Air abrasion is a technology that was revived in the early 1990s from its early roots in the middle of the 20th century. During its revival, it was heavily promoted along with expensive, canister-like units, which were rolled into the treatment room when they were needed. However, it has definitely been on the decline in recent years. If it is used, a small, relatively inexpensive instrument is more likely to be employed compared to the large units of yesteryear.
Nevertheless, proponents of this technology are still enthusiastic about the technical as well as the financial boost it can bring to a dental practice. The technical aspects relate to being able to treat many types of lesions in a manner that is, perhaps, kinder to teeth than a highspeed handpiece and, in many instances, without an injection. That latter advantage opens the doors of dentistry to many people who just shudder at the unpleasant whirl of a highspeed handpiece and/or the dreaded "needle". So, even though dentists should be able to profit handsomely by using one of these machines, the patient wins too.
On the other hand, the opponents criticize this technology as just a messy fad. They argue that you can still treat most patients with conventional instrumentation, so why bother. We feel the technology has merits, but the character of your practice will really decide if you should buy into it.
There are two main considerations:
1. Should you consider buying an air abrasion unit?
3. Should this category's name be changed to "water abrasion"?
Should You Consider Buying into this Technology?
There is no doubt that these machines give you the ability to treat patients in a less threatening way, which is a real quantum leap when dental phobics are considered. In addition, simple lesions, discovered during routine recall (recare) visits, can be prepared and restored immediately. With this technology, local anesthesia can probably be eliminated and, in combination with a flowable composite, the restoration can be completed in as little as 10 minutes. Not only do patients appreciate the fact that they do not have to come back at another time for the restoration, you can also earn unscheduled income. This is truly a win-win scenario.
However, none of these units are designed for precision indirect procedures, such as veneers, inlays, onlays, and crowns. Therefore, the decision to buy into this technology still really depends on the character of your practice. Furthermore, with the emergence of hard tissue lasers, the future of this category is increasingly cloudy.
Is it "Air Abrasion" or "Water Abrasion"?
The trend is to move away from using air as a propellant for the abrasive particles and move toward water, which adds an interesting option that minimizes or eliminates the "dust storm" created by the air-only devices. With water, the devices produce an aluminum oxide slurry as the abrasive agent. The abrasive slurry reduces the overspray and the virtual dust cloud that is produced whenever an air abrasion instrument is used dry. In this respect, all of our evaluators agreed that it is less messy compared to air-only versions. The slurry is easier to clean intraorally and there is less "dust" to clean extraorally. In addition, at least one evaluator believed that patients were more comfortable with the water slurry.
The most common use of these machines is to prepare various types of cavities to be restored with an adhesive material. Even though simple occlusal preparations are most prevalent, experienced users can perform just about any type of cavity preparation destined for a direct restoration. In addition, restoration repairs can be facilitated using this equipment.
As an example, a patient presents with a small cervical fragment of a porcelain veneer fractured, leaving a defect where the resin cement is still bonded to the tooth. The procedure to repair the veneer includes masking the unaffected porcelain except for about 1.0mm at the junction of the veneer and fracture site plus covering the gingiva with a resin block-out material. Air abrasion can then be used to remove the remaining resin cement and to prepare a chamfer on the exposed porcelain adjacent to the fracture site. During the preparation of this chamfer, the porcelain is automatically microabraded for the repair procedure to follow. Thus, it is possible to remove the remaining resin cement and sandblast the porcelain all in one quick procedure.
Besides using these machines for cavity preparations and special repairs as described above, they can also perform all the duties of the small handheld sandblasters including the roughening of the inside of restorations prior to bonding. Our tests showed there is no difference in bond strength when sandblasting composite or porcelain using 27µ or 50µ aluminum oxide. Therefore, since most air abrasion units are using 27µ aluminum oxide for cavity preparations, there is no need to change to the larger particle sand for roughening most restorations.
The two main areas where this technology comes up short are indirect restorative preparations and amalgam removal. Even though it had been suggested by at least one manufacturer (now out of business) that amalgam can be removed with these products, we urge you to resist using it for this purpose due to the dust generated. And, despite the initial claims that the abrasive action of these machines on enamel and dentin can eliminate the need to acid etch, most research has found just the opposite. It is still necessary to follow the same steps in placing an adhesive restoration as you would if a cavity was prepared with a highspeed handpiece and bur.
In addition, when removing caries-softened dentin in deeper lesions, conventional instruments such as a round bur in a slowspeed handpiece and/or a spoon excavator are more effective than air abrasion and give more control as you approach the pulp.
