Co-editor: Dr Caroline Pankhurst
formerly Senior Lecturer in Oral Microbiology, Kings College London, UK
Implementation of standard infection control precautions in dentistry (previously termed universal precautions) entails prevention of infection transmission within the dental clinic environment, and assumes that ALL patients are carriers of infectious diseases. Such a policy protects both patients and staff, reduces staff concerns and prevents discrimination against patients. As mentioned in Chapter 36, when standard precautions alone cannot prevent transmission, they are supplemented with transmission-based precautions. This second tier of infection prevention is used when patients have diseases that can spread through contact, droplet or airborne routes (e.g., skin contact, sneezing, coughing) and are always used in addition to standard precautions. In this chapter, the major features reflecting the best current practice of standard infection control are outlined, but the reader is strongly advised to keep up to date with the literature because of the constant flux of changes occurring in this area, due to the emergence of new infectious diseases, as well as the advances in applied technology.
Practice management and staff development
All staff who join a practice should undergo a formal education programme that includes the theory and practice of infection control in dentistry. In addition, a written infection control protocol specific for the practice should be available for inspection by patients and other interested parties.
An in-service training programme, updating techniques and material, should be provided for the staff. This may take the form of regular attendance at local scientific meetings and access to current information such as journals and the Internet.
Infection control: specific practical features
There are a number of elements in a comprehensive infection control protocol:
■ patient evaluation
■ personal protection
■ respiratory hygiene
■ instrument decontamination: cleaning, disinfection, sterilization and storage
■ use of disposables (single-use devices and personal protective equipment (PPE))
■ disinfection of the environment
■ clinical and laboratory asepsis
■ disposal of waste
■ staff training, including continuing education.
A thorough medical history should be taken from each patient and updated at each recall visit. It is not only good clinical practice but may also reveal disease that is important in relation to cross infection and relevant to the dental procedure to be undertaken. If a questionnaire is used for this purpose, it should always be supported by direct discussions with the patient. The medical history should not be used to categorize patients as high or low risk, as was the procedure prior to the introduction of standard infection control precautions. In taking a history, the practitioner should identify the infectious disease of concern, and relevant questions should be asked in an environment conducive to the disclosure of sensitive personal information. It is also important that:
■ all staff are trained in the proper management of records, including keeping them away from the public view in the front office, safe storage and maintenance with due regard to appropriate data protection legislation
■ a written policy on confidentiality should be signed by all staff members
■ personal medical or dental details are not disclosed to other health care workers without the consent of the patient.
This subject is dealt with under the following headings:
■ personal hygiene
■ clinic clothing
■ barrier protection (gloves, eye shield, face masks, rubber dam isolation)
■ immunization procedures.
The personal hygiene of all members of staff who are either directly or indirectly in contact with patients should be scrupulous. A rigidly followed code of hygiene will greatly reduce cross infection in the dental clinic. In general, when working with patients, dental personnel should observe the following precautions:
■ Refrain from touching anything not required for the particular procedure. Specifically, staff should keep their hands away from their eyes, nose, mouth and hair, and avoid touching sores or abrasions.
■ Cover cuts and bruises on fingers with dressings because they serve as easy portals for pathogens.
■ Hair should be kept short or tied up, or a hair net should be worn.
Fingers are the most common vehicles of infection transmission. This fact is poorly recognized by all. The World Health Organization (WHO) promotes the ‘five moments for hand hygiene', which recommends health care workers to clean their hands:
1. before touching a patient
2. before clean/aseptic procedures
3. after body fluid exposure/risk (e.g., saliva, blood or other bodily fluid)
4. after touching a patient
5. after touching patient surroundings.
The whole dental team should pay attention to meticulous hand care:
■ A dedicated clean and clutter-free sink should be provided in the clinic for hand-washing, and the taps should be operated by elbow or foot controls or sensors (no-touch technique). The sink should have no overflows or plugs in order to prevent contamination of the taps with Pseudomonas spp. and other environmental microbes resident in sink traps and U-bends. Wall mounted hand hygiene solutions should be dispensed in disposable rather than refillable cartridges/bottles.
