Oral Biology- structure and functions Flashcards
What are the 3 main functions of the periodontium
- Retain tooth in socket
- Resist masticatory loads
- Defensive barrier, protecting tissues against threats from the oral environments
What is the junctional epithelium?
The physical barrier separating the body tissues from the oral environment
What are the 2 types of typical types of cementum and define them
- Acellular cementum
- no cells within
- usually adjacent to dentine
- first formed - Cellular cementum
- contains cementocytes
- later formed
- present in apical part of root and furcation regions
What are the alternative classifications for cementum? Define them
Acellular extrinsic fibre cementum
- collagen fibres from PDL (sharpeys fibres) penetrate it
- equivalent to primary cementum
- present at cervical 2/3 of roots
Cellular intrinsic fibre cementum
- no sharpeys fibres
- intrinsic collagen fibres parallel to surface
- no role in tooth attachment
What is the function of alveolar bone and what role does it play in attachment?
Alveolar bone supports the teeth
It provides attachment for periodontal ligament fibres (sharpeys fibres)
What happens to the alveolar bone when teeth are lost?
The alveolar process is resorbed, leaving a ‘residual ridge’
What is the periodontal ligament and what 5 things does it contain?
A connective tissue
- cells
- extra cellular matrix
- fibres
- nerves
- blood vessels
What property does the extracellular matrix in the PDL have?
Behaves as a viscoelastic gel
What 5 types of cells are present in the PDL?
Fibroblasts Cementoblasts Osteoclasts and cementoclast Epithelial cells Defence cells
What 2 main divisions of nerves are in the PDL? And any subdivisions within them
- Sensory
i) mechanoreceptors (Aβ and Aδ fibres)
- rapidly and slowly adapting
- proprioception: chewing control
ii) nociceptors (Aδ and C fibres)
- protective reflexes
- inhibit jaw elevator motor neurons - Autonomic (sympathetic)
- blood vessel control- vasoconstriction
What is the PDL blood supply for
a) the PDL passing into the alveolar bone
b) the gingiva
a) inferior and superior alveolar arteries
b) lingual and palatine arteries
What are the 2 types of periodontal fibres
True periodontal ligament
- fibres connecting tooth to bone, at or apical to alveolar crest
‘Gingival’ ligament
- fibres mainly ABOVE alveolar crest
- including ‘free gingival’ fibres
What is the function of the periodontal ligament?
Attaches tooth to jaw
Transmits biting forces to alveolar bone
What is the width of the PDL
Approx 0.2mm
What 3 types of fibres are present in the PDL
- Collagen (types I and III)
- principal fibres- true periodontal ligament
- support tooth; load bearing - Oxytalan fibres
- present in human PDL
- function uncertain - Elastic fibres
- absent in humans
What is the function of gingival fibre groups in the peridontium?
Name the 4 types
Support the free gingiva
Dento-gingival
Alveolo-gingival
Dento-periosteal
Circular
Name 4 circumstances the PDL is most subjected to intrusive forces
Mastication
Swallowing
Speech
Parafunctions (e.g. Clenching, grinding)
What is the periodontium?
The tissues surrounding and supporting the teeth
Describe regional variations in enamel in terms of mineralisation and hardness
Surface enamel is more mineralised and harder than deeper enamel
Hardness decreases from cusp tip/incisal edge to cervical region
What is the basic unit of enamel and what is its dimensions?
Enamel rod (or prism)
5 μm x 2.5 mm
From where and to where do enamel rods run?
How many HA crystallites are in each rod?
Run from ADJ to enamel surface (whole length)
Rods contain >10^6 HA crystallites
What is the composition of enamel?
HA: 95% weight 90% volume
Water: 4% weight. 5-10% volume
Organic matrix: 1% weight. 1-2% volume
What makes up HA and what is its chemical formula?
Calcium, phosphate and hydroxyl
Ca10(PO4)6(OH)2
What are the dimensions of HA crystallites?
70 nm x 25 nm x upto 1 μm
Define enamel tufts (histological)
Hypo mineralised regions in enamel due to residual matrix protein at prism boundaries
Define enamel lamella (histological)
Incomplete maturation of groups of prisms
‘Fault’ line extending through enamel thickness
Define enamel spindles (histological)
Odontoblast processes extending into enamel
What is dental pulp?
