Temporary medicated fillings (zinc oxide eugenol or ZOE)can be used when a tooth is too sensitive with a regular filling and the dentist wants to see if it will calm down before putting a permanent filling back in, or he may think you need one to begin with for a while before he puts in a permanent.
I would try to go to a biologic dentist; many regular dentists would rather make money selling you a root canal or crown. it is possible the tooth will need a crown if the filling is very big, but they could most likely calm the tooth down with a ZOE filling first. it usually feels better within 2 weeks, but you should normally leave it 2 to 3 months before putting back in a regular filling and maybe a little longer if a crown is needed (do what the dentist says).
Temporary fillings are made of two major components: Oil of clove (eugenol), which has been used for centuries to relieve toothaches, and Zinc Oxide which is the ingredient that makes Desitin diaper rash ointment white. Zinc oxide is an excellent disinfectant. The oil and oxide mix together to make a stiff paste that eventually hardens into a waterproof substance which soothes the nerve of the tooth and kills germs while protecting the cavity like a hard band aid. When used as a temporary filling material or cement, this material is called “zinc oxide and eugenol”, ZOE for short.
Zinc Oxide and Eugenol is not very durable, and it wears away after just a few weeks, but it works to relieve pain, calm the nerve and protect the tooth until an appointment can be made to get it filled permanently. During the Vietnam war, the US Army invented a more durable form of ZOE called Intermediate Restorative Material (IRM) which is fortified with plastic powder. (It originally came in red, white or blue colors.) IRM is used almost universally in dental offices throughout the world for temporary fillings. The increase in durability allows the temporary to last three to 6 months (sometimes even longer).
Never plan to keep a temporary filling more than 6 months. They are not meant to last that long, and while the eugenol lulls the patient into a false sense of security, the restoration wears rapidly and begins to leak. If you wait too long, the nerve could die, the temporary filling will wear away, the tooth will decay further, and then you will need a root canal or extraction.