■ Keep fingernails short and clean. Dental personnel should work ‘bare below the elbow' in order to facilitate good hand hygiene. Jewellery such as rings and watches should be removed as rings tend to entrap organisms and damage gloves; do not wear nail polish, artificial fingernails or extenders when having direct contact with patients. If long-sleeved clothing is worn, it should be rolled up above the elbow.
■ For routine dental examinations and nonsurgical procedures, use water and plain soap (hand-washing) or antimicrobial soap (hand antisepsis) specific for health care settings or use an alcohol-based hand rub. Thoroughly clean the hands before putting on and removing gloves and before and after treating each patient.
■ Alcohol-based hand rubs are effective for hand hygiene in health care settings. Alcohol-based hand rubs have the advantage of causing less skin dehydration than soaps, are faster to use and do not require running water. However, hand rubs are only effective as hand disinfectants on visibly clean hands, that is, in the absence of blood or dirt. Plain soap and water are used to wash dirty hands. Hands should also be cleaned before leaving the surgery for any purpose and upon return.
■ A good hand-hygiene technique, as shown in Fig. 37.1, which can be used with hand rubs or soaps, should be developed by all staff so that all areas of the hands and wrists are cleaned consistently (Fig. 37.2). Finger tips, finger and thumb webs, backs of hands and the wrists are often missed when cleaning hands.
Fig. 37.1 A schematic presentation of a suggested hand-washing technique. (Courtesy the World Health Organization.)
■ Any obvious cuts or abrasions must be covered with adhesive waterproof dressings.
■ Liquid (not bar) soap should be used for routine hand-washing, and antimicrobial liquids should be used for hand-washing prior to surgical procedures. A surgical scrub, also referred to as antisepsis, is a more extensive disinfection of the hands and arms that reduces the numbers of resident bacteria to a minimum; however, it is not possible to achieve sterilization of the skin.
Fig. 37.2 Areas of the hand that are not thoroughly washed owing to poor handwashing technique.
■ Hands washed with soaps and antimicrobial solutions should be dried thoroughly using disposable paper towels, and gloves should be donned as the last step before treatment commences.
■ Moisturizing cream should be used as a routine at the end of each treatment session to maintain a healthy skin. Take care not to contaminate the cream during use by not sharing moisturizers and by using elbow-operated dispensers.
■ Consider the compatibility of lotions and antiseptic products and the effect of petroleum or other oil emollients on the integrity of gloves during product selection and glove usage.
■ A ready reckoner for hand hygiene and antisepsis is provided in Table 37.1.
A freshly laundered uniform or overgarment should be worn by all clinical personnel. Garments should be changed at least daily, and more frequently if they become visibly contaminated. Renewable overgarments should be washed at an appropriate temperature (e.g., 60°C) in a well-maintained washing machine. Grossly contaminated clothing should be dealt with separately.
Wear overgarments only in the clinic premises, not in corridors, canteens or lifts. An additional waterproof vinyl apron could be worn to protect the overgarment if there is a risk of exposure to body fluids during dental treatment, when working in the instrument-cleaning area or the laboratory (e.g., denture trimming).
Personal hygiene measures reduce the level of possible pathogens on our bodies and clothes, although they do not completely eliminate them. In order to minimize further the spread of organisms from staff to patients (and vice versa), the following PPE, which form a protective barrier, should be used. Dental staff should be trained to select and don and remove the appropriate PPE so that the risk of clothing or skin contamination is reduced:
■ eye shields (goggles or visors)
■ face masks
■ rubber dam isolation.
Hand hygiene is always the final step after removing and disposing of PPE. Always remove PPE before leaving the work area.
All dentists and close support personnel should routinely wear disposable nitrile, latex or vinyl gloves. In many countries, nitrile gloves have replaced the use of latex gloves in dentistry to prevent latex allergy being triggered in the dental team and susceptible patients. The main aim of wearing gloves in routine dentistry is not to achieve consistent surgical sterility but to establish reasonable standards of hygiene in order to safeguard both the dental personnel and the patient.
The efficacy of gloves greatly diminishes if they are perforated. As gloves may perforate during surgical procedures, it is advisable to change gloves at least hourly during long operative procedures on the same patient. Gloves should be checked for visible defects immediately after wearing them, and immediately changed when breaches occur; never wash and reuse gloves. Irritant and contact dermatitis and allergies to chemicals and gloves used in dentistry are relatively commonly seen in dental team or can develop in sensitized patients. Skin creams, a spray-on microfilm on the skin or a cotton glove liner may help these individuals.