The connective tissue ‘core’ of the tooth
What 5 components make up dental pulp, and examples where appropriate
- Cells
- odontoblasts
- fibroblasts
- defence cells - Extracellular components
- fibres: collagen, oxytalan
- matrix: proteoglycans, chondroitin sulphate, dermatan sulphate - Nerves
- sensory
- autonomic (sympathetic) - Blood vessels
- Lymphatics
Name 5 pulp functions and how it achieves them
- Nutritive- blood vessels
- Dentine growth (primary, secondary)
- Dentine repair (tertiary)
- Defence- immune cells; lymphatics
- Neural- sensory
- control of dentinogenesis
From what do dentine and pulp develop?
Dental papilla
Name 6 causes of tooth wear
- Mastication (abrasion)
- Bruxism (attrition)
- Abfraction- occlusal overload- fractures and cervical lesions
- Diet (erosion)
- Caries
- Operative procedures- occlusal equilibrium
- cavity cutting; crown prep etc.
When is tertiary dentine laid down?
In response to stimulation
What are the 2 types of tertiary dentine, when are they laid down and by what?
- Reactionary dentine
- in response to a mild stimulus
- laid down by primary odontoblasts - Reparative dentine
- in response to intense stimulus that destroys primary odontoblasts
- laid down by secondary odontoblasts
What characteristic makes tertiary dentine different from the other dentines?
Tertiary dentine doesn’t have tubules because the odontoblasts lay it down so fast and they don’t bother with structure
What is the function of the odontoblast layer?
Acts as permeability barrier
Separates pulp and tubular space
Regulates movement of material between pulp and tubular ECF
Movement may be in either direction
What types of material are exchanged from the pulp to dentine and why?
Nutrients
- to sustain cells
What type of materials are exchanged from dentine to pulp, and where do they come from?
‘Toxins’ are diffused out
From bacteria; components of filling material
From what nerves do pulp nerves originate?
Alveolar nerves
How do neurovascular bundles enter the pulp?
Via the apical foramen (opening at base of root)
What 5 effects does outward dentinal fluid flow have?
Cooling Drying Evaporation Hypertonic solutions Decreased hydrostatic pressure
What 3 effects does inwards dentinal fluid flow have?
Heating
Mechanical
Increased hydrostatic pressure
What activates the Aβ and Aδ fibres in pulp nerves?
Hydrodynamic stimuli applied to dentine
What activates C fibres in pulp nerves?
Probably activated directly by stimuli
Respond to most forms of intense stimulation
Probably mediate pain associated with pulp inflammation
What 4 things control pulp blood flow?
- Local factors e.g. Metabolites
- Nerves
- sympathetic
- somatic afferents - Circulating hormones e.g. Adrenaline
- Drugs e.g. LA preparations with vasoconstrictors
What 4 functions do pulp nerves have?
- Sensory- mediating pain
- Control of pulp blood vessels
- sympathetic: vasoconstrictor
- afferents: vasodilator (axon reflex) - Promote neurogenic inflammation
- Promote dentine formation
(Facilitate immune response?)
Immediate pulp response to injury?
Nociceptors activation- pain
Pulp response approx. one minute after injury?
Early inflammatory response
Konica, prostaglandins, neuropeptides
Vasodilation
Pulp response approx 10 minutes after injury?
Nociceptor sensitisation
Extravasation (leakage) of fluid, oedema
Polymorph (WBC) migration
Pulp response approx 100 minutes after injury?
Nerve sprouting (NGF- nerve growth factor)
Increased axonal transport
Accelerated excitability of CNS synapses
Pulp response approx 1 week after injury?
Repair, tertiary dentine
Define pulpitis
Acute inflammation in the dental pulp
What is different about pulpal inflammation to inflammations elsewhere?
Pulp cannot swell as it is confined within pulp chamber
What function does the hydrodynamic mechanism have?
It activates intradental sensory nerves
Explain the hydrodynamic mechanism
Stimulated by- thermal, mechanical, evaporative, chemical
Acts on- exposed dentine to open tubules
This increases rate of dentinal fluid flow
Action potentials are generated in the intradental nerves
These APs pass to brain and cause PAIN
Name and describe the 2 types of macroscopic bone
- Cortical, compact bone
- dense outer plate
- 80-85% skeleton - Cancellous, spongy bone
- internal trabecular scaffolding (irregular latticework)
- 15-20% of skeleton
What is the cortical bone lining tooth sockets penetrated by?
