Orofacial sensation

Question 1

How do we perceive the world around us?

Answer 1

Through sensory stimuli.

The sensations can be preceve through general and special sensations

Question 2

What are the importance of sensory preception?

Answer 2

1. Sensation
2. Control of movement
3. Maintaining arousal/cortical consiousness - e.g. maintaining arousal when there is pain
4. Safety - e.g. smell
5. For future reference - brain recognition
6. Emotions - e.g. self explanation

Question 3

What are the main types of sensory receptor in the body?

Answer 3

1. Photoreceptors - light
2. Chemoreceptors - taste, smell, pH
3. Thermoreceptors - temperature
4. Mechanoreceptors - mechanical forces like touch, pressure, sound
5. Nociceptors - pain

Question 4

What are some of classification of sensory receptors based on speed of adaptation?

Answer 4

1. Slowly adapting - slowly adapting receptors are related to nociception - think about tooth ache, the stimulus is continuous but also the receptor will be affected continuously - think about ongoing tooth ache
2. Rapidly adapting - example is a mechanoreceptors relating to light touch - the response is quick but the touch perception is reduced quick - the sensation occurs only due to intial stimulus and reduction of stimulus

Question 5

What are some of classification of sensory receptors based on speed of adaptation?

Answer 5

1. Slowly adapting - slowly adapting receptors are related to nociception - think about tooth ache, the stimulus is continuous but also the receptor will be affected continuously - think about ongoing tooth ache
2. Rapidly adapting - example is a mechanoreceptors relating to light touch - the response is quick but the touch perception is reduced quick - the sensation occurs only due to intial stimulus and reduction of stimulus

Question 6

What are the classification of sensory receptors based on the source of the stimuli?

Answer 6

1. Exteroceptors - provide information from the external environment - e.g. touch, pressure, temperature
2. Enteroreceptos - provide information from the internal environment - blood pressure, plasma osmolality, blood pH
3. Proprioceptors - provide information from the musculoskeletal system (position sense) - muscles, tendons and the joints

Question 7

What is kinaesthesia?

Answer 7

It is the awareness of the position and movement of the parts of the body by means of sensory organs (proprioceptors) in the muscles and joints.

Question 8

What are the essential receptors for kinaesthesia?

Answer 8

1. Exteroceptors: in eye, ear and skin
2. Proprioceptors: in muscles, tendons and joints

Question 9

What are some of exteroceptors located in the oral cavity?

Answer 9

1. Receptors in the PDL
2. Receptors in alveolar mucosa
3. Receptors in gingiva
4. Receptors in periosteum of the jaw bone

They inform about the external loading when for example we chew

Question 10

What are some of the proprioceptors in the oral cavity?

Answer 10

1. Muscle spindles in mastictory muscles
2. TMJ spindles

Question 11

What is the basic pathway pf sensory processing in the brain?

Answer 11

The simple model is:
1. Sensory input - stimuli
2. Integration - understanding of stimuli
3. Perception - feeling of a certain sense
4. Motor response

Question 12

What is the basic pathway of the stimulus to the somatic sensory area in the brain?

Answer 12

1. Stimulus detected by receptors
2. The signal is propogated via the sensory nerve by ascending sensory pathway
3. The stimulus reaches the somatic sensory area in the brain

Question 13

How does the sensory information travel from the teeth?

Answer 13

The information from the teeth and supporting structures transmitted to the brain via the trigeminal nerve.

In certain situations, the infromation transmitted from different teeth may converge into the same secondary neruon from the primary neuron thus the brain may process the pain sensation as non-localised thus localisation of pain could be a clinical problem .

Question 14

Please explain the pain and temperature pathway of the spinal trigeminal tract?

Answer 14

1. Intial stimulus occurs
2. Primary neuron caries the signal from the sensory ogran to the trigeminal ganglion
3. From the trigeminal ganglion, primary neuron carries it below to the spinal trigeminal nucleus where a cross over occurs and the signal it transducted to the secondary nucleus
4. The secondary neuron through the ventral trigeminal leminscus and crus cerebri
5. The final transduction to the ventral posteromedial nuceleus and later the signal is transducted to postcentral gyrus

Question 15

Please explain the touch pathway of the sensory trigeminal tract?

Answer 15

1. Initial stimulus occurs
2. Primary neuron caries the signal to the trigemina ganglion
3. After, the primary neruon caries the signal to the main sensory trigeminal nucleus where transductio of the signal occurs to the secondary neuron
4. The secondary neuron propogates the signal through the crus cerebri towars the intralaminar nuclei
5. The final transduction to the intralaminar nuclei and later the signal is transducted to postcentral gyrus

Question 16

Why is the oral cavity one of the most densely innervated parts of the body?

Answer 16

1. It is linked to the key role of oral sensorimotor control of the oral motor functions
2. Mouth contains a large range of different tissue types in close proximity and constant interaction
3. Oral sensations provide an important interface experience: internal and external surface of the body

Question 17

What are the types of principal somatosensory receptors that are innervating the oral tissues?