There are three main types of gloves used in dentistry: their different uses should be clear:
1. Clean, high-quality, protective nitrile or latex gloves should be used whenever examining a patient's mouth or providing routine dental treatment when no blood-letting procedures are undertaken.
2. Sterile gloves should be used for surgical procedures or procedures that may lead to blood-letting. The wearing of two pairs of gloves during oral surgical procedures leads to a lower frequency of inner glove perforation and visible blood on the surgeon's hands; however, the effectiveness of the latter procedure in preventing disease transmission has not been demonstrated.
3. Heavy-duty utility gloves should be used for cleaning instruments or surfaces or handling chemicals.
Care should be taken to prevent contact between gloves and incompatible material (e.g., some impression materials) or naked flames.
Gloves should be removed as soon as patient contact is over. The hands should then be cleaned, and hand cream should be applied to prevent excessive drying of the skin. In addition, dental personnel should wash their hands with an alcohol-based hand rub or soap and water before leaving the clinic. Dental personnel with exudative lesions or weeping dermatitis should refrain from all direct patient care and from handling equipment until the condition resolves.
A new pair of gloves should be worn for each patient. Gloves should never be reused, as this will result in defects that will diminish their value as an effective barrier, and adequate removal of previous patients' pathogens cannot be guaranteed. Treat gloves as surgical waste and dispose of them accordingly.
Contact dermatitis and latex hypersensitivity
All health care workers should be educated on the signs, symptoms and diagnoses of skin reactions associated with frequent hand hygiene and glove use. Patients should be screened for latex allergy through a health history questionnaire and referred for medical consultation when latex allergy is suspected. Emergency treatment kits with latex-free products should be available at all times.
Eye shields (goggles or visors) should be worn by dentists and close support personnel during all procedures to protect the conjunctivae from spatter and debris generated by high-speed handpieces, scaling (manual or ultrasonic) and polishing and cleaning of instruments:
■ Eyewear and face shields should be cleaned regularly and when visibly soiled.
■ It is preferable to use eyewear with side protection.
■ A patient's eyes should always be protected during examination and treatment.
Wearing a face mask, such as a surgical mask, is a necessary hygienic measure, particularly during high-speed instrumentation, as it acts as a barrier to reduce the inhalation of contaminated splatter and aerosols that might lead to both upper and lower respiratory tract infections. The filtration efficacy of such aerosols depends upon:
■ the material used for mask manufacture (paper masks are inferior to respirator masks)
■ the length of time the mask is worn: the useful life of a mask is thought to be about 30-60 min, particularly if the mask is wet. Thus masks are considered single-use items and clean mask should be worn for each patient.
Always ensure that masks are well adapted so that the nose and mouth are completely covered. Masks with metal inserts are preferable as they can be tailored to fit the individual's profile.
Masks should not be touched with gloves during treatment or worn outside the treatment zone; they should be worn beneath face shields as the latter provide only minimal protection from aerosols.
Although surgical masks have partial particulate filtration properties, only respirator masks have the filtering efficiencies required for adequate respiratory protection against contaminated aerosols generated when treating a patient with an infection transmitted by the airborne route, for example, Mycobacterium tuberculosis.
Respirator masks are manufactured with a range of filtering efficiencies. Masks with the highest filtering efficiency FFP3 (equivalent to N99 in USA) with 98% filtering efficiency are recommended for protection against infectious aerosols in health care. Respirator masks must be fit tested and checked for facial seal according to the manufacturer's instructions by the wearer before use.
Rubber dam isolation
As far as possible, a rubber dam should be used in operative procedures to minimize saliva and blood-contaminated aerosol production. Use of a rubber dam during operative procedures:
■ provides a clear visual field as the tissues are retracted
■ minimizes instrument contact with the mucosa (thus minimizing tissue injury and subsequent bleeding)
■ reduces aerosol formation, as saliva pooling does not occur on the rubber dam surface
■ minimizes the retraction of contaminated oral fluids into the dental unit water systems as the rubber dam prevents pooling of oral fluids and the possibility of suck-back into the water lines.