Bundles of collagen fibres of PDL (Sharpey’s fibres)
By weight, what is the composition of bone?
60% inorganic
- hydroxyapatite
25% organic
- collagen (90%)
- glycoproteins- osteocalcin, osteonectin, osteopontin, sialoproteins
- proteoglycans (GAGs)- chondroitin sulphate, heparan sulphate
15% water
What are the 2 types of microscopic bone?
Woven bone
Lamellar bone
Describe woven bone
Rapidly laid down Irregular deposition of collagen Present in fetus Fracture repair (callus) Contains many osteocytes
Describe lamellar bone
Laid down more slowly
Collagen fibres laid down in parallel
Normal form in adults
Contains fewer osteocytes
Describe the structure of compact bone
Consists of osteons (haversian systems) that contain lamellae (concentric rings of hard, calcified ECM), lacunae (small hollow space), osteocytes and Central Haversian canals (containing blood vessels)
Lateral (volkmann’s) canals link the Haversian canals
Describe the structure of cancellous, spongy bone
Network of thin trabeculae (columns)
The spaces between the trabeculae are filled with bone marrow
Where are osteoblasts found, what are they derived from and how do they help in bone formation?
Lie on surface of bone
Derived from mesenchymal stem cells
Synthesise and secrete collagen fibres forming a matrix
The matrix is later mineralised by calcium salts forming bone
Define osteocytes
Osteoblasts that become trapped in mineralised bone
Where are osteocytes in bone and how are they in contact?
Lie within spaces- lacunae- in the bone
Contact other osteocytes via cytoplasmic processes that run in canaliculi (small canals)
What are osteoclasts derived from, what are they related to and what is there function?
Derived from haemopoietic stem cells
Related to macrophages
They resort bone
Where are osteoclasts found?
Lie in concavities of bone- Howships’s lacunae
What percentage of cortical and cancellous bone is replaced every year?
Cortical bone- 2%
Cancellous bone- 25%
Define cartilage
Semi-rigid, unmineralised connective tissue
Name 3 types of cartilage and where they are found
Hyaline cartilage (widespread) - larynx, nasal septum, trachea, embryonic skeleton (precursor to bone)
Fibrocartilage
- intervertebral discs, pubic symphysis
Elastic cartilage
- external ear, epiglottis
What forms cartilage?
Chrondroblasts
What are the 2 types of bone growth?
Endochondral ossification
- cartilage precursor
- ‘long bones’
Intramembranous ossification
- no cartilage precursor
- ‘flat bones’
Define achondroplasia
Genetic defect of cartilage growth
Endochondral bone growth is impaired
Name the muscles of mastication
Temporalis
Masseter
Lateral pterygoid
Medial pterygoid
Where is the origin of the masseter?
Zygomatic arch
Where is the insertion of the masseter?
Lateral surface and angle of mandible
What is the action of the masseter?
Elevates mandible
How is the masseter examined?
It is tender in patients who have a clenching habit
To examine- place on finger intra-orally and other on the cheek
Where is the origin of the temporalis?
The floor of the temporal fossa
Where is the insertion of the temporalis?
At the coronoid process and anterior border of ramus
What is the action of the temporalis?
Elevates and retracts mandible
How would you examine the temporalis?
It is tender in patients who have bruxist habit
To examine- palpate its origin by asking the patient to clench their teeth together
Digital palpation is performed between the superior and inferior temporal lines just above the ears, extending forwards towards the supra-orbital region
Where is the origin of the lateral pterygoid muscle?
From the lateral surface of the lateral pterygoid plate
Where is the insertion of the lateral pterygoid?
The anterior border of the condyle and intra-articular disc via two independent heads
What is the action of the lateral pterygoid?
Protrudes mandible, depresses mandible and moves mandible side to side
Where does the inferior belly and the anterior belly of the lateral pterygoid attach?
Inferior belly- head of condyle
Superior belly- intra-articular disc
How is the lateral pterygoid examined?
Not accessible to manual palpation
Best examined by recording its response to resisted movement
Where is the origin of the medial pterygoid?
