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Periodontal Ligament Flashcards

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1
Q

what kind of tissue are cementum and alveolar bone

A

hard tissues

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2
Q

what connects the cementum and alveolar bone

A

periodontal ligament

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3
Q

what does the periodontal ligament connect

A

cementum and alveolar bone

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4
Q

what are the main cells found in connective tissues

A

fibroblasts

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5
Q

what is the periodontal ligament innervated with and why

A

nerves and blood vessels in order to provide information

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6
Q

what branch of the nervous system controls blood vessels

A

sympathetic

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7
Q

what is found within the periodontal ligament matrix

A
  • glycoproteins
  • proteoglycans
  • hyaluronate glycosaminoglycans
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8
Q

what are glycoproteins

A

proteins that have sugars on their side

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9
Q

what are proteoglycans

A

proteins with the core made of sugar and the side made of protein

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10
Q

what is hyluronate glycosaminoglycan

A

a special type of glycan

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11
Q

why is it important that there are proteins in the matrix of periodontal ligaments

A

the matrix can be affected by periodontal disease, and the property of the matrix proteins is to behave as a viscous elastic gel which is important for the ligament

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12
Q

what are the cells that are found in periodontal ligament

A
  • cementoblasts
  • fibroblasts
  • osteoclasts and cementoclasts
  • epithelial cells
  • defence cells
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13
Q

what do cementoblasts do

A

synthesise cementum

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14
Q

why are there cementoclasts and osteoclasts in the periodontal ligament

A

to destroy alveolar bone and cementum

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15
Q

why are there epithelial cells in the periodontal ligament

A

the root is formed by epithelial cells, and once the root is formed they do not have a use and will remain there and become cell rests of malassex.

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16
Q

what are the sensorial nerves in the periodontal ligament

A

mechanoreceptors and the nociceptors

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17
Q

what are nociceptors important for in the periodontal ligament

A

reflexes like jaw movement

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18
Q

what is the purpose of sympathetic innervation of the periodontal ligament

A

control of blood flow thorugh vascoconstriction

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19
Q

what is the main vasoconstrictor used in local anaesthetic when doing procedures to reduce blood flow

A

adrenaline

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20
Q

what groups are periodontal fibres subdivided into

A

true periodontal ligament and the gingival ligament

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21
Q

what does the gingival ligament connect

A

soft tissue to hard tissue

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22
Q

what is the periodontal ligament

A

an ordanised connective tissue - it has the order of what things are and what things do.

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23
Q

what is the periodontal space

A

this is the width of the periodontal ligament and is very thin. the space depends on the health of the patient

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24
Q

what is ankylosis

A

whenthe tooth is attached to the bone and does not have any periodontal ligament there

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25
Q

what reflex is in place to prevent fracturing from the force of biting

A

the jaw jerk reflex which is responsible for the protection of teeth when biting. sensitivity for this reflex are the nociceptors found in the periodontal ligament

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26
Q

what is the alveolo dental ligament

A

the connective from cementum to bone

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27
Q

what can affect the speed and force of chewing

A

the consistency of food

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28
Q

how does the arrangement of periodontal ligament fibre groups differ

A

depending on their function

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29
Q

what is the function of periodontal fibres

A

provide resistance for movement

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30
Q

what is the function of the matrix

A

provide a cushion

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31
Q

are the forces on teeth linear

A

no they are applied through the fibres

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32
Q

where are the fibres found

A

alveolar crest near the gingiva, horizontal, mid of the tooth and the apex of the tooth

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33
Q

what are the different fibre groups

A

oblique, apical, horizontal, alveolar crest

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34
Q

what does periodontitis affect

A

the fibres and how they stretch as well as the viscous elasticity of the matrix.

