The oral environment and oral tissues Flashcards
what are the four classes of dental materials
preventative
restorative
auxiliary
biomaterials
what are examples of preventative materials
sealants cements liners and bases glass ionomers casein phosphopeptide amorphous calcium phosphate
what are the three types of restorative materials
direct ( typical restoration)
indirect (crown, use of cements)
temporary (temporary crown)
examples of direct restorative materials
amalgam and dental composite
goes directly into the tooth and finished intraorally
examples of indirect restorative materials
these are fabricated extraorally on casts or using other means.
crowns, veneers, inlays, onlays, cement (luted)
examples of temporary or provisional materials
materials used to restore teeth for a short period of time, a few days to a year, with understanding that they are to be replaces.
what are definitive restorations
restorative services that are provided to serve as final, long term treatment
what are auxiliary materials
materials that are used to fabricate restorations, but do not become part of the restorations
eg. stone, waxes, impression materials, tray and mouthguard acrylic, finishing and polishing abrasives,
gypsum and phosphate-bonded investments
what are biomaterials
any material that interacts with biological systems.
tissue engineering
using biomaterials to repair, shape or direct the growth of host tissues.
eg. injection of cells, guided tissue regeneration, cell induction, scaffolds
injection of cells method
stem cells are injected into the general vicinity of the site in which they are intended to propagate.
guided tissue regeneration method
a surgical procedure for regenerating tissue by enhancing the opportunity for one cell type to proliferate.
eg. a membrane is used to exclude unwanted cell types
cell induction method
growth factors and developmental proteins are administered locally to induce progenitor cells to differentiate into desired tissues
scaffold method
promoting new tissue formation by providing a surface and void volume that encourages the migration and proliferation of desired cell types.
typically allowed to attach and proliferate in vitro then grafted into a host site.
three types of biomaterials as scaffolds
natural
ceramic or glass
polymeric
enamel composition
96% inorganic material(mineralized), 1% organic, and 3% water
dentin, cementum and bone are all composed of what type of collagen and what mineral?
collagen type I
Hydroxyapatite(also in enamel)
what is enamel formed by?
ameloblasts.
Enamel apposition begins at the DEJ and proceeds outward towards the surface of the tooth
enamel composition structurally
- made of long hexagonal crystals that span the entire enamel thickness (40 nm wide)
- the crystals are then packed into enamel rods or prisms that are 5 microns across
- about 100 crystals needs to span diameter of prism. visible after etching
why is the protein coat important for enamel
increases the toughness
what are the interfaces between prisms called?
inter-rod enamel
contain, organic components of enamel, allow flow of water and ions.
-known as prism sheaths
what kind of acid is the etch
phosphoric acid and it dissolves the enamel crystals in each prism
type I enamel etching
prism core is preferentially etched
type II enamel etching
the prism periphery is preferentially etched
type III enamel etching
results in a uniform or mixed pattern of etching
T/F there is a difference in bond strength between the types of etching?
false, no difference in bond strength has been established
what type of bond does the bonding agent make with the enamel after etching has roughened the surface of the enamel making it look frosty?
micromechanical bond
is the enamel near the DEJ prismatic or aprismatic?
aprismatic, this makes it harder to etch
where is fluoride concentration highest in enamel?
higher in the subsurface making it harder to etch deeper into the enamel
with hydroxyapatite what commonly displaces the Calcium, phosphate and hydroxyl groups seen in enamel and dentin?
calcium: sodium and magnesium
phosphate: carbonate
hydroxyl: fluoride (most important)
what is hydorxyapatite called when fluoride has replace the hydroxy group?
fluoroapatite, which is stronger and less soluble in acids.
what type of cells make dentin and where are they found?
odontoblasts, found on the outer wall of the pulp immediately medial to the advancing wall of dentin.
what is a distinct feature of dentin?
tubules created by odontoblast moving in from the DEJ .
Composition of dentin
50% carbonate rich, calcium-deficient apatite
30% organic material, primarily type 1 collagen
20% fluid
what is peritubular or intratubular dentin?
the lumen of the tubules and is highly mineralized apatite crystals and little to no organic collagen
what is intertubular dentin
the stuff between the tubules, and consists of type I collagen matrix reinforced by apatite.
where is tubular density most dense?
near the pulp
what are the 4 types of dentin?
- Primary: dentin formed by odontoblasts before tooth eruption
- Secondary: dentin formed by odontoblasts after tooth erruption
- Tertiary: reparative dentin that forms quickly in response to trauma. *only found under dentinal tubules that have been exposed to trauma, at the outer pulpal wall
- Transparent or sclerotic: a type of tertiary dentin that develops following trauma, tubules are partially occluded with mineral.
what does acid etching do in dentin?
clears the debris from the smear layer and alters the external lumen of the tubules allowing better infiltration by bonding agents.
**peritubular dentin is preferentially removed since is has no organic component thus widening the tubule creating a funnel shape.
why is transparent dentin hard to bond to?
because of the plugs formed by the minerals from the trauma, etching doesn’t always remove the plug thus making it not as permeable to the bonding agent.
what is another important component of etching other than widening the tubules and removing the smear layer?
removes the mineralized component of intertubular dentin leaving a network of collagen fibrils.
This allows for the micromechanical basis for dentin bonding.
why is dental conditioning important?
if you allow the dentin to become dry to collagen matrix flattens and the tubules shrink, making bonding more difficult.
