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D32/33 award The qualification that used to be required in order to become a fully trained National Vocational Qualification (NVQ) assessor for trainee dental nurses. The D32/D33 was replaced in 2003 with the A1 and A2 qualifications.

Dakin’s solution [H. D. Dakin (1880–1952), American chemist] A dilute solution of *sodium hypochlorite and boric acid used as an *antiseptic.

Damon system See BRACKET.

dangerous drugs See MISUSE OF DRUGS ACT.

dappen dish (dappen glass) n. A small decagonal glass receptacle with a depression at both ends used to hold medicaments during operative procedures.

D’Arcet’s metal [J. D’Arcet (1727–1801), French physician] An alloy of tin lead and bismuth which was historically used as a restorative material in its fused state. It was abandoned because of the high working temperature at which the metal fused (212°F; 100°C), which caused pain and pulpal damage and the shrinkage from the cavity walls on cooling. The metal has also been used in the past as a low-fusing die material.

Darier’s disease [F.-J. Darier (1856–1938), French dermatologist] A rare genetic disorder of the skin characterized by a rash usually affecting the chest, neck, back, forehead, and groin. It may present with oral lesions consisting of coalescing white papules on the gingivae and palate.

dark zone An area of demineralized *enamel which is part of a carious lesion visible on ground sections of a tooth viewed under transmitted light. It lies between the outer intact layer and the deeper *translucent zone. Unlike the translucent zone, it represents an area of previous remineralization.

data pl. n. A collection of facts or organized information, usually the results of observation, experience, or experiment, or a set of premises from which conclusions may be drawn. Data may consist of numbers, words, or images.

Continuous data are observations made on a scale that has a natural zero and a well-defined unit of measurement, and can have an infinite number of values e.g. the weight of an individual. Interval data are measured on a scale of which the intervals are equal. Nominal data consist of observations classified into categories that are different in character and cannot be ordered e.g. blood types. Ordinal data consist of observations which have a common character and can be grouped into a limited number of categories that can be ordered in a series or rank e.g. a satisfaction survey. Ratio data are interval data that have an additional property in that the ratios are meaningful e.g. birth weight in kg. Statistical data are observations made on independent units or individuals.

Data Protection Act 1998 (in the UK) A British act of parliament that provides a legal basis for the privacy and protection of data of UK citizens and businesses. Users of data information are required to be registered. The act requires that personal data must be processed fairly and lawfully, for specific declared purposes, and in accordance with the rights of data subjects. It also states that data should not be transferred outside the European Economic Area without adequate protection. Patients who make a written application to see their medical or dental records must be provided with a copy within 40 days, together with an explanation of the content if they so wish and can demand to have inaccurate or misleading information amended. Disclosure of dental records to a third party can be resisted where there are grounds to believe that disclosure might be detrimental to the physical or mental health of the patient.

day-patient A person who is admitted to hospital for treatment, examination, or observation but who does not remain there overnight. Compare IN-PATIENT; OUT-PATIENT.

dead space volume 1. (anatomical) The amount of inspired air that occupies the airway passages and where no gaseous exchange takes place. 2. (physiological) The space relating to a reduction in the area for ventilation or perfusion.

dead tract n. An area of empty *dentinal tubules beneath a *carious lesion where the *odontoblasts have died and not laid down sclerotic dentine.

Dean, Trendley (1893–1962) An American dentist and epidemiologist who researched the effects of water fluoridation on tooth enamel. In 1931 he conducted a major research study for the National Institutes of Health (NIH) which demonstrated the link between a lower incidence of caries and water fluoridation. He created the Dean Index of *fluorosis classification.

debilitate v. To make feeble, to weaken.

debonding n. 1. The process by which orthodontic *brackets and associated *bonding resin are removed from the enamel surface of a tooth and the tooth is restored to its original condition. 2. The failure of the micromechanical bond between a resin restorative material and the enamel or dentine surface.

debridement n. (v. debride) 1. The removal of foreign or dead material from a wound to aid the healing process. 2. The removal of deposits on a tooth surface; root debridement (the removal of deposits on the root surface) should be contrasted with *root planing (the removal of deposits and the surface layer of cementum containing bacterial toxins).

decalcification n. The loss of *calcium or calcium salts from mineralized tissue such as enamel, dentine, or *bone.

decay n. See CARIES.

deciduous teeth The teeth constituting the first dentition. See PRIMARY DENTITION.

