Dry socket seems to be a recurring theme on here so...
Dry socket or acute alveolar osteitis occurs when the clot in an extraction site doesn't form properly or is disturbed. It happens as frequently as one in 20 extractions and the risk factors are:
Difficult extraction in the
Lower Jaw in a
Smoker who is taking the
Oral Contraceptive Pill
It is very common after the extraction of impacted wisdom teeth. The symptoms are pain, generally throbbing in nature and a bad taste or bad breath.
As the name suggests, it is an inflammatory condition, not an infection which is why antibiotics are often not the first choice of treatment. What usually happens is that the socket fills with food, badly formed blood clot and other mouth detritus. Commonly it is treated by irrigating the socket with antibacterial mouthwash and placing an "obtundant" dressing in there. This dressing (most commonly Alveogyl) fills the socket to prevent food packing, it contains oils which will reduce and sooth any inflammation and it will resorb away once it has done its job.
Essentially anything that disturbs the clot increases the risk of dry socket, smoking, vigorous rinsing, drinking through a straw, poking etc. The lower jaw has a poor blood supply so it is more prone to dry socket as well as the presence of any pre existing infections like acute gum disease (like a condition called AUG), infected wisdom tooth etc. No "normal" dry socket should last for more than a month, if pain or healing is prolonged this much then there is likely to be an additional factor involved.
When the dressing is placed, the main effect is to soothe the pain, it won't speed the healing as that will only occur as fast as the gums can repair themselves so if a dressing comes out then if the pain is manageable, you don't necessarily need to return to the dentist.
A point to note, this condition is described in textbooks as "exquisitely painful".