As far as my fertility clinic goes I believe my doctor has been very honest with me and my chances of conceiving based upon the facts, my age, and test results. I believe my clinic is reputable and I trust them. However I am sure there are dishonest doctors out there.
Now with the dentist, that is another story. When I was about 19 years old I saw a dentist that said I needed to have all of my baby fillings replaced? So I went to a different dentist and he said all of my fillings were perfect and there was no reason to change a filling unless there was a problem with it. I am 44 years old now and still have all those baby fillings! The second dentist told me the first dentist was lying to me to create work for himself. I absolutely believe that now.