I agree with my wonderful colleague on the undetected fracture it is a common phenomenon that is very hard to diagnose let alone see (probably more undected ones in Jerry's practice with his age and failing eyesight, sometimers disease,...sorry Jerry just had too..)There is however a way that I have used on many occasions to determine if the tooth is, in fact fractured. Think of the small filling as the wedge in the wood that you bang on to split it. The forces applied to the wedge make it much easier to split the larger piece into smaller pieces. So...when you bite on this small filling if the bite is not perfect it puts adverse forces on the rest of the tooth. When the tooth starts to flex to the point where the stress is beyond normal the patient gets a sharp stabbing pain or "zing" in the tooth and subsequently doesn't chew on it (..and then blames the dentist for practicing substandard ...never mind). If a dentist cements a properly fitted orthodontic band around the circumference of the tooth all the adverse forces are directed down the root of the tooth and viola no more pain. If pain remains then I would suspect that a root canal or extraction would be in order. If the pain goes away the band can remain almost indefinately or a crown can be placed on the tooth.

Wow...I can certainly make a short story long...sorry..but you get the idea.
Cheers,
Mike