Infection Control Manual

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Zoning of Work Areas, use of Barrier for Protection of Equipment and Surface Disinfection

Dental aerosols and splatter

Sneezing , coughing and aerosols generated by rotary instruments produce airborne particles, which vary greatly in size from 0.001 microns to 10,000microns. Larger particles or water droplets with a diameter greater than 100 microns are referred to as splatter, which travels through the air for short distances and settles within a radius of 1 metre from the source e.g. patient, airturbine or basin tap.

Whereas aerosols consist of smaller (less than or equal to 10 microns) airborne particles that are capable of remaining in the air for several hours and of travelling on air currents for long distance, such as into the waiting room. Aerosols are generated by a wide variety of dental procedures including - use of dental handpieces, ultrasonic instrumentation, orthodontic debonding, and air and water syringing. Coolant dental unit water mixes with blood, saliva, tooth tissue and oral bacteria to produce a contaminated aerosol that can be inhaled into the respiratory passages or deposited on the skin, or the mucous membranes of the eyes and mouth. Microbes carried in airborne particulates or from particulate debris remaining after the water has evaporated (droplet nuclei) can be inhaled directly. Currently there is no clinical evidence to suggest that the bacterial species in the normal oral flora pose a serious infectious health risk when aerosolised. Aerosol contamination of the surgery can be reduced by simple measures e.g.

• Use of high-volume suction
• Rubber dam
• Proper patient positioning
• Rinsing with chlorhexidine mouth wash pre scaling (reduces aerosol contamination for approximately 40 minutes after rinsing)
• Ventilation ( 8-10 air changes per hour, with air exhausting to the outside)

Airborne particulates generated during dental treatment were shown by Bennett et al 2000 to decrease to background levels within 10-30minutes due to the rapid deposition of particles at approximately 1metre from the ground or patient head height. Ultrasonic scaling produces the highest concentrations of microbes in the dental aerosol, with peak concentrations recovered approximately 150-300mm from the operator. Surface cleaning and disinfection removes particulates that have settled out and deposited on equipment and work surfaces ( see section on Zoning ). High volume suction remove approximately 90% of the coolant spray, greatly reducing the dental aerosol. Aspirators should exhaust externally to avoid the spread potential contamination material within the dental surgery.

Blood can be recovered from saliva samples after many routine dental procedures (e.g. ultrasonic scaling, orthodontic debonding) even if it is not visible to the naked eye. BBV such as HIV and Hepatitis B can be aersolised during dental procedures but it is considered very unlikely that BBV viruses are transmitted via the airborne route. BBV can be transmitted by direct contact following splatter (greater than or equal to 100 micron size particles) exposure of mucous membranes, although the risk of serconversion is very much lower than after a needlestick injury. Routine use of masks, goggles and visors by dentists, hygienists/therapists and dental nurses will reduce the risks of infection associated with splatter.

Aerosol generation during treatment on patients harbouring respiratory pathogens such as influenza or M. tuberculosis may pose a risk to the dental team. If the aerosol is permitted to persist or is transported around the practice on air currents then subsequent patients or those sitting in the waiting area may be affected. The occupational risk of exposure to potentially hazardous respiratory aerosols can be reduced by the use of PPE e.g. respirator masks (See section 2)

Surface cleaning and decontamination

The area around the dental unit becomes contaminated by direct splatter, droplet nuclei and by touching surfaces with gloved hands. Surface cleaning prevents transmission of infection by direct contact with hands and equipment. (N.B. Hand hygiene also prevents transmission of surface contaminants). Dental chair, dental handpiece unit, 3 in 1 syringe handle and hoses, lights, bracket table, cabinets will all require surface cleaning and disinfection. Try to avoid touching and thereby contaminating drawer handles, pens, computer keyboards, and door handles with gloved hands. Pens are a well recognised vehicle for transmission of MRSA!

You will need to check with the manufacturer's instructions whether individual items of surgery equipment can be cleaned with a detergent and/or disinfectant. Commonly used- surgery surface disinfectants are virucidal and low residue, such as isopropyl alcohol spray or diluted hypochlorite solution (1 in 100 dilution). Alcohol wipes are preferred to spray on products because of the generation of unnecessary aerosols, which may cause sensitization of staff and patients. Avoid whenever possible using hypochlorite on metal surfaces.

Disinfectants and hand antiseptics

(Examples only the list is not exhaustive)