Declaration of Geneva The medical code of ethics first adopted in 1948 by the 2nd World Assembly of the World Medical Association in Geneva, Switzerland. It calls upon doctors and dentists not to allow considerations of age, disease, or disability, creed, ethnic origin, gender, nationality, political affiliation, race, sexual orientation, or social standing to influence their approach to patient care. It has replaced the Hippocratic oath.

decontamination n. A process or treatment that renders a medical device, instrument, or environmental surface safe to handle. It encompasses both cleaning and sterilization. The UK Department of Health document HTM 01–05 defines essential and best practice standards of care for instrument decontamination.

Further Reading: Decontamination Health Technical Memorandum 01-01 Department of Health 2008, available at www.dh.gov.uk/en/Publications
andstatistics/Publications/Publications
PolicyAndGuidance/DH_089245

decoronation n. The removal of the crown of a tooth.

decussation n. The crossing over of fibres from one side of the central nervous system to the other e.g. the decussation of the pyramids.

DEF (decayed, extracted, filled) index A dental *caries index applied to the primary dentition similar to the *DMF index used for the permanent dentition. See also DMF INDEX.

Defence Dental Service (in the UK) A tri-service organization which provides dental services to the Armed Forces through Royal Navy, Army, and Royal Air Force personnel and civilians to contribute to the operational effectiveness of the armed forces by achieving and maintaining, in the most cost-effective way, the dental fitness of its personnel stationed throughout the world. It also provides facilities for dental hygiene, therapy, and technology training.

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Image The Defence Dental Services web site.

defibrillation n. The use of an electric shock to stop the rapid uncoordinated fibrillating movements of the heart and restore a normal rhythm. Defibrillation depolarizes most or all of the heart muscle simultaneously, allowing the natural pacemaking tissues to take over normal control of the heart. Defibrillation within 5 minutes of collapse gives the best possible outcome. The electrical impulse is provided by a defibrillator. Defibrillators have a power source which provides a direct current and a capacitor which is charged to a predetermined level and then discharged through two electrodes placed on the patient’s chest. An automated external defibrillator (AED) is a type of defibrillator which detects the electrical activity in the heart and gives the rescuer automated instructions on what to do. The use of a defibrillator is part of *advanced life support.

degassing n. The process of removing unwanted gases trapped in a metal casting to improve the quality of the casting.

degloving n. The removal of an area of skin or mucous membrane to expose the underlying tissues. It may occur in response to trauma or by intentional surgery.

deglutition n. The process of swallowing by which food is transferred from the mouth to the *oesophagus. Food is forced backwards by voluntary movement of the *tongue followed by a reflex raising of the *soft palate to close the nasal passages and closure of the *larynx by the *epiglottis to prevent food entering the *trachea. Food enters the oesophagus and moves down towards the stomach by gravity and the muscular action of *peristalsis.

degrees of freedom A statistical term used to describe the number of values in the final calculation of a statistic that are free to vary. It is the number of categories or classes being tested minus 1.

dehiscence n. A defect shaped in the form of a fissure. It can occur as a cleft-like defect in the cortical bone of the jaw exposing the tooth root, particularly in the anterior region.

dehydration n. A loss or deficiency of water in the body or from tissues. Gingival dehydration can be the result of *mouth breathing and render the gingival tissues susceptible to *inflammation or infection.

