ADA Classification of Gold Alloys According to their Use: Type Name Brinell Hardness

Number (BHN) Pure Gold (%)

Melting Temperature

Use Characteristics

I Soft Gold Alloy 40 – 75 83% 950 – 1050°C

(High) Simple Inlay Restorations

§ Used in cavities not subjected to high stresses, e.g. gingival cavities

§ HIGHLY DUCTILE & readily burnished

II Medium Gold Alloy (Inlay Gold)

10 – 100 78% 630 – 970°C Large Inlay Restorations

§ Age Hardening § Most popular type

for inlays

III Hard Gold Alloy 90 – 140 76% 930 – 970°C Crown & Bridge § High Proportional

Limit, resisting deformation

IV Extra Hard Gold Alloy

> 130 75% 870 – 980°C Partial Denture § Strength &

resiliency required § LACK DUCTILITY

V White Gold Alloy > 100 ---- ---- Crown & Bridge

§ Addition of platinum, palladium & silver

§ LESS DUCTILE than gold colored alloys

§ Less resistance to tarnish

By: Noor Al-Deen M. Al-Khanati