Dentist Notes

Casting

Dental MaterialsUpdated 1 min read
On this page 2 sections

💡Defects

DefectMain reasonPrevention
Gaseous porosityGas trapped in metalAvoid overheating, proper venting
Shrinkage porosityMetal contracts during solidificationProper sprue + reservoir
MicroporositySmall-scale shrinkageProper spruing + temperature
Suck-back porosityShrinkage near sprue junctionProper sprue/reservoir
Back-pressure porosityAir can't escape moldGood permeability/venting
PinholesGas reaction/trappingProper burnout + clean alloy
Incomplete castingMetal solidifies before filling moldIncrease/maintain casting temperature
Fin/flashInvestment crackProper investment technique
NodulesAir bubbles/investment particlesVacuum mixing, remove bubbles
Rough castingRough wax/investment/burnout problemProper investment + burnout
DistortionWax pattern deformationCareful handling
CracksInvestment/casting stressProper technique + controlled cooling

💡Quenching

Quenching ConditionTemperature RangeResult / EffectPractical Outcome
Dull Red Glow ~ 500C - 700CAnneals (softens) alloy & shatters moldThe soft, ductile gold is easy to burnish and finish; rapid steam explosion cleans investment off the casting.
Cherry Red / Light Orange Glow> 700 CThermal shock & excessive stressQuenching too early can warp the restoration, cause internal micro-cracks, or alter the grain structure.
Dull Grey / Completely Cool< 400 CAge-hardening (hardening heat treatment)Allows intermetallic compounds to precipitate, making the alloy hard, brittle, and difficult to adjust or burnish.