Hi.. Can understand your concern.. As per your query if you have an abscessed tooth it means you have pus below the tips of tooth root.. The swelling occurs due to inflammation and collection of pus.. Antibiotics can reduce infection in that area and slowly the swelling also reduces but it takes time.. You are recalled after two days so that once the infection goes down to some extent the dentist can make a way for drainage of pus by creating an opening in your tooth so that the pus comes out and give you immediate relief from pain and discomfort due to swelling.. Ideally a dosage of 5 days is given and then the patient is recalled but in cases where the pain and swelling does not go away even a little bit after 2 to 3 days root canal treatment is initiated to drain pus and relieve the patient.. In some patients within a day or two the pain and swelling starts relieving and root canal is initiated after two to three days of medication.. You need not to worry as after the initiation of root canal also your dentist will continue the course of medicine and root canal treatment once started will give you faster relief.. Hope your query is solved.. Thanks and regards..