A note on pre-procedural mouthrinse
Chlorhexidine gluconate (0.1%-0.2%), essential oils or povidone- iodine mouthwash prior to a surgical procedure is recommended by some, to reduce the intraoral microbial load leading to systemic bacteraemias as well as the number of airborne pathogens. There is no scientific evidence to indicate that pre-procedural mouth rinsing prevents or reduces clinical infections among care providers or patients. However, studies have demonstrated that a pre-procedural rinse with an antimicrobial product can reduce the level of oral microorganisms in aerosols and spatter generated during routine dental procedures with rotary instruments (e.g., dental handpieces or ultrasonic scalers).
Aspiration and ventilation
Routine use of efficient high-speed aspirators with external vents and good ventilation will minimize cross infection from aerosols. Aspirator tips should be single use and the lines regularly cleaned according to the manufacturer's instructions.
Handling sharps and related injuries
Numerous objects with sharp edges are used in dentistry (e.g., needles, blades, burs, endodontic files, orthodontic wires and matrix bands). A list of all the types of sharps used in the practice should be kept, identifying those that are disposable and those that may be reused and hence need to be processed. Items of equipment designated as single use carry the international symbol of a 2 crossed through with a line and are not designed to withstand decontamination and are likely to fail if reused. Sharps containers of approved type should be used in each working area and kept as close as possible to the point of use. They should not be overfilled and the lid must be kept in the closed position when not in use, and then locked prior to disposal to prevent tampering. Containers must be disposed of as clinical waste, ideally by incineration.
Most exposures in dentistry are preventable or avoidable particularly during cleaning the surgery site, instrument decontamination and single-use sharps disposal. Hence dental practice should have policies and procedures in place that address the safety of sharps.
Fig. 37.3 A needle-resheathing device.
Two main approaches are used to reduce sharps injuries: work-practice controls and engineering control. Extreme care should be taken particularly when re-capping needles; work- practice controls such as a single-handed 'bayonet technique' or alternatively engineering controls employing a self-sheathing sharp or a resheathing device (Fig. 37.3) should be used for this purpose. Within the European Union and UK, legislation requires the avoidance of re-capping needles where possible. Safety sharps designed with an integral safety device such as a retractable sheath should be used. Other sharp safe measures include:
■ Not bending or breaking needles before disposal.
■ Not passing a syringe with an unsheathed needle from the hand of the operator to the hand of the assistant.
■ Removing burs before disassembling the handpiece from the dental unit.
■ Using instruments in place of fingers for tissue retraction. The dental team should be conversant with all sharps handling procedures, which should be an integral part of ongoing staff education.
Sharps injury protocol
It is normally recommended that the practice nominates a person to coordinate the administration of staff health and the reporting and recording of accidents and near misses within the practice. All sharps injuries should be recorded in a designated register (accident book) and followed up. A standard protocol for sharps injury should be displayed clearly. However, a detailed risk assessment of the incident and counselling should be provided by a specialist in occupational health or a microbiologist, to allay any concerns, undertake serological testing and recommend a suitable prophylaxis regimen. Guidelines for the management of sharps injuries are shown in Table 37.2, whilst a ready reckoner and an action plan for post-exposure prophylaxis is given in Fig. 37.4 showing the relative risk of contracting bloodborne virus infections through a sharps injury.
Practitioners should have a written policy on the vaccination (including administration of boosters) of all staff and maintain an up-to-date immunization record of themselves and their staff, which should be kept confidential. In the USA recommended immunizations for dental health care personnel include hepatitis B, MMR (measles, mumps, and rubella) varicella (chickenpox), Tdap (tetanus, diphtheria, pertussis).
In the UK dental staff must comply with national regulations for pre-employment standard health clearance checks and vaccinations. For those staff performing exposure-prone procedures as part of their role, then compliance with additional health clearance checks is mandatory. A list of vaccines that are available to dental health care workers is shown in Chapter 10 (Table 10.2). In the UK, vaccination against hepatitis B virus, tuberculosis (TB), MMR and varicella has been recommended for clinical dental staff, in addition to routine immunization against tetanus, poliomyelitis and diphtheria. A brief outline of vaccines available to dental personnel is given in the following sections.
