Dental Transmission Risk for HCV Disease Transmission

Klein et al 1991 anti-HCV was found in 4 (9.3%) of 43 oral surgeons compared with 4 (0.97%) of 413 other dentists (OR 10.5, 95% CI 1.9, 58)

Thomas et al 1996....among 343 oral surgeons and 305 general dentists, recruited at national meetings of the American Dental Association, anti-HCV was found in 2.0 and 0.7 per cent, respectively (OR 3.2, P=0.13), associated with older age, longer time in practice, and evidence of past HBV exposure...

For exposure of dental staff to HCV to occur, HCV must be present in the population of dental patients and the dentist must experience an exposure-prone injury. That dentists are at risk of occupational injury conducive to exposure to blood-borne viruses is undoubted. A survey of 310 dental practitioners in Scotland found that 56 per cent of respondents reported at least one such injury within the preceding year, half of which were judged to have constituted a moderate or high risk of transmission to the dental practitioner (Felix et al 1994).

That HCV is present in dental populations is equally undoubted: it has been estimated that in an average dental practice in the USA that treats 20 patients each day, one HCV-infected patient will be encountered every 2 weeks (Wisnom and Kelly 1993).

A study of 500 dental school patients in the USA found more than 5 per cent were HCV seropositive; it also found that responses to questionnaires of risk factors were not of practical value in predicting who was seropositive (Shopper et al 1995)

dental procedures constitute a risk for HCV infection for the patient, there are few studies which have identified a history of dental work as a risk factor among HCV-infected people. In Hangzhou, China, 22 per cent of 1,248 people with acute viral hepatitis were NANBH, and among these cases ‘seeing dentist was the main risky factor’[sic] (Sun 1990).

A second study in China found that for three (7.5%) of 40 HCV-seropositive patients frequent visits to the dentist were the only discoverable risk factor (Garassini et al 1995).

An analysis of data on acute viral hepatitis collected by an Italian surveillance system found that 9 per cent of all cases of acute HCV infection had only a history of dental work as a risk factor in the preceding six months (Piazza et al 1995).

On the basis of Piazza et al (1995), environmental contamination of dental surgeries by HCV was investigated by following 35 anti-HCV and HCV-RNA-positive patients with chronic hepatitis through dental treatment; 328 samples were collected from instruments and surfaces after their dental treatment. Twenty (6.1%) were positive for HCV RNA, including samples from work benches, air turbine handpieces, holders, suction units, forceps, dental mirrors and burs. The authors conclude that ‘these data indicate that there is extensive contamination by HCV of dental surgeries after treatment of anti-HCV patients and that if sterilization and disinfection are inadequate there is the possible risk of transmission to susceptible individuals’ (Piazza et al 1995).

Also see

1999 Hepatitis C Survives Commercial Sterilants and Disinfectants

Donating Blood Risk... CDC 2009 Report- Hemodialysis Unit

Boot Camp Paris Island 1968               

Occupational risk for hepatitis C virus infection among New York City dentists. 

Lancet 1991 Dec 21-28;338(8782-8783):1539-42 Klein RS, Freeman K, Taylor PE, Stevens CE Department of Medicine, Montefiore Medical Center, Bronx, New York 10467. 

Since dentists have numerous patients and are exposed to blood, they are likely to have the maximum risk.... Anti-HCV was found in 4 (9.3%) of 43 oral surgeons compared with 4 (0.97%) of 413 other dentists (OR 10.5, 95% CI 1.9 to 58). Our findings show that dentists are at increased risk for hepatitis C infection. All health-care workers should regard patients as potentially infected with a communicable bloodborne agent. Comments:  in: Lancet 1992 Feb 1;339(8788):304  Comment in: Lancet 1992 May 9;339(8802):1178-9 PMID: 1683969, UI: 92079638
 

PERCUTANEOUS INJURIES: WHO'S TRULY AT GREATEST RISK?
Percutaneous injuries among dental health care workers.
Kerr SP, Blank LW. Gen Dent 1999;47:146-151.

