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Authors : Dr. Sachin Shivanaikar, Sanketa Patil


The various procedures in the dental treatment causes the exposure to the bacterial aerosols. Among all the procedures used, The use of ultrasonic scaling produces the high amount of bacterial aerosols, since there are many ways to overcome the aerosols but still it is usually neglected. Air- water aerosol produced during treatment procedures emerges from a patient’s mouth and mixes with the surrounding air, thus influencing its composition which could cause a potential threat to the dentist’s health and even to the patient. The use of various protective measures should be incorporated to prevent such hazard.

Key Words: Aerosols, Occupational Hazard, ultrasonic Scaling.


The oral cavity is a unique environment which provides an ideal medium for microbial growth. Dental health professionals, because of repeated exposures to these microorganisms, are at high risk for developing infectious diseases. Transmission of microorganisms from person to person may occur by direct contact contaminated tissues or instruments or by aerosols containing infectious agents.1,2 Scaling is a basic periodontal treatment for the periodontal disease where there is removal of the bacterial plaque and calculus deposits from the surface of the teeth and obtaining a biologically acceptable root surface while protecting the healthy dental tissues.3 Techniques used for scaling, root planing and curettage are hand instruments, sonic and ultrasonic instrumentation, laser scaling, demineralisation and chemical scaling.4 Ultrasonic scalers are driven by generators, which convert electrical energy into ultrasonic waves via piezoelectricity or magnetostriction and are designed to facilitate scaling and root planing process.5 Magnetostrictive units operative betweeen 18000 and 45000 cps, using flat metal strip in a stack or a metal rod attached to a scaling tip. When an electrical current is supplied to a wire coil in the hand piece, a magnetic field is created around the stack or rod transducer causing it to constrict. An alternating current then produces an alternating magnetic field that causes the tip to vibrate.6

Piezoelectric units operate in the 25000-50000 cps range and are reactivated by dimensional changes in crystals housed within headpiece as electricity passed over the surface of the crystals. The resultant vibration produces tip movement that is primarily linear in direction.7 The instruments create friction and heat when placed next to the teeth, so they are cooled by stream of water that flow over the instrument tip or the insert. The vibrating tip causes cavitation of the water and generates significant aerosol when the tip is placed next to the tooth and oral fuids are added to the mix of contaminants in the air around the patient and the operator.8

Cavitation is the formation of pocket of vapour in a liquid. It is created by highly intensive ultrasonic waves Cavitational activity encompasses all of the linear and non linear oscillatory motions of gas and/or vapour-filled bubbles in an acoustic field.The cavitating water spray also serves to flush calculus, plaque, and debris dislodged by the vibrating tip from the pocket.

Aerosols are defined as suspensions of liquid and/ or solid particles in air. Aerosols containing particles more than 50 µm in diameter are referred to as spatter, while particles measuring less than 50 µm are called droplet nuclei. Because gravitational pull causes splatter aerosols to settle very quickly on surfaces, they are less likely to carry microorganisms that induce infection.9 Droplet nuclei however, remain suspended in the airway for many hours and can infect health care professionals and patients by direct inhalation and penetration into the lungs. Particles larger than 10-15 µm of droplet nuclei are closely related to upper respiratory infections, while prticles smaller than 0.5-5µm droplet nuclei can accumulate in the lower respiratory tract and may cause viral respiratory infections.10 Since the tips are placed subgingivally into periodontally infected pockets, this adds pathogenic bacteria into the aerosols and splatter that have been shown to contain blood.11

Composition of aerosols

Quantitative and qualitative analysis of the make up of dental aerosols would be extremely difficult and the composition of aerosols probably varies with patient and operative site. However it is reasonable to suppose that components of saliva, nasopharyngeal secretions, plaque, blood, tooth components and any material used in the dental procedure, such as abrasives for polishing and air abrasion, all are produced in dental aerosols.12 Although there is no evidence of hepatitis B or human immunodeficiency virus (HIV) transmission through inhaling aerosols. It is not unlikely that aerosol spray might contain hepatitis B, hepatitis C, herpes simplex, or HIV viruses when the blood is aerosolized and incorporated into the aerosol of the cooling water. Furthermore, inhalation is the major transmission route of the viruses of measles and mumps along with respiratory viruses such as influenza virus, rhinovirus, and adenovirus, and all of these viruses might also be present in the aerosol.13 Diseases spread by aerosols or droplet.12
Influenza Apparently associated with coughing but may require direct contact with the patient
Legionnaires’ Disease Aerosolization of Legionella pneumophila has been associated with air conditioning systems and hot tub spas
Severe Acute Respiratory
Spread by direct contact and aerosolized droplets
Tuberculosis Droplet nuclei expelled from the patient by coughing; once considered an occupational disease for dentists
Pneumonic Plague Patient to patient without the usual insect vector (flea); apparently by inhalation of the causative bacteria
Methods of reducing risk of aerosols

There are various methods to reduce the risk of aerosols during ultrasonic scaling

