Female Reproductive Hazards in the Dental Office
Are female dental assistants at risk?
Jacob L. Masters, DDS
Dental professionals may be at risk for exposure to numerous workplace hazards. There are currently no specific standards for dentistry, but rather workplace hazards that may apply to dentistry are addressed to the entire healthcare industry.1 However, there are numerous different materials, chemicals, and supplies commonly used in the general dentist’s office that are left out of the expansive collection of workplace hazards.
Concerns arose about the health risks from dental materials since at least the 1960s. The medical literature and government agencies have both examined and made recommendations to reduce risk of miscarriage, birth defects, and reduced female fertility at different levels of exposure to several hazards (materials, chemicals, supplies, radiation, etc).2 Fortunately, several steps can be taken to control the level of exposure from these agents, either voluntarily or under the regulations of the Occupational Safety and Health Administration (OSHA). These include, but are not limited to, handling the agents properly, monitoring the levels of exposure, using devices to lower the levels, and properly disposing of the agents. The agents can be divided into infectious health hazards and noninfectious health hazards.
Infectious Health Hazards
Dental healthcare workers (DHCW) are susceptible to accidental contact with contaminated objects that may penetrate the skin. These contaminated objects include, but are not limited to, needles, scalpels, broken glass, and exposed ends of dental wires. Any of these items have the potential to be contaminated by infectious materials such as saliva and blood. DHCW may also be exposed to contaminated, infectious materials passing through to the worker’s clothing, skin, eyes, mouth, or other mucous membranes, such as the nasal mucosa. Taking precautions can avoid some threatening situations.
To prevent injuries in dentistry, contaminated needles and other contaminated sharps should not be bent, recapped, or removed unless no alternative is feasible or such action is required by the procedure. In these unique situations, the process can often be completed with the use of a mechanical device or a one-handed technique. All sharps must be placed in a puncture-resistant, labeled, and leak-proof container as soon as possible.
These universal precautions must be used to eliminate or minimize employee exposure to bloodborne pathogens. Employers must provide personal protective equipment (PPE) to employees at no cost to the employee. The use of personal protective equipment and other universal precautions in the healthcare industry are explained in detail on OSHA’s website, www.osha.gov.1
Noninfectious Health Hazards
Mercury, the main component in dental amalgam, has been used for more than 150 years in hundreds of millions of patients. Amalgam fillings are composed of a mixture of metal alloys and liquid mercury, with 50% of this mixture being elemental mercury.3 In 2009, the Food and Drug Administration issued a final ruling that classified dental amalgam as a class II device (more risk than lower classifications). It was officially stated that dental amalgam releases low levels of elementary mercury vapor. Vapor concentrations are highest immediately after placement and removal of dental amalgam, but decline thereafter.4
Elementary mercury (the form used in dental amalgam) is absorbed mainly by inhaling its vapor, which is then distributed throughout the body. Excretion of mercury occurs predominately through the kidneys, and is finally expelled in urine.5 An examination of the level of mercury in the urine of dentists revealed that dentists had about three times higher levels of urinary mercury than the control subjects.6 However, finding a measurable amount of mercury in blood or urine does not mean that the level of mercury causes an adverse health effect.5 In fact, the evidence that mercury vapor may impair female fertility is limited. However, exposure to mercury vapor can be reduced by properly handling dental amalgam.7-10
In 1999, the ADA Council on Scientific Affairs recommended a program to ensure the safety of all dental personnel involved in the handling of mercury or dental amalgam. The ADA recommends against the use of bulk elemental mercury, which is still available for purchase. General precautions include training all personnel that handle dental amalgam of the potential hazards of mercury vapor and observing good mercury hygiene practices. Poor handling of dental amalgam and the exposure to the vapor in the operating areas can be limited.
Dental offices using amalgam are required to have a mercury spill kit available. The specific type and number of spill kits that the facility must make available is based on the information on the chemical’s MSDS.11 Mercury spill kits are available from both Patterson Dental Supply and Henry Schein.
It is further recommended to periodically check the dental operatory atmosphere for mercury vapor. Dosimeter badges and mercury vapor analyzers are available. The dosimeter badges monitor the specific amounts of mercury levels to the specific individual wearing the badge.
