What they found is that the iPhone 4 glass is protected by the mighty Gorilla Glass!
The front glass panel of the iPhone is constructed of Corning Gorilla Glass, a chemically strengthened alkali-aluminosilicate thin sheet glass that is reported to be 20 times stiffer and 30 times harder than plastic.
Gorilla Glass holds many advantages as the iPhone 4s front panel including its high resistance to wear and increased strength from a strengthening process.
Full Teardown: HERE