Answer 17

1. Mechanoreceptors that detect touch - mostly A-beta receptors but sometimes also C type receptors
2. Nociceptors that detect pain and temperature changes - A-delta and C receptors

Question 18

What is the importance of periodontal mechanoreceptors in clinical prectice?

Answer 18

They enable patients to detect new restoration which are high in occlusion

Question 19

What is the purpose of TMJ receptors?

Answer 19

They function as pain receptors and proprioceptors. They may act as velocity detectors and static-position of the TMJ detectors.

Question 20

How do we know that the tongue is so sensitive?

Answer 20

Because during two-point discrimination test, the tongue can detect 2 distinct points at around 1.4mm distance between them.

This sensitivity is related to tongue function and can be damped with local anaesthetics.

Tongue is also very very sensitive to temperature changes especially o n the dorsum area.

Question 21

What is osseoperception?

Answer 21

It is a type of perception that occurs int eh absence of a functional periodontal mechanoreceptive input.

The mechanoreceptors are derived from TMJ, muscles or periosteal mechanoreceptors.

They provide mechanosensory infromation for oral kinaesthetic sensibility in relation to the jaw function and the contacts of artificial teeth.

Question 22

What is oral stereognosis?

Answer 22

It is the ability to recognise and discriminate forms. Oral stereognosis is the ability to feel depth and understanding of 3 dimentions of objects.

Oral stereognosis can be used to measure oral functions.

Oral stereognosis is influences by forms, size and surface characteristics of the test piece.

Oral steregnosis is associated with health.

Oral stergnosis is HIGHLY DEPENDENT ON PERIODONTAL MECHANO RECEPTORS.

PULP IS NOT INVOLVED

Question 23

What is pain?

Answer 23

An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.

Question 24

What is somatic pain?

Answer 24

It is pain that can usually be attributed to one area of the body.

The somatic pain can be separated into superficial pain (usually related to skin stimuli or musculoskeletal stimuli) and deep pain (usually derived from damage to the deep organs.

Question 25

What are the factors that affect pain preception?

Answer 25

1. Intensity of the stimulation or tissue damage 2. Emotions 3. Past experience and memories of pain 4. Other concomitant sensory experiences 5. Sex, ethnicity and age 6. Placebo effect

Question 26

What are the two different types of pain and WHAT FIBRES are responsible for them?

Answer 26

1. Fast pain - sharp pain that is well localised and has a short duration - facilitate by A-delta fibres 2. Slow pain - aching, burning pain that is poorly localised and is long in duration - involves unmyelinated C fibres

Question 27

What causes pain?

Answer 27

1. First there is injury or tissue damage 2. That leads to a release in chemicals 3. Some chemicals are able to actuallly activate nociceptors - like potassium 4. Other are able to sensitise the nociceptors making them more excitable - like prostaglandins

Question 28

What is antidromic activation of nociceptors? Explain how it relates to the 'hot pulp' syndrome.

Answer 28

it is belied that in some cases, injury that is detected by the receptor through orhodromic means, meaning due to the injury itself, may cause propogation of the action potential to other receptors thus causing the pain to intensify through Substance P release. Hot pulps: 1. In 'hot pulps' the pain from the lesion is able to causes antidromic activation though the stimulus thus releasing substance P and Calcitonin gene related peptide (CGRP) 2. Substance P is able to induce oedema formation through plasma extravasation and also cause mast cells degranulation, releasing histamines which activate more nociceptors 3. CGRP are able to cause aditional oedema through dilation of peripheral blood vessels 4. The increase in oedema causes an additional release of bradykinin which activates more nociceptors 5. Through this multi step process, patient has a large number of nociceptors released thus causing hyperlgesia meaning the action potential threshold is considerably lower

Question 29

How does some patient adapt so quickly to dental occlusal change or rehabilitative procedures?

Answer 29

It relates to central sensitisation and neuroplasticity. Central sensitisation is process of shifting of the sensation by the central nervous system due to new stimuli. Neuroplasticity is a process in which the central nervous system may change it's ability to detect different stimuli. The adaptation to the new stimuli occurs first to central sensitisation and lead to the changes to the face sensorimotor cortex due to neuroplastic changes.

Question 30

What are the two main characteristics of central sensitisation?

Answer 30

1. Allodynia - pain due to a stimulus that does not normally provoke pain 2. Hyperalgesia - increased pain form a stimulus that normally provokes pain

Question 31

Of what 3 parts is the spinal nucleus of the trigeminal system composed of?

Answer 31

1. Oralis 2. Interpolaris 3. Caudalis The first order A-delta and C fiber neuron will always go through the Caudalis

Question 32

What is the main theory which is used to explain pain and pain perception?

Answer 32

Nerumatrix theory. It states that pain is a multifactorial feeling thus multiple factors regulate it like: 1. Cognitive-related to brain 2. Sensory signaling systems 3. Emotions-related brain area 4. Pain preception 5.Action programs 6.Stress-regulation programs

Question 33

What is referred pain?