Even though patients do not react to air abrasion in the same manner that they react to having their teeth prepared with a highspeed handpiece, it is not universally painless. There is still an air/powder or water/powder stream. Nevertheless, patients generally prefer air abrasion to conventional cavity preparation due to the lack of the highspeed whirl and vibration. The air/water instruments may be able to take this comfort level to an even higher limit.
Eyes Patients should wear protective goggles that seal the eyes.
Soft Tissue Whenever possible, especially posteriorly, use a rubber dam. For Class V restorations, cover the gingiva with a resin block-out material.
Adjacent Teeth During cavity preparation, adjacent teeth must be protected from the abrasive. Rubber dam material is helpful but can get in the way. Metal and plastic matrices are less obtrusive, but can be penetrated by the abrasive. Therefore, we recommend trying rubber dam material first and only using a matrix if the rubber dam obscures your visual access to the preparation. If you use a matrix, be very careful with proximal preparations.
Dental Team Protection
Besides a well-fitting mask, both the operator and assistant should use a facial shield to protect their own glasses or magnification loupes. If you do get the abrasive on your loupes, rinse with water first and then wipe dry.
When you first begin using an air abrasion unit, you should stop frequently to check your progress. With an adjustable unit, it is always best to start with low pressure and low powder flow, increasing one or the other or both as you become more experienced (assuming your unit is adjustable). After using it for a while, you'll know when to stop, when to cut, and the best pressures and powder flow for specific procedures. Hold the tip of the handpiece about 1-2mm from the tooth and activate the unit. Always have the tip moving as if you were using a highspeed handpiece. If you hold the tip stationary, the abrasive stream can cut a hole that is narrow and deep very quickly. Be aware that any of these units will ruin your dental mirrors, so having a supply of inexpensive disposable mirrors on hand is prudent.
If you invest the time to learn how to use air abrasion and money to purchase a unit, you should make a point of telling patients about its benefits. Even if a specific patient cannot benefit from it, the patient will still spread the word. Be enthusiastic, but resist the temptation to overhype it.
Items to Consider
You have two choices: countertop model or no base unit, where the handpiece incorporates the abrasive reservoir. The countertop units reduce available horizontal work areas and their weight sometimes limits their mobility. However, the very small units are much lighter, making portability much more feasible.
Source of Air Pressure
Most units today use an air line to your dental unit.
Range of Air Pressure
Since you will most likely be operating off a connection to your central compressor, your top pressure will be whatever your compressor generates. This is typically 80psi, although at least one unit can increase this pressure by using a booster. Higher air pressure can help cutting efficiency but can also cause more patient discomfort.
Air Pressure Gradient
In addition to the range of air pressure, the other convenience factor is the jump between settings. For example, a machine that allows you to increase or decrease pressure in small increments (5psi or less) is more versatile than one that has large jumps between settings. Most units today do not have this adjustment.
There are different sizes and shapes to accommodate different treatment situations. For example, if you want to sandblast the inside of a veneer, the best option would be a tip with a relatively large orifice since you want to cover a broad area. On the other hand, for more precision cutting, a small tip would be necessary. Different shapes for anterior and posterior teeth can definitely help in accessing hard-to-reach areas. Even though you will probably settle into using one or two tips, having the extra shapes and sizes on hand is a nice option.
Size of Abrasive
The current line-up of products only have one reservoir. And this is probably adequate since our tests suggest that the smaller size of the 27µ particles is more than adequate for roughening composite and porcelain when completing repairs and seems to cause less pain for cavity preparations.
Abrasive Flow Control
Some units allow you to increase or decrease the powder flow based on the specific procedure. Turning down the powder flow can minimize the mess and help with sensitivity.
External Suction Device
Even though the EPA rates airborne aluminum oxide as a "nuisance dust" and not hazardous, it is still prudent to take reasonable measures to keep this dust out of your lungs as well as those of your staff and patients. In addition, these machines have a potential to be very messy due to overspray.
Therefore, the use of an external suction device in addition to your high volume evacuator helps to keep the overspray to a minimum and protects everyone's lungs. Some of the larger, canister-type machines had their own suction devices, but the current portable models require you to use a separate unit or merely your high volume evacuator. Keep the tip of the evacuator as close to the operative site as possible. Be aware that the effect of the aluminum oxide abrasive on your central vacuum system can cause damage that may not be apparent for several years and could be expensive to repair.
Note: Units using water as a propellant definitely minimize the dust cloud, but their overflow of slurry is still messy. In addition, since an external evacuation device is not an option with an air/water model, there could be an effect on your tubings and other equipment that still needs to be investigated.
For heavy users, the ease of refilling the unit with abrasive could be important.
All machines require some maintenance and it can be messy. However, less is always better in this case.