Air abrasion for restoration preparation removes tooth structure using a stream of aluminium oxide particles generated from compressed air or bottled carbon dioxide or nitrogen gas. The abrasive particles strike the tooth with high velocity and remove small amounts of tooth structure. Efficiency of removal is relative to the hardness of the tissue or material being removed and the operating parameters of the air abrasion device.
A number of parameters such as the amount of air pressure, particle size, quantity of particles passing through the nozzle, nozzle diameter of the handpiece, angulation of nozzle of the handpiece, distance from object, and time of exposure to the object vary the quantity of tooth removal and depth of penetration.
· Generally, air pressures range from 40 to 160 psi. The recommended levels are at 100 psi for cutting and 80 psi for surface etching.
· The most common particle sizes are either 27 or 50 μm in diameter. The larger particles allow the clinician to work faster but will result in comparatively larger-sized cavity preparations than those with the 27 μm particles.
· Higher particle flow rate will allow more particles to abrade the working surface faster.
· The speed of the abrasive particles when they hit the tooth depends upon the gas pressure, nozzle diameter, particle size, and distance from the surface.
· Typical operating distances from the tooth range from 0.5 to 2 mm. Further distances produce a more diffuse stream that results in a diminished cutting ability.
· A number of variations in tip angulations and nozzle diameters are available. Smaller nozzle diameters can be used for areas that are difficult to access. The various tip angulations allow easy placement and orientation of the handpiece thus easing the strain off the operator’s hands.
