I have been going to this office for more than 5 years I believe. I have heard that recently (I'm not quite sure how recent) there had been changes in dentists and possibly owners. I'm sure other commenters here have more accurate details about that.
I have ALWAYS had trouble with the billing practices here. Here are a few to illustrate:
1. I had double "Premera" dental coverage through the Marine Reserves and my other work employment. Through both I should have been completely covered and Oak Tree Dental was going to invoice them. Oak Tree could not get the invoicing straight and kept sending me bills for the work, so that I could pay them and my coverage could "reimburse" me. Through trying to work through this issue with Oak Tree, they told me that I was "no longer welcome at the office". I was floored at their incompetence in handling the billing and then their reaction to their mistakes.
(I had moved overseas for a couple years, and when I came back I explained the situation to a new office manager, and they said they were fine with seeing me again.)
2. In 2006 I was told that I needed some major work done. I think it was called "scaling", where they go deep into your gum pockets. I was told that I was in serious risk for this to get drastically worse... The bill was going to be huge with my insurance paying most, and I was going to be out of pocket $400 or so. TWICE I had confirmed the pricing saying that I was not comfortable with paying more than that and they specifically confirmed that this was the cost. Immediately after the work they asked me for another $350. I was sore, shocked, and bordering irate. I asked how this could be and they said that they had "made a mistake earlier, and this is what the cost would be". I asked if there was a way to discuss this and come to an agreement, but they threatened if I did not pay it, it would be invoiced to me until eventually it went to collections. I begrudgingly paid. This had happened on 2 previous occasions.
I'm a bit embarassed to say that the hygienists had been nice and I was pleased with the work done, but after reading through these similar experiences, it is clear to me to find a different dentist. Clearly not all dentist offices are this shady.