Table 37.2 Principles guiding the management of sharps injuries
• Wash puncture site thoroughly with soap and warm water; antiseptics may be used in addition
• Encourage bleeding by squeezing the injured area
• Dry aseptically and report to supervisor according to the local regulations
• Review hepatitis B, C and human immunodeficiency virus (HIV) risk of source patient
• Inform source patient of the incident and counsel patient regarding HIV test, if indicated
• Arrange for venesection of the patient
• Contact occupational health authority, as per local regulations
Action by occupational health authority
• Record in detail circumstances of the sharps injury (i.e., demographic information of the exposed worker, details of the exposure)
• Check hepatitis B vaccination status of staff. If unvaccinated or hepatitis B vaccine non-responder, immediately commence hepatitis B vaccination procedure together with intramuscular hepatitis B immunoglobulin
• Offer counselling to the recipient with regard to HIV risk. If there is significant exposure, commence HIV prophylaxis drugs and continue for 28 days; serological monitoring at 4 weeks (and in some instances additional testing at 8 weeks)
There is no prophylaxis available for hepatitis C. Antiviral therapy is available following seroconversion to hepatitis C virus (HCV)
• Arrange venesection of the recipient for baseline serum antibody levels
• Arrange follow-up antibody testing at 6 months for hepatitis B virus (HBV) and 6, 12 and 24 weeks for HCV
• Return details to the occupational health authority and the infection control team as appropriate
Bacille Calmette-Guérin vaccine
Active against Mycobacterium tuberculosis. The vaccine contains live Mycobacterium bovis (termed bacille Calmette-Guérin (BCG)) attenuated by propagation in a bile-potato medium. Killed vaccines do not produce the cell-mediated immune response essential for protection against TB.
In the UK, the BCG vaccination is used as an occupational vaccine for those working in health care whose tuberculin test indicates no reaction. Until 2005, UK school children were vaccinated against TB at the age of 12-14 years. This vaccination schedule was replaced with a targeted, risk-based immunization protocol for susceptible neonates and infants who may be exposed to TB from family members or in locations where there are high rates of TB. The most effective use of BCG vaccination is to give it as soon as possible after birth to prevent infants at increased risk of exposure to TB from becoming infected. These infants are at increased risk of developing severe disease, such as miliary TB and TB meningitis. BCG is less effective at protecting against adult-type disease in older age groups.
Single dose intradermally in the deltoid muscle.
Poliomyelitis is an acute illness that follows invasion through the gastrointestinal tract by one of the three serotypes of polio virus (serotypes 1, 2 and 3). The virus replicates in the gut and has a high affinity for nervous tissue. Transmission is through contact with the faeces or pharyngeal secretions of an infected person. Polio virus replicates for longer periods and it can be excreted for 3-6 weeks in faeces and 2 weeks in saliva. There are two types of vaccine. The Salk, an inactivated (killed) poliovirus (IPV), is a trivalent vaccine, which is delivered by intramuscular (IM) injection. The alternative vaccine is the Sabin vaccine (oral poliovirus vaccine (OPV)), which is an oral live attenuated poliovirus types 1, 2 and 3 that has been utilized for the Global Polio Eradication initiative because of the ease of delivery. The OPV live attenuated vaccine virus retains the potential to revert to a virulent form that can rarely cause paralytic disease. This is called vaccine-associated paralytic polio (VAPP). When wild viruses have been eliminated, VAPP cases occur rarely where live attenuated vaccines are used. In countries that are deemed free of indigenous polio, and with health systems capable of delivering almost universal vaccine coverage, then the use of inactivated polio vaccine (IPV) for routine immunization is favoured as this avoids the risk of infection from VAPP strains. The trivalent vaccine was withdrawn in April 2016 and replaced with the bivalent oral poliovirus vaccine (bOPV), which contains only attenuated virus of types 1 and 3. This is because continued use of trivalent vaccine threatened to continue seeding new type 2 circulating vaccine-derived polioviruses despite the wild type 2 virus being eradicated in 1999. However, WHO recommends that OPV should remain the vaccine of choice for routine infant immunization in most countries.
All infants, after 6 weeks with OPV-based schedules and 8 weeks with IPV-based schedules but the exact programmes are country specific.