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35
Q

what are the targets for treating periodontitis

A

periodontal fibres and how they stretch as well as the viscous elasticity of the matrix

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36
Q

what fibres connect cementum to cementum

A

interdental ligament fibres

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37
Q

how does movement get transferred to teeth

A

the movement is delayed rather than being directly transferred to the teeth, which reduces the forces. the periodontal ligament therefore reduces the forces as the bone is not supposed to receive the movement

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38
Q

how is force detection differed by dentures

A

there is no periodontal fibre so the forces transmitted are not recognised. the gingiva can give some recognition but not a lot. therefore implants are better as there are more forces being detected, however there is still loss of mechanoreceptors and nociceptors.

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39
Q

describe the features of periodontal ligament

A
  • non mineralised connective tissue
  • highly vascularised and innervated
  • reacts to orthodontic loads
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40
Q

what do the mechanoreceptors do in the periodontal ligament

A

they convey sensory information to the brainstem and the trigeminal nerve

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41
Q

what are the fetal like properties of the peridontal ligament

A

high turnover of the extracellular matrix and a high proportion of type III collagen

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42
Q

what does the peridontal ligament occupy

A

the space between the root of the tooth and the alveolar bone

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43
Q

what is the periodontal ligament derived from

A

dental follicle

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44
Q

when is the continuity of the periodontal ligament with the gingiva important to consider

A

when considering the progression of periodontitis

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45
Q

what is the periodontal ligament continuous with

A

the gingiva

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46
Q

how does the width of the periodontal space differ

A

by the health of the tooth but also the region. narrower in the mid root region

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47
Q

when is periodontal space increased

A

when teeth are subjected to heavy occlusal stress

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48
Q

what is tooth ankylosis

A

the tooth fuses to the alveolar bone.

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49
Q

what suggests the presence of signalling systems that maintain the periodontal space

A

the fact that alveolar bone rarely ever colonises the periodontal space - how does it know to do this

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50
Q

what are the main functions of the periodontal ligament

A
  • resisting displacement forces and protecting the dental tissues from damage by excessive occlusal loads
  • responsible for the mechanisms where a tooth attains and maintains a functional position.
  • maintain and repair both alveolar bone and cementum
  • neurological controls of mastication due to the presence of mechanoreceptors
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51
Q

what makes up the majority of periodontal fibres

A

collagenous fibres - roughly 90% of all periodontal ligament fibres

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52
Q

break down the collagenous fibre components of the periodontal ligament

A

70% is type 1 collagen
20% is type 3 collagen
much of the collagen is gathered to form bundles called principle fibres that appear to be more numerous at their attachments to cementum than at alveolar bone. cellular processes surround the fibre bundles

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53
Q

what surround the principle fibres

A

cellular processes

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54
Q

what are principle fibres

A

bundles of collagen fibres

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55
Q

where are principle fibres found to be more numerous

A

their attachments to cementum

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56
Q

what is the major protein component of most connective tissue

A

type I collagen

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57
Q

what is type III collagen associated with

A

rapid turnover

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58
Q

is type III collagen localised at a specific region of the peridontal ligament, and if so where

A

no it is not

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59
Q

how do the orientations of principle fibres differ

A

depending on the region of the periodontal ligament.

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60
Q

are there specific functions for each group of the principle fibres

A

no

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61
Q

what are the different regional names for the principle collagen fibre bundles

A
  • dentoalveolar crest fibres
  • horizontal fibres
  • oblique fibres
  • apical fibres
62
Q

describe the course that principle fibres take as they pass from the region of the alveolar bone to the tooth

A

not a straight course - said to be wavy (it is not known whether the waviness is real or an artefact of histological preparation)

63
Q

what are fibroblasts responsible for

A

the synthesis and degradation of collagen

64
Q

what can be found within each collagen bundle

A

subunits of structure called collagen fibrils.

65
Q

how are collagen fibrils formed

A

the packing together of individual tropocollagen molecules

66
Q

what does the diameter of collagen fibrils reflect

A

the mechanial demands put upon the connective tissue

67
Q

what are sharpeys fibres

A

principle fibres of the periodontal ligament that are embedded into the cementum and the bone lining of the tooth socket

68
Q

where are the sharpeys fibres most numerous

A

at the attachments into cementum. they are also smaller here

69
Q

describe the rate of turnover of collagen within the periodontal ligament

A

faster than virtually all other connective tissues.