Deep head: medial surface of lateral pterygoid plate
Superficial head: tuberosity of maxilla
Where is the insertion of the medial pterygoid?
Medial surface of angle of mandible
What is the action of the medial pterygoid?
Elevates and assists in protrusion of mandible
How is the medial pterygoid examined?
Not accessible to palpation
Doesn’t respond well to resistive movement test
No reliable way of examining
What do the suprahyoid muscles connect?
Connect hyoid bone with mandible and skull
What is the function of the suprahyoid muscles?
To elevate hyoid bone and related structures
Name the 4 suprahyoid muscles
Digastric
Mylohyoid
Geniohyoid
Stylohyoid
Dicks make girls scream
What do infrahyoid (‘strap’) muscles connect?
Connect hyoid bone, thyroid cartilage and shoulder girdle
Name the 4 infrahyoid muscles
Sternohyoid
Omohyoid
Thyrohyoid
Sternothyroid
Sam often tickles shoulders
What are the two types of tongue muscles and what are their functions?
Intrinsic- alter shape
Extrinsic- alter shape, position
Name the 3 intrinsic tongue muscles
Longitudinal
Vertical
Transverse
Lindseys vagina talks
Name the 4 extrinsic tongue muscles
Genioglossus
Hyoglossus
Palatoglossus
Styloglossus
Get her pumped, son
What is the TMJ and what does that mean?
TMJ is a synovial diarthrodial joint
Means that joint is lubricated by synovial fluid and that the joint space is divided into two separate compartments by means of an intra-articular disc
What 2 ways can you examine the TMJ?
Lateral palpation- TMJ should be palpated in the immediate pre-auricular area
Intra-auricular palpation- the little finger should be placed in the external auditory meatus and gentle forward pressure applied
What is rotational jaw opening?
Purely rotational opening (rotating inside socket)
Condyle rotates in a hinge movement
What is translation jaw opening?
A protrusive opening- TMJ comes out of socket
Condyle moves forward onto articular eminence
Maximum mouth opening
Protrusive and retrusive movements
What are the usual maximum biting force between molars?
200-700 N
What can cause an increase in biting force?
Increased muscle mass can increase biting forces
What limits biting force?
The teeth themselves (could fracture)
What are the 2 types of muscle fibres?
Type I and Type II
Describe type I muscle fibres
Slow, weak
Very resilient (not easily fatigued)
Used under normal circumstances
Describe type II muscle fibres
Fast, strong forces
Fatigue easily
Used for increased force- biting hard
Used under stress
What are the subtypes of Type II muscle fibres
IIA, IIX, IIB
Where is the greatest biting force and why?
Between the first molars
Molars are nearer the force generating muscles and the fulcrum (TMJ)
The also have a large root area- PDL support
What sensory nerves are involved in innervating lower molar?
Inferior alveolar nerve
From the mandibular branch of the trigeminal nerve (CN V)
What is the function of the gagging reflex?
To prevent material entering pharynx
What cranial nerves are involved in the gag reflex?
V (trigeminal), IX (glossopharyngeal), X (vagus), XI (accessory) and XII (hypoglossal)
What are 12 cranial nerves?
Olfactory Optic Occulomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Accessory Hypoglossus
What is Bell’s palsy?
Type of facial paralysis that does not have any other associated causes
What are clinical features of Bell’s palsy?
Inability to wrinkle brow
Drooping eyelid; inability to close eye
Inability to puff cheeks
Drooping mouth; food stuck in cheek
What motor nerve controls facial muscle and what are it’s branches?
Facial nerve
Temporal Zygomatic Buccal Mandibular Cervical
The zuberi’s bummed my cat
Name 5 causes of Bell’s palsy
Infections Diabetes Trauma Toxins Temporarily by infiltration of LA to facial nerve branches
Name 4 general senses
Touch (mechanoreceptors)
Proprioception (proprioceptors)
Temperature (thermoreceptors)
Pain (nociceptors)
Name 2 special senses
Taste (oral chemoreceptors)
Smell (nasal chemoreceptors)
Give the 4 types of α nerve fibres and give their function
Aα - sensory (proprioception)
Motor (skeletal)
Aβ - sensory (mechanoreception and proprioception)
Aγ - motor (muscle spindles)
Aδ - sensory (mech, thermo, noci)
What is the function of B nerve axons?
