Biocompatibility and Tissue response

Question 1

what is biocompatibility?

Answer 1

ability of a material to elicit an appropriate response in a given application in the body-Implication of function

Question 2

what is histocompatibility?

Answer 2

being compatible with surrounding tissues

Question 3

What is cytocompatibility?

Answer 3

being compatible with a single cell

Question 4

what are Ex vivo tests?

Answer 4

• out of the living-experiments performed using whole tissues extracted from organisms.
• like taking hole punch through a tooth and testing the whole thing outside of the body

Question 5

In vivo tests

Answer 5

in the living-experiments performed in whole live organisms

Question 6

usage tests

Answer 6

in vivo experiments using a material within its clinical context
aka clinical trial

Question 7

In vitro tests

Answer 7

in glass-experiments using isolated populations of cells

Question 8

Direct in vitro tests

Answer 8

relevant cells(single type of cell) places directly in contact with material and observation of cell response is recorded

Question 9

Indirect in vitro testing

Answer 9

• cells placed on the opposite sides of a relevant barrier to a material.
• allows assessment of materials impact on cells through a barrier

Question 10

progression of testing and comlexity

Answer 10

initial test: in vitro, and in vivo
secondary testing: in vivo
Final testing: usage tests with FDA approval

Question 11

how can teeth respond to external stimuli

Answer 11

by producing new dentin

*critical that materials bond tightly with dentin to prevent microleakage

Question 12

how much pulp in sufficient to prevent diffusion to pulp?

Answer 12

0. 5 mm

* *etchants cause release of sequestered bioactive factors in dentin**

Question 13

what is the hybrid layer?

Answer 13

the exposed collagen of dentin in direct contact with resin composite(bond)

Question 14

the ability of a material to penetrate dentin is often a good indicator of ?

Answer 14

how biocompatible it is.

Question 15

What is most important about the dentin bridge formation?

Answer 15

prevents micro-leakage and to prevent cytotoxic material of composite resin from touching the pulp.

Question 16

stuff about resin based restoratives

Answer 16

combined organic/inorganic components
cytotoxic
cytotoxicity decreases over the age of the restoration
use of basement materials and bonding agents helps reduce pulp irritation
**can shrink slightly as they cure

Question 17

why is the hybrid layer susceptible to enzymatic attack?

Answer 17

because the collagen fibers can be degraded thus decreasing the bond strength between the tooth and bond material

Question 18

Matrix Metalloproteases MMPs

Answer 18

zinc dependent proteases
**play a major role in matrix remodeling and response to foreign bodies
released from dentin

Question 19

what cells can release MMPs

Answer 19

fibroblasts
odontoblasts
osteoblasts
macs
neuts

Question 20

what role do bacteria play in MMP activation

Answer 20

they can interfere with MMP inhibitors like TIMPs and thus activate MMPs.

Question 21

Why is chlorhexidine important

Answer 21

is breaks down bacteria and MMPs

Question 22

Amalgam in vitro, in vivo, and usage test results

Answer 22

in vitro: cytotoxic
in vivo: severe tissue response
Usage: amalgams very well tolerated

Question 23

Why are amalgams a better option for longevity?

Answer 23

there is initial micro-leakage around margins, but this diminishes as corrosion products build up
-also do not cause pulp damage, but can cause pulpal inflammation in deep unlined restorations resulting in pain

Question 24

Bonding agents

Answer 24

generally cytotoxic, safe if exposure is limited

examples: HEMA, Bis-GMA, UDMA, Triethylene glycol dimethacrylate

Question 25

Glass ionomers

Answer 25

• polyacrylic acid used as cement, lining material, base and restorative material
• release fluoride as they set
• In vitro-cytotoxicity
• doesn’t cause sustained adverse rxns in pulp
• may etch dentin to potentially release bioactive factors which enhance dentin bridge, but also MMPs

Question 26

Liners and resin cements

calcium hydroxide

Answer 26

calcium hydroxide is frequently used as a lining material
high pH, cytotoxic, better when combined with Dycal
-direct exposure to pulp causes immediate necrosis, but when combined with resin necrosis is significantly reduced/eliminated
-may release bioactive factors from dentin

Question 27

Liners and resin cements

Zinc phosphate, Zinc polyacrylate, ZOE

Answer 27

Zinc phos: cytotoxic, necrosis of pulp
Zinc poly: less cytotoxic
ZOE: eugenol has cytotoxic effects, has an anesthetic property
zinc poly and ZOE mild inflammation, which resolves relatively quickly
*these are not very bioactive materials and don’t form a strong dentin bridge

Question 28

Liners and resin cements

Mineralized Trioxide Aggregate (MTA)

Answer 28

**NOT CYTOTOXIC
increases cell proliferation/migration and synthesis of mineralized matrix specific proteins
encourages dentin bridge formation

Question 29

Bleaching agents

Answer 29

• almost all contain peroxide
• high levels of cytotoxicity
• can rapidly transverse enamel, dentin and come in contact with pulp
• also can burn gingiva