70
Q

how does the rate of turnover differ within the periodontal ligament

A

varies in different parts of the same tooth. highest toward the root apex.

71
Q

why may there be a high rate of turnover in periodontal ligament

A

could relate to the functional demands placed upon the tooth in terms of remodelling as a reaction to occlusal stress and to tooth movements

72
Q

what are elastic system fibres composed of

A

elastin, elaunin and oxytalin fibres

73
Q

which elastic fibres are found in human periodontal ligament

A

elaunin and oxytalin

74
Q

what is oxytalin

A

immature elastin fibres with elastin and collagen components

75
Q

what are oxytalin fibres attached to

A

the cementum of the tooth and the course out through the periodontal ligament in various directions.

76
Q

are oxytalin fibres incorporated into the bone

A

only rarely

77
Q

how can oxytalin fibres be recognised

A

as a collection of unbanded fibrils arranged parallel to the long axis of the fibre

78
Q

do oxytalin fibres change with age or with masticatory loading

A

neither

79
Q

what is reticulin

A

argyrophilic - known to be type III collagen. the reticular fibres crosslink and form a fine meshwork to aid tissue support. they are also related to basement membranes within the periodontal ligament

80
Q

what are the rests of malassex

A

epithelial cells found within the periodontal ligament

81
Q

what role do fibroblasts have in relation to teeth

A

they have an essential role in the adaptive responses to mechanical loading of the tooth

82
Q

what are the features of fibroblasts in periodontal ligament that are not particularly common in fibroblasts of other connective tissues

A

cilia and many intercellular contacts

83
Q

how do the periodontal fibroblasts and the gingival fibroblasts differ

A

they are derived from different sources and the gingival fibroblasts are less proliferative

84
Q

what may the information associated with periodontal disease lead to

A

an increase expression of MMP and aggressive loss of collagen in the periodontal ligament that results in tissue destruction

85
Q

what are cementoblasts

A

connective tissue cells of the periodontal ligament - cement forming
they are rich in cytoplasm and have large nuclei. they contain all the intracytoplasmic organelles necessary for protein synthesis and secretion

86
Q

what are osteoblasts

A

bone forming cells lining the tooth socket, resembling cementoblasts. the layer is prominent only when there is active bone formation.

87
Q

where are cementoclasts and osteoclasts found

A

in areas where bone and cementum are being resorbed

88
Q

what occurs when osteoclasts resorb alveolar bone

A

the surface of the alveolar bone shows resorption concavities called howship’s lacunae, where the osteoclasts lie

89
Q

what are howship’s lacunae

A

resorption cavities on the surface of the alveolar bone following resorption of the bone from osteoclasts

90
Q

what can be found on the part of the osteoclasts that lie adjacent to the bone

A

a brush border which gives a striated appearance. the border is comprised of many tighly packed microvilli which may be coated with fine, bristle like structures.

91
Q

what are rests of malassez aggregations of

A

epithelial cell rests

92
Q

how can rests of malassez be distinguised form adjacent fibroblasts

A

by the close packing of their cuboidal cells and their tendency to stain more deeply

93
Q

what can rests of malassez proliferate to form if stimulated by chronic inflammation

A

cysts and tumours

94
Q

what have epithelial cell rests been shown to produce

A

matrix molecles, proteins, growth factors, cytokines and neuropeptides

95
Q

what are the different defence cells of the periodontal ligament

A

macrophages, mast cells and eosinophils

96
Q

what percentage composition do macrophages make up in the periodontal ligament cell population

A

about 4%

97
Q

where are the macrophages located within the periodontal ligament

A

near the nerves and blood vessels

98
Q

what are mast cells associated with

A

blood vessels

99
Q

which defence cells are associated with blood vessels

A

macrophages and mast cells

100
Q

what are eosinophils

A

defence cells occasionally seen in the normal periodontal ligament that are capable of phagocytosis