dementia n. A *chronic or persistent disorder of behaviour due to organic brain disease. It is characterized by a decrease in intellectual function with changes in personality, mood, and behaviour. Presenile dementia occurs in young or middle-aged people. A common form of dementia is *Alzheimer’s disease.

demi- Prefix denoting half.

demineralization n. A loss or removal of mineral salts from the tissues of the body. It occurs in *dentine and *enamel as part of the *carious process. Enamel starts to demineralize when the *plaque or saliva *pH drops below 5.5. See also STEPHAN’S CURVE.

demography n. The statistical study of human populations on a national, regional, or local basis, especially with reference to size and density, distribution, and vital statistics. It is used in dentistry to identify oral health needs and *risk factors for a given population.

demulcent n. A substance that protects the mucous membranes and relieves irritation. Demulcents form a protective film and are used in *mouthwashes to reduce irritation or inflammation in the mouth. *Gum tragacanth or milk can act as demulcents.

dendrite n. A branching process of a neuron that receives incoming messages from other nerve cells and transmits impulses to the body of the neuron.

dense bone island (idiopathic osteosclerosis) A localized area of *sclerotic bone occuring in the premolar or molar regions of the mandible. The cause is unknown.

dens evaginatus n. A developmental anomaly characterized by the occurrence of an extra cusp shaped as a tubercle projecting from the palatal or buccal surfaces (*talon cusp) of a tooth. In the anterior dentition, dens evaginatus is more commonly found on the palatal surface of the maxillary teeth. They are easily fractured exposing the pulp.

dens in dente (dens invaginatus) n. A developmental malformation of the teeth in which there is an invagination of the enamel giving the radiographic appearance of a ‘tooth within a tooth’. It can be caused by the prolific growth of the *ameloblast and *odontoblast cell layers during tooth formation. It most commonly occurs on the palatal surface of permanent maxillary lateral incisors and presents as a blind channel opening on the *cingulum pit which is susceptible to caries. They may be described according to the extent of the invagination (Oehlers’ classification, as described by F. A. Oehlers in 1957): type 1 is an enamel-lined invagination occurring within the confines of the crown of the tooth, not extending beyond the *cemento-enamel junction; type 2 is an enamel-lined blind sac which invades the root and which may or may not connect with the dental pulp; type 3 is an invagination which penetrates through the root, perforating the apical area and forming a second foramen but with no immediate connection with the pulp. See also ODONTOMA.

Further Reading: Vaidyanathan M., Whatling R., Fearne J. M. An overview of the dens invaginatus with case examples. Dent Update 2008;35:655–63.

dent- (denti-, dento-) Prefix denoting the teeth e.g. dentoalveolar (relating to the teeth and supporting structures).

dental adj. Relating to the teeth.

Dental Access Centre A part of the UK primary dental care services within the *National Health Service which provide emergency care and occasional care to patients who are not registered with a dentist.

dental anxiety n. See ANXIETY.

dental anxiety scale A method of assessing the anxiety of an individual developed by Norman L. Corah, an American behavioural scientist, in 1969. The scale consists of four questions about different dental situations. Each question is scored from 1 (not anxious) to 5 (extremely anxious) so the range of possible scores is 4 to 20. Scores of 15 or more indicate profound anxiety. See also MODIFIED DENTAL ANXIETY SCALE.

Further Reading: Corah n. H. Development of a dental anxiety scale J Dent Res 1969;48:596.

Dental Auxiliaries Committee (in the UK) A committee of the *General Dental Council which deals with professional and disciplinary issues relating to *dental care professionals.

