It’s a safe bet that you rely on compressed air, yet the compressor is usually thought of only when purchased or when it demands immediate attention. In addition, dental compressors are often selected based on purchase price and quick availability — criteria that rarely lead to acquiring a quality product. Since a practice cannot run without them, it makes sense to pay attention to what you buy.
Sizing your compressor
To properly size a compressor, you need to know your air consumption and the capacity of the compressor. Consumption is usually determined by how many operatories are in use at a time. Capacity is the compressor output in cubic feet per minute (cfm), and can usually be found in product literature. As a rule of thumb, each chair needs approximately 2 cfm
Dental compressor suppliers often simplify all this and just tell how many users a compressor will support. This is helpful, but you must check the duty cycle and actual flow to ensure you’re getting what you expect. Product literature may state pump displacement but not true capacity, which is a combination of actual volume output, duty cycle, and tank size.
Capacity and reliability are related because many compressors are designed with a limited “duty cycle” — the percentage of time a compressor can run without cooling off. For example, some dental compressors have a 30% duty cycle. This does not mean it can run three hours straight in a 10-hour day, but more like 18 minutes in an hour.
The key point is that two compressors may put out the same cfm, but the one with the lower duty cycle cannot run as much without reducing its service life. Duty cycle varies widely among compressors, so ask your supplier about it.
Compressed air quality depends on the inlet air and what the compressor adds to it. Both oil-less and lubricated compressors are used in dentistry. Both require particulate filters to remove any airborne dirt and dust. With a lubricated compressor, the system must also include reliable coalescing filters to ensure patient safety.
Most dental compressors include a dryer to remove moisture. The common types are desiccant and membrane. Both types use air to purge the saturated desiccant material or membranes. This reduces the air available chairside. When selecting, consider how much dried, compressed air is needed for the purge.
Sometimes, less is more
Dental compressors have “heads,” with each one housing one or more pistons. Some models employ a single head, while others use a multihead design. A common misunderstanding is that a machine with multiple heads has built-in backup. When a multihead compressor has a malfunctioning pump, it may not be able to continue running on another head.
Assuming equal quality in two machines, the machine with more moving parts has a greater chance of failure. Single-head machines, by necessity, are generally designed for longer life. They are designed for higher efficiency and greater duty cycle to take on a constant, more demanding workload that many multihead units simply cannot handle.
Not all compressors are created equal
Manufacturers make choices in design and materials to meet target price points, so quality varies widely. Following are some points to consider when comparing compressors.
Heads should be made of quality materials and designed to remove heat. Finned cylinders, large cooling fans, and filters are important features. Components should be designed to be serviced, not replaced. For example, antifriction coatings like Teflon are widely used to reduce piston wear.
Eventually, the coating wears off and the whole piston must be replaced. An alternative method is using replaceable Teflon guide sleeves and compression rings. These may last for years, and replacing them is simple and less expensive than installing an entire new piston or head assembly.
Other signs of quality include robust tubing and fittings, as well as good vibration isolation to prevent loose wires and fittings. With respect to safety, electrical connections should be neat and touch-proof. In addition, compressors used in dental offices should be clearly marked with full UL certification. Another safety item is the storage tank, which should be ASME certified.
Though it is often hard to quantify up front, your experience has probably shown that good quality equipment pays for itself. In the long run, quality compressors last longer, with less frequent repair and lower service costs. Can you afford the downtime?
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