The polio vaccine is only given as part of combined products injected IM in the UK. The appropriate vaccine for each age group is determined also by the need to protect individuals against tetanus, pertussis, Hib and diphtheria. Td/IPV can be used as an occupational vaccine or as a booster to protect against polio in adults.
Fig. 37.4 A ready reckoner and an action plan for post-exposure prophylaxis of a needle-stick injury. HBV, hepatitis B virus; HBIG, hepatitis B immunoglobulin; HCV, hepatitis C virus; HIV, human immunodeficiency virus; PEP post-exposure prophylaxis PEG-IFN, Pegylated interferon.
The objective of the primary immunization programme is to provide a minimum of five doses of a polio-containing vaccine at appropriate intervals for all individuals. In most circumstances, a total of five doses of vaccine at the appropriate intervals are considered to give satisfactory long-term protection.
Excellent for both vaccines.
Live-attenuated strains of measles, mumps and rubella viruses.
All children in the second year of life, to prevent complications of common childhood fevers, such as respiratory tract infection and encephalitis associated with measles, meningitis associated with mumps and congenital infections associated with rubella. The last is especially relevant for women of childbearing age working in dentistry. Therefore MMR is offered as an occupational vaccine to non-immune members of the dental team of both sexes.
Two doses by the IM route.
Shingles (herpes zoster) is caused by the reactivation of a latent varicella-zoster virus (VZV) infection, resulting in a painful, vesicular skin rash, which may occur many years after the primary infection with chickenpox. The VZV vesicles contain virus and are infectious.
Following primary VZV infection, the virus enters the sensory nerves and travels along the nerve to the sensory dorsal root ganglia and establishes a permanent latent infection. The trigger to reactivation of the latent virus leading to shingles is not well understood, but reactivation is often associated with depression of the immune system due immunosuppressive therapy or disease including rheumatoid arthritis and systemic lupus. The risk and severity of shingles increase markedly with age and are associated with very painful post-herpetic neuralgia, which can be difficult to manage successfully. Furthermore, chickenpox can cause severe maternal disease, and 10% to 20% of pregnant women infected later in pregnancy may develop varicella pneumonia, which can be fatal. During the first 20 weeks of pregnancy, maternal chickenpox may damage the foetus, resulting in congenital varicella syndrome, stillbirth or shingles during infancy.
Vaccine is used as a childhood vaccine, occupational vaccine to prevent the primary disease chicken pox and prophylactically in the elderly greater than 70 years of age to prevent recurrence of shingles. When used as an occupational vaccine in health care professionals, evidence of natural immunity is tested serologically and vaccination is only required for non-immune health care workers.
Immunization comprises two doses of the live attenuated vaccine 4-8 weeks apart. Varicella vaccine is contraindicated in pregnancy and as a precaution pregnancy should be avoided for 1 month following the last dose of varicella vaccine. Different strength vaccines are used for primary immunization and vaccination of the elderly due to waning immunity and vaccine response in older people.
Triple vaccine: diphtheria-tetanus-pertussis
Three-in-one vaccine for prevention against diphtheria caused by Corynebacterium diphtheriae, whooping cough caused by Bordetella pertussis and tetanus caused by Clostridium tetani. Contains killed B. pertussis and diphtheria and tetanus toxoid.
All infants and as an occupational vaccine in the USA.
Three spaced doses by injection; subsequent booster doses of diphtheria and tetanus toxoids only.
Effective, but booster doses of tetanus and diphtheria are required to maintain immunity.
The toxin of Clostridium tetani that has been formol treated.
Active immunization of the entire population. Although the disease is rare, tetanus can develop after very trivial wounds.
Three spaced injections in infancy, as a component of the triple vaccine. Booster doses at 5 years and in the event of injury.
Hepatitis B vaccine
The surface antigen of the hepatitis B virus, hepatitis B surface antigen (HBsAg; see Chapter 29), manufactured in yeasts by genetic recombination and absorbed on to aluminium salt. Successful vaccination also offers protection against delta hepatitis (hepatitis D).
