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gag n. An instrument with jaws which are placed between a patient’s teeth to prise and hold the mouth open, particularly during the extraction of teeth during a general anaesthetic; they are most commonly used when a mouth prop is being changed from one side of the mouth to the other. The Ferguson gag has jaws in line with the handles and a single-handed ratchet to allow the insertion of a *mouth prop.

gag reflex (pharyngeal reflex) Normal reflex action caused by contraction of the pharyngeal muscles when the soft *palate or posterior region of the hard palate is touched or stimulated. It protects something from entering the oesophagus or trachea except as part of normal swallowing. It is used as a test for the integrity of the glossopharyngeal and vagus nerves. When excessive during dental procedures, it may need to be controlled by topical *analgesia, hypnosis, conscious *sedation, or acupuncture.

Further Reading: Packer M. E., Joarder C., Lall B. A. The use of relative analgesia in the prosthetic treatment of the ‘gagging’ patient. Dent Update 2005; 32(9):544–6, 548–50.

galactose n. A simple (*monosaccharide) sugar converted by *enzyme action to *glucose in the liver. It is a constituent of *lactose (milk sugar).

gallipot n. A small glazed receptacle used to contain ointments, solutions, or lotions.

galvanism [L. Galvani (1737–98), Italian physicist and physician] n. The production of an electric current when two dissimilar metals, such as *amalgam and *gold, are brought into contact with each other, usually with the *saliva acting as an *electrolyte; it can result in a sharp pain on initial contact.

Gamgee tissue [J. S. Gamgee (1828–86), English physician] n. A surgical dressing material consisting of a thick layer of absorbent cotton wool between two layers of absorbent gauze. It is also used as a throat pack.

ganglion n. (pl. ganglia) 1. (in anatomy) A knot or collection of nerve cells e.g. the trigeminal ganglion of the trigeminal nerve, the geniculate ganglion of the facial nerve, and the vestibular and cochlear ganglia of the vestibulocochlear nerve. There are four pairs of *parasympathetic ganglia in the head; these are the ciliary, pterygopalatine, submandibular, and otic ganglia. 2. An abnormal swelling on a tendon.

gangrene n. Death and decay of a tissue or part of the body due to deficiency or cessation of blood supply. The causes include disease, trauma, frostbite, severe burns, and blockage of major blood vessels. It may occur in the absence of infection (dry gangrene) or accompanied by putrefaction due to bacterial infection (wet gangrene), such as may occur in infected *pulp tissue.

Gardner’s syndrome [E. J. Gardner (1909–89), US physician] An inherited condition characterized by multiple *osteomas, *cysts, and multiple *polyps in the colon. Multiple *supernumerary teeth are often associated with this condition.

gargle 1. v. To rinse the upper part of the throat (fauces) with a fluid through which expired air is forced to create a bubbling effect while the head is tilted backwards. 2. n. A medicated solution used for gargling.

gastric insufflation The blowing of air into the stomach which can result from over-enthusiastic inflation of the lungs during emergency pulmonary ventilation.

gastric juice The digestive secretions in the stomach consisting mainly of hydrochloric acid, pepsinogen (converted to pepsin by the acid), rennin, and mucin. Reflux of the gastric juices into the mouth can result in *erosion of tooth enamel because of the high concentration of *hydrochloric acid. See GASTRO-OESOPHAGEAL REFLUX DISEASE.

gastritis n. Inflammation of the mucosal lining of the stomach. Acute gastritis is characterized by gastric pain, anorexia, nausea, and vomiting. Chronic gastritis is frequently a symptom of underlying disease.

gastrointestinal tract The digestive tract which extends from the mouth to the anus and is approximately 8.3 metres long; it includes the mouth, pharynx, oesophagus, stomach, duodenum, jejunum, ileum, caecum, colon, and rectum.

