I had a filling done 6 weeks ago and noticed it has progressively gotten more sensitive to temperature changes. Yesterday it became painful so I took a look and the same tooth is now cracked. What is the best treatment and should is it unreasonable to expect my dentist to fix it free of charge? I don't chew ice, lollipops, pens, etc, and have never had a cracked tooth before, so I highly doubt this was caused by me.