All health care workers who are at special risk, including dentists, dental hygienists, dental surgery assistants, medical laboratory workers and those handling blood products. Currently, the WHO recommends universal administration of infants at birth with hepatitis B to prevent early childhood HBV infection and to eventually protect adolescents and adults from infection. This approach has been adopted in the USA, many countries in Europe and by countries in South-East Asia where the disease is endemic, with the aim of eradicating the disease worldwide. Chronically infected persons are at increased lifetime risk for cirrhosis and hepatocellular carcinoma (HCC) and also serve as the main reservoir for continued HBV transmission.
Three doses (two doses at an interval of 1 month, followed by a third 6 months later) IM in the deltoid.
Approximately 10%-15% of adults fail to respond to three doses of vaccine or respond poorly. Poor responses are mostly associated with age over 40, obesity, smoking and advanced liver disease. If antibody levels are suboptimal, then a fourth (booster) dose may be given. Non-responders to the vaccine are tested for markers of current or past infection with HBV, in order to exclude asymptomatic carriers.
Individuals having the initial course of vaccination should undergo pre- and post-immunization tests, and those who fail to seroconvert should be followed up as appropriate.
Vaccine protection is very good offering approximately 95% protection. There is controversy over the necessity of reinforcing booster doses. Some authorities in the UK advocate boosters after 5 years, whereas others, especially in the USA, contend that booster doses are unnecessary because of the anamnestic response of the immune system.
Passive immunization with hepatitis B immunoglobulin
Passive immunization with hepatitis B immunoglobulin (HBIG) should be instituted within 48 h if an unprotected health care worker sustains an accident with blood or saliva containing hepatitis B antigens. This should be followed by a complete course of the hepatitis B vaccine, the first dose of which may be administered immediately or within 7 days of the accident. If the person declines the vaccine, then a second dose of HBIG should be administered 1 month after the first dose.
Usually contains two of the influenza A virus strains that are currently circulating, together with the influenza B strain. It is important to recognize that, because of the phenomenon of antigenic 'drift' and 'shift' seen in influenza viruses, the vaccine composition needs to be reviewed and altered each year, which is a formidable task. The vaccine contains partially purified, disrupted virus particles or the surface antigens (haemagglutinin and neuraminidase).
In recent years the indications for influenza vaccination have widened from elderly individuals, those people living in residential facilities or long-stay hospitals, to include pregnant women, infants and those people with underlying health conditions
such as respiratory or cardiac disease, chronic neurological conditions or immunosuppression. All these groups are prone to develop a range of more serious respiratory infections with influenza. Influenza during pregnancy may also be associated with perinatal mortality, prematurity, smaller neonatal size and lower birth weight.
In many countries, seasonal influenza vaccination is recommended for frontline health care workers including dental workers.
One dose by injection, repeated each winter, which is the usual period of outbreak.
Relatively short (approximately a year).
Occupationally acquired infections
Health care workers routinely run the risk of acquiring infections by virtue of their profession, so-called occupationally acquired infections. Particular concerns for health care workers are bloodborne viral infections, including hepatitis B and C, and human immunodeficiency virus (HIV) infection. Hepatitis B infection used to be about 10 times more common among dental health care workers than the public, but with the advent of the extremely effective hepatitis B vaccine, this danger is now minimal. The average risks of transmission of these diseases after exposure to blood are:
■ 0.3% for percutaneous exposure to HIV-infected blood
■ 0.1% for mucocutaneous exposure to HIV-infected blood
■ 0.5%-1.8% for percutaneous exposure to hepatitis C virus (HCV)-infected blood with detectable RNA
■ 6.0% for hepatitis B of a non-immune individual to an HBsAg-positive source
■ 30% for percutaneous exposure of a non-immune individual to a hepatitis B 'e' antigen (HBeAg)-positive source.
(Note: hepatitis B is most infectious and the least infectious in this context is HIV.)
Other than viral infections, rarely bacterial infections such as tuberculosis and legionella infections may be acquired by exposed dental care workers.
Additionally, it should be noted that certain features of a percutaneous injury carry a particularly high risk of infection transmission, as follows:
■ a deep injury
■ terminal HIV-related illness in the source patient
■ visible blood on the device that caused the injury
■ injury with a needle that had been placed in a source patient's artery or vein.
