No one really knows the exact process Google (or any other search engine) uses to deliver organic results. At best they are making educated guesses based on observations. Many web companies claim to be able to give you more juice, to improve or optimize your chances of a high search engine ranking. They sell this service as SEO (Search Engine Optimization).
At one time SEO for specific key words such as “dentist” may have been useful. Today in any big city it has very limited utility. The organic results for a keyword search like dentist will be less than 1/5th of the page and includes very few dentists. Instead of dentists the organic results trend to pages with much more juice than any dentist could ever acquire. Sites like Wikipedia, Yelp and the ADA.