BASIC STRUCTURE AND FUNCTION OF ORAL AND DENTAL ANATOMY Flashcards

1
Q

FUNCTIONS OF THE TEETH:

A
  • to cut up and masticate food into suitably sized portions before swallowing
  • to expose the food structures to enzymes and allow digestion to begin
  • to support the oral soft tissues of the cheeks and tongue, and therefore enable clear speech
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2
Q

ENAMEL

A

this is a highly calcified, protective outer covering of the crown and is the hardest substance in the body.

  • made up of 96% mineral crystals (inorganic) arranged as psims in an organic matrix called the INTERPRISMATIC SUBSTANCE
  • the main mineral crystals are CALCIUM HYDROXYAPATITE
  • the prisms lie at right angles to the junction with the next tooth layer, the DENTINE
  • the junction between these two layers is called the AMELODENTINAL JUNCTION (ADJ)
  • enamel is formed before tooth eruption by the ameloblast cells, which lie at the ADJ7
  • it contains no nerves or blood vessels and therefore cannot experience any sensation
  • it is a non-living tissue that cannot gwoe and repair itself, so progressive damage caused by injury or tooth decay is permanent
  • it can, however, remineralise its surface after an acid attack, by taking in minerals from saliva and from oral health products such as toothpaste and mouthwash
  • the crystal structure can also be altered without undergoing acid attack, by the exchange og hydrpxyl ions in the hydroxyapatite with FLUORIDE, to form FLUORAPATITE CRYSTALS - these make the enamel surface harder and more resistant to acid attack
  • the enamel layer is the thickest over the biting surface of the tooth and thinnest at the neck of the tooth - the cervical margin
  • it is translucent in appearance, so the shade of a tooth is determined by the colour of the underlying dentine
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3
Q

DENTINE:

A

this tissue forms the main bulk of a tooth and occupie the interior of the crown and root. it is also mineralised, but to a lesser extent than enamel, and is covered by enamel in the crown of the tooth and by cementum in the root of the tooth.

  • it consists of up to 80% inorganic tissue, mainly CALCIUM HYDROXYAPATITE crystals
  • it is composed of HOLLOW TUBES that originally surrounded the cells within the dentine structure as it was first being formed
  • in a fully formed tooth, these ODONTOBLAST cells lie along the inner edge of the pulp chamber only, but are present throughout life and can lay down more xentine as required
  • in this way, it can repair itself by laying down secondary dentine
  • this type of dentine is also formed as part of the natural ageing process, and its formation gradually narrows the pulp chamber
  • the hollow tubes contain sensory nerve endings called FIBRILS, which run from the nerve tissue within the pulp chamber
  • dentine is therefore a living tissue and can transmit sensations of pain and thermal changes to the brain
  • its hollow structure allows it a degree of elasticity do that it can absorb normal chewing forces without breaking
  • however, it also allows tooth decay (CARIES) to spread more raapidly through its hollow structure
  • dentine is a yellowish colour, and gives teeth their individual shade
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4
Q

CEMENTUM

A

this is the calcified protective outer covering of the root and is similar in structure to bone. cementum meets enamel at the neck of the tooth, and normally lies beneath the gingivae.

  • around 65% mineralised, with calcium hyrdroxyapitite cyrstals
  • the crystals lie within a matrix of fibrous tissue, with the ends of colagen fibres from the periodontal ligament inserted into the outer layer of the cementum
  • this allows the attachment of the root to the periodontal ligament inserted into the outer layer of the cementum
  • the cementum is formed by cells called CEMENTOBLASTS and they can continue laying down more tissue layers when required
  • the thickness of cementum may vary at different parts of the root, and changes throughout life, depending on the forces exerted on individual teeth
  • the cementum contains no nerves or blood vessels itself, so it recieves nutrients from the periodontal ligament
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5
Q

PULP

A

unlike enamel, dentine and cementum, the pulp contains no mineral crystals and is composed purely of soft tissue. it lies within the very centre of every tooth, from the crown as the coronal pulp and into each root as the radicular pulp. the radicular pulp is often referred to as the “root canal” of the tooth.

