What would be the best way to approach dentists about joining our provider list?

I'm working for a dental savings service, which is similar to a preffered provider organization. Basically we have dentists sign up with us and agree to give our members 30% off on dental costs. This is mutually beneficial because dentists get more customers and give them the 30% they'd give the customer anyway if they had insurance, and our members save money. We are working to expand this to Los angeles. What is the best way to approach a dentist to joining our provider list.
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Write them a letter explaining how your service could increase their patient load. Point out the benefits to them, such as advertising and incentives (for them and their patients, such as free toothbrushes and other supplies). Give them statistics on their local area as to the number of people use YOUR service already. Point out specifics from their office that would set them apart from other providers on your current list that would help them get more patients, for example targeting an office that specializes in TMJ treatment in adults or an orthodontist's office that specializes in adult treatment or one that does lingual braces --- show the office how their office would be unique to having an assoication with your company. Point out how your company needs an office like theirs that specializes in "something" that many of the other offices on your list do not.
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