101
Q

what are dendritic cells

A

defence cells found in the periodontal ligament that are derived from bone marrow

102
Q

what are the various defence cells of the periodontal ligament capable of synthesising and releasing

A

bioactive molecules such as cytokines, growth factors, and cell adhesion molecules

103
Q

why must there be replacement cells for when the osteoblasts and cementoblasts of the periodontal ligament become incorporated into the alveolar bone

A

to permit osteogenesis and cementogenesis

104
Q

is apoptosis a common feature in mature connective tissues of the periodontal ligament

A

no

105
Q

where is the rich blood supply of the periodontal ligament derived from

A

the appropriate superior and inferior alveolar arteries. arteries from the gingiva may also be involved

106
Q

where are the arteries that supply the periodontal ligament derived from

A

a series of perforation arteries passing through the alveolar bone

107
Q

how does the volume of the periodontal ligament occupied by blood vessels vary

A

between 10 and 30% according to species, tooth type, and whether the tooth is erupted or erupting

108
Q

what forms a capillary plexus

A

blood vessels found near the root surface

109
Q

where do many of the vessels of the periodontal ligament lie

A

between principle fibre bundles and close to the wall of the alveolus

110
Q

what is a special feature of the periodontal ligament

A

presence of large numebrs of fenestrations in the capillaries. this is unusual, as fibrous connective tissue usually has continuous capillaries

111
Q

how do the veins of the periodontal ligament differ from the arteries

A

the veins do not usually accompany the arteries and instead pass through the alveolar walls into the intraalveolar venous networks

112
Q

how do the junctions between the vascular endothelial cells in the periodontal ligament vary

A

from close to tight to open. the open junctions are more permeable and provide pathways for fluid and molecular transport. open junctions appear to be characteristic of the venous capillaries in the periodontal ligament

113
Q

what is anastomosis

A

the connection of blood vessels - in the periodontal ligament the blood vessels connect with the the veins of the gingiva also

114
Q

what are the different nerves found in the periodontal ligament

A

some are sensory and some are autonomic. sensory are associated with the nociception and mechanoreception. autonomic are associated with supply of the periodontal blood vessels

115
Q

is periodontal ligament more or less innervated than other dense fibrous connective tissue

A

more

116
Q

how do the nerve fibres enter the periodontal ligament

A

some enter through the root apex and pass up through the periodontal ligament. others enter the middle and cervical portions of the ligament as finer branches through openings in the alveolar walls

117
Q

are periodontal nerve fibres myelinated or unmyelinated

A

both

118
Q

which nerve fibres are myelinated

A

sensory

119
Q

which nerve fibres are unmyelinated

A

sensory and autonomic

120
Q

what is the function of mechanoreceptors

A

performing a major role in the transmission of touch and textural information when eating, as well as providig afferent feedback essential in the control of salivation, mastication and swallowing

121
Q

where are rapidly adapting responses seen

A

from receptors close to the fulcrum of the tooth about which movement is taking place

122
Q

where are slowly adapting responses seen

A

receptors close to the apex of the tooth

123
Q

what do mechanoreceptors exhibit directional sensitivity in response to

A

forces applied to the crown of the tooth, which can be explained by their discrete receptive fields

124
Q

what do the cell bodies of the neurons that innervate the mechanoreceptors in the periodontal tissues mostly lie within

A

the trigmenial ganglion

125
Q

what is found within the trigeminal ganglion

A

neurons that respond to mechanical stimulation of the teeth that have been found in the spinal trigeminal nucleus and the main sensory nucleus

126
Q

do the neurons that respond to forces applied to the teeth still exhibit directional sensitivity?

