The most influential review citations are not only the ones that Google scrapes and displays on the Google+ Local page, but the ones that most often appear on high ranking listings.
The local review space consists of many industry-specific and niche directories within an already fragmented local search arena. The most popular review sites for hotels and restaurants are not the same for dentists and doctors.
Outside of Yelp (whose review snippets were removed from Google) and native Google+ Local reviews, here are the top third-party sources for dentist reviews in the US:
When it comes to dentist reviews (based on the above), Google is really digging Demandforce (Intuit Local) listings -- they must really be pumping them out. Yahoo Local ranks second (with 53 citations). Is this Google’s way of throwing Yelp a bone?
Over a five day period up until April 29, 2014, our team manually compiled review data from 750 of the highest ranking dentist listings across the top 50 US cities by population. Our method was simple. For each city, we did a Google Maps search for [dentist] + [reviews] + [cityname, state] and selected the top 15 cited sources from the Google+ Local page “Reviews from around the web” section. We only included Google+ Local listings primary categories: dentist, dental clinic, dental implants periodontist, cosmetic dentist and pediatric dentist.
To keep the list focused on the most influential citation sources we only included sites which were cited at least three times. Honorable mentions to botw.org and dentistdig.com for almost making the list.
What is a Review Citation?
A review citation is a mention of a business name (anchored by address and phone and/or website) along with a unique customer review. For many business types, review citations are an important factor for ranking in Google's local search results. Real reviews from quality sources are very important for competitive business types such as dentists. Claiming your business listing at the sites on this page (along with Yelp), and encouraging reviews, is likely to improve your rankings over time.