oxide particles (27 or 50 um) are blasted against the teeth under a range of pressures
(30-160 psi) with variable particle flow rates.
One very obvious concern is the safety aspect due to the presence of quantities of free
aluminium oxide in the surgery environment. In theory aluminium oxide is considered
harmless. It is found in a wide variety of products from toothpastes to polishing
wheels. The size of the particles is considered too big to enter the distal airways or
alveoli of the lungs. What dust does enter the lungs should be easily removed by
ciliary action. However, anyone who has used one of these units will know that
control of the dust is an ongoing challenge; rubber dam and very good suction help,
but it still seems to spread.
Air abrasion produces a cavity preparation with both rounded cavo-surface margins
and internal line angles. The surface it creates is irregular with many fine voids and
defects. Initially it was considered that this surface might provide enough retention
without etching but studies show this as erroneous.
Some of the clear advantages proposed for air abrasion are:
- Elimination of vibration, less noise, and decreased pressure.
- Reduction in pain during cavity preparation; 85% of patients do not require local
analgesia. - Less damaging pulpal effects than with conventional hand-piece usage, when used
at higher pressures of 160 psi and with smaller particle size of 27 um. - Less fracture and crazing of enamel and dentine during cavity preparation.
- Root canal access through porcelain crowns without fracturing porcelain.
Air abrasion has been proposed for:
- Cleaning and removing stains and incipient caries from pits and fissures prior to
sealant and PRRs. - Small class I, III, IV, and V cavity preparations and selected class II preparations.
- Repair and removal of composites, glass ionomers, and porcelain restorations.
- Cleaning and preparation of castings, orthodontic bands, and brackets prior to
cementation.
What it cannot do is remove leathery dentinal caries or prepare extensive cavities
requiring classical retentive form.
To use it successfully, the clinician must learn a new technique as the tip does not
touch the tooth and therefore there is no tactile feedback. The tip width and the tip to
tooth distance seem to have most influence on the cavity width and depth. Increasing
the distance produces larger shallower cuts. Increasing the tip diameter produces
larger deeper cuts. Therefore, the most precise removal of tooth tissue is achieved
with a small inner diameter tip (0.38 mm), held 2 mm from the tooth surface. If
cutting a class II cavity, it is essential to protect the adjacent tooth. Care must also be
taken around the soft tissues to prevent surgical emphysema. Glass/mirror surfaces
may be damaged by the dust.