Dental Auxiliaries Regulations 1986 (in the UK) Regulations which provide for the enrolment and regulation of dental hygienists and dental therapists. These regulations were amended by statutory instrument in 2002. The amendments extend the work permitted to be carried out by dental hygienists to include removal of excess cement, taking impressions, administration of inferior dental nerve block anaesthesia, and replacing crowns which have been dislodged with a temporary cement. They are also permitted to carry out dental work on a patient under local or regional block anaesthesia administered by a registered dentist, or, provided there is a registered dentist in the room in which the dental work is carried out throughout the procedure, under conscious sedation.

dental care professional (DCP) A classification of healthcare professional in the UK, formerly known as professionals complementary to dentistry, which includes dental nurses, dental hygienists, dental therapists, dental technicians, clinical dental technicians, and orthodontic therapists.

dental chair unit (DCU) A complex medical device designed to provide the equipment and services necessary for the provision of a wide variety of dental procedures. It can include electric and air turbine handpieces, aspiration devices, and suction hoses. Because DCUs are used in the treatment of many patients during normal clinical activity, microbial contamination of specific component parts is an important potential source of *cross-infection and cross-contamination.

Dental Complaints Service (DCS) A mechanism run under the auspices of the *General Dental Council (GDC) in the UK to help dental patients resolve complaints about private dental care provided by a dentist or *dental care professional. It operates independently of, but is funded by, the GDC. If the staff of the DCS fail to achieve a satisfactory resolution, a local dental complaints panel may be set up which will make a recommendation. The panel consists of two lay members (chair and panellist) and a dental practitioner.

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Image The website of the Dental Complaints Service.

dental dam (rubber dam) A thin sheet of rubber which is pierced by a dental dam punch to allow the crowns of one or more teeth to protrude through and provide improved moisture control, operator visibility, airway protection, patient comfort, and infection control. It is manufactured in different thicknesses, colours, and sizes (usually 6-inch square), and may be made of latex or non-latex materials. It is normally supported by a dental dam frame and retained on the teeth by dental dam *clamps, floss, or rubber (latex or latex-free) strips. Dental dam clamp forceps, the tips of which engage in holes on the clamp, are used to place the clamp on the tooth and subsequently to remove it.

dental floss n. See FLOSS.

dental follicle n. A fibrous capsule which surrounds the *enamel organ during *tooth germ development. It eventually becomes the *periodontal ligament.

dental formula A method of describing the number and arrangement of teeth in man and animals using letters and figures. It is written as an expression of the number of each type of tooth in one side of the upper jaw over the number of teeth in one side of the lower jaw. The letters correspond to the type of teeth (I = Incisor, C = Canine, P = Premolar, M = Molar). Humans have two dental formulae, one for the primary dentition and one for the permanent dentition. The dental formulae for different animals varies according to diet and function.

Dental formulae of humans and some animals

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dental health education See ORAL HEALTH EDUCATION.

dental health promotion See ORAL HEALTH PROMOTION.

dental hygienist A dental care professional statutorily registered in the UK with the *General Dental Council and working to the written prescription of a registered dentist. Their primary clinical remit is the prevention and treatment of *periodontal disease and dental caries by scaling and polishing teeth, applying prophylactic and antibacterial materials, *topical fluoride, and *fissure sealants, and delivering oral health advice. The clinical remit was extended in the UK following legislative changes in 2002, to include taking *impressions, administering inferior dental block *analgesia, temporarily cementing dislodged *crowns, and treating patients under *conscious sedation; these changes are subject to appropriate training. The clinical remit varies in different countries.

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Image The British Society of Dental Hygiene and Therapy website; it provides information on the current clinical remit of dental hygienists and therapists.

dental index See FLOWER’S DENTAL INDEX.

dental laboratory A location within or external to a dental practice or clinic where custom-made dental *appliances are fabricated which in the UK are manufactured to meet the requirements of the *Medical Devices Directive.

dental lamina n. A band of *epithelial tissue which connects the developing *tooth bud (*enamel organ) to the *oral epithelium. The dental lamina eventually disintegrates into small clusters of epithelium and is resorbed.

dental nurse A dental care professional who has received appropriate training to provide chairside assistance for the dentist which includes *aspiration, the preparation of materials, and the passing of instruments. As from July 2008, all dental nurses in the UK who have completed their professional training must be statutorily registered with the *General Dental Council. Dental nurses in the UK may undertake additional post-certification training in dental sedation, special care nursing, oral health, orthodontics, and radiology assessed by the *National Examining Board for Dental Nurses (NEBDN).

