Pre-empt the Gatekeeper - Be an actor
Just go for it, be an actor:
'Hello, is that ABC Dental Care? I understand you are all busy over there and no doubt your ears probably usually tune out when you hear a sales call - am I correct? This won't take a minute - I promise. Our company offers a radically different repair service that has saved dental practices like yours across the country up to ..$ per year. I'm sure the partners of your practice like saving money don't they? Is one of them about? Or perhaps the person in charge of repairs, this is likely to be the most important call they will receive all day!! I'll hold, thanks.'