Percutaneous injuries have the potential to transmit bloodborne pathogens in the dental health care environment. The risk of bloodborne transmission is dependent upon the type of injury, amount of blood, virus titer, resistance of health care worker, response to environment, virulence of pathogen, and procedure during which the injury occurred. Prevention still remains the best method of reducing occupational transmission. There are limited reports on percutaneous injuries in dentistry, with no prospective studies involving the entire dental team in a variety of private practice settings. The purpose of this study was to determine whether a difference exists in the rate of percutaneous injuries among dentists, dental hygienists, and dental assistants in generalized and specialty private practices. Also this study compared the number of extraoral and intraoral percutaneous injuries among dental health care workers as a whole, and within each occupational group. The findings were that dental assistants reported the highest number of percutaneous injuries. Extraoral injuries occurred with greater frequency (90 percent) than intraoral percutaneous injuries for all occupational groups and as a whole.

http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-cditech-hepc.htm/$FILE/hepc_epidemiology.pdf

1999 OSHA Preambles	OSHA Preambles -  Bloodborne Pathogens (29 CFR 1910.1030)Revision Date: Jul 30 1999 Most healthcare workers who have transmitted to patients have several factors in common):  (1) The dentists and surgeons were chronic... had high titers...were unaware that they were infected.  ____________________________________________________________________________________________
2003 Risk of EMG Needles	“Platinum single fiber electrodes ... including the use of disposable NCS electrodes, .. with patients.. with agents ...Hepatitis C virus, Creutzfeldt-Jakob disease, and human immunodeficiency virus”. ____________________________________________________________________________________________
2008 HCV Dental Implants Transmission	Hepatitis patient sues, blames dental implants-A woman who underwent dental implant surgery ...suing the makers of products ... after she learned the products had been recalled and she had contracted Hepatitis C. ____________________________________________________________________________________________
2008 Multi-Risk Transmission Factors	Frequency distribution of hepatitis C virus genotypes in different geographical regions of Pakistan and their possible routes of transmission- Infectious Diseases 2008, 8:69...More than 70% of the cases were acquired in hospitals through reuse of needles/syringes and major/minor surgery... ____________________________________________________________________________________________
Dental treatment: 278 (32.55%) was the commonest conventional risk factor
HCV Detected in Dental Surgeries	Our data indicate that there is extensive contamination by HCV of dental surgeries after treatment of anti-HCV patients and that if sterilisation and disinfection are inadequate there is the possible risk of transmission to susceptible individuals ­­­­­­­­­­­­­­­­­­­­­­­­­­­­____________________________________________________________________________________________
HCV Disease Dental Transmission Risk
Hepatitis C: Dental- The deadly drill	second largest cause of the spread of hepatitis...even reputed hospitals don’t have proper means of cleaning ____________________________________________________________________________________________

Epidemiology of the hepatitis C virus - Chapter 4
4.2.7 Hepatitis C virus and dentistry

It is a commonly believed that there are ‘large numbers of hepatitis C carriers in whom no route of infection can be identified’ (Tibbs 1995). Given the findings of HCV RNA in saliva and higher than expected prevalences of HBV in dentists, some of these cases (if this is indeed the case) may be explained by transmission in the dental setting.

There is also the question of the degree to which dental staff are at occupational risk of HCV infection. Presence of hepatitis C virus in saliva HCV RNA has been detected in saliva in the dental setting, both with and without blood contamination. In one study of 26 anti-HCV-positive patients, of whom 11 were coinfected with HIV, HCV RNA was detected in the sera of 23 (88%) and in the saliva of 4 (17%) of these viraemic patients.

The authors suggest that HCV is present in saliva in less than 25 per cent of HCV viraemic people, and the virus in saliva is restricted to the cell fraction, so that saliva may serve as a nonparenteral transmission route of HCV but at a low probability, which would be increased by blood contamination of saliva during and after oral surgery (Chen et al 1995). A second study of 21 HCV-seropositive patients with haemophilia attending an Oral Surgery Unit, all of whom were HCV-RNA positive and six of whom were also HIV-antibody positive, found HCV in saliva from 10 of the subjects (8 HIV seronegative, 2 HIV seropositive) (Roy et al 1996).

