The oral environment and oral tissues

Question 1

what are the four classes of dental materials

Answer 1

preventative
restorative
auxiliary
biomaterials

Question 2

what are examples of preventative materials

Answer 2

sealants
cements
liners and bases
glass ionomers
casein phosphopeptide
amorphous calcium phosphate

Question 3

what are the three types of restorative materials

Answer 3

direct ( typical restoration)
indirect (crown, use of cements)
temporary (temporary crown)

Question 4

examples of direct restorative materials

Answer 4

amalgam and dental composite

goes directly into the tooth and finished intraorally

Question 5

examples of indirect restorative materials

Answer 5

these are fabricated extraorally on casts or using other means.
crowns, veneers, inlays, onlays, cement (luted)

Question 6

examples of temporary or provisional materials

Answer 6

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.

Question 7

what are definitive restorations

Answer 7

restorative services that are provided to serve as final, long term treatment

Question 8

what are auxiliary materials

Answer 8

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

Question 9

what are biomaterials

Answer 9

any material that interacts with biological systems.

Question 10

tissue engineering

Answer 10

using biomaterials to repair, shape or direct the growth of host tissues.
eg. injection of cells, guided tissue regeneration, cell induction, scaffolds

Question 11

injection of cells method

Answer 11

stem cells are injected into the general vicinity of the site in which they are intended to propagate.

Question 12

guided tissue regeneration method

Answer 12

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

Question 13

cell induction method

Answer 13

growth factors and developmental proteins are administered locally to induce progenitor cells to differentiate into desired tissues

Question 14

scaffold method

Answer 14

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.

Question 15

three types of biomaterials as scaffolds

Answer 15

natural
ceramic or glass
polymeric

Question 16

enamel composition

Answer 16

96% inorganic material(mineralized), 1% organic, and 3% water

Question 17

dentin, cementum and bone are all composed of what type of collagen and what mineral?

Answer 17

collagen type I

Hydroxyapatite(also in enamel)

Question 18

what is enamel formed by?

Answer 18

ameloblasts.

Enamel apposition begins at the DEJ and proceeds outward towards the surface of the tooth

Question 19

enamel composition structurally

Answer 19

• 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

Question 20

why is the protein coat important for enamel

Answer 20

increases the toughness

Question 21

what are the interfaces between prisms called?

Answer 21

inter-rod enamel
contain, organic components of enamel, allow flow of water and ions.
-known as prism sheaths

Question 22

what kind of acid is the etch

Answer 22

phosphoric acid and it dissolves the enamel crystals in each prism

Question 23

type I enamel etching

Answer 23

prism core is preferentially etched

Question 24

type II enamel etching

Answer 24

the prism periphery is preferentially etched

Question 25

type III enamel etching

Answer 25

results in a uniform or mixed pattern of etching

Question 26

T/F there is a difference in bond strength between the types of etching?

Answer 26

false, no difference in bond strength has been established

Question 27

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?

Answer 27

micromechanical bond

Question 28

is the enamel near the DEJ prismatic or aprismatic?

Answer 28

aprismatic, this makes it harder to etch

Question 29

where is fluoride concentration highest in enamel?

Answer 29

higher in the subsurface making it harder to etch deeper into the enamel

Question 30

with hydroxyapatite what commonly displaces the Calcium, phosphate and hydroxyl groups seen in enamel and dentin?

Answer 30

calcium: sodium and magnesium phosphate: carbonate hydroxyl: fluoride (most important)

Question 31

what is hydorxyapatite called when fluoride has replace the hydroxy group?

Answer 31

fluoroapatite, which is stronger and less soluble in acids.

Question 32

what type of cells make dentin and where are they found?

Answer 32

odontoblasts, found on the outer wall of the pulp immediately medial to the advancing wall of dentin.

Question 33

what is a distinct feature of dentin?

Answer 33

tubules created by odontoblast moving in from the DEJ .

Question 34

Composition of dentin

Answer 34

50% carbonate rich, calcium-deficient apatite 30% organic material, primarily type 1 collagen 20% fluid

Question 35

what is peritubular or intratubular dentin?

Answer 35

the lumen of the tubules and is highly mineralized apatite crystals and little to no organic collagen

Question 36

what is intertubular dentin

Answer 36

the stuff between the tubules, and consists of type I collagen matrix reinforced by apatite.

Question 37

where is tubular density most dense?

Answer 37

near the pulp

Question 38

what are the 4 types of dentin?

Answer 38

- 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.

Question 39

what does acid etching do in dentin?

Answer 39

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.

Question 40

why is transparent dentin hard to bond to?

Answer 40

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.

Question 41

what is another important component of etching other than widening the tubules and removing the smear layer?

Answer 41

removes the mineralized component of intertubular dentin leaving a network of collagen fibrils. This allows for the micromechanical basis for dentin bonding.

Question 42

why is dental conditioning important?

Answer 42

if you allow the dentin to become dry to collagen matrix flattens and the tubules shrink, making bonding more difficult.