Maybe one of the 3 sided ASD toothbrushes I've seen advertised? I've never used it with my kid....but it looks awesome and would make it quicker to brush his teeth. Might be worth a try.

It doesn't sound like a sensory issue since you said he does brush his teeth in the morning. Part of it sounds like a typical teen but it may have to do with routine also. Does he have the same routine every night since our kids love routine. For example, after school take a break until this time, then work on homework until dinner, after dinner do this until this time, at this time every night we brush our teeth and do the "if/then" "if you brush your teeth at this time, then you can do (favorite activity) until this time. If you don't, then you lose this privilege." Stick to the routine and it may fall into place where he will do it himself. I know we had the same issues at that age with brushing at night b/c they 'became too busy" and didn't want to do it, but I kept at it.

I sedated my daughter abd had her teeth cleaned. And applied sealants

Rewards don't work with him and ABA/Hab don't work for him either. Pics work for a little way and then they just become background noise.

Yea rewards didn't work for my boys either still fighting with my 13yr old he brushes now but still can't get him to shower