general principle concerning dental abscesses is ubi pus, ibi evacua ("where there is pus, drain it"), which applies to any case where there is a collection of pus in the tissues (such as a periodontal abscess, pericoronal abscess, or apical abscess). The pus within the abscess is under pressure, and the surrounding tissues are deformed and stretched to accommodate the swelling. This leads to a sensation of throbbing (often in time with the pulse) and constant pain. Pus may be evacuated via the tooth by drilling into the pulp chamber (an endodontic access cavity). Such a treatment is sometimes termed open drainage. Drainage can also be performed via the tooth socket, once the causative tooth is extracted. If neither of those measures succeeds, or they are impossible, incision and drainage may be required, in which a small incision is made in the soft tissues directly over the abscess at the most dependent point. A surgical instrument such as a pair of tweezers is gently inserted into the incision and opened, while the abscess is massaged to encourage the pus to drain out. Usually, the reduction in pain when the pus drains is immediate and marked as the built up pressure is relieved. If the pus drains into the mouth, there is usually a bad or offensive taste. Antibiotics Antibiotics tend to be extensively used for emergency dental problems. As samples for microbiologic culture and sensitivity are hardly ever carried out in general dental practice, broad-spectrum antibiotics such as amoxicillin are typically used for a short course of about three to seven days. Antibiotics are seen as a "quick fix" by both dentists, who generally only have a very short time to manage dental emergencies, and by patients, who tend to want to avoid treatments (such as tooth extraction) which are perceived negatively. However, antibiotics typically only temporarily suppress an infection, and the need for definitive treatment is only postponed for an unpredictable length of time. An estimated 10% of all antibiotic prescriptions are made by dentists, a major factor in antibiotic resistance. They are often used inappropriately, in conditions for which they are ineffective, or their risks outweigh the benefits, such as irreversible pulpitis, apical abscess, dry socket, or mild pericoronitis. However, the reality is that antibiotics are rarely needed, and they should be used restrictively in dentistry. Local measures such as incision and drainage, and removal of the cause