When considering the source patient, the risk is higher than average in people who are:
■ from countries where the condition is endemic
■ have had multiple blood transfusions
■ dialysis patients
■ intravenous drug users.
• The policy of standard infection control or standard precautions, which assumes that ALL patients are potential carriers of infectious diseases and all body fluids except for sweat are potentially infectious, should be the norm in dental practice.
• The main features in a comprehensive infection control protocol are patient evaluation, personal protection, instrument cleaning, sterilization and storage, use of disposables, cleaning and disinfection of surfaces, laboratory asepsis, disposal of waste and staff training, including continuing education.
• Personal protection should incorporate appropriate clinic clothing, personal hygiene, barrier protection (gloves, eye
shield, face masks, rubber dam isolation) and immunization procedures.
As far as possible, rubber dam should be used in operative procedures to minimize saliva/blood-contaminated aerosol production.
Use of efficient high-speed aspirators will minimize cross infection from aerosols.
To avoid sharps injuries, be conversant with all sharps handling procedures, which should be an integral part of staff education.
Have a written policy on the vaccination of all staff and maintain a confidential, up-to-date immunization record for all staff members.
Review questions (answers on p. 368)
Please indicate which answers are true, and which are false.
37.1 Which of the following procedures can be regarded as optimal for controlling cross infection in a dental clinic?
A. wearing a single face mask for 3 h
B. wearing headgear for all operational procedures
C. washing the gloves and reusing after visual examination of a patient
D. wearing gloves after removal of all hand jewellery
E. changing clinic attire once in 3 days
37.2 Which of the following vaccines would you recommend to your new female dental surgery assistant starting work with you?
A. hepatitis A
B. measles-mumps-rubella (MMR)
C. hepatitis B immunoglobulin
D. tetanus toxoid
E. flu vaccine
37.3 You treat a human immunodeficiency virus (HIV)- infected patient in your surgery. Your dental surgery assistant sustains a needle-stick injury while attempting to resheath the needle used for local anaesthetic of this patient. You will:
A. blame the dental surgery assistant for resheathing the needle
B. wash the puncture site thoroughly with soap, warm water and a disinfectant
C. review the infection control procedures that led to this situation
D. review the patient's medical history to check their hepatitis B status
E. record in detail the circumstances of the injury
37.4 The following infectious agents are likely to be transmitted in dental care settings:
A. hepatitis G
B. Streptococcus pyogenes
C. Candida albicans
D. hepatitis C
Beltramy, E. M., Williams, I. T., Shapiro, C. N., et al. (2000). Risk and management of blood-borne infections in health care workers. Clinical Microbiology Reviews, 13, 385-407.
Centers for Disease Control and Prevention (2016). Summary of infection prevention practices in dental settings: Basic expectations for safe care. Atlanta, GA: Centers for Disease Control and Prevention, US Department of Health and Human Services.
Coia, J. E., Ritchie, L., Adisesh, A., et al. (2013). Guidance on the use of respiratory and facial protection equipment. Journal of Hospital Infection, 85, 170-182.
Loveday, H. P., Wilson, J. A., Pratta, R. J., et al. (2014). Epic3: national evidence-based guidelines for preventing healthcare-associated infections in NHS hospitals in England. Journal of Hospital Infection, 86S1, S1-S70.
Pankhurst, C. L., & Coulter, W. A. (2017). Basic guide to infection prevention and control (2nd ed.). Chichester: Wiley-Blackwell.
Public Health England. (2013). Immunisation against infectious disease - 'The green book' (3rd ed.). Available from: https://www.gov.uk/ government/collections/immunisation-against-infectious-disease -the-green-book.
Samaranayake, L., & Scully, C. (2013). Needlestick and occupational exposure to infections: A compendium of current guidelines. British Dental Journal, 215, 163-166.
Samaranayake, L. P. (1989). Cross infection prevention in dentistry. Part II: Practical procedures. Dental Update, 16, 108-112.
Samaranayake, L. P., Scheutz, F., & Cottone, J. (1991). Infection control for the dental team. Copenhagen: Munksgaard.
Sax, H., Allegranzi, B., Larson, E., et al. (2007). My five moments for hand hygiene': A user-centered design approach to understand, train, monitor and report hand hygiene. Journal of Hospital Infection, 67, 9-21.