Oral biology, enamel, dentine and bonding: oral biology lecture 1 Flashcards
oral biology lecture 1
what can over drying of the etched dentine result in
collapse of the collagen layer
this results in reduced bond strength
it is essential to keep it slightly wet, also called WET BONDING
dentine is classified as peritubular and intertubular
how is inter-tubular represented
is the main body of dentin, located between zone of peritubular dentin. Type 1 collagen present in this region.
what is the name of the condition, where incremental lines appear on the surface of the tooth enamel, as a series of linear growth
perikymata
what does this image represent
hydroxyapatite
when would the Striae of Retzius appear as concentric circles
in a cross section
where would you find specialised connective tissue
dentine
what is the function of odontoblast found on the outer surface of the dental pulp
dentinogensis = formation of dentin
in the enamel prism where would you find tightly packed hydroxyapatite crystals
prism core
what can be determined from the striae of retzius
indicates enamel development, the lines indicate weekly growth.
which zone sits between the cell rich zone and the predentine
cell free zone of weil
dentine can be classified as primary, secondary and tertiary dentine
what is tertiary dentine
tertiary dentin is reactive dentine, this is localised formation of dentin on the pulp-dentin border, formed in reaction to trauma such as caries or restorative procedure.
which part of the tooth is comprised of 70% mineral and 20% organic collagen
dentine
which of the following mechnaisms of tertiary dentine responds the quickest to trauma
reparative - quickest
reactionary - slow formation
what is occuring at the body of lesion
- The largest part and centre of lesion
- 25-50% porosity
- Enamel is relatively translucent
- Striae of Retzius more obvious
- Corresponds to the radiographic appearance
what is occurin on the surface zone
- Relatively intact
- 30 um thick
- Highly mineralised – high fluorine content
- Porosity of 1-2%
- Forms/reforms during carious process
- Redeposition of mineral dissolved from deeper layers
(KHN 360-390)
which part of the tooth represents that figure
enamel
what is a white spot lesion
enamel caries
what is in dental tubules
depending on the location of the cross section of the dentinal tubules. different contents are found.
developmental dentine is broken down to 2 components mantle and circumpulpal dentine:
where is circumpulpal dentine located.
(Circumpulpal dentin, more mineralized dentin which makes up most of the dentin layer and is secreted after the mantle dentin by the odontoblasts)
in other words makes up most of the dentine
what is referred as a keyhole shape
enamel prism
what is aprismatic enamel
Aprismatic enamel is a thin surface layer of the tooth, thought to be solid without individual enamel rods or prisms.
- Surface of Aprismatic layer is 30um
- Apatite crystals parallel and tightly packed
- Essentially no sheath like enamel
- High fluoride content (more acid resistant)
- More difficult to achieve optimal etch
where is the most mineralised tissue located in a tooth.
enamel
dentine
cementum
bone
dentine can be classified as primary, secondary and tertiary dentine
what is secondary dentine
(it develops after root formation has been completed and representing the continuing but much slower, deposition of dentin by odontoblast. The ratio of mineral to organic material is the same as for primary dentin)
developmental dentine is broken down to 2 components mantle and circumpulpal dentine:
where is mantle dentine located.
(The outer layer closest to enamel is known as mantle dentin. … Mantle dentin is formed by newly differentiated odontoblasts and forms a layer consistently 15-20 micrometres (µm) wide)
what is a smear layer
The smear layer is a layer of microcrystalline and organic particle debris that is found spread on root canal walls after root canal instrumentation.
which of the following region of the tooth has the most water region
dentine
enamel
cementum
bone
water
what is occuring in the translucent zone
- 1st carious change
- Loss of 1-2% mineral
- 50% of cases
which cell is of neural crest origin
odontoblast
what is the function of the hybrid layer placed after acid conditioning
: a hybrid layer is placed on the exposed collagen. They hybrid layer is a resin which consists of a collagen network. The layer is an interface between dentin and adhesive resin.
what is the purpose of acid etch
These acids have an etching effect that causes surface roughening
The dentine is present with dentine tubules inside, these tubules have curvatures, in the form of?
primary and secondary curvatures
what is the name of the incremental lines present on the enamel
Striae of Retziius
what does this structure form
enamel prisms
the direction of the collagen fibres present in the dentine follow the shape of what
they follow the shape of the ADJ
this gives the dentine reinforced strength
which of the following region of the tooth has the second most mineralised region
dentine
enamel
cementum
bone
what is indicated on the cuspal region of the histology
gnarled enamel
what supportive feature does the gnarled enamel provide
increase in strength
are enamel tufts hypomineralised or hypermineralised
hypomineralised
what is a ground section of a tooth
- A section of bone or tooth prepared for histological study by polishing until thin enough for microscope viewing
which two cells are found in the cell rich zone
odontoblasts and fibroblasts
give an example of an an epithelical product
the enamel
what is occuring in the dark zone
- Dark brown with quinoline
- Seen in 90-95% of lesions
- Porosity now 5-10%
- Consists of large pores and small pores
- In the dark zone – demineralisation and remineralisation occurring
sclerosis of the dentine is a result of dental insult.
what happens to the tubules during sclerosis
tubules blocked off
appears transparent
where would you expect to find the greatest concentration of nerves in tubules
pulp horn - greatest concentration
cervical margin - 7%
root <7%
The enamel structure contains tightly packed hydroxyapatite crystals
A basic unit =
enamel prism or rod
when would the Striae of Retzius appear as dark bands
in a longitudinal section
is the enamel vital or non vital
non vital
mantle and circumpalpal dentine can be classified as?
primary dentine
which of the following region of the tooth has the second least mineralised region
dentine
enamel
cementum
bone
which of the following region of the tooth has the second most water region
dentine
enamel
cementum
bone
cementum
which of the following mechnaisms of tertiary dentine responds by destroying odontoblast and recurits newly differentiated “odontoblast” for repair
reparative
tertiary dentine repairs through two mechanisms what are they
reactionary and reparative
dentine is classified as peritubular and intertubular
how is peritubular represented
peritubular/intratubular are represented by tubules in the dentine. no collagen present in the tubules
dentine can be classified as primary, secondary and tertiary dentine
what is primary dentine
it is the dentin formed before complete root formation. Most of the tooth formed by primary dentin which outlines the pulp chamber
KHN 75
which part of the tooth represents this figure
dentine
which of the following mechnaisms of tertiary dentine responds by using existing odontoblast for repair
reactionary
what are enamel spindles
dentinal tubules in enamel
what is the definition given when something has a smoothly rising and falling form or outline
undulating
with the removal of the smear layer and the process of demineralisation has exposed what?
collagen
where would you expect to find the greates concentration of dentinal tubules?
Amelodentinal Junction or Predentine
predentine
where would you find in the enamel prism, less tightly packed
prism sheath
how is micromechanical retention achieved
the use of acid etch to cause prisms forming
where would you find the most organic components in a enamel prism
prism sheath - lless tightly packed