Prevalence of hepatitis C virus in and risks of transmission to dental staff

For exposure of dental staff to HCV to occur, HCV must be present in the population of dental patients and the dentist must experience an exposure-prone injury. That dentists are at risk of occupational injury conducive to exposure to blood-borne viruses is undoubted. A survey of 310 dental practitioners in Scotland found that 56 per cent of respondents reported at least one such injury within the preceding year, half of which were judged to have constituted a moderate or high risk of transmission to the dental practitioner (Felix et al 1994). That HCV is present in dental populations is equally undoubted: it has been estimated that in an average dental practice in the USA that treats 20 patients each day, one HCV-infected patient will be encountered every 2 weeks (Wisnom and Kelly 1993). A study of 500 dental school patients in the USA found more than 5 per cent were HCV seropositive; it also found that responses to questionnaires of risk factors were not of practical value in predicting who was seropositive (Shopper et al 1995).

Given the presence of HCV in saliva, the prevalence of occupational exposure-prone incidents among dentists and the prevalence of HCV in some dental populations, it would be expected that there would be a high prevalence of HCV exposure among dental staff. There have been four major surveys of dentists and oral surgeons examining prevalence and associations of HCV, and their conclusions are not totally in accord.

In a survey of dental professionals attending the annual meeting of the College of Dental Surgeons of British Columbia, Canada, in June 1990, 401 of 1,995 convention attendees (20%) participated. Fourteen (3.5%) had markers of HBV infection, of whom one (0.25%) was also HCV-seropositive: none was positive for antibody to HIV (Roscoe et al 1991). In Taiwan in 1990-91, 3 of 461 dentists (0.65%) were HCV-seropositive, comparable with the prevalence in healthy blood donors (0.95%) and pregnant women (0.63%), leading to the conclusion that in this area the practice of dentistry carries no increased risk of HCV infection (Kuo et al 1993). Among 456 dentists in the New York City area anti-HCV was found in 8 (1.75%), compared with 1 (0.14%) of 723 controls (OR 12.9, 95% CI 1.7, 573). Seropositive dentists claimed to have treated more IDUs in the week (P=0.04) or month (P=0.03) before the study than did seronegative dentists. In this study, anti-HCV was found in 4 (9.3%) of 43 oral surgeons compared with 4 (0.97%) of 413 other dentists (OR 10.5, 95% CI 1.9, 58) (Klein et al 1991). And lastly, among 343 oral surgeons and 305 general dentists, recruited at national meetings of the American Dental Association, anti-HCV was found in 2.0 and 0.7 per cent, respectively (OR 3.2, P=0.13), associated with older age, longer time in practice, and evidence of past HBV exposure (Thomas et al 1996).

Two other studies that have included dentists along with other HCWs have similarly found low rates of exposure to HCV, even where prevalence is high in the patient population. One study in the USA found anti-HCV prevalence to be 1.6 per cent (95% CI 0.0, 3.2%), similar to volunteer blood donors, despite high degrees of blood exposure in the HCWs (Cooper et al 1992). A survey of hospital-diagnosed acute viral hepatitis in the United States Air Force staff from 1980 to 1989 found an increased risk of HCV for ‘procedurally oriented medical personnel’ (including dentists) when compared to all other occupations, but this increase was not large (RR 1.5, 95% CI 1.1, 1.9).

Taken together, these data tend to confirm high rates of HBV exposure among dental staff, but suggest that the risk of HCV infection is considerably lower: it seems to be increased with risk of blood contamination and degree and frequency of exposure-prone procedure.

32
Knowledge of transmission of viral pathogens among dental staff
Some researchers have investigated dentists’ awareness of the risks of transmission of viral pathogens, and their response to these risks. A survey in British Columbia, Canada, showed that many of the mechanisms, routes and risks for the transmission of viral pathogens in the dental setting were not clearly understood by the dentists surveyed, and recommended continuing education to ensure that compliance with current infection control recommendations be based on a clear understanding of the mechanisms of infection (Epstein et al 1995). The
Roscoe et al (1991) survey of dental professionals in British Columbia also assessed compliance with infection control guidelines, and found acceptance to be high, with 92 per cent of participants reporting use of gloves for all patients and 82 per cent reporting use of masks and eye protection. Risks of patient-to-patient transmission in the dental setting
Returning to the question of whether