The OSHA standard for mercury is 0.1 mg per cubic meter of air averaged over an 8-hour work shift. The National Institute for Occupational Safety and Health (NIOSH) has recommended the permissible exposure limit to be changed to 0.05 mg/m3 averaged over an 8-hour work shift over a 40-hour workweek.12
Exposure to mercury vapor may involve some risk for birth defects; however, the results are limited. Most studies on this topic have been retrospective in nature and, naturally, many variables, such as other health conditions, smoking, drug use, physical strain, and age, were difficult to discern. On the other hand, there are no reported strong associations of miscarriage or fetal death due to the levels of mercury used in the dental office.2,8-10
Nitrous oxide (N2O), commonly called laughing gas, is an anesthetic agent. Workers are exposed to N2O while administering the anesthetic gas to patients. Scavenging systems that vent unused and exhaled gas away from the work area help to protect workers from the health risks associated with N2O (Figure 1). Research has shown that these systems can significantly reduce the risk of impaired fertility among female dental assistants exposed to N2O.13 The NIOSH has suggested an occupational exposure limit (OEL) of 25 parts per million (ppm) for the duration of exposure as a time-weighted average (TWA), while the American Conference of Governmental Industrial Hygienists (ACGIH) has assigned a threshold limit value (TLV) of 50 ppm as a TWA for a normal 8-hour workday/40-hour workweek. Without a scavenger in place, concentrations of N2O were routinely reported as 1,000 ppm to 2,000 ppm in the dental operatory or 40 times or more exposure than the suggested exposure limit.14,15 Alarmingly, a NIOSH Alert reports that even with scavenging systems in place, researchers measured exposures more than 1,000 ppm than the NIOSH-recommended limit in dental operating rooms.13 This indicates that even with a scavenging system in place, the exposure to higher levels of N2O is possible. Using a scavenger system is not sufficient unless it is continuously monitored and maintained to effectively reduce exposure to N2O.13
In addition, the Centers for Disease Control and Prevention (CDC) has issued a hazard statement on the control of N2O in the dental operatory.14 This report states that N2O exposures should be minimized to prevent short-term behavioral and long-term reproductive health effects. Epidemiological studies conducted mostly on operating room personnel (who are possibly the nearest comparison in the literature to dental assistant personnel) have shown increased risks of spontaneous abortion, premature delivery, and involuntary infertility among those occupationally exposed.14
There are three systems that can be used to reduce N2O concentrations to approximately 25 ppm (the maximum level of exposure recommended by NIOSH) during clinical use in the dental operatory:
- System maintenance should be done by inspecting and maintaining the anesthetic delivery system to prevent N2O leaks in all hoses, connections, and fittings—leaks must be repaired immediately.
- Ventilation should be accomplished by the use of a scavenging system with an air flow rate from the patient’s mask at 45 LPM, measured by a calibrated flow device and then vented outdoors. The operatory, where possible, should use 100% clean outdoor air for ventilation. Finally, a local exhaust hood should be placed near the patient’s mouth to capture excess N2O.
- The proper-sized scavenging mask must be used on the patient. In addition, only the minimum amount of N2O needed should be used. Finally, the air concentration of N2O must be monitored to ensure the above controls are effective in achieving low levels of N2O in the dental operatory.
NIOSH recommends air sampling for N2O periodically. A diffusive sampler is easily available from dental supply companies and various manufacturers. The diffusive samplers are easy to use and inexpensive. It can be used to measure a dental worker’s exposure by attaching it to the lapel (breathing zone) and uncapping/recapping it during N2O use. Manufacturer’s directions should be followed to have the results interpreted.15,16
All dental workers must follow precautions to prevent exposure to radiation emitted from dental x-ray machines.17 All workers, especially pregnant workers, should consider wearing a monitoring dosimeter film badge on uniforms. DHCW must stand at least 6 feet away from an x-ray machine or behind a lead-lined wall, and should never attempt to hold film in a patient’s mouth during x-ray exposure.17
Another precaution that may help limit exposure is ensuring the machines are properly collimated. Workers should never be in the room or in the path of the active beam. Settings should include the proper kVP and MA. Also, the highest speed film to reduce the radiation needed to expose the film should be used.17-20
The dose for total body exposure is measured as a level of rem (a person’s risk that he or she will suffer health effects from an exposure of radiation). The level of exposure from one dental x-ray is 0.004 rem to 0.015 rem. Digital imaging using a sensor rather than film may offer reduced radiation exposure compared to film. Three-dimensional imaging with cone beam computed tomography (CBCT) is being used with increasing frequency in dentistry. The radiation dosage in a CBCT can be anywhere between 4 and 42 times higher than a comparable panoramic radiograph.18-20
The permissible dosage for the total body is 5 rem per year, or no more than 3 rem permitted within a 13-week period. An exposure equivalent to 5 rem per year is believed to permit a lifetime occupational exposure without reaching an injurious level. In addition, the dose limit for the fetus of an occupationally exposed woman is 0.5 rem for the entire gestation period. Prenatal radiation exposure may result in prenatal death. Doses of 10 rem to 19 rem received by human fetuses have been shown to produce small head size, whereas doses above 150 rem have been associated with mental retardation.18-20
Dental sealants and composite filling materials contain bisphenol A (BPA) derivatives. These materials are increasingly being used in childhood dentistry.21 Recent news has focused on the dangers of bisphenol A and related compounds in dental materials. Although continued use (with strict adherence to precautionary application techniques) is recommended, the use of these materials should be minimized during pregnancy.22 It appears that BPA levels in the saliva peak over a 3-hour period following sealant placement and returned to baseline within 24 hours. To reduce the potential risk for BPA toxicity from sealants, a mild abrasive (such as pumice, either on a cotton applicator or in a prophy cup) should be used after the restoration is complete. In addition, the provider can wash the sealant surface for 30 seconds with an air-water syringe while suctioning fluids from the mouth.23 In the long term, manufacturers should be encouraged to develop materials with fewer effects on the reproductive system (specifically, less estrogenic potential).22
In the literature, concerns about the reproductive risks associated with occupational exposure to other agents exist. The most common warning of a chemical’s presence is its odor. However, people cannot detect odors equally well and not all chemicals with a strong smell are harmful to the fetus. Therefore, odor should not be relied upon to warn of the presence of a hazard, but it can indicate the presence of a chemical. The CDC has listed several chemicals in dentistry and other fields of healthcare that may be hazardous to reproduction. Most of the risks can be reduced with appropriate protective clothing, such as gloves and face shields. Splash-proof safety goggles should also be provided and required for use.
