The use of Dental Instrument Cassettes in the Dental Sterilization Procedure

The use of Dental Sterilization Cassettes in the Dental Industry is fairly new and is mostly used in larger practices, clinics and hospitals in conjunction with pouches. However, Dental Sterilization Cassettes not only sterilizes your instruments, they also protect them better and facilitate a better dental Practice, sterilization procedure and Office Management.

‘Use of a system utilizing locked cassettes eliminates the need to sort, handle and hand scrub individual instruments – reducing the risk of infection from contaminated instruments – and results in savings of, on average, five minutes during instrument reprocessing, as well as fewer damaged instruments, since the instruments are locked in position during reprocessing’

In this article, we will focus on the processes of:

1. Cleaning,

2. Dental Sterilization as well as

3. Packaging Materials recommended for various types of Sterilization Processes

Cleaning: Why must dental instruments be cleaned before being sterilized?

Cleaning should precede all disinfection and dental sterilization processes. Cleaning involves the removal of debris (organic or inorganic) from an denta instrument or device. If visible debris is not removed, it will interfere with microbial inactivation and can compromise the disinfection or sterilization process.
In general, three classifications of mechanical cleaning devices are available for the dental office. They are:

1. ultrasonic cleaner,
2. instrument washer and
3. instrument washer/disinfector.

Ultrasonic cleaning devices

dental sterilization

An ultrasonic cleaner uses sound waves, that are outside the human hearing range to form oscillating bubbles, a process called cavitation. These bubbles act on debris to remove it from the instruments. Some manufacturers also use intermittent or sweeping sound waves to help improve the device’s cleaning ability and to decrease the potential for hot spots in the ultrasonic bath. Specialized detergent formulations are available for the solutions in ultrasonic machines. When selecting a cleaning agent to use in the ultrasonic cleaner, always consider the effect on materials and instruments.

In general, the timer is activated for ten to twenty minutes for dental instrument cassettes, and the timing is adjusted as necessary. While the ultrasonic device is running, the lid or cover should be kept on to reduce the release of aerosol and spatter into the area from the ultrasonic cleaner. Routinely replacing the cleaning solution in the ultrasonic machine is important, and is necessary at least once a day, more often with heavy usage.

Instrument washers

dental sterilization equipment

Instrument washers use high-velocity hot water and a detergent to clean instruments. Widely used for decades in hospitals and large facilities as part of the central sterilization process, these devices have recently become available for the dental office. These devices require personnel to either place instruments in a basket or to use instrument cassettes during the cleaning and drying cycles. Instrument washers for dental offices come in two different designs. One is a counter-top model. This type does not require professional installation. The other type is built-in and resembles a kitchen dishwasher (Figure 4). It functions much the same as the counter-top model, but it has a larger capacity and requires professional installation. Some models have the ability to dry the instruments after washing, some do not.

Instrument washers/thermal disinfectors


These devices may look like the instrument washers described above; however, there is one important difference. The high temperature of the water and chemical additives in these devices cleans and disinfects the dental instruments. The significance of this lies in how personnel can handle the instruments after the process. Upon removal from a thermal disinfector, instruments can be more safely handled, and if the dental healthcare professional were to sustain a puncture injury, it would not require the follow-up that a contaminated exposure requires.
All instrument washers and thermal disinfectors use either a detergent or a water-softening agent. It is possible for the pH of some of these chemicals to be incompatible with certain metals in dental instruments. For specific recommendations, the manufacturer of the dental instruments and the manufacturer of the instrument washer should be consulted.
Instrument washers and thermal disinfectors are approved medical devices that have been rigorously tested to meet Food and Drug Administration (FDA) requirements for safety and efficacy of medical devices; household dishwashers are not appropriate for use in a dental office.

Dental Sterilization: The three types of sterilizers most commonly used in dental offices are:

1. Steam sterilization (autoclave)
2. Dry heat sterilization
3. Unsaturated chemical vapor sterilizers

use steam and are either gravity displacement or pre-vacuum-type sterilizers. Temperatures reach approximately 250 degrees F to 273 degrees F. Sterilization times range from four to 30 minutes depending on temperature, whether instruments are wrapped or unwrapped, and manufacturer’s instructions. The drying cycle may be 25 to 40 minutes.

Dry heat sterilizers
are either static air or forced air. The high heat and extended time are major factors in achieving sterilization. Temperatures reach approximately 300 degrees F to 375 degrees F. Sterilization times vary from 12 to 150 minutes depending on temperature and manufacturer’s instructions.

Unsaturated chemical vapour sterilizers
use a combination of alcohol, formaldehyde, ketone, acetone, and water to create a vapour for sterilizing. The combination of pressure, temperature, and time are the major factors in achieving sterilization. Pressure should measure 20 psi, temperatures should reach 270 degrees F, and sterilization time is approximately 20 to 40 minutes.

All devices used for heat sterilization of dental instruments must be medical sterilization equipment that has been cleared by the FDA. Always follow the manufacturer’s instructions for sterilization times, temperatures, and other operating parameters, as well as instructions for correct use of containers, wraps, and chemical or biological indicators. Toaster ovens or glass bead sterilizers are not considered acceptable devices for sterilizing dental instruments and could jeopardize patient safety. Leslie Canham, CDA, RDA

Packaging Materials Appropriate for Varying Types of Sterilization.


Type of Sterilizer Operational
Advantages Concerns Packaging Materials
• Standard Cycle
Steam Autoclave• “Flash” Cycle
Steam Autoclave• Unsaturated
Chemical Vapor• Static Air Dry Heat• Rapid Heat Transfer
Dry Heat—Wrapped
• Rapid Heat Transfer
Dry Heat—Unwrapped
20 to 30 minutes
at 250°F/121°C3 to 10 minutes
at 273°F/134°C20 minutes
at 270°F/132°C60 to 120
at 320°F/160°C
12 minutes
at 375°F/191°C6 minutes
at 375°F/191°C
• time efficient
• good penetration
• sterilizes aqueous solutions#
• ease of use• time efficient
• no corrosion
• items dry after processing• can use closed containers&
• low cost
• items dry after cycle
• no corrosion• short cycle
• items dry after cycle
• no corrosion
• no closed containers
• can damage plastic and rubber
• carbon steel items corrode
• unwrapped items easily
• hard water leaves deposits
• no closed containers
• can damage plastic and rubber
• must use special solution
• predry instruments
• adequate ventilation required
• cannot sterilize liquids
• cloth wraps may absorb chemicals
• unwrapped items quickly
contaminated after processing• longer cycle
• can damage plastic and rubber
• must use special solution
• predry instruments
• do not open door during cycle
• cannot sterilize liquids
• unwrapped items quickly
contaminated after processing• damage to some plastic and rubber
• predry instruments
• do not open door during cycle
• cannot sterilize liquids
• unwrapped items quickly
contaminated after processing
• paper wrap
• nylon “plastic” tubing
• paper/plastic pouches
• thin cloth
• wrapped perforated cassettes• paper wrap
• plastic/paper pouches
• wrapped perforated cassettes• paper wrap
• appropriate nylon “plastic”
• closed containers&
• aluminum foil@
• wrapped perforated cassettes• paper wrap
• appropriate nylon “plastic” tubing
• closed containers&
• aluminum foil@
• wrapped perforated cassettes–sp-22652523