final liners and bases Flashcards
liners are used to?
prevent chemical irritation to the pulp, some therapeutic effects
liner composition
- suspensions of calcium hydroxide in aqueous solvent
* barium sulfate provides radiopacity and fluoride
liners do not provide ______ strength and _____ protections?
mechanical strength and thermal protection
why shouldn’t liners be applied to margins?
they can dissolved and leave the area susceptible to leakage
bases are placed under?
matallic restorations when less than 2mm of dentin remains between restoration and pulp to prevent chemical and thermal irritation of the pulp
*typically cements
what is the most commonly used base under amalgam? why? what dispense system?
calcium hydroxide.
- ability to stimulate reparative dentin formation
- two paste system, equal amounts used
ZOE cements should not be placed under?
composite resin restorations because they will inhibit polymerization
base materials provide adequate thermal protection when placed as what thickness? too thick is bad why?
- 75 to 1.0 mm thick
* thicker than 1.0 mm should be avoided because they weaken the overlying restoration
bases can also be used to block out?
minor undercut areas in casting preparations prior to impression making
why should covering the entire pulpal floor with amalgum be avoided?
the best support for amalgam is sound dentin
rules for using base?
1) only when indicated
2) minimum thickness necessary
3) lost dentin should not be replaced with a base “basing to ideal form”
4) do not cover entire pulpal floor