gastro-oesophageal reflux disease (GORD) A condition in which the gastric contents are regurgitated back up into the *oesophagus and sometimes into the mouth. The chronic condition can result in oesophageal ulceration because of the low pH of the *hydrochloric acid. It may occur because of intra-abdominal pressure, such as obesity and late pregnancy, but can also be related to lifestyle factors such as *smoking and high alcohol intake. If dental *erosion occurs, it is usually evident on the palatal surfaces of the upper teeth and on the *occlusal and sometimes *buccal surfaces of the lower teeth.

gate control theory States that pain is a function of the balance between the information travelling to the spinal cord through large nerve fibres, which do not carry painful stimuli, and information travelling to the spinal cord through small nerve fibres, which do. It was first postulated by Ronald Melzack (1929–), Canadian psychologist, and Patrick Wall (1925–2001), English anatomist, in 1962. If the relative amount of activity is greater in large nerve fibres, there should be little or no pain. However, if there is more activity in small nerve fibres, then there will be pain.

Gates–Glidden drill n. See DRILL.

gauge n. An instrument used to determine measurements of an object, such as the bore of a needle. A Willis bite gauge is used to measure the *vertical dimension during the construction of a *complete denture; two measuring points are selected in the midline of the face, one related to the nose and one to the chin.

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Willis bite gauge

An undercut gauge is a device attached to a dental cast *surveyor to measure the extent of the convexity of a tooth.

Further Reading: McCord J. F., Grant A. A. Registration: Stage II—intermaxillary relations. Br Dent J 2000;188;11:601–08.

gauze n. 1. Bleached cotton cloth of plain weave used for dressings, bandages, and intra-oral moisture control. 2. A thin silk, plastic, or metal woven mesh.

gel n. A colloidal jelly-like suspension. It is used as a vehicle for applying topical agents to the surfaces of the teeth, usually sodium or stannous fluoride in a glycerine base or chlorhexidine gel.

gelatin sponge n. An absorbable material inserted into a wound space to provide a structure to aid *blood clotting (haemostasis); it may be impregnated with an antiseptic or antibiotic. Trade name: Gelfoam®. See also CELLULOSE FOAM.

gemination (schizodontia) n. The partial development of two teeth from a single tooth bud following incomplete division; they appear clinically as double teeth. Unlike *fusion, the number of teeth in the arch is not reduced and there is a single root structure with an enlarged pulp canal. It most commonly affects the anterior teeth. See also CONNATION. Image

gene n. The basic unit of genetic material located at a specific site on a *chromosome.

general anaesthesia n. See ANAESTHESIA.

General Dental Council (GDC) The statutory body that controls the practice of dentistry in the UK. Its aim is the protection of the public by the registration of dental professionals, overseeing mandatory recertification and defining and monitoring educational training standards. It consists of a chairman elected by council, 12 lay members appointed by the Appointments Commission on behalf of the Privy Council, and 12 registered members, made up of 8 dentists and 4 dental care professionals.

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Image The General Dental Council website.

general dental practitioner (GDP) n. A person registered with a statutory authority (such as the *General Dental Council in the UK) to undertake the practice of *dentistry.

general dental services (GDS) A part of the National Health Service (NHS) dental service in the UK. The GDS was reformed in 2006 to become the nGDS in which all *general dental practitioners working within the NHS in England are required to enter into a service level agreement with a Primary Care Trust (Local Health Board in Wales and Scotland). Payment for the dental care provided is measured primarily in *units of dental activity (UDAs).

generalizability n. (in statistics) The application of general principles or conclusions to a specific instance. For example, if a statistical model generalizes it assumes that predictions from the model can be applied to a wider population from which the sample originally came.

General Medical Council (GMC) The statutory body that controls the practice of medicine in the UK.

