Human Mouth is Highly Contaminated environment. The mouth contains bacteria and viruses from many sources. The saliva of a healthy patient contains large numbers of streptococci, staphylococci, and gram negative bacteria. While many of these organisms are relatively innocuous for a healthy person, they carry the possibility of infection for the increasing number of people with compromised immune systems.The use of hand scalers, prophy angles, and air-water syringes produce some splatter in the form of relatively large droplets. While large droplets contain potentially pathogenic organisms, they are usually controlled by standard barrier techniques such as gloves, masks, and eye protection. However, the ultrasonic scaler and the air polisher are the greatest producers of small particle aerosol contamination in dentistry. Several studies show that the ultrasonic scaler produces more airborne contamination than any other instrument in dentistry. The air polisher creates an almost equal amount of airborne contamination. The use of these instruments places hygienists at the forefront of risk for the airborne transmission of infections.
Scientific literature detailing the spread of infection by an aerosol route is available. Recent examples include the spread of TB on an airplane and the spread of measles through the ventilation system of a pediatric office. Traditionally, the greatest danger inherent in dental aerosols was TB. In the past, TB was considered an occupational hazard for dentistry. Currently in the United States, TB is rare. However, in certain populations such as recent immigrants, prisons, and the homeless there is a much higher prevalence of TB. Hygienists working with patients from these groups need to approach treatment with great care due to the potential for undiagnosed TB. In private clinical practice, the greatest danger comes from viruses harbored in the nasopharynx and blood particles arising from the operative site.
Blood
Several studies have shown that blood is universally found in the aerosols produced by an ultrasonic scaler during root planing. These studies further demonstrate that even when the operator cannot see blood contamination there is an adequate amount of blood in the aerosols from root planing to be detected by an occult blood test. This is true no matter what type of ultrasonic scaler or scaler tip is used. The use of ultrasonic and sonic vibration in the presence of a liquid, ie, blood, aerosolizes the liquid. Whatever bloodborne infection the patient may carry is probably present in the dental aerosols from root planing with an ultrasonic scaler.
Several studies have shown that blood is universally found in the aerosols produced by an ultrasonic scaler during root planing. These studies further demonstrate that even when the operator cannot see blood contamination there is an adequate amount of blood in the aerosols from root planing to be detected by an occult blood test. This is true no matter what type of ultrasonic scaler or scaler tip is used. The use of ultrasonic and sonic vibration in the presence of a liquid, ie, blood, aerosolizes the liquid. Whatever bloodborne infection the patient may carry is probably present in the dental aerosols from root planing with an ultrasonic scaler.
Preventative Measures
Gloves, well-fitting masks, and eye protection should always be used and greatly lowers the risk of infection. However, a true aerosol stays airborne for up to 30 minutes and larger droplets evaporate and the contamination they carry can become re-airborne as a dust particle, ie, a droplet nuclei. Therefore, the risk of contamination continues long after the procedure is over. Because of this extended risk time as well as the often poor fit of masks and eye protection, other precautions should be followed. Using a preprocedural rinse such as chlorhexidine lowers the number of aerobic bacteria in the air. However, it will not affect blood coming from the operative site or viruses, such as SARS, coming from the respiratory tract. Using a preprocedural rinse should not be relied on to prevent airborne contamination.
The use of a high volume evacuator (HVE) has been shown to universally reduce airborne contamination, no matter what the dental source by 90% to 98%. However, a saliva ejector does not qualify as a high volume evacuator. The small diameter of a saliva ejector keeps it from removing enough air to be effective in reducing aerosols. A large diameter HVE may be held separately by an assistant or the hygienist, attached to the ultrasonic scaler, or possibly attached to one of the “dry field” devices. Using an HVE is a mandatory infection control precaution during the use of an ultrasonic scaler.
The aerosols from air polishing are more difficult to control than those from an ultrasonic scaler due to the compressed air used during air polishing. The only method proven to control the aerosols from air polishing combines a barrier placed around the air polishing tip combined with a vacuum. The barrier blocks the high speed particles from ricocheting off the tooth into the air and the vacuum removes the water and abrasive particles from the operating site within the barrier. This method has been shown to reduce the airborne contamination from air polishing by 97%.
Gloves, well-fitting masks, and eye protection should always be used and greatly lowers the risk of infection. However, a true aerosol stays airborne for up to 30 minutes and larger droplets evaporate and the contamination they carry can become re-airborne as a dust particle, ie, a droplet nuclei. Therefore, the risk of contamination continues long after the procedure is over. Because of this extended risk time as well as the often poor fit of masks and eye protection, other precautions should be followed. Using a preprocedural rinse such as chlorhexidine lowers the number of aerobic bacteria in the air. However, it will not affect blood coming from the operative site or viruses, such as SARS, coming from the respiratory tract. Using a preprocedural rinse should not be relied on to prevent airborne contamination.
The use of a high volume evacuator (HVE) has been shown to universally reduce airborne contamination, no matter what the dental source by 90% to 98%. However, a saliva ejector does not qualify as a high volume evacuator. The small diameter of a saliva ejector keeps it from removing enough air to be effective in reducing aerosols. A large diameter HVE may be held separately by an assistant or the hygienist, attached to the ultrasonic scaler, or possibly attached to one of the “dry field” devices. Using an HVE is a mandatory infection control precaution during the use of an ultrasonic scaler.
The aerosols from air polishing are more difficult to control than those from an ultrasonic scaler due to the compressed air used during air polishing. The only method proven to control the aerosols from air polishing combines a barrier placed around the air polishing tip combined with a vacuum. The barrier blocks the high speed particles from ricocheting off the tooth into the air and the vacuum removes the water and abrasive particles from the operating site within the barrier. This method has been shown to reduce the airborne contamination from air polishing by 97%.
Summary
Dental aerosols represent an infection hazard for dental hygienists due to their gross contamination with microorganisms and blood. The advent of SARS and its predicted reemergence during the upcoming flu season have brought the dangers of dental aerosols to a higher level. Aerosols are easily controlled with the appropriate precautions.
Dental aerosols represent an infection hazard for dental hygienists due to their gross contamination with microorganisms and blood. The advent of SARS and its predicted reemergence during the upcoming flu season have brought the dangers of dental aerosols to a higher level. Aerosols are easily controlled with the appropriate precautions.
Whenever an ultrasonic scaler or air polisher is used the following steps should be followed:
(1) barrier protection
(2) high volume evacuation, and
(3) preprocedural rinsing.
Each of these adds a layer of protection for the operator and others in the dental office. All three steps must be followed for adequate protection. The use of only one or two of the steps will not yield the necessary level of protection adequate for safety.
Notice the precautions that are being used against exposure to highly-toxic mercury vapor.
Both the dentist and his assistant are wearing special breathing apparatus. Their bodies are also completely covered to prevent mercury vapor from falling on their skin. The patient's body is mostly covered as well.
Numerous other precautions are also used including mercury-vapor air filters, rubber dams, chlorella and activated charcoal beneath the tongue which is changed often, etc
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