Material Science Flashcards
What luting cement is used to bond a metal crown and why
aquacem - glass ionomer cement
smaller particles than restoration material, allows crown to seat fully
used as unable to bond to tooth
what luting cement is used to bond a porcelain veneer + why
dual or light cure composite luting cement - NX3
bonds to tooth - DBA on tooth surface, silane coupling agent bonds to porcelain making both surfaces hydrophobic and able to bond to composite
silane coupling agent bonds to porcelain via oxide groups
what is panavia and when is it used
anaerobic cure composite luting cement
used for RBB
MDP bonds to metal via oxide groups and C=C to composite
composite bonds to DBA on tooth
why would a gold/ metal crown be used
aesthetics not of importance
minimal prep required
patient bruxist - strong and durable
why would metal ceramic crown be used
acceptable aesthetics but not optimal
strong and durable
compromised prep but not as much as porcelain
why would lithium discillate crown be used
aesthetics are of major importance
good bond to tooth so prep less than porcelain - requires 2-3mm circumferential
but requires good quality enamel and dentine for bond to work
why would amalgam be used over composite
aesthetics not important
moisture control is compromised
stronger than composite
why would composite be used over amalgam
aesthetics important
moisture control is adequate - able to get good bond
cavity is non-retentive, would require more prep for amalgam retention - destructive
describe dentine bonding
dentine conditioner - 35% phosphoric acid, remove smear layer and open dentine tubules
dentine primer - increases surface energy of dentine, makes hydrophillic surface hydrophobic, HEMA bifunctional - one side hydrophillic bonds via attraction to dentine, one side C=C bonds
dentine adhesive - Bis GMA resin - C=C to polymerise and bond to conditioner and composite
what is the composition of GI
glass - aluminium silica calcium fluoride
acid - polyacrylic acid tartaric acid
describe GI setting
dissolution - acid attacks glass and releases ions, unreacted silica coated in gel
gelation - calcium ions are bivalent, form 2 bonds - will feel hard in mouth
hardening - alumium ions are trivalent, form 3 bonds - will take 30 mins to one week to fully set
what is the diff between GI and RMGI
RMGI has addition of resin and photoinitiator - on demand set and increased strength + improved aesthetics
still not as strong as composite or amalgam
