Abrasion is the loss of tooth substance by wear due to other factors than tooth contact. eg pipes, clothes pegs, nail biting etc. see also attrition and erosion

Abscess A localized infection in the bone or gingivae (gum). An apical abscess may occur when the pulp is dead and infected with pus gathering at the tip of the root (apex).The tooth will require root canal treatment or extraction. A periodontal abscess is a collection of pus within a gingival or periodontal pocket. The tooth needs a deep scaling around the gum and may eventually need to be extracted if the periodontitis can not be controlled. In the case of severe abscesses, antibiotics may be prescribed. These are often penicillin derivatives eg amoxycillin although depending upon the infection other prescriptions such as metronidazole may be indicated.

Acid etch is used prior to bonding a composite filling. It prepares the enamel and dentine by producing microscopic holes. This allows a strong bond to be made between the filling and the tooth

Acute Necrotising Ulcerative Gingivitis (ANUG) is an acute ulcerating condition affecting the marginal gingivae. It is painful, of sudden onset and may lead to the loss of the contour of the gum between the teeth (interdental papillae). Sufferers may complain of pain, bad breath (halitosis), and a metallic taste. Usually occurs in twenties or thirties, of people who smoke, are stressed, have an impaired immune response, or who have poor oral hygiene. (see tooth brushing). Treatment involves oral hygiene instruction, smoking cessation, mechanical debridement (cleaning by dentist), and in severe infections, metronidazole may be prescribed.

Air abrasion A device that uses microscopic particles of aluminium oxide blasted in a stream of air at the tooth. This removes decay and it is often possible to avoid the use of local anaesthetic. This process does not work for the removal of old fillings however when the drill must be used.

Amalgam is an alloy of mercury, silver, tin, etc used in restoring posterior (back) teeth. It is the most common filling material for back teeth, however, with advancing technology, posterior composites are becoming more feasible in many situations.

Amoxicillin is a derivative of penicillin and is often used to treat dental infections.

Anaesthesia is the blocking of the sensation of pain. This may be done locally with a local anaesthetic (LA) which is injected into the gum. Sedation and General Anaesthetic block the perception of pain by altering the conscious state, however for most procedures LA will still be used to decrease post procedural pain.

Antibiotics are used in dentistry to help treat severe or recurrent infections. see amoxycillin.

Apicectomy The amputation of the very tip of the root (apex) of a tooth followed by thorough cleaning and placement of a filling to seal the root. A flap is often raised and some bone may need to be cleared. This treats a chronic (long lasting) infection should root canal treatment not be successful. A suture is required to help the gum heal after this procedure.

Aspirator Dental tool used to suck up water and debris produced while caries or old fillings etc are removed from a tooth with the drill.
Autoclave A device in  which dental instruments are sterilized after use. This is part of cross infection control and prevents contamination between patients.

Attrition is the loss of tooth substance by wear due to mastication or contact between the occluding surfaces. See also abrasion and erosion.