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The Dental Handpiece: Maintenance and Infection Control

Dental Handpiece

The Spaulding Classification -which divides patient care items into three categories: critical, semi-critical, and non-critical [5,6]- is utilized by The Centers for Disease Control (CDC), and is also recommended by the AHA [7,8]. Instruments and devices that are used to penetrate the soft tissue, contact bone, enter into or make contact with the bloodstream or other normally-sterile tissues of the mouth, have the greatest risk of transmitting infection and are considered“critical” items. Because these items—surgical instruments, periodontal scalers/curettes, scalpel blades and surgical dental burs—present the most significant risk, they must be sterilized after each use, by autoclave, dry heat or heat/chemical vapor methodologies. “Semi-critical” items have a lower risk of transmission, but because the majority of semicritical items in dentistry are heat-tolerant, they too should be heat sterilized.[6-8]

Both the CDC and the ADA recommend strict adherence to the principles of sterilization.[6-8] Accordingly, all critical and noncritical dental instruments that are heat-stable should be sterilized after each use by steam under pressure through the autoclave, dry heat, or heat/chemical vapor process.

Flushing and Antiretraction Valves:

High-speed air Dental Handpiece  operate when compressed air, controlled by the rheostat in the foot pedal, is released into the head where the air spins the blades of the turbine [Figure 2]. Coolant water is carried by separate tubing and is also discharged at the same time. The air is released from the top and bottom of the head as the turbine rotates. However, when the air pressure is released, the handpiece shuts down, creating a vacuum that can aspirate oral microorganisms, blood, saliva, and other debris into the turbine and dental unit waterlines (DUWLs).

Figure 2: Because of this phenomenon, handpieces and other dental devices, such as ultrasonic scalers, or air or water syringes that are connected to the DUWLs and enter the patient’s mouth, should be flushed to discharge water and air for a minimum of 20 to 30 seconds after each patient.[6] The goal of this 20 to 30 second flush is to eliminate patient material that may have entered the turbine, air, or water lines.

Figure 3: Some handpiece manufacturers overcome this by inserting an antiretraction valve into the device, which provides a tremendous infection control advantage and should be considered before the purchase of new high-speed air motors [Figures 2 and 3].

Electric handpieces operate by the introduction of direct-current (DC) into an electric motor sealed in the housing of handpiece [Figure 4]. These motors do not use compressed air, and when the current driving the motor is stopped by releasing the foot pedal, the motor stops. Because there is no air to create a vacuum, there is little or no retraction of oral fluid back into the waterline or turbine—an important infection control factor.


Figure 4: Regardless of the type of handpiece utilized, High Speed Handpiece units should have a system or device to eliminate the retraction of oral fluids and other contaminates. Technological advances in dental unit designs have lead many manufacturers to equip units with specialized engineering to prevent the retraction of oral fluids. However, most older dental units are equipped simply with antiretraction valves.

Anti-retraction valves have been shown to prevent fluid retraction into DUWLs when new, but most substantially fail after a few months of use.[20] Unless the devices are periodically maintained, an overwhelming majority of the antiretraction devices do not prevent the retraction of oral fluids and debris, which could lead to contamination of the water lines or possible cross-contamination to subsequent patients.[21]

Dentists should follow the manufacturer’s maintenance manual or contact the manufacturer directly to determine what types of testing or maintenance of antiretraction valves (or other such devices) is required, and how frequently they should be performed.[6] Even with antiretraction valves, flushing devices for a minimum of 20 to 30 seconds between patients is recommended.[6]

Additionally, the CDC recommends that the dental unit coolant water be of acceptable quality (<500 CFU/mL). Dentists should consult the manufacturer of their dental unit or water delivery system to determine the best method for consistently obtaining and maintaining water of acceptable quality along with the recommended frequency of monitoring.

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