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
Glass ionomers
- 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
Liners and resin cements
calcium hydroxide
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
Liners and resin cements
Zinc phosphate, Zinc polyacrylate, ZOE
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
Liners and resin cements
Mineralized Trioxide Aggregate (MTA)
**NOT CYTOTOXIC
increases cell proliferation/migration and synthesis of mineralized matrix specific proteins
encourages dentin bridge formation
Bleaching agents
- almost all contain peroxide
- high levels of cytotoxicity
- can rapidly transverse enamel, dentin and come in contact with pulp
- also can burn gingiva
