Usually a dentist would ask you if you're sensible to cold, hot, sweet or acid foods or drinks. The dentist may even expose the suspect tooth to compresed air, but what cues do this information give? for example: does sensibility to sweet mean a deeper cavity than to cold ? does any of them mean infection ?
Which is worst or do they all mean the same ?
Edit: For any sensibility to happen the emanel must let the substance pass throught the dentin. What I belive is that: hot or cold change the temperature of dentin which in turn change the presure around the nerve, but doesn't necesarily need to touch it directly, acid and sweet (that became acid thanks to bacteria) get to the nerve by the pores of dentin, while air needs a direct road to the nerve, thus making it the worst sign.