Access burs through the crown:
Carbide fissure burs : cut through metal ( amalgam alloy or cast metal ) or composite resin.
Porcelain fused to metal :
-A round diamond is used to cut through the porcelain layer
-Transmetal bur to cut through metal
-transmetal bur has several blades to cut metal properly.
-Porcelain jacket crown :
-Diamond bur with copious coolant water spray to minimize micro fractures