Autonomic (pre-ganglionic)
What are the functions of C nerve axons?
Sensory (mech, thermo, noci)
Autonomic (post-ganglionic)
What is a mechanoreceptor?
A sensory receptor that responds to mechanical pressure and distortion
How sensitive are periodontal mechoreceptors?
Very sensitive
Able to detect material down to 20 μm (half the width of hair)
What are the 2 types of thermoreceptors, where are they found and what nerve fibres do they involve?
Cold- increased firing rate with decreased temp
Located at dermis-epidermis junction
Aδ and C-fibre afferents axons
Warm- increased firing rate with increased temp.
Located in dermis
C-fibre afferent axons
What is proprioception?
Awareness of position and orientation of body parts
What in interdental discrimination?
Ability to gauge extent of mouth opening
Monitoring size of food particles
Detection of ‘high spots’
What is the innervation of the taste buds?
Anterior 2/3 of tongue: chorda tympani (branch of facial nerve)
Posterior 1/3 of tongue: glossopharyngeal (IX)
Epiglottis: vagus (X)
What is perception?
The organisation, identification and interpretation of sensory information
Define dysphagia
Inability to swallow
What are 5 cause of dysphagia?
Stroke (unilateral) Brain injury MS Gastroesophageal reflux disorder (GORD) Tumours
What are the three stages of swallowing? State whether they are voluntary or involuntary
- Buccal/oral phase (voluntary)
- Pharyngeal phase (involuntary)
- Eosophageal phase (involuntary)
What are the 2 functions of swallowing?
Transportation of accumulated food through lower pharynx and oesophagus into the stomach = FEEDING function
Prevention of ingested material entering lower airway
= PROTECTIVE function
Describe the 3 stages of swallowing liquids
- Liquid gathered anterior to the pillars of the fauces in the mouth
- Posterior oral seal forms between oral cavity and pharynx
- Liquid propelled through oropharynx and laryngopharynx into oesophagus
Describe the 2 stages of swallowing solids
- Food is masticatory and bolus is gathered on pharyngeal part of tongue and vallecula (oropharynx)
- Bolus is propelled from tongue through hypo-pharynx into the oesophagus
Describe the squeeze-back mechanism
Forward movement of tongue creates contact between tongue and hard palate
Contact point moves backwards, squeezing the processed food through the fauces
Name 4 ways airway protection is achieved during swallowing
- Upward and forward movement of larynx
- Closure of laryngeal inlet
- aryepiglottic muscles
- epiglottis - Adduction (movement) of vocal folds
- Stop breathing (apnoea)
Describe the oral/buccal phase of swallowing
Voluntary
Squeeze-back mechanism
Bolus pushed into oropharynx
Duration NOT dependant on food CONSISTENCY
Describe the pharyngeal phase of swallowing
Involuntary
Controlled by medulla oblongata
Larynx/upper oesophageal sphincter relaxes to allow food through
Duration DEPENDANT on food consistency
Describe the oesophageal phase of swallowing
Involuntary
Peristalsis; rhythmic contraction of oesophagus
What are the 3 stages in the chewing cycle?
Occlusal phase- intercuspal position (mandible is stationary, teeth joined)
Opening phase- lateral pterygoid and gravity depress mandible
Closing phase- masseter, medial pterygoid and temporalis elevate mandible back to phase 1
What are the key roles of the tongue in the chewing process?
Controlling and transporting food ‘bolts’ within mouth
Define dysphasia
A specific language disorder
Involving damage to particular parts of the brain
Define dysarthria
Difficulty speaking caused by problems with muscles used in speech
Due to neuro-muscular defects
Name 4 oral causes of language and speech defects
Malocclusions
Loss of teeth
Cleft palate- oral and nasal cavities not seperated
Dry mouth (xerostomia)
Define a consonant
Letter which causes the partial or complete stoppage of airflow
What term is used for a consonant where air escapes through constriction
Give 4 examples
Fricatives
S, f, v, th
What term is used for consonants that have a sudden release after complete stoppage of airflow?
Give 6 examples
Plosives
B,p,t,d,k,g
What term is used for consonants where air flows through the nose
Give 3 examples
Nasals
M, n, ng
Define a vowel
Letter with continuous airflow
Define embouchure
The position and use of lips, tongue and teeth while playing a wind instrument
