In skilled hands, air abrasion equipment can be a useful adjunct to a dentist who wishes to do conservative dental procedures. The ability to cut small and shallow holes may make local anesthesia unnecessary. When used with improved composite resins (white plastic fillings), the technique of air abrasion can provide early treatment of simple tooth decay with small, conservative restorations. In the wrong hands, the technique can be extremely dangerous.
Air abrasion systems consist of an air compressor and a delivery unit that holds an abrasive powder that is delivered through a handpiece similar in size to a dental drill [A, B]. The cut areas are then filled with composite bonding material. The FDA has approved more than 30 systems, which it classifies as “air brush” devices .
The technology is similar to a sandblaster with a fine tip. These machines blast aluminum oxide particles through a very small opening (0.375 -0.5 mm) with high-pressure air (up to about 160 pounds per square inch) on a surface area of 0.11 square millimeters. This can rapidly abrade tooth enamel or dentin. Proponents say that these machines are a major advance in dentistry because “micro-dentistry” is now possible. Tiny holes can be cut to shallow depths without rotary cutting tools (drills or burrs). Actually, however, the smallest drills can equal the smallest hole cut by these machines and provide more precision.
Potential for Injury
Because the machine cuts so quickly and does not touch the tooth while cutting, the operator can only gauge the cut after it is made. Dentists normally rely upon touch to know when they have removed softer decayed material and reached harder sound tooth structure beneath. But air abrasion systems do not enable the dentist to feel the depth or “softness” of tooth structure, and a fog of particles obscures the operator’s vision. Also, the stream of abrasive particles is one-directional. To cut the right and left sides of a hole the handpiece of the instrument must be stopped, reversed and restarted. In contrast, rotary tools cut in all directions using the same positioning. Also, when the foot pedal is released, the machine continues to work until the pressure is bled from the tip. Rotary tools stop cutting instantly when you lift them from the tooth.
The potential hazards of air abrasion systems are excessive frictional heat, major soft tissue damage, air embolism, particle showers with aspiration, and vaporization of mercury if the machine is used to remove amalgam fillings. To avoid most of these hazards, the machine manufacturer’s labeling requires use of a rubber barrier (dam), short cutting times, and careful control of the device. In addition it should not be used to remove amalgam fillings.
Used improperly, air abrasion can be extremely dangerous. Its high-speed jet of air can punch through soft tissue and inflate it rapidly. For this reason, a rubber dam should be used to protect the soft tissue. Several cases of rapid inflation of tissue have been reported in the hands of practitioners who did not use a rubber dam. Very large quantities of air can be pumped into soft tissue spaces in the neck in a few seconds. This air can infiltrate the neck and surround and compress the heart. Air can also erode into a vein to produce bubbles (air emboli) that can block the flow of blood within the heart and to distant parts of the body. In addition, the air pressure can blast food particles and bacteria from the mouth into nearby tissues to cause infections similar to those produced by a shotgun injury that drives dirty clothing and skin fragments into deeper tissues.
Alloy or amalgam fillings are harder than enamel and cannot be easily removed by air abrasion. The surrounding tooth structure will erode faster than the filling. The heat generated by an air abrasion system can injure the dental pulp, creating a need for a root-canal treatment. Further, heat and friction can cause amalgam to decompose and release mercury vapor.
Potential for Abuse
Air abrasion offers considerable potential for abuse. Overtreatment has been reported among people covered by insurance programs, particularly Medicaid, and several state dental boards are investigating this problem.
Proponents suggest that air abrasion can be used to not only to treat but also to diagnose early caries (tooth decay). A dark stain in the depth of a tooth fissure may represent early caries or merely stain. Opening the fissure with the air abrader can make the area accessible to probing. Most dental decay is diagnosed by using a fine metal-tipped instrument (dental explorer) and feeling a soft spot in a pit or fissure where the explorer tip sinks in and then sticks tightly. Caries represents loss of mineral from hard tooth structure caused by secretion of acid by bacteria. No single type of bacteria is specific for caries. Thus the condition is diagnosed by clinical examination as described above. Once caries has progressed, it continues to dissolve the outer tooth layer (enamel), which is more than 95% mineral, and eventually penetrates the deeper layer of dentin (another hard tissue, similar to bone in mineral content, 65% mineral). As mineral is removed. the protein matrix of the dentin is exposed. Dentin with caries is soft and can be scooped out with a spoon-like instrument. Excavation continues until firm dentin is encountered, after which a dentist would fill the hole with an appropriate filling material. Dentists can use caries-detecting dyes to disclose whether they have removed all of the softened material. These dyes stain the exposed protein. Their exact composition may be a trade secret. Despite their name, caries detection dyes are not specific for caries, and are less than 60% accurate in most studies.
Dental scams occur when these caries detecting dyes are misused. Here a dentist claims that many teeth have caries in the pits and fissures through use of these dyes. The dyes are not intended for this use. The dentist then places inordinately high numbers of unnecessary fillings, having justified the work by the use of the dye. Once the tooth has been cut it is impossible to tell what was previously present. The dentist is like the detective, prosecutor, judge, jury, executioner, and collector of fines all at once. When coupled with an air abrasion system, the misuse of the caries-detecting dyes can be quite lucrative. A dentist can “diagnose” a mouth full of caries (literally every tooth) and place many fillings in a short time. The machine cuts very quickly, and many teeth can be cut in a few minutes. The dentist then places many shallow fillings and bills a high fee for a plastic filling in each tooth. In effect these are unnecessary in the first place, and not fillings in the usual sense. Moreover, many are put in without proper conditions of dryness, such as would be obtained by use of a rubber dam. Thus, these fillings are similar to splotches of thick paint and don’t last. Cases where a Medicaid recipient had virtually every tooth filled in an hour have been noted. A variant on this theme is merely to do a few at a time to try to avoid detection. Some insurance companies have software monitoring programs to detect increases in billing patterns among dentists. Increased billing for composite plastic fillings has correlated directly with acquisition of an air abrasion machine in several cases.
Since air abrasion machines are expensive to purchase and maintain, the dentist has an added incentive to use them excessively. Medicaid does not require preapproval for routine dental fillings, and Medicaid fees are generally lower for each procedure than fees from self-pay or private insurance. Thus, practices with high numbers of Medicaid recipients (mostly children) and air abrasion machines should receive special scrutiny to ensure that only appropriate and necessary work is being done. Cutting natural teeth unnecessarily can lead to life-long problems.
Even if early caries is present, it can often be arrested and the enamel simply remineralizes so that no filling is required. Even with more advanced caries that is shallow, ten-year studies have shown that sealants can stop the decay process as effectively as fillings. In some studies, the placement of a sealant alone effectively smothered the decay and killed up to 99.9% of the responsible organisms. Sealants are inexpensive and easy to apply and do not involve cutting the teeth. They are readily replaceable and do not significantly alter tooth structure. Given this evidence, the use of an air abrasion system for early caries detection or treatment is difficult to justify.
Thus, whereas air abrasion is a useful new tool in the dental arsenal, much work needs to be done to determine and enforce appropriate standards for its use.
- 510(k) search for product code “KOJ,” June 29, 2002.
This page was posted on July 1, 2002.