there are still a few problems in dentistry which cannot be solved by any means today
one of them is a vertical tooth fracture wherein a tooth is fractured from the root to the crown. no choice in these cases except to remove the tooth, especially when there's inflammation following the line of fracture.
as suggested by one of my professors in college who have seen these pictures, expansion of old silver amalgam fillings may be one such culprit.
nightgriding or bruxism is another possible contributory factor.
root canal or endodontically treated teeth are also vulnerably to fractures, because filing action in the canal can also weaken tooth.
so better have those fillings checked if you experience any sudden change in feeling those fillings. (like sensitivity, pain upon biting)
and ask your housemates whether you sleep 'loudly' or 'noisy' from grinding teeth.
RIP Teeth - both molar fractures occurred within the same patient, 7 months apart, on opposite sides of the mouth.