Biocompatibility and Tissue response Flashcards
what is biocompatibility?
ability of a material to elicit an appropriate response in a given application in the body-Implication of function
what is histocompatibility?
being compatible with surrounding tissues
What is cytocompatibility?
being compatible with a single cell
what are Ex vivo tests?
- 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
In vivo tests
in the living-experiments performed in whole live organisms
usage tests
in vivo experiments using a material within its clinical context
aka clinical trial
In vitro tests
in glass-experiments using isolated populations of cells
Direct in vitro tests
relevant cells(single type of cell) places directly in contact with material and observation of cell response is recorded
Indirect in vitro testing
- cells placed on the opposite sides of a relevant barrier to a material.
- allows assessment of materials impact on cells through a barrier
progression of testing and comlexity
initial test: in vitro, and in vivo
secondary testing: in vivo
Final testing: usage tests with FDA approval
how can teeth respond to external stimuli
by producing new dentin
*critical that materials bond tightly with dentin to prevent microleakage
how much pulp in sufficient to prevent diffusion to pulp?
- 5 mm
* *etchants cause release of sequestered bioactive factors in dentin**
what is the hybrid layer?
the exposed collagen of dentin in direct contact with resin composite(bond)
the ability of a material to penetrate dentin is often a good indicator of ?
how biocompatible it is.
What is most important about the dentin bridge formation?
prevents micro-leakage and to prevent cytotoxic material of composite resin from touching the pulp.
stuff about resin based restoratives
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
why is the hybrid layer susceptible to enzymatic attack?
because the collagen fibers can be degraded thus decreasing the bond strength between the tooth and bond material
Matrix Metalloproteases MMPs
zinc dependent proteases
**play a major role in matrix remodeling and response to foreign bodies
released from dentin
what cells can release MMPs
fibroblasts odontoblasts osteoblasts macs neuts
what role do bacteria play in MMP activation
they can interfere with MMP inhibitors like TIMPs and thus activate MMPs.
Why is chlorhexidine important
is breaks down bacteria and MMPs
Amalgam in vitro, in vivo, and usage test results
in vitro: cytotoxic
in vivo: severe tissue response
Usage: amalgams very well tolerated
Why are amalgams a better option for longevity?
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
Bonding agents
generally cytotoxic, safe if exposure is limited
examples: HEMA, Bis-GMA, UDMA, Triethylene glycol dimethacrylate