Evacuation procedures

High velocity evacuation (HVE) have significantly shown in the reduction of aerosols and splatter. It has been shown a 93% reduction in the contamination.HVE can be used with the help of the assistant. In the absence of the assistance, the saliva ejector should be used as efficiently as possible.14

Additional barriers

The standard infection control procedures should be followed in the dental practice. The barriers like face shield and a protective eye wear should be worn by the operator and the assistant. The use of face mask along with the face barrier gives an additional benefit .The theatre or dome type facemask is preferable to the paper type which rapidly becomes permeable and insufficient.14

The following are some basic protocols to be observed in relation to masks. They must:
  • be fitted and worn according to the manufacturer’s instructions
  • cover both the nose and mouth
  • be removed as soon as practicable after becoming moist or visibly soiled and it is recommended, where possible, that the mask be changed after 20 minutes in an aerosol environment
  • be removed by touching the strings and loops only; and
  • be removed and discarded after every patient.
They must not:
  • be touched by the hands while being worn or
  • be worn loosely around the neck while the dental care provider or dental staff member walks around the premises, but be removed and discarded.
Protective clothing

Protective clothing (e.g., reusable or disposable gown, laboratory coat or uniform) should be worn to cover street clothing while treating patients when aerosols or splatter are likely to be generated or when contamination with blood or saliva is possible. The most suitable type of gown varies according to the nature of the procedure and the equipment used and is a matter of professional judgement. Where there is a risk of large splashes with blood or body substances an impermeable gown must be worn. Disposable gowns should be placed in general waste after use, or if visibly contaminated with blood they must be disposed of according to local regulations.

Gowns must be changed as soon as possible when visibly soiled or after repeated exposure to contaminated aerosols. The protective gown worn in the clinical area must be removed before eating, drinking, taking a break or leaving the practice.15

Disinfecting patients mouth

The use of various mouth wash as a pre procedural rinse during ultrasonic scaling will effectively reduce the aerosol cross contamination. In a study the efficacy of pre procedural rinsing with 0.2% chlorhexidine and essential oil containing mouth wash was done and was found that a regimen of 1 minute pre-procedural rinsing with 0.2% chlorhexidine gluconate before dental procedure consistently reduced the colony forming units than prerinsing with essential oil containing mouth wash, and was concluded that chlorhexidine is effective in reducing the aerosol cross contamination.13 Chlorhexidine is an effective antiseptic for free floating oral bacteria such as those found in the saliva and those loosely adhering to mucus membranes. Although many studies have been reported evaluating the effectiveness of preprocedural mouth rinses, chlorhexidine has received most of the attention in the literature. Using a pre-procedural rinse may reduce the bacterial load, but has no demonstrated effect on blood borne pathogens, viruses, or pathogens aerosolized from the subgingival flora.


Ultrasonic scaling pose a high cross infection risk for patients and dental health care workers. The hazards of the aerosols should be taken into serious consideration. The risk of staff and patient exposure to aerosolised microbial pathogens in the dental office must be controlled by efficient preventive measures.The need for universal barrier precaution is essential . There is no single measure to adopt to prevent the risk. The various methods like use of mouth mask, face shield, protective eye wear, preprocedural mouth rinses, high volume avacuation should be practised for the best protection of staff and patients. However these preventions and precautions taken have to be evaluated and monitored periodically to prevent an occupational hazzard

  1. Lu DP, Zambito RF (1981). Aerosols and cross infection in dental practice— a historic view. Gen Dent ;29:136–143.
  2. King TB, Muzzin KB, Berry CW, Anders LM (1997) .The effectiveness of an aerosol reduction device for ultrasonic scalers. J Periodontol;68:45–49.
  3. Drisko CH. Root instrumentation power driven versus manual scalers, which one? (1998) Dent Clin North Am;42:229-244.
  4. Petersilka GJ, Draenert M, Hickel R, Flemming TF(2003) Safety and efficiency of novel sonic scaler tip in vitro. J Clin Periodontol; 30:551-555.
  5. Lie T, Leknes KN,( 1985) Evaluation of the effect on root surfaces of air turbine scalers and ultrasonic instrumentation. J Periodontol;56:522-531.
  6. American acedemy of periodontology (2000) Sonic and ultrasonic scalers in periodontics. J Periodontol;71:1792-1801.
  7. Trenter Sc, Walmsley AD (2003) Ultrasonic dental scaler associated hazards. J Clin Periodontol;30:95-101.
  8. Rivera-Hildalgo F, Branes JB, Harrel SK.( 1999) Aerosol and splatter production by focused spray and standard ultrasonic inserts. J Periodontol;70:473-477.
  9. Samaranayake LP. (1998) Essentials of Microbiology For Dentistry 2nd ed. Edinburgh: Churchill Livingstone;:263–320.
  10. Micik RE, Miller RL, Mazarella MA, Gunnar R.(1969) Studies on dental aerobiology: I. Bacterial aerosols generated during dental procedures.J. Dent.Res.;48:49–56.

References are available on request