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Image The General Medical Council website.

general medical practitioner (GMP) A person registered with a statutory authority (the *General Medical Council in the UK) to undertake the practice of medicine.

genial tubercle (mental spine) n. See TUBERCLE, GENIAL.

genion n. The tip of the mental protuberance; a *craniometric point.

genioplasty n. A surgical procedure designed to reshape the contour of the *chin, usually by reduction or extension by augmentation with grafted *bone, *cartilage, or artificial material.

genome n. The total genetic information of a particular organism. The normal human genome consists of 3 billion base pairs of *deoxyribonucleic acid (DNA) in each set of 23 *chromosomes from one parent.

genomics n. The study of *genomes (including their molecular characterization) and the production of their gene products (proteins), their role in health and disease, and the effects of manipulation of these systems by agents such as pharmaceuticals and radiation.

gentamycin n. An aminoglycoside *antibiotic used to treat a wide range of bacterial conditions such as infective bacterial *endocarditis. It acts by inhibiting bacterial protein synthesis. Trade names: Cidomycin, Genticin.

gentian violet (methyl violet) n. A rosaniline dye used in an aqueous solution as an *antiseptic in the treatment of minor lesions of the oral mucosa. It is a *fungicide and is effective in the treatment of *Candida albicans infections (thrush). It is the active ingredient in *Gram’s stain.

geographic tongue (benign migratory glossitis) n. See TONGUE, GEOGRAPHIC.

GERD n. See GASTRO-OESOPHAGEAL REFLUX DISEASE.

geriatric dentistry See GERODONTOLOGY.

German measles (rubella) A highly contagious viral disease. After an incubation period of 2–3 weeks, it is characterized by a widespread pink rash, *lymph node enlargement, sore throat, and a mild fever; there are flat red spots intra-orally. When rubella occurs in pregnant women it can result in severe malformations of the foetus.

germicide n. An agent capable of destroying micro-organisms, particularly those causing disease.

gerodontology (gerodontics) n. A specialized area of dentistry which deals with the *diagnosis, management, and treatment of dental conditions relating to the elderly. These include physiological and pathological age changes, disease and drug therapy, and the problems associated with the delivery of dental care. Dental conditions particularly relevant to the care of the elderly include root caries, tooth wear, and reduced adaptive capacity to the wearing of dentures. Oral health maintenance may be influenced by reduced manual dexterity and visual acuity. See also AGE CHANGE.

Further Reading: Milward M., Cooper P. Periodontal disease and the ageing patient. Dent Update 2005;32(10):598–600, 602–4.

ghost teeth See ODONTODYSPLASIA.

giant cell granuloma See GRANULOMA.

Gibson bandage [K. C. Gibson (1849–1925), US dentist] A bandage for stabilizing a fracture of the mandible.

Gillick competent A condition used in English law that defines a level of competence, demonstrated by a child under the age of 16 years, to *consent to treatment. Children under 16 can consent to treatment if they understand its nature, purpose, and hazards. That ability will vary with age, the child, and the nature of the treatment. To be able to consent, the child must understand the nature of the proposed treatment and fully understand and appreciate the consequences of the treatment, the alternatives, and the failure to treat. A dentist who judges the child to be ‘Gillick competent’ can disclose information to the parent only with the child’s consent, regardless of parental responsibility. The name is derived from the name of the claimant in the case that established the principle (Gillick, 1985). The term Fraser competent is also used as an alternative term, after Lord Fraser who was the judge who ruled on the case.

Gillies’ operation [Sir H. D. Gillies (1882–1960), New Zealand-born otolaryngologist] A technique for reducing fractures of the zygoma and the *zygomatic arch through an incision in the temporal region above the hairline. An elevator is passed blindly deep to the temporal fascia and the depressed bone.

Gillmore needle [Q. Gillmore (1825–1888), American engineer] A device which uses a penetration test to measure the difference between the initial and final setting time of dental cement. A ¼ pound needle is used for determining the initial set and a one pound needle is used for defining the final set.