Type of disinfectant/antiseptic	Proprietary name	Use in dental surgery
CHLORHEXIDINES
Chlorhexidine gluconate liquid 4%	Hibiscrub surgical scrub	Hand washing
Chlorhexidine 2.5% / 70% alcohol solution in a glycerine base	Hibisol handrub	Hand rub
Chlorhexidine 0.5% in 70% alcohol	Alcoholic chlorhexidine	Skin disinfection prior to peri-oral biopsy, implant surgery and periodontal surgery
	Bio Blue	Biocide for disinfection for dental unit waterlines and reservoir bottles
IODOPHORS
Povidone iodine 7.5% solution	Betadine surgical scrub	Hand washing
ALCOHOLS
Alcohol gel/solutions	Purell, Sterillium, Desderman	Hand rub
70% Isopropyl alcohol wipes	Azowipes or Cliniwipes	Surgery hard surface disinfection or external surface of handpieces
Ethanol and 1-propanol alcohol spray	Mikrozoid	Surgery hard surface disinfection
CHLORINE RELEASING AGENTS
Sodium Dichloroisocyanurate solution tablets 4.75 g (= 2.5 g available chlorine) or granules	Haz-Tabs tablet or granules Presept tablets or granules	Spillage of blood or other body fluids
Sodium hypochlorite + detergent	Chloros	Surgery hard surface disinfection
TRICLOSAN
Triclosan 2%	Aquasept	Hand disinfection
PHENOLIC
Hycolin 2% solution	Stericol	Disinfection of environmental surfaces e.g. floors
Halogenic alkyl +aryl phenolic	Orotol	Suction tubing disinfectant
PERACETIC ACID
Peracetic acid	Nu-cidex Gigasept PA	High level disinfection of heat labile instruments, only for intermediate and low risk procedures
SUPEROXIDISED WATER
Electrolysed salt solution produced by a dedicated generator	Sterilox	Biocide for disinfection for dental unit waterlines and reservoir bottles
ALKALINE PEROXIDE
Alkaline peroxide based	Sterilex ultra, Dentisept	Biocide for disinfection for dental unit waterlines and reservoir bottles
CITRIC ACID BASED
Edentin acid, tosychloramide sodium phenylalamine	Alpron	Biocide for disinfection for dental unit waterlines and reservoir bottles

 

Zoning

Zoning (delineating areas) simplifies and speeds up the decontamination process. The aim is to separate the areas that are likely to become contaminated by direct contact or splatter during treatment procedures ("dirty zones") from those areas unlikely to be directly contaminated ("clean zones"). Most of the splatter settles out within 1 metre radius of the patient's mouth.

"Dirty zones"

• Bracket table and handle
• Dental handpiece unit, connectors and switches
• Dental chair head rest
• Light handle and switch
• Chair handle controls
• Suction connectors/manifold
• Spittoon

Only the "dirty zones" or visibly soiled areas need to be cleaned and disinfected between each patient, which reduces the time required for decontamination. Dirty areas which cannot be disinfected easily between patients or which are not practical to disinfect between patients such light handle and switches, dental unit switches, buttons on 3 in1, ultrasonic handle, control buttons on the dental chair can be covered with clear plastic wrap (cling film) or impervious plastic sleeves. Because such covering become contaminated by splatter and direct contact with gloved hands, the covering should be disposed of (wearing gloves) into hazardous waste bags and replaced between patients. If impermeable plastic coverings are not employed then a surface disinfectant should be used to disinfect these items and surfaces between patients.

At the end of the clinical session all work surfaces whether within the clean or dirty zones need to be thoroughly cleaned and disinfected. Wearing of heavy duty household gloves offers greater protection to the skin when using chemical disinfectants. Protective eyewear and masks should be worn during environmental cleaning to protect the staff from exposure to hazardous chemicals and infectious material.

The exception is the dental chair headrest where a detergent should be used, unless the headrest is visibly soiled with blood or saliva; as repeated use of chemical disinfectants can cause damage to the dental chair. The dental chair manufacturer will recommend a suitable cleaning agent.

 

Method for zoning and surface cleaning

This method of zoning ensures that dirty instruments are segregated from clean ones and will minimize contamination of work surfaces, instruments and equipment stored in the clean areas.

Before and during patient treatment

• Designate dirty zones (likely to be contaminated during dental treatment) from clean zones
• Clean zones: Cabinets, surgery drawers, radiographs, patients notes, computer keyboards and pens are clean zones and should not be touched with contaminated gloved hands or instruments
• During patient treatment impervious clinical sheets or plastic sheaves should cover all work surfaces that cannot be readily disinfected between patients
• Items can be passed into "dirty zones" but contaminated items should not be passed out into "clean zones"
• Storage containers of dental materials should not be placed in the "dirty zone"
• Remove cling film/plastic sheaves and disinfect "dirty zones" between patient
• At the end of a working session all surfaces should be thoroughly cleaned and disinfected using alcohol spray/wipe or proprietary antimicrobial disinfectant spray/wipe
• Cleaning of spittoons : Clean outer surface first. Inner surface of bowl- add (metered) dose of non-foaming disinfectant, wipe evenly around inside of bowl, leave for time interval specified by manufacturer for disinfectant to destroy microorganisms, rinse with bowl flush and then discard disinfection cloth as hazardous waste.
• Suction apparatus, aspirators, drains and spittoons should be flushed daily with a non-foaming disinfectant/ detergent (e.g. Tridaclens, Dekaseptol or Orotol) according to the manufacturer's instructions.
• Trap filters must be removed and cleaned on a daily basis. Rinse thoroughly before replacing. Bleach or hypochlorite should not be used as they rust metal. Replace with new filters as specified by the manufacturer.
• Dental unit waterlines should be drained down at the end of the day and purged with a biocide for the time recommended by the manufacturer
• Work surfaces should be kept clear overnight