Health of DHWs

The standardized mortality ratio (SMR) – the ratio of observed deaths in an occupation or from any disease to the national average death rate for the same age and sex – is lower in dentists than in the general population. The main causes of death among dentists in UK, USA and other industrialized countries are cardiovascular disease, cancer and suicides, as in non-dental groups of similar socioeconomic status.

The risks in male dentists from liver cirrhosis and suicide are somewhat higher than in the general population, and dentists are also a risk group for malignant melanoma – presumably a consequence of sun exposure on holiday. Dentists, however, have a lower SMR for cancers, ischaemic heart disease, cerebrovascular disease and chronic lung diseases (bronchitis, emphysema and asthma).

Infections and physical, chemical and radiation hazards are the main occupational problems for DHWs. Nearly half of DHWs report sharp instrument injury at some time while treating patients. There are also risks from other accidents, and damage to eyes, hearing, mental health, musculoskeletal system, the fetus in pregnancy, respiratory systems and the skin (Table 31.1). Significantly greater numbers of female DHWs seem to experience musculoskeletal disorders and allergy to latex than males. The most prevalent preventive measure reported by DHWs is changing gloves between patients and using a face mask. Also, most DHWs have undergone hepatitis B virus and other vaccinations.

In the UK, governmental concern and the defining of safe work practices have brought the question of occupational hazards into sharper focus, as have the measures for implementing safe practices enshrined in the Health and Safety at Work etc. Act (1974) and regulations such as the Ionizing Radiations Regulations (1988) and Control of Substances Hazardous to Health Regulations (1988). In the USA, the Department of Labor Occupational Safety and Health Administration (OSHA) has extensive legislation, which may be found at http://www.osha.gov/SLTC/dentistry/standards.html (accessed 30 September 2013).

Infections (See Also Ch. 21)

Overall, the major infectious hazards are respiratory and hepatitis B (HBV) and C virus (HCV) infections, and, to a very much lesser extent, human immunodeficiency virus (HIV), prions and health-care-associated infections (HCAIs), such as meticillin-resistant Staphylococcus aureus, Clostridium difficile, tuberculosis and Legionella.

Blood, serum and saliva are the sources most likely to transmit serious infection, as well as dental instruments that are often contaminated after use, and also bites. The transmission of blood-borne viruses is determined by the dose and viral concentration of an exposure. Whereas HBV transmission can be prevented by immunization of DHWs, controlling HCV and HIV requires efforts to reduce the incidence and dosage of exposures to blood and body fluids. Such strategies include the design and use of safe devices, targeted interventions, the use of gloves and other barriers, and ongoing surveillance and analysis of exposures.

Since there is a potential for transmission of various infections, dental equipment should, where at all possible, be single-use and all reusable instruments must be sterilized or at least decontaminated (Fig. 31.1). DHWs should pay considerable attention to avoidance of needle-stick (percutaneous inoculation; sharps) infections/injuries and bites.

Standard (universal) infection control must be implemented; infection control guidelines can be found at http://www.bda.org/dentists/advice/ba/ic.aspx (accessed 30 September 2013).

The main points to remember in order to minimize cross-infection are shown in Box 31.1.

Needlestick/Occupational Exposure to Infections

Exposure-prone procedures (EPPs) are defined by the UK Department of Health as those where there is a risk that injury to the worker may result in exposure of the patient’s open tissues to the blood of the worker. These procedures include those where the worker’s gloved hands may be in contact with sharp instruments, needle tips or sharp tissues (spicules of bone or teeth) inside a patient’s open body cavity, wound or confined anatomical space where the hands or fingertips may not be completely visible at all times. Most procedures in dentistry are defined as EPPs, with the exception of:

However, taking impressions from dentate or partially dentate patients would be considered exposure-prone, as would the fitting of partial dentures and fixed or removable orthodontic appliances, where clasps and other pieces of metal could result in injury to the dentist.

DHWs need not refrain from performing EPPs pending follow-up of occupational exposure to an HIV-infected source. The combined risks of contracting HIV infection from the source patient and then transmitting this to another patient during an EPP are so low as to be considered negligible.

Blood-borne microorganisms that can be transmitted via blood exposure include:

Accidental exposure to blood caused by needle injuries or injuries following, cutting, biting or splashing incidents carries the risk of infection, particularly by blood-borne viruses though risks vary (Table 31.2).

Preventing needlestick injury and avoiding infection

The single most important measure that will help to prevent needle-stick injury is to avoid recapping and resheathing. Keep a rigid puncture-proof container close to hand for used needles to avoid the temptation of recapping. It is equally important to use proper protective clothing such as gloves, mouth mask and goggles.

