Curious,
From what you have described, your situation is completely different than Chemar's. At 12 years old, you had either "retained" premolar baby or adult teeth that had either never come down through the gum or due to overcrowding, those teeth were coming through the palate as there was no room for them to fit into your small upper jaw.

Since Chemar is an adult, my interpretation of her post is that her tooth is fully erupted, but the root(s) may be located in or near her sinus cavity. A truly different situation and surgery altogether.

Chemar, please correct me if I have misinterpreted you ~'.'~

Bryanna