Milling Units
Milling Units CATEGORY DESCRIPTION
Milling systems for the fabrication of complete and partial restorations operate via CAM software-generated programs/sequences, with some programs integrated into the CAD or design software and others acting as standalones. Most milling tools are made of carbide steel, but diamond-encrusted tools are sometimes used to mill glass ceramics.
Mills are available in tabletop, bench-top, and standalone sizes.
- Easily portable, most tabletop units ($30,000 to $50,000) are configured to mill single-unit blocks but some have fixtures for small frames or disks. These units sometimes have fixed tool changers, requiring manual switching of burs.
- Bench-top mills ($50,000 to $150,000) weigh up to 500 pounds, often requiring special lifting and support equipment. Automatic tool changers are standard, and some units have extra tool positions for additional detail and can mill certain metal and glass ceramic configurations.
- Freestanding units ($100,000 to $500,000) can mill the toughest materials in larger stocks, and can mill anything the smaller units can when a fixture is used to hold the material. These units weigh over 1,000 pounds and sometimes require floor reinforcement.
Wet versus dry. Most mills operate as either wet or dry, but some dry mills can be converted to operate as wet, and others can operate as dry or wet. Certain ceramics (e.g., lithium disilicate and feldspathic porcelains) and some metals (e.g., chrome cobalt) generally require wet milling, wax and acrylic for temporaries are typically milled dry, and zirconia and titanium can be milled dry or wet.
Wet milling uses liquid for cooling and to remove material from the milling disk or block, while dry milling uses pressurized air, vacuum or both to remove scrap. Both systems require maintenance cleanings and wet mills require periodic replacement of cutting liquid. With no drying required before sintering, dry-milled restorations can be fabricated chairside.