Gilmer’s splint [T. L. Gilmer (1849–1931), American oral surgeon] The immobilization of a fractured mandible using wire intermaxillary fixation involving the mandibular and maxillary teeth.

gingiva n. (pl. gingivae) Connective tissue and overlying keratinized *mucosa that immediately surrounds the teeth. The attached gingiva forms a strong protective cuff around the necks of the teeth and is tightly adherent to the underlying *connective tissue. At the apical aspect of the attached gingiva is the muco-gingival junction which separates the attached gingiva from the loose and more flexible *alveolar mucosa. Its external *keratinized layer of stratified squamous epithelium provides protection during masticatory function; it is characterized by a pale pink appearance with stippling, due to the fibrous attachment of the *epithelium to the *periosteum which prevents gingival movement. The free gingiva is the unattached coronal portion of the gingival margin which encircles the tooth to create a *gingival crevice (sulcus). The marginal gingiva is the most coronal part of the free gingiva.

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Gingiva

The gingiva between the teeth (interproximal or interdental gingiva) fills the space between two contacting teeth to form the *gingival papilla. The gingival blood supply is largely from the underlying periosteum and *anastomoses with the blood vessels of the *periodontal membrane. gingival adj. Image

gingival abrasion n. See ABRASION.

gingival bleeding index A method of numerically recording the extent of gingival bleeding as a result of inflammation. Each tooth present is gently probed with a *periodontal probe at six sites (mesial, mid, and distal on both buccal and lingual surfaces): bleeding is scored as present or absent and the number of sites where bleeding is present is recorded. The number of sites where bleeding is recorded is divided by the total number of available sites in the mouth and multiplied by 100 to express the bleeding index as a percentage.

gingival cleft n. See CLEFT.

gingival crater n. A depression in the gingival papilla as a result of *necrosis of the tissue caused by necrotizing *gingivitis.

gingival crevice (sulcus) n. The space between the inner aspect of the free *gingiva and the tooth. It is normally 1–3mm in depth and deepest interproximally. The epithelium is non-keratinized. The gingiva is attached to the tooth at the base of the gingival crevice by the *junctional epithelium beneath which is a band of connective tissue/free gingival fibres. The gingival crevice produces a serum *exudate (gingival *crevicular fluid) which alters when disease is present.

gingival crevicular sulcus fluid n. See CREVICULAR FLUID.

gingival enlargement A swelling of the gingival tissues. There may be an increase in the size of the fibrous tissue cells (*hypertrophy) or an increase in their number (*hyperplasia). It can be drug induced e.g. by *phenytoin for the treatment of *epilepsy.

gingival fibres See PERIODONTAL FIBRES.

gingivalgia n. Pain in the gingival tissues.

gingival hyperplasia See HYPERPLASIA.

gingival index A method of recording the clinical severity of gingival inflammation. There are a large number of gingival indices used in current clinical practice: two commonly used gingival indices are modifications of the Loe and Silness Gingival Index, namely the Mandel–Chilton Gingival Index and the Modified Gingival Index. See also SULCUS BLEEDING INDEX.

Further Reading: Ciancio S. G. Current status of indices of gingivitis. J Clin Periodontol 1986;13:375–8.

Loe H., Silness J. Periodontal disease in pregnancy. I. Prevalence and severity. Acta Odontologica Scand 1963;21:533–51.

Loe H. The Gingival Index, the Plaque Index, and the Retention Index. J Periodontol 1967;38:610–16.

Marks R. G., Magnusson I., Taylor M., Clouser B., Maruniak J., Clark W. B. Evaluation of reliability and reproducibility of dental indices. J Clin Periodontol 1993;20:54–8.

gingival margin trimmer See MARGIN TRIMMER.

gingival overlay A removable resin overlay used to simulate lost gingival tissue and restore aesthetics, usually following gingival surgery on completion of healing. Image

gingival papilla A triangular extension of the free gingiva located interproximally between two contacting teeth. When viewed transversely, it resembles two peaks and a trough below the tooth contact area (interdental col). The structure of the gingival (interdental) papilla is dependent on the supporting alveolar bone and the integrity of the dental arch. Preservation of the papilla is important in aesthetic dentistry to avoid the appearance of a ‘black triangle’. Inflammatory *necrotizing gingival conditions can result in the formation of an interproximal gingival crater. Image

gingival pigmentation

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