The xray would show a blockage as it does show feces.
Yes, dental pain can cause a cat to stop eating, but normally they would be drooling too.
What are you feeding your cat? I highly recommend Kitten Wellness, canned, it is an excellent, palatable food that is easy for your kitten to digest.
And since you are a new kitty owner, here is about the best website for nutritional info on your cat. Please take the time to go through it, it is amazing what you will learn
Cat maid to:
Puddles, female Himalayan (16 yrs)
Jasper, male Ragdoll ?? (approx 9 yrs)
Sweet Pea, female silver tabby DSH (approx 7 yrs)
Rose semi feral, a cpietra rescue, female tabby (approx 6 yrs)
Snowball RIP (1991-2005)
In a cat's eye, all things belong to cats.-English Proverb
“While we are free to choose our actions, we are not free to choose the consequences of our actions.” Stephen R. Covey