A

yes, but it may appear to respond to forces over a broader range of stimulus direction

127
Q

what is another role of periodontal mechanoreceptors besides transmission of forces

A

they modulate the activity of motor neurones of the hypoglossal cranial nerve, helping to control tongue position during mastication

128
Q

what are the pain fibres of the periodontal tissue represented by

A

fine, unmyelinated fibres terminating as free nerve endings

129
Q

what are neuropeptides released by

A

sensory nerve endings in the periodontal ligaments

130
Q

what effect can neuropeptides have in the periodontal ligament

A

widespread effects on blood vessels and cells

131
Q

is it still advantageous to retain tooth fragments and roots if teeth are badly damaged

A

yes - for sensation

132
Q

why is it important to try reimplantation of teeth

A

there will be some regeneration of periodontal mechanoreceptors

133
Q

what are features common to both the periodontal ligament and other fetal like connective tissue

A

high rates of turnover
sharp, unimodel size and frequency distributions of small collagen fibrils
significant amounts of type III collagen
large volumes of ground substance
high content glucuronate rich proteoglycans
presence of pre elastin fibres
high cellularity like the fibroblast like cells possessing numerous intercellular contacts
similar biochemical proprties

134
Q

what are the features of the periodontal ligament that indicate it is a specialised adult connective tissue

A
  • principle collagen fibres have characteristic orientation
  • in some species, pre elastin like fibres called oxytalan is present within the periodontal ligament
  • rate of turnover is very fast
  • cellular and rich in ground substance
  • hydrostatic pressure is high
  • ligament fibroblasts have features unusual for fibroblasts in adult fibrous connective tissues
  • periodontal ligament has cells concerned with the formation of dental tissues
  • rich vascular and nerve supply
  • capillaries are fenestrated
135
Q

what does the term tooth support mechanism describe

A

the manner whereby the periodontal ligament resists the axially directed instrusive loads that occur during biting

136
Q

what occurs when there is loading onto the periodontal tissue

A

the loads are dissipated to the alveolar bone primarily through the oblique principle fibres of the ligament. on release of the load, there is elastic recoil of the tissue which enables the tooth to recover its resting position

137
Q

what is an important clinical consideration for periodontal ligament

A

chronic inflammatory periodontal disease - toxic products released by dental plaque result in the destruction and loss of periodontal ligament tissue and adjacent alveolar bone

138
Q

what occurs within the periodontal ligament when there is orthodontic loading

A

wide areas of pressure on one side of the root and corresponding areas of tension on the other side are produced.
- on the side under the tension the periodontal space will become wider where the tooth is drawn away from the alveolar bone following the application of a continuous orthodontic load. bundles of fibres are stretched and the alveolar crest is pulled in the same direction.
- on the side under pressure, the periodontal space becomes narrower and the crest of the alveolar bone is slightly deformed. vascular activity is low.

139
Q

what are the two main functions of oblique periodontal fibres

A

provide support during biting compression and suspend the tooth

140
Q

how are oblique periodontal fibres inclined

A

cervically or attached the cementum more apically

141
Q

why are fibres more concentrated on the cementum than the bone

A

to distribute forces from biting

142
Q

how does staining intensity change on lining mucosa

A

decreases as you go to the surface

143
Q

what are von ebner salivary glands

A

minor salivary glands found in the circumvallate papillae on the tongue

144
Q

why is the dorsal surface of the tongue irregular

A

presence of several types of papillae

145
Q

which surface of the tongue is keratinised

A

the dorsum

146
Q

where is cellular cementum located on the teeth

A

furcation regions alongside the apex of the root of the tooth

147
Q

why do the furcations and apex of the tooth have cellular cementum

A

there is more wear and requires fresh cementum built all the time due to attrition

148
Q
A
149
Q

when do mechanoreceptors respond maximally

A

when the area in which they lie is put into tension.

150
Q

what are the nerves found in the periodontal ligament

A

sensorial nerves
sympathetic nerves

151
Q

what is the issue with the presence of cell rests of malassez

A

they are the origin of cysts

Oral Biology (23 decks)

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