Anaerobic Bacteria is the kind of bacteria, which can grow and develop in the environment, where there is either poor or no oxygen supply. As a rule these bacteria are associated with periodontal disease. 
Analgesia is the term, which is used to describe the loss of feeling of a pain without loss of consciousness.
Anatomical Crown is the part of the tooth, which is normally covered by, and including enamel.
Anesthesia is the name of a medication, which is applied to relieve the sensation of pain.
There are the following kinds of anesthesia: General Anesthesia, Non-Intravenous Conscious Sedation, Local or Regional Anesthesia, Intravenous Analgesia, each of them is described in accordance to their alphabetical order.
Ankylosis is the name of a condition, when there appear two hard tissues fused together. In case if this occurs with a tooth and the alveolar bone, the tooth gets erupted partially.
Anodontia is one of the teeth number abnormalities, which is generally known as Anodontia Vera. It is the condition, when there is either complete or partial missing of teeth. 
Anticulating Paper is the carbon paper. In the dentist office it is applied in order to be placed between the upper and lower teeth to mark contact.
Antimicrobial is something which can destroy or inhibit bacteria’s growth and development process.
Antiseptic is the kind of a chemical agent, which is applied to living tissues with the aim of destroying germs.
ANUG is the abbreviation for Acute Ulcerative Gingivitis, is a condition, also called a trench mouth or Vincent’s disease. This health condition is mostly aggravated by stress and smoking.
Apicoectomy is the process, as well as the result of a removal of the tip of a tooth root.
Artificial Crown is the process, as well as the result of the restoration covering or replacing the greater part, or the whole of the clinical crown of a tooth.
Assignment of Benefits is the name of the clause, listed in an insurance policy, with the help of which the insured person is able to direct the carrier’s payment to the dentist. Aspirator is how the tube – like straw, which the doctor places in the mouth for suction, called.
Asymmetry / Symmetry is the term, which is used to describe the difference / identity of teeth shapes, sizes and contour of the gums. In order to have an esthetic look, the size of the teeth, as well as their shape should be as close to identical form one side of the mouth to the other, as possible.
Attachment Level is called a numerical measure of the periodontal ligament to a tooth amount of attachment. This is considered one of the most important measures of periodontal disease progress to successful treatment. This number can usually be determined by combining the depth of a pocket measurement with those of gingival recession.
Attrition occurs, when the tooth structure gets worn away through such normal use as biting, chewing, etc.