Because of a dental issue, I have been sleeping with a bite splint in my mouth. I will likely need to wear it also on Pesach. I think it is completely plastic and acrylic (transparent material). I usually only wear it at night after brushing my teeth, but there have been a few times that I put it on without brushing after eating. How I should clean this for Pesach? I am also wondering how to clean it on Pesach. I am supposed to use only antibacterial hand soap on it (no toothpaste, or mouthwash or the like). Is there a hand-soap that definitely is kosher for Pesach?
If there was never any hot food that came in contact with the bite splint you can suffice with cleaning it immaculately in all crevices. Use a brand new tooth brush to scrub it with soap. Use a kosher for Pesach soap which will also nullify any taste or remnants that there could possibly be.
See Shulchan Aruch Admur Hazaken (Orach Chayim 447:8).
Regarding a kosher for Pesach hand soap: Look in the kosher markets. There are Heimishe Hechsherim that give kosher for Pesach supervision on hand soaps.