Air-abrasion units in dentistry
Air-abrasion units attached to standard handpiece couplings of dental units (or as stand-alone units) are always operated in dental medicine (unlike the sandblasters in dental technology) using a mixed jet of downstream separated (avoids clumping) water, compressed air and powder. The powder is stored in a refillable reservoir ("powder chamber") in the unit.
Introduced as far back as the mid-20th century, air-abrasion units have again been used since about the year 2000 ("cavity air polishers") operating at a pressure of between 4 and 10 bar for reducing hard tooth structure (air abrasion, "kinetic cavity preparation", abbreviated as "KCP"). The impact of water-insoluble aluminium oxide particles (equivalent to dental technological "abrasive grit") prepares non-contact (no tactile sensation), smaller, minimally invasive cavities quietly and with only low pain, without generating heat (unlike rotary instruments). The cavities, however, are not prepared with predictable geometries (undefined margins). Other areas of application are the intensive cleaning of fissures before sealing and conditioning (roughening, creation of micro-retention and/or chemical changes) of restorations or tooth surfaces for improving the bond strength, particularly of adhesive systems (also to veneering porcelains, e.g. for intraoral repairs).
The more widely used powder/water jet units (since approx. 1980) operate at a pressure of 2 to 3 bar with angular crystals made from water-soluble, very salty tasting, sodium hydrogen carbonate (NaHCO3, "natron"; obsolete also "sodium bicarbonate") powder (due to "refined" hydrophobic substances), later also reputedly less abrasive, water-insoluble "floury" calcium carbonate (CaCO3). They are used for targeted supragingival removal of discoloration from enamel (professional cosmetic teeth cleaning).
The classically used "salt jet" can cause damage to adjacent restoration surfaces, exposed dentine surfaces or injury to the gingiva. Applied at an unfavourable angle, the jet of air can lead to gingival emphysema, in the worst-case scenario later to air embolisms. When using air-abrasion units, special safety precautions should also be taken to avoid germ transfer, blocked tubing, damage to objects, inhalation or eye injuries.
In recent years, water-soluble amino acid glycine has been increasingly used for "perio-polishing", i.e. for subgingival removal of accretion and bacteria from the gingival pockets for prophylactic and periodontal therapy purposes. In the absence of calculus, this procedure is deemed superior to scaling with instruments.