Looks like a second molar which is infected. It may need  a root canal and crown or if the tooth is very badly destroyed then extraction and replacing. This is what I can gauge from the pictures you have sent and symptoms explained. Please visit a dentist asap to prevent loss of that tooth if it's still salvageable. Take care.

please first tell your mother not to take medication on counter. its dangerous. will u take self medication for any other problem in the body, like for eye, ear, nose etc.. tooth is part of the body, and the toothache can be result of just caries or apical periodontitis, or apical abcess or anything else.. you must visit dentist first. let the dentist carryout the diagnostic procedures to find out the cause and initiate treatment.

the last tooth is on the upper side or lower? in any case she will have to visit a dentist & do proper consultation to know what exactly is wrong with the tooth.  the dentist might even take an xray to give  you the right diagnosis & treatment plan. Hope this helps  and please don't antibiotics & painkillers like this.  it will cause more harm than benefits in the future.

Consultant endodontist for this tooth. It may go for root canal treatment. After the X-Ray doctor 'll give exact opinion.

Hi..she needs either root canal or extraction. Regards

dear practo user as ur complain last tooth in upper left region,there is a difference in last teeth n third molar.if it is third molar n it is decayed n totally black its better to extract it n if it is 2nd molar n ur sayng last then its better to save it but for this u have to visit a dentist for the expert opinion.