Every DHW at risk from accidental exposure to blood should be trained in infection control and vaccinated against HBV (there are no preventive vaccines available for HCV or HIV).

Action after exposure to potentially contaminated material includes (Fig. 31.2) the following measures:

Under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (1995), it is not usually necessary to tell the Health and Safety Executive (HSE) about an occupational exposure to blood or saliva; however, if the occupational exposure involves a known carrier of a blood-borne disease, this is classified as a dangerous occurrence and reporting then becomes mandatory – as it is when acute ill health has resulted from exposure to, or transference of, a biological pathogen. Recording of occupational exposure to blood or saliva in an accident report book is strongly advised and the incident should be reported immediately to the department dealing with occupational accidents.

Post-exposure prophylaxis (PEP) against HIV has been estimated to reduce the risk of transmission by 75%; it should be carried out within 1 hour for maximum effect, so an initial assessment must be performed as soon as possible. Even if there is a delay, it is still worth considering PEP within 24 hours of the exposure. A blood sample should be taken from the exposed person as soon as possible after the injury to act as a baseline value in case infection does arise. Further blood samples to test for HBV, HCV and HIV are collected after 1, 3, 6 and 12 months. If the source of the blood is known, the patient must be asked for permission to take a sample of blood for an HCV and HIV test. If the patient refuses, then they must be assumed to be a carrier. If the origin of the blood is unknown, then any blood present on the needle can be used for a serological examination.

Management is based on determining the level of risk of contracting HBV, HCV or HIV, depending on whether or not the injured person is non-immune, partially immune or fully immune for HBV (from vaccination or otherwise). If there is only limited immunity to HBV, then 5 mL intramuscular hepatitis B immunoglobulin (HBIG) should be given within 48 hours of the injury. After a potential HCV infection, combination treatment of pegylated interferon and ribavirin is the treatment of choice. A liver specialist should be consulted.

No PEP is currently available for hepatitis C. However, early treatment of acute hepatitis C infection may prevent chronic hepatitis C infection. Follow-up of exposed patients should be as that described in management for occupational exposure to hepatitis C.

A course of hepatitis B vaccination with or without immunoglobulin may be recommended as PEP following exposure to hepatitis B.

Post-exposure prophylaxis for HIV infection

After a potential HIV infection, the actual risk depends on the type of contact and on the amount of virus in the contaminated material. The risk of an HIV infection following exposure to blood is very small but factors associated with a higher risk are:

Decision 1: What is the level of risk of HIV transmission?

Level of risk is classed as low or negligible, which does not require PEP, or as a significant injury with a higher risk of transmission, which may require PEP. In the latter case, the source should be informed that the injury is significant enough to carry a risk of transmission and their permission should be obtained for a review of their social and medical histories. In the case of a splash, the volume of exposure should be assessed, as both HIV and HCV are reported to have been transmitted through only 0.5 mL of blood to the conjunctiva. In the unlikely event of a splash to a mucous membrane, then the exposure would be classed as a significant injury.

Decision 2: Is your patient at risk of carrying HIV?

A social and medical history can help determine whether HIV transmission is likely to have occurred and the associated degree of risk of that happening. Questions will relate to the patient’s sexuality and lifestyle; ideally, questioning should take place in a private room and the patient needs to be reassured that the discussion will remain confidential. The recipient of the injury should not ask the questions because he or she may be too anxious. When assessing the risk factors for acquiring HIV, the operator should concentrate on high-risk activities (Box 31.2) that increase the potential for transmission of the infection rather than concentrating on the main risk groups. The patient should be informed that guidelines are laid down by the UK health departments for the management of occupational exposures to blood or saliva, and that some questions need to be asked that relate to the risk of the patient having acquired HIV.

Low risk

If it is decided that the patient is in the low-risk category for HIV, then the procedure outlined under mild injury is followed.

High risk

If the patient admits to having participated in a high-risk activity, in an area with a high prevalence of HIV, then the specialist may recommend an HIV test. The test must not be carried out until trained health-care advisors have counselled the patient about the consequences of such a test. This takes more than an hour to carry out and the specialist may advise the recipient to attend a local hospital to be given initial doses of PEP drugs. Once the initial doses have been taken, a formal risk assessment for HIV may be carried out and a decision made as to whether to continue PEP until the HIV test result is known. If the injury occurs outside normal working hours, an alternative source of advice must be found and, if necessary, the first few doses of PEP obtained. The designated specialist can give guidance on this and the local accident and emergency department would probably be the first contact for advice and PEP.