Hello,
Let me try to remove some of your confusion and straighten things out a bit. The new changes you see here
https://www.dentistry.iu.edu/index.php/prospective-students/admissions/dds-prerequisites/ for IUSD are there to tell you to take a certain amount of credits such as 20 in bio and 12 in chem... etc. Then IUSD has listed below classes that they strongly recommend you are CORRECT they are NOT required to apply to the D.D.S program. HOWEVER!!!!!! This is where it will hurt you if you do not take at least some of the recommended classes.
Applicants are looked at based on their GPA and DAT (we all know that) but IUSD does a holistic review so ya you might have a 3.9 GPA but what classes did you take. So going to that list that they strangely recommend and by taking those classes this is not only showing your ability to follow directions (IUSD likes that) but if you do well in those classes it is kinda like an extra point on your overall score to be accepted. Ok now yes if you have a killer GPA with high level bio and chem this might not apply to you. But if your GPA is average and DAT about that too these classes that you took that they recommended will help you in the long run. When the committee goes over the applications they will look at who is prepared and who took what. IUSD wants to assure that the students that get in can handle the class load (as it is a VERY HEAVY load!) so if you can take what they recommend I STRONGLY ADVISE YOU TOO!
If you cant take them its ok you can still apply and give it a try. Also by taking those classes you will help yourself when it comes to the material in dental school.