Whether hot sensitivity tooth needs root canal?

[Du_deleted]

Hi,
I had recently replaced(3 weeks back) old fillings with new one on one tooth. I am experiencing some sensitivity in that tooth whenever I chew hard and crunchy foods. Also, I feel a sharp pinch like pain whenever I sip a hot beverage. I feel this only for the first sip. The second sip i feel like normal. The same for hot food too. I haven't tried with very cold items yet. I have just tried with normal tap water(little cold) and I feel little sharp and sensitivity. I would like to know if it's treated using only root canal? Is root canal necessary?
I had some discomfort with my first filling and replaced it. The sensitivity was not there with my first filling and it stared after my refilling which is 3 weeks back.
What is the treatment for this? A crown or root canal? I am just looking for some valuable inputs, so that I am not scammed with new dentists which I am gonna visit.
Another additional question. When is root canal neccessary and to be done? I have no idea on this.
Thank you.

 

[MattKW]

1. Why was the filling replaced?
2. What was it replaced with? Composite or amalgam?
3. Do you have any digital Xrays to show us?

 

[Du_deleted]

1. Why was the filling replaced?
2. What was it replaced with? Composite or amalgam?
3. Do you have any digital Xrays to show us?

Thank you so much for your reply @MattKW. Appreciate it.
1. It was giving some discomfort for 8 months. No sensitivity. Just some discomfort on the left lower side. So he replaced it.
2. Composite.
3. I have x-rays which was taken before this replacement. I don't have any x-rays after this refilling.