DMS Flashcards
What are the components of composite?
Dimethylacrylate
Camphorquinone
Silane coupling agent
Glass filler
Soft resin
Function of the dimethylacrylate and silane coupling agent?
DMA = forms two bonds rather than one in resin
SCA = forms bond between resin and the hard filler
Function of camphorquinone and soft resin and the glass filler?
Cam = light activated free radical addition polymerisation
SR = polymerised by Cam
Hard filler = added mechanical properties
What are the components of amalgam?
Mercury
Silver
Tin
Copper
Zinc
What are the three gamma phases?
Gamma is unreacted material of mercury and tin
Gamma 1 is strong, corrosion resistant silver-mercury
Gamma 2 is very weak corrosive tin-mercury
What do mercury and zinc function as in amalgam?
Mercury is a liquid so it is workable
Zinc is an oxidiser
What does silver do in amalgam?
Silver adds strength, reduces creep too, also increases setting strength
What does copper do in amalgam
Copper enriched amalgam has less gamma 2 phase
So less creep and corrosion, and stronger properties
What does tin function as in amalgam
Tin contributes to small amounts of corrosion
This helps seal restoration margins however causes creep
What are the three setting stages for GIC
Dissolution, gelation and hardening
Describe dissolution
Polyacrylic acid attacks glass particles releasing metal ions Ca, Na, Al, and F
Describe gelation.
Calcium bivalve to ions crosslink between poly salt chains.
Calcium can bind to same chain with both links so does not always create increased strength with every molecule
Describe hardening
Trivalent aluminium ions crosslink between 3 chains and harden the substance, increasing strength
How does GIC bind to enamel?
Calcium in enamel cross links with polyacrylic acid in the GIC
What are the components of ZOE?
Zinc oxide base powder
Eugenol and glycol liquid with some water
Setting reaction of ZOE?
Chelation reaction between Zinc oxide with eugenol to form zinc eugenolate matrix which encases unreacted ZnO particles
Pros of ZOE
Best biological seal of dentinal tubules however not biocompatible
Eugenol acts as obtundant
Neutral pH
Rapid setting time
Low thermal conductivity
Cons of ZOE?
No reparative dentine
Soluble
No fluoride
Cannot be used under composite or amalgam
Components of GIC?
Solid : Glass silica powder, ionic salts, calcium fluoride
Liquid : polyacrylic acid and tartaric acid
What are the three cavity liners you can use on paeds teeth
MTA, Ca(OH)2, GIC
What is MTA? And where is it used?
Mineral trioxide aggregate
Used as an apical barrier is open apex Endodontics
Can also be used as a cavity liner above the roots
What are the two types of Ca(OH)2 liner?
Ultracal - liner, non-setting
Dycal, exposures, setting
What are benefits of Ca(OH)2
Radiopaque
Sets fast
Bactericidal and produces reparative dentin due to alkalinity
What are the cons of Ca(OH)2
Soluble
Low compressive strength
Should be covered by rmgic
Why is ZOE typically not used as a liner
Low compressive strength and also reduced bond strength of composite as it is not compatible
Soluble which can be good and bad as it dissolves away but eugenol can decrease pulpal pain
Where may ZOE be used?
To fill voids in root canal surgery, main use in GP and around go to seal cone
How does CaOH set?
Acid base reaction
Catalyst paste of CaOH and a base paste containing zinc oxide in glycol salicylate react to form CaOH liner
Benefits of using MTA?
Highly biocompatible optimising healing
Similar expansion and contraction to dentine allowing for a very good marginal seal and preventing bacterial ingress
Low solubility
sets in a moist environment and produces Ca(OH)2 leading to a high pH
Cons of using MTA?
Long setting time, so not optimal when treating an uncooperative patient or child
Potential for discolouration of tooth
Pros of GIC
F release No shrinkage Good thermal prop Good compressive strength Natural bond to enamel and dentine
Cons of GIC
Brittle Poor aesthetics Requires etch High initial solubility
