results.
We have noticed recently that Google Places results are showing businesses further away from the centroid. This is good news for those dental offices who are located on the outskirts of their city as they will have a better chance of their Google Places listing (dot) being included in the results.
As you can see from the example screenshot, dentists not only from Denver, but surrounding suburbs are represented, albeit with smaller dots. In the past only the largest balloons would have been shown.
To take advantage of this be sure your Google Places listing is claimed, optimized (add photos, videos, office hours, etc.) and that you have citations (your office listed on local directories).