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Image The British Association of Dental Nurses website.

Dental Nurse Standards and Training Advisory Board (DNSTAB) A General Dental Council advisory body with representatives from dental nursing organizations such as the British Association of Dental Nurses and the National Examining Board for Dental Nurses. This body ceased to exist following the statutory registration of dental nurses in 2008.

dental panoramic tomogram (DPT) n. A tomogram or slice through the jaws which displays all the teeth and supporting structures on one film. Only structures within the focal trough will be visualized. The focal trough for a DPT is usually horseshoe-shaped. The image quality is always inferior to that of intra-oral films, and radiographic interpretation needs to take into account tomographic blur and ghost shadows produced by anatomical structures. Formerly known as an orthopantomogram. Image

dental papilla See PAPILLA.

Dental Practice Board See BUSINESS SERVICES AUTHORITY.

dental practice manager A person responsible for the administration of a clinic or practice. The Dental Practice Managers Association (DPMA) is an organization founded in the UK in 1993 to promote the training, career structure, and interests of those who are managing dental practices or clinics.

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Image The British Dental Practice Managers Association website.

dental public health The non-clinical specialty of preventing and controlling dental diseases and *oral health promotion, delivered to a target population or a community, on a regional or national basis rather than on an individual patient basis. It involves the *epidemiology of the causes and distribution of oral disease and the assessment of dental health needs and ensuring dental services meet those needs. It is also known as public health dentistry.

dental pulp See PULP.

dental record See CLINICAL RECORD.

Dental Reference Service (DRS) A part of the National Health Service which employs a team of experienced and calibrated dentists (dental reference officers) to monitor and advise on quality within the *General and *Personal Dental Services.

Dental Register A list of all dental professionals registered with the *General Dental Council in the UK, who are thereby legally permitted to practise as a dentist, specialist, or a *dental care professional.

dental tape See TAPE, DENTAL.

dental technician A dental care professional who makes custom-made dental appliances including *dentures, *crowns, *bridges, *implants, and *orthodontic appliances. As from July 2008 all dental technicians in the UK must be registered with the *General Dental Council. Clinical dental technicians form a new class of dental care professional in the UK and are qualified dental technicians who have received additional training to develop their clinical skills; they are able to provide clinically a range of removeable complete and partial dentures without prior review by a dentist.

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Image The British Dental Technicians Association website.

Image The British Clinical Dental Technicians Association website.

dental therapist See THERAPIST, DENTAL.

dental unit water lines (DUWLs) Part of a *dental chair unit (DCU) used to provide water to cool and irrigate a variety of DCU-supplied instruments (i.e. turbine and conventional handpieces, ultrasonic scalers, and three-in-one air/water syringes), and tooth surfaces during dental procedures, as the heat generated during instrument operation can be harmful to teeth. DUWLs also supply water used by patients for oral rinsing during and following dental procedures and to rinse the DCU *cuspidor after oral rinsing. Water supplied by DUWLs is frequently contaminated with high densities of micro-organisms, especially bacterial species, due to the formation of *biofilm on the internal surfaces of the waterlines. The waterline network in a DCU consists of several meters of narrow-bore (i.e. a few mm) plastic tubing in which water stagnates when the DCU is not being used. Micro-organisms, in the DCU supply water, attach to the internal surfaces and form microcolonies that eventually give rise to multi-species biofilm. Water at the internal surface of DUWLs flows more slowly than water at the centre and thus there is little disturbance to any micro-organisms present. This allows the micro-organisms to multiply and disperse throughout the waterline network as planktonic forms. Micro-organisms from DUWLs can be transferred directly into the mouths of patients during dental procedures and can be aerosolized during the operation of high-speed handpieces and ultrasonic scalers. The most common micro-organisms recovered from DUWL output water are aerobic heterotrophic Gram-negative environmental bacterial species, although pathogenic organisms such as Pseudomonas aeruginosa, Legionella pneumophila, and non-tuberculosis Mycobacterium species can also be present. The presence of high densities of micro-organisms in DUWL output water provides a potential risk of infection of dental patients and healthcare staff and is contrary to good *cross-infection control and prevention practices. Exposure to bacterial *endotoxin in DUWL output water poses additional potential adverse health effects. Biofilm in DUWLs can be effectively controlled by regular disinfection with disinfectants or biocides that effectively remove biofilm. A wide range of such agents are available commercially but only some have been shown to be effective in long-term studies.