The authorities on occupational health cannot provide specific medical advice concerning potential risk factors for those currently pregnant or trying to become pregnant.25,26 Workers should consult with their primary care physician and/or an obstetrician for medical advice and recommendations. Before working with any chemical, the manufacturer’s instructions should be read and followed. It is also important to refer the material safety data sheets (MSDS) for more information.17,25,26 Workers should ensure that they have received all recommended immunizations and consult with their personal physician regarding which immunizations may require booster doses.25,26
As mentioned, many of the results from the studies are retrospective in nature, which allows many variables to cast uncertainty on the results obtained. Due to the variety of agents and the lack of research, the increased risk of reproductive hazards cannot be excluded for all dental materials. Additionally, there is not enough evidence in human trials to determine whether or not these dental materials will have an adverse effect on female fertility or pregnancy.
1. Occupational Safety and Health Administration. Safety and Health Topics: Dentistry. http://www.osha.gov/SLTC/dentistry/index.html. Updated March 29, 2007. Accessed May 6, 2011.
2. Olfert SM. Reproductive outcomes among dental personnel: A review of selected exposures. J Can Dent Assoc. 2006;72(9):821-825.
3. Organization for Safety and Asepsis Procedures. Amalgam Issue Toolkit–OSAP. Available at: http://www.osap.org/?page=issues_amalgam2010&terms=amalgam. Accessed April 30, 2011.
4. United States Food and Drug Administration. FDA Appendix I: Summary of changes to the classification of dental amalgam and mercury. Available at: http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DentalProducts/DentalAmalgam/ucm171120.htm. Updated August 11, 2009. Accessed May 1, 2011.
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6. Karahalil B, Rahravi H, Ertas N. Examination of urinary mercury levels in dentists in Turkey. Hum Exp Toxicol. 2005;24(8):383-388.
7. Rowland AS, Baird DD, Weinberg CR, et al. The effect of occupational exposure to mercury vapour on the fertility of female dental assistants. Occup Environ Med. 1994;51(1):28-34.
8. Lindbohm, M, Ylöstalo P, Sallmén M, et al. Occupational exposure in dentistry and miscarriage. Occup Environ Med. 2007;64(2):127-133.
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11. American Dental Association. ADA Council on Sci-
entific Affairs. Dental mercury hygiene recommendations. J Am Dent Assoc. 2003;134(11):1498-1499.
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14. McGlothin JD, Dames BL, Flesch JP. NIOSH Hazard Controls. Control of Nitrous Oxide in Dental Operatories. Available at: http://www.cdc.gov/niosh/nitoxide.html. Updated March 2, 1998. Accessed April 30, 2011.
15. Occupational Safety and Health Administration. Guideline for Nitrous Oxide. Available at: http://www.osha.gov/SLTC/healthguidelines/nitrousoxide/recognition.html. Accessed April 30, 2011.
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17. Centers for Disease Control and Prevention. Guidelines for protecting the safety and health of health care workers. Available at: http://www.cdc.gov/niosh/docs/88-119/. Accessed May 6, 2011.
18. Centers for Disease Control and Prevention. Radiation Emergencies. Available at: http://emergency.cdc.gov/radiation/pdf/measurement.pdf. Updated December 23, 2003. Accessed May 7, 2011.
19. United States Food and Drug Administration. The Selection of Patients for Dental Radiographic Examinations. Available at: http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm116504.htm. Updated May 6, 2009. Accessed May 21, 2011.
20. Ludlow JB, Davies-Ludlow LE, Brooks SL, Howerton WB. Dosimetry of 3 CBCT devices for oral and maxillofacial radiology: CB Mercuray, New Tom 3G and i-CAT. Dentomaxillofacial Radiology. 2006;35(4):219-226.
21. Fleisch AF, