What caused my root canal to die?

[Root canal curios]

I have recently been informed I need a root canal treatment on an upper incisor (7). I was even told that I could possibly loose the tooth due to the severity of the root damage.

I am just curious what could have caused this. I had an injury that fractured 2 other upper incisors (8 & 9) 15 years ago, and had a similar root canal treatment on tooth 8 14 years ago. But I always thought tooth 7 was untouched, there is no external damage and the tooth has never bothered me.

Is it really possible that the root was damaged internally 15 years ago, and has sat there slowly dieing this whole time??

For reference, I am 26 years old and my dentist confirmed the exterior of my teath appeared healthy.

 

[Dr M]

Good day
Do you perhaps have any x-rays to share?