Answer 33

It is the pain from internal organs is felt as pain in more superficial region of the body due to visceral cross-over

Question 34

What are neuralgias?

Answer 34

It is pain that relates to nerve pathways. In the dental senario it could be due to compression of the trigeminal sensory root or due to degenerative changes in myelinanted fibres in the ganglion

Question 35

What is phantom pain?

Answer 35

It is a sensation that can occur in a part of the body that have been amputated or extracted (e.g. wisdom teeth). This occurs due to hyperactivity of the neurons in spinal cord or trigeminal nucleus

Question 36

What nerve fibres are present in the pulp?

Answer 36

A-beta A-delta C unmyelinated fibres - close to the pulp

Question 37

What are some of the factors that influence susceptibility of nerve fibre to LA?

Answer 37

1. Size of nerve fibre - smallest to largest: C, A-delta, A-beta 2. State of myelination 3. Rate of firing

Question 38

What is the importance of taste and smell?

Answer 38

1. Protective/survival function 2. Elicit physiological responses 3. Modulate masticatory movement and initiation of the swallowing reflex

Question 39

What are the factors that affect taste?

Answer 39

1. Age 2. Hunger 3. Smoking 4. Obesity 5. Pregnancy 6. Disease 7. Taste adaptation

Question 40

What are the primary taste sensations?

Answer 40

1. Sour 2. Salty 3. Sweet 4. Bitter 5. Umami

Question 41

What are the papilla involved in taste?

Answer 41

1. Vallate papilla 2. Foliate 3. Fungiform

Question 42

What is the design of the taste buds?

Answer 42

Taste buds were designed to recognise toxins in the food - that is why the threshold to bitter taste is considerably lower than to something sweet. They look like onions with microvili exposed to the chemical stimuli and taste afferent on the conter side.

Question 42

What are the 3 areas of the body that are able to detect taste and what nerves are able to carry the action potential form those areas?

Answer 42

1. Anterior 2/3 of the tongue - nerve supply: Chorda tympani - VII 2. Posterior 1/3 of the tongue nd pharynx - nerve supply: Glossopharyngeal - IX 3. Anterior epiglotis and larynx - nerve supply: Vagus - X

Question 43

What are some of the common taste disorders?

Answer 43

1. Ageusia - total loss of taste 2. Dysgeusia - taste distortion 3. Hypergeusia - increased sensitivity 4. Hypogeusia - decreased sensativity 5. Phantom Taste Perception

Question 44

How can we separate the aeitology of taste disorders?

Answer 44

1. Due to transport loss - interfere with access of a tastant to the taste bud - associated with xerostomia 2. Due to sensory loss - Injury to the receptor cells - could be due to drugs, inflammatory disease or other 3. Due to neural loss - damage to the gustatory afferent nerves and the central gustatory pathways - for example after third molar extractions or neoplasma in the oral area

Question 45

In which space does smell reception occur?

Answer 45

The smell reception occurs in the area known as the olfactory membrane - which is a pigmented yellowish-brown membrane that is located in the mucosa of each of the nostrils. It is an areas that sit in between the cribiform plate. The epithelium ahs bipolar nerve that carry the stimuli from the receptors to the olfactory bulb. Before being transported, the chemical of smell are first desolved in mucos released by the bowman gland.

Question 46

What conditions must the chemical meet in order to become detected and cause an olfactory stimulus?

Answer 46

1. Must be volatile 2. Must have sufficient water solubility 3. Must be lipid soluble ]4. Must have a minimal concentration and minimal time of exposure to be detected

Question 47

What are the common olfactory disorders?

Answer 47

1. Anosmia - total loss 2. Dysosmia - distortion of taste 3. Hyperosmia - increased in smell sensitivity 4. Hyposmia - decrease in smell sensitivity 5. Presbyosmia - loss of smell due to aging

Question 48

What is the aetiology of smell related disorders?

Answer 48

1. Transport loss - loss in interference between the odorant to the olfactory epithelium - e.g. in swollen nasal mucuous 2. Sensory loss - injury to receptor cells - e.g. after exposure to toxic chemicals 3. Neural loss - due to damage in the olfactory afferent nerve and the central olfactory pathways - e.g. due to neoplasms

Question 49

What are some of the possible oral sources of smell and taste disorders in the elderly?

Answer 49

1. Oral trauma - burns, lacerations etc. 2. Oral diseases and symptoms - dental caries, periodontal diseases, NG, NPD etc 3. Treatment of oral and systemic diseases - Chlorexedine use and other

Question 50

What are peridontal mechanoreceptors, what is their function and what is their make up and ability?

Answer 50

Periodontal mechanoreceptors are ruffini type receptors that are within periodontal ligament. They regulate the forces applied by the teeth in occlusion and mastication. Response of the receptors vary ith the force applied to the tooth, but there is greater sensativity at low force levels. This allows the mechanoreceptors to aid patient with finding high spots on restorations