normal periodontium :) Flashcards
components of the periodontoium
cementum
alveolar bone
PDL
gingivae
cementum
part of tooth but functions for PD support
acellular and cellular
alveolar bone
forms the tooth socket and attachment of PDL
PDL
connects cementum and protects other PD structures
diseases of the periodontium
gingivitis
- inflammation of gingiva
periodontitis
- inflammation of surrounding structres
what is the cerviz
where the head and neck meet
- where the tooth begins to narrow
what happens as the roots form
cementum and periodontal tissues develop from the dental follicle
what does the alveolar bone form from
existing basal components of maxilla/mandible and surrounds the roots as it forms
what produces the enamel on the crown
enamel organ
what is underneath the EO
dental papilla
what surrounds the EO and DP
dental follicle
what are the components of the cervial loop
external dental epithelium
internal dental epithelium
- in the region of the cervix
what happens as the cevcal loop grows deeper from th crown
grows into surrounding ectomesenchyme of dental follicle
encloses more of the DP as loop cell proliferates
forms Hertwigs epithelial root sheath
induces dentine formation
what is the dental follicle
mesenchymal cells surrodunding from the developing teeth
follicular cells of the DF are precursors to
fibroblasts
osteoblasts
cementoblasts
what does the epithelial root sheath do
secretes a hyaline later
- induces cementoblasts and fibroblasts to differentiate from dental follicle
where is the cervical loop found
lower part of the EO
- grows to form the roots of the teeth
what does breakdown of the epithelial root sheath lead to
production of a network
- allows the root dentine to contact the follcile
what is cementum
calcified connective tissue that covers root dentine
what inserts into the cementum
periodontal fibre bundles
what is cementum derived from
dental follicle (ectomesenchyme)
properties of cementum
softer than dentine and more permeable
55% HAP and 45% organic matrix
avascular, no innervation
non labile
types of cementum
acellular
cellular
acellular
occupies cervical and middle root of root
very thin layer
no cells
featureless (but faint lines of sharpens fibres)
cellular
occupies apical third of root (increases with age)
cementocytes in lacunae
forms more rapidly than acellular
how do the cementycytes communicate in cellular cementum
communicate with each other through a network of canaliculi
arrangement of the main fibres in cementum
from PDL embedded as sharpens fibres in the calcified martrix
- incorporated the cememtum (extrinsic)
how are main fibres arranged in acellular cementum
closely packed
mainly calcified
how are main collagen fibres arranged in cellular cementum
widely spaced
partially calcified
other collagen fibres within cementum
dense irregular network within matrix (intrinsic i.e. within cementum tissue)
made by cementoblasts
what does cementum provide
attachment for PDL fibres
- remains intact during orthodontics
what is hypercementosis
excessive formation of cementum
what causes hypercementois
hereditary
pagets disease
what are small spherical masses on the PDL
cementicles
what can cementum resorption occur due to
excessive occlusal stress orthodontic movement pressure from tumours or cysts Vit A/D deficiencies metabolic disease
what is ankylosis
where the PDL is lost
- leads to stiffening of joint
- fusion of cementum of roots to alveolar bone, tooth becomes fixed
how is the root connected to alveolar bone
PDL
- supports tooth in socket and absorbs loads on tooth
what do the cells of the PDL d
maintain and repair alveolar bone and cementum
alveolar bone
parts of maxilla and mandible that form the tooth sockets and support teeth
when does the alveolar bone erupt
only develops as tooth erupts
resorbed if teeth are lost/extracted
when is the alveolar bone absent
in anodontia (no teeth)
what does the alveolar bone consitis of
buccal and lingual cortical plates of compact bone (cancellous between plates)
cancellous bone is around the tooth forming the socket wall/inner cortical plate
compact bone in alveolar bone
no hacersian systems
contains bundles of collagen from the PDL on internal aspect
inner cortical plates
perforated
vascualar
has neural connections between the PDL and trabecular spaces
bundle bone
collagen fibres of PDL insert into socket wall
what does the inner cortical plate respond to and marked by
pressure -resportion
tension - doposition
marked by reversal lines
what is the inner cortical bone also known as
bundle bone
how does development of alveolar bone form
alveolar process forms label/buccal and lingual plates either side of the tooth organ
where is interradicular bone found
in between roots of mutlirooted teeth
what does alveolar bone respond to
mechanical stress and metabolic need for Ca and P
types of tooth movement
pre eruptive movement
eruptive tooth movement
post eruptive movement
how does bone remodelling occur
osteoclasts and osteoblasts
what leads to eruption
due to growth factors released form dental follicle causing
- resorption of overlying bone to create eruption pathway
growth of alveolar bone
what is needed to start alveolar bone formation
dental follicle secretes BMP 2 to induce osteoblasts
how does exfoliation occur
pressure from underlying permanent tooth causes resprotio of dentine and cementum by osteoclasrs
loss of PDL (mobile tooth)
inflammation in ligament causes more resportion
monocytes invade coronal part of dental follicle and convert to osteoclasts to create pathway
what happens after an eruption pathway is made for exfoliation
DF secretes
-CSF
- monocyte chemotactic protein 1
- endothelial monocyte activating polypeptide 2
signal for secretion from stellate reticulum secreting
- TGF beta 1
- Interleukin 1a
basal part of DF stimulates alveolar bone growth providing the force moving tooth up (due to secretion of BMP2 stimulating osteoblast formation)
pre eruptive tooth movemnt
made by tooth germs within the tissues of jaw before eruption
- during crown formation
- position changes with adjacent crowns and developing Md/Mx
- all movements occur within the crypts before root formation
eruptive tooth movment
made by a tooth from its position within the bone of jaw to its functional position in occlusion
stages of eruptive tooth movemtn
root formation
movement through any crypt to oral mucosa
tip of crown penetrates though fused epithelial layers into the OC
intraoral occlusal movement of erupting tooth until contacts opposing crown
what happens in root format of eruptive tooth movemtn
proliferation of epithelial root sheath, initiation of root dentine and formation of pulp tissues of the root
what happens when teeth move to reach the oral epithelium during eruptive tooth movemtn
Reduced enamel epithelium contracts and fuses with oral epithelium
- a RE layer overlying the erupting crown arises from the REE
post eruptive tooth movement
accommodate growing jaws
compensate for occlusal wear
accommodate inter proximal wear
