DENTAL UNIT

Two types of dental units used in Navy dentistry are the mobile and chair-mounted types. The chair-mounted is the most common type in use. Most units provide the basic utilities for dental treatment including water, compressed air, electricity, and vacuum. It may also include handpiece controls, foot controls, a bracket tray, tubing flush system, 3-way syringes, cuspidor, and a suction apparatus. The unit should be designed so that it is compact and doesn't occupy space needed by the assistant. Hose-attached equipment, such as handpieces, syringes, and oral evacuation devices, should be conveniently positioned to both the provider and the assistant.

Operation

As with the dental chair, begin each day by making a visual inspection and operational check of the unit. During the inspection, first look for obvious problem areas, such as frayed electrical wiring, missing screws, and water leaks. Then conduct an operational check for each system. For example, you can test the water, air, electrical, and vacuum systems by operating the 3-way syringe, fiber-optic handpiece, dental light, and saliva ejector.

Water System

Many dental units operate with water that comes from the clinic's main water line. With the emphasis on infection control and the advances in dental equipment, the Navy is replacing older dental units and purchasing new units that have self-contained water systems. A malfunctioning water system affects the operation of the 3-way syringe, cuspidor, cup filler, and handpiece water spray. If any of these items fail to work, first make sure that the necessary valves and switches are turned on. If you can't solve the problem at this point, read the manufacturer's instructions before continuing. Water leaks are usually the result of loose connections or defective washers and valves. When necessary, have the DET replace any defective parts.

The new self-contained water systems are designed so you can optimize the quality of your dental unit water. The benefits from this system only occur when periodic system flushing and disinfection procedures are followed. Failure to follow the procedures for the type of self-contained water system you use may expose patients to water with higher than normal microbe counts. Most systems can use either tap, distilled, or sterile water to operate. Do not use saline solutions, mouthrinses, or any chemical solutions. These solutions may damage the water system components and cause the failure of your dental unit. A 750ml bottle constructed of polyethylene plastic is used to hold the water for the system. The bottle cannot be heat sterilized, but can be sterilized using ethylene oxide. Before attempting to use a self-contained water system, read the manufacturer's instructions for operation and maintenance.

Air System

A large central air compressor in your clinic provides compressed air. This enables most dental units to operate up to three dental handpieces and the 3-way syringe. Because of the noise level and for safety reasons, this system is located outside of the patient treatment area.

Most dental handpieces operate on air pressure within 20- to 80- pounds per square inch (psi) range, with a specific pressure recommended for each handpiece. Most units have a type of control system located on the bracket tray where air pressure can be adjusted. If you locate any air leaks, have a DET correct them as soon as possible.

Electrical System

Probably the most complex system on a dental unit is the electrical system. When there is a problem with this system, report it to the DET. Among the items affected by a dental unit's electrical system are the water heaters and solenoids (electrically operated switches).

Central Vacuum System

Generally, a central vacuum system provides suction to numerous dental units. The vacuum is connected to the unit with hoses and oral evacuation equipment, such as high-volume evacuator (HVE) and saliva ejector. A filtering component of the central vacuum for both the HVE and saliva ejector is the solids separator (fig 11-4). It contains a strainer which collects large pieces of debris that could clog suction hoses. At least once a week or if a decrease in vacuum is detected, remove and clean the strainer. This ensures proper suction from the central vacuum and maintains proper DTR infection control.

HIGH-VOLUME EVACUATOR.\The water spray from the handpieces and three-way syringes, along with debris from the patient's mouth, must be removed. The most efficient way to do this is with an

Figure 11-4.\Solids separator.

HVE (fig 11-5). The principle of this evacuator is low pressure and high volume. A tip is placed into the HVE handpiece and the suction turned off and on by a control valve or button on the handle. Some of the newer models of HVEs have a quick disconnect device and are now autoclavable. Follow the manufacturer's instructions for maintenance.

SALIVA EJECTOR.\During certain procedures, the provider may choose to keep the working site dry by using the saliva ejector. This type of suction is effective only when there is a limited amount of fluids, such as saliva, to remove from the patient's mouth. It can also be used to hold the tongue away from the working site and keep an area dry for placement of material that takes a long time to set A disposable plastic saliva tip inserts into the rubber end of the saliva ejector assembly and is turned on/off by a control valve. Follow the manufacturer's instructions for maintenance.

Figure 11-5.\High-volume evacuator (HVE).

Control System

This system delivers the drive air and coolant to whichever handpiece is lifted from the dental unit. The control system is made up of two parts: handpiece controls and a foot control.

HANDPIECE CONTROLS.\Most handpiece controls are located on the bracket tray that can accommodate three handpieces (fig. 11-6). The water coolant flow and maximum drive pressure are individually adjustable for each handpiece.

Most units use the following international symbols:

A blue dot identifies a water control.

A yellow dot identifies an air control.

A red dot identifies the ON or active position.

Every dental unit has a master ON-OFF toggle or switch. It turns on the air and water to the control system. When it is turned off, none of the items on the unit will function. This switch should be OFF whenever the unit is not in use to prevent flooding in the event of a leak while the system is unattended. The ON/OFF indicator provides a visual indication that the system is pressurized when the master switch is ON.