I have a deep dent across the top of my butt. What can help fill in the dent so I can have an even butt?(photos)

From your photos, it is difficult to tell if liposuction of the pre-sacral area alone would solve your issue, or if liposuction with fat transfer would be optimum.  I recommend being seen in person so you can be evaluated and discuss your options & desires.

You need a combination of liposuction and fat transfer to get the best result. I could not see your lower back area but you might could use some lipo there also to enhance the final look of the buttock. See a surgeon that has experience with lipo and fat transfer. Good luck.

Based upon your photo, i would recommend liposuction contouring of that area to sculpt down the area above the dent and +/- transfer that fat into the dent itself. An in person consultation with physical exam would first be necessary to confirm my recommendation. Glad to help. 

Hello dear!
Thanks for the pictures and provided information as well.
Looks like you could be a good candidate for liposuction and fat transfer, to fix your problem and improve your buttocks, and I think you'll get very good results. 
l recommend you to make an in-person consultation with a board certified plastic surgeon for a proper answer and to talk about your goals and anything you need to know.
Good luck :)

After reviewing your photographs I think you will need some liposuction to sculpt your buttocks into a more aesthetic appearance.  Please see a board certified plastic surgeon for evaluation.

Looking at your pictures, I think that the best option would be a combination of liposuction to reduce the high spots and fat transfer to fill in the low spots.  It may take more than one treatment to get this as smooth as you might want it to be.  I would recommend a consultation with a plastic surgeon but this is likely something that can be done under local anesthesia.  Good luck.