To be honest with you, some dentists really don't care whether you have been certified or not! Many like to just hire those that they think would be a good fit for the office. I was one of those lucky ones to be hired on and trained with ZERO experience. There were a few offices that laughed in my face, but I found a place that really needed me. I believe the experiences I had there have been monumental in my acceptances into dental school. It really beefed up my application to be able to say that I had over 2000 hours of paid patient exposure!
That's great that you have already put yourself out there and visited 60+ offices! It's the first step to have the courage to do that. There are a couple of tricks, however, that can set you apart from the applicant pool:
Always dress professionally! We're talking shirt and tie for guys, skirt for girls. It helps send the message that you really care about the job and that you take things seriously.
Present your resume in one of those nice resume protectors. It helps it stand out a lot more when the doctor reviews a whole pile of applications. The doctor I work for told me this made a very good first impression on her!
Finally, be persistent and come back a couple of weeks later. Ask the office manager of they were able to review your resume and if they had any questions. The day I did this, I was offered the job. I didn't receive a call to come in and interview or anything. We just chatted for a little bit and they felt good about it.
So don't get discouraged and keep trying. The lessons I learned in the office not only made my application competitive, but I also learned so many invaluable lessons on practice management. Good luck to you! Hope this helps!