Further Reading: Coleman D. C., O’Donnell M. J., Shore A. C., Swan J., Russell, R. J. The role of manufacturers in reducing biofilms in dental unit waterlines. Journal of Dentistry 2007;35:701–11.

Pankhurst C. L., Coulter W. A. Do contaminated dental unit waterlines pose a risk of infection? Journal of Dentistry 2007;35:712–20.

Walker J. T., Marsh P. D. Microbial biofilm formation in DUWS and their control using disinfectants. Journal of Dentistry 2007;35:721–30.

dentate adj. Describing the condition of having teeth. Compare EDENTULOUS.

dentia praecox Premature tooth eruption.

denticle n. 1. A small tooth or tooth-like projection. 2. A calcified mass found in the pulp chamber of a tooth also known as an endolith or pulp stone. It may be composed of irregular *dentine (true denticle)or an ectopic calcification of pulp tissue (false denticle).

denticulate adj. Finely toothed, serrated, or notched.

dentifrice n. A paste (*toothpaste), powder, or liquid used in conjunction with a *toothbrush to clean teeth and to act as a vehicle for bringing therapeutic agents into contact with the teeth. The constituents of a dentifrice relate to their function. See also FLUORIDE TOOTHPASTE, BLEACHING.

The main constituents of a dentifrice and their functions

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Further Reading: Netuveli G. S., Sheiham A. A systematic review of the effectiveness of anticalculus dentifrices. Oral Health Prev Dent 2004;2(1):49–58.

dentigerous adj. Containing or bearing teeth. Dentigerous cyst See CYST.

dentine (dentin)

n. The mineralized organic tissue that makes up the bulk of the tooth surrounding the *pulp, covered on the root surface by *cementum and on the crown surface by *enamel. It is pale yellow in colour and is harder than bone but not as hard as enamel or cementum. Dentine is 70% inorganic by weight consisting mainly of *calcium hydroxyapatite [Ca10(PO4)6(OH)2] and 20% organic by weight consisting mainly of *collagen. The remaining 10% is water. Dentine is made up of many fine parallel *tubules (dentinal tubules) extending from the pulpal surface to the *amelodentinal junction. Each tubule contains an *odontoblast cell lying in a layer on the pulpal surface with the nucleus situated at the pulpal end of each cell. Each odontoblast cell has a process extending along the tubule and is surrounded by intercellular ground substance. Dentine may be divided into intertubular dentine and peritubular dentine.

Intertubular dentine is the main product of the odontoblasts constituting the largest volume of the dentine; it consists of a fibrous network of collagen with deposited mineral crystals. The peritubular (intratubular) dentine forms a highly mineralized sheath about 0.5–1.0μ thick around the dentinal tubule consisting mainly of crystals of carbonated apatite together with a small amount of collagen. The peritubular dentine is sensitive to various external stimuli although sensitivity is not uniform in either teeth or individuals. See DENTINE HYPERSENSITIVITY. Dentine formation (*dentinogenesis) begins at about the 14th week of intrauterine life (late *bell stage) when the *inner enamel epithelium induces cells at the periphery of the *dental papilla to differentiate into dentine-forming columnar odontoblast cells. These cells secrete an unmineralized dentine matrix (predentine

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