  • the pulp contains sensory nerves and blood vessels
  • the sensory nerves are end sections of the trigeminal nerve (fifth cranial nerve), either as the inferior dental nerve for the lower teeth or one of the superior dental nerves for the upper teeth
  • they allow the tooth to feel hot, cold, touch and pain by the stimulation of its sensory nerve endings which run as fibrils in the hollow dentine tubules
  • these pulp tissues enter the tooth through the APICAL FORAMEN, lying at the root apex of every tooth
  • the pulp chamber is lined by the odontoblast cells which form dentine
  • the chamber gradually narrows with age, so that it can become completely obliterated in older patients, making endodontic treatment very difficult
  • it can become blocked by PULP STONES which are formed by lumps of calcium-containing crystals
  • the point where the cementum and the root dentine are in contact with each other is called the DENTINOCEMENTAL JUNCTION
  • some teeth have additional contact between the pulp and the surrounding periodontal ligament via accessory canals, the presence of which can make successful endodontic treatment of the tooth very difficult to achieve
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6
Q

HOW MANY TEETH ARE IN THE PRIMARY DENTITION?

A

20 teeth

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7
Q

HOW MANY TEETH ARE IN THE SECONDARY DENTITION?

A

32

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8
Q

WHAT IS - ALVEOLAR BONE?

A

specialised ridge of bone over the bony arch of each jaw, where the teeth sit in their sockets

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9
Q

WHAT IS - GINGIVA?

A

specialised soft tissue covering of the alveolar processes, which are also in attachment with the teeth at their necks

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10
Q

WHAT IS - PERIODONTAL LIGAMENT?

A

connective tissue attachment between the tooth and the alveolar bone

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11
Q

WHAT IS - CEMENTUM?

A

hard tissue covering of the root that anchors the periodontal ligament to the tooth

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12
Q

ALVEOLAR BONE IN-DEPTH

A

it is here that the teeth form during the growth of the foetus and later the child, and from where they erupt into the mouth at various ages

  • it is a specialised bone found only in the jaws
  • its outer layer is made of, COMPACT BONE, the outer surface of which is called the LAMINA DURA
  • the inner layer is called CANCELLOUS BONE and is sponge-like appearance, to allow the passage of the various nerves and blood vessels that supply the jaws, teeth and surrounding oral soft tissues
  • the sole purpose of the avelor bone is to support the teeth, and it is gradually lost whem a tooth is extracted as the bone slowly resorbs away
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13
Q

GINGIVA IN-DEPTH

A

this is the correct anatomical term for the gums, it is a continous layer of specialised epethelium found only in the oral cavity and which is firmly attached to the underlying alveolar bone as a MUCOPERIOSTEAL LAYER of tissue. this layer is raised as a flap during oral surgical procedures, to expose the bone below

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14
Q

THE THREE DISTINCT AREAS OF GINGIVAL COVERAGE:

A
  • ATTACHED GINGIVA - that covering the majority of the alveolar process, which is firmly attached to the underlying bone as the MUCOPERIOSTEUM
  • MARGINAL GINGIVA - that forming the gingival margin of the teeth, which is free from the underlying bone and follows the shape of each tooth in the arch, as well as extending between the teeth in the contact areas; the level at which these two areas meet is called the FREE GINGIVAL GROOVE
  • JUNCTIONAL TISSUES - the specialised gingival tissue lying within the gingival crevice and forming the anatomical junction between the teeth and the oral epithelium; this point is called the JUNCTIONAL EPITHELIUM
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15
Q

THE PROPERTIES OF THE GINGIVA ARE:

A
  • when healthy, the gingivae fit around the neck of every tooth like a tight cuff
  • the GINGIVAL CREVICE exists as a shallow space of less than 3mm between the tooth surface and the gingival margin, and contains the junctional epithelium
  • a natural mound of gingival tissue occurs between each tooth and is called the INTERDENTAL PAPILLA
  • in health, the ginigivae are pink in colour with a stippled surface, like orange peel
  • inflammation of the gingivae is called GINGIVITIS; it affects the marginal gingivae and occurs in the presence of DENTAL PLAQUE due to poor oeal hygiene control
  • gingivitis appears as red and shiny gingivae that are swollen due to their inflammation and that bleed easily on touching
  • the swollen appearance of the inflamed gingivae presents as “false pockets” when probed, giving the impression that the gingival crevice is depper than 3mm
  • the gingiva can also be stimulated to overgrow and become HYPERPLASTIC as side-effect of various drugs being taken by the patient, including some antihypertensives and some drugs used to control epilepsy
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16
Q

PERIODONTAL LIGAMENT:

A

is a specialised fibrous tissue that attaches the teeth to the alveolar bone and the surrounding gingivae. it acts as a shock absorber to the teeth during chewing and its main fibres run between the alveolar bone and the cementum covering the root of the tooth. other fibres run between the necks of the teeth, and from the cementum into the surrounding gingivae.

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17
Q

THE VARIOUS PERIODONTAL LIGAMENT FIBRE GROUPS:

A
  • Alveolar crest fibres
  • Horizontal fibres
  • Oblique fibres
  • Apical fibres
  • Transeptal fibres
  • Free gingival fibres
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18
Q

FUNCTION OF ALVEOLAR CREST FIBRES:

A

run from the alveolar bone crest to the cementum at the neck of the tooth; they prevent tooth movements in and out of the socket, as well as resisting tilting and rotation

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19
Q

FUNCTION OF HORIZONTAL FIBRES:

A

run horizontally from the alveolar bone to the cementum, just below the crest fibres; they resist tilting and rotation of the tooth

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20
Q

FUNCTION OF OBLIQUE FIBRES:

A

run at an angle from the alveolar bone down to the cementum; they prevent intrusion and rotation of the tooth

21
Q

FUNCTION OF APICAL FIBRES:

A

occur at the root apex and run between the bone and cementum; they prevent extrusion and rotation of the tooth

22
Q

FUNCTION OF TRANSEPTAL FIBRES:

A

run between the cementum of adjacent teeth through the interdental region; they maintain the gingival attachments between the teeth and therefore their position in the dental arch

23
Q

FUNCTION OF FREE GINGIVAL FIBRES:

A

run from the cervical cementum into the gingival papillae; they maintain the gingival cuff around each tooth

24
Q

THE PROPERTIES OF THE PERIODONTAL LIGAMENT:

A
  • its fibres are made up of a protein called COLLAGEN
  • they run in various directions, the end result being that the teeth are held in their sockets but can ‘bounce’ under normal chewing forces - this prevents tooth fracture and pain during normal occlusal loading and chewing actions
  • when excessive occlusal forces are applied, the resultant pain experienced by the patient tends to stop further overuse from occuring
  • the ligament has a sensory nerve supply which transmits pressure, pain, touch and temperature changes - the ability of the tooth to detect and transmit these sensation is called PROPRIOCEPTION
  • inflammation of the ligament is called PERIODONTITIS and occurs during periodontal disease
25
Q

THE THREE PAIRS OF MAJOR SALIVARY GLANDS:

A
  • PAROTID SALIVARY GLANDS
  • SUBMANDIBULAR SALIVARY GLANDS
  • SUBLINGUAL SALIVARY GLANDS
26
Q

PAROTID SALIVARY GLANDS -

A

located between the ramus of the mandible and the ear, and deep to the muscles in that area

27
Q

SUBMANDIBULAR SALIVARY GLANDS -

A

located in the posterior area of the floor of the mouth, beneath the mylohyoid muscle

28
Q

SUBLINGUAL SALIVARY GLANDS -

A

located in the anterior area of the floor of the mouth, above the mylohyoid muscle

29
Q

THE FUNCTION OF ALL SALIVARY GLANDS:

A

to produce the secretion SALIVA, which is deposited from the glands into the oral cavity only. the saliva is transported to the oral cavity through tube-like structures called ducts, so the salivary glands are classed as EXOCRINE GLANDS

30
Q

ENDOCRINE GLANDS -

A

their secretions pass directly into the adjacent blood vessels and are transported to their area of action by the circulatory system. examples are certain glands within the pancreas, the stomach, the liver and the adrenal glands, which lie over the kidneys

31
Q

BOTH EXO AND ENDOCRINE GLANDS HAVE THEIR SECRETIONS CONTROLLED BY WHAT?

A

the effects of motor nerve transmissions, via the autonomic nervous system

32
Q

PAROTID GLAND:

A

the parotid gland lies partly over the outside and partly behind the ramus of the mandible, in front of the ear. it is the largest of the three major salivary glands and the only one to be affected by the viral infection MUMPS, which is caused by a paramyxovirus.
the tube connecting the gland to the oral cavity, the STENSON DUCT, passes forwards across the surface of the masseter muscle and then inwards through the cheek to open into the buccal sulcus opposite the upper second molar. the parotid gland is innervated by the glossopharyngeal nerve and is the commonest salivary gland to be associated with both benign and malignant tumours

33
Q

SUBMANDIBULAR GLANDS:

A

the submandibular gland lies in the posterior region of the floor of the mouth below the mylohyoid line, against the inner and lower surface of the body of the mandible and near the angle. the submandibular duct passes forward in the floor of the mouth to pen at the midline, beside the lingual frenum. it is the longest of the salivary ducts and the most likely to become blocked by salivary stones. the submandibular gland is innervated by the facial nerve

34
Q

SUBLINGUAL GLAND:

A

the sublingual gland also lies in the floor of the mouth, but above the mylohyoid line and much further forward than the submandibular gland. there are several sublingual ducts, and these open into the floor of the mouth just behind the orifice of the submandibular duct. the sublingual gland is also innervated by the facial nerve

35
Q

FUNCTIONS OF SALIVA - MINERALS (sodium, calcium, pottasium and their electrolytes FUNCTIONS OF SALIVA - MINERALS (sodium, calcium, pottasium and their electrolytes such as phosphatesuch as phosphates

A
  • Neutralise dietary acids
  • buffering to maintain stable pH in the oral cavity
  • Also allow mineralisation of plaque to form supergingival calculus
36
Q

FUNCTIONS OF SALIVA - SALIVARY AMYLASE

A
  • Digestive enzyme that begins starch digestion, before food is swallowed
  • also called ptyalin
37
Q

FUNCTIONS OF SALIVA - ANTIBODIES

A
  • immunoglobulins present to fight infections, such as periodontal disease
  • promotes wound healing
    IgA (immunoglobulin A) is the commonest antibody of the immune system
38
Q

FUNCTIONS OF SALIVA - LEUCOCYTES

A
  • white blood cells, as a defence mechanism against oral infection and disease
39
Q

FUNCTIONS OF SALIVA - MUCUS

A
  • from the mucous secretory cells - to aid lubrication and allow speech and swallowing to occur
40
Q

FUNCTIONS OF SALIVA - OTHER ENZYMES

A
  • antibacterial enzymes - to aid in the defence of the oral cavity
  • promote wound healing
41
Q

FUNCTIONS OF SALIVA - WATER

A
  • carrying agent for other components
  • aids with lubrication for speech and swallowing
  • dissolves food particles to allow taste sensation
  • cleansing action by dislodging food particles from around the teeth
42
Q

WHAT IS XEORSTOMIA?

A

this is the uncomfartable condition of having a constantly dry mouth to the decreased production of saliva.

43
Q

CAUSES OF ZEROSTOMIA

A
  • IRRIDATION - of the head and neck area, usually as radiotherapy treatment for cancer in this area
  • MEDICATIONS - any that affect the nerve supply to the salivary glands to reduce their salivary flow, or that act as a diuretic and stimulate fluid loss, as well as certain drugs such as tricyclic antidepressants which cause dry mouth as a side-affect
  • Sjögren’s SYNDROME - a syndrome that occurs in conjunction with an autoimmune disorder, such as rheumatoid arthritis, where the body’s defence system attack itself and destroys its own glandular tissue, including the salivary glands and the lacrimal glands in the eye
44
Q

REDUCTION IN SALIVA WILL HAVE SERIOUS ORAL CONSEQUENCES, INCLUDING:

A

DENTAL CARIES, as the self-cleansing ability is lost

  • increased risk of ORAL INFECTIONS, as the defence capability is reduced
  • increased risk of ORAL SOFT TISSUE TRAUMA, as the protective mechanism is reduced
  • PROBLEMS WITH SPEECH SWALLOWING AND CHEWING, as the lubrication effect is reduced
  • POOR TASTE SENSATION and lack of food enjoyment, as the taste buds cannot function correctly in a dry field
45
Q

DENTAL PATIENTS SUFFERING FROM XEROSTOMIA SHOULD BE ADVISED BY THE DENTAL TEAM AS FOLLOWS:

A
  • frequent recall attendance to monitor for the onset of caries and other oral problems
  • use of artificial saliva sprays or constant sipping of plain water
  • high standard of oral hygiene, and especially the use of topical fluoride products to strengthen teeth against caries
  • dietry advice to avoid cariogenic products
  • avoidance of oral health products containg alcohol, as these tend to worsen the drying effect
46
Q

WHAT IS PTYALISM?

A

excessive salivation, or ptyalism, is a symptom associated with an underlying disease rather than a disorder in its own right.

47
Q

PTYALSIM CAN OCCUR DUE TO ANY OF THE FOLLOWING DISORDERS:

A
  • periodontal disease
  • oral soft tissue injury, or trauma, including that caused by sharp-edged dental appliannces
  • oesophagitis and otheer conditions causing acid reflux
  • disorders affecting the nervous system, including pakinsons disease and mercury poisoning
48
Q

ATROPINE

A

ATROPINE may be used during oral and maxillofacial surgery to significantly reduce saliva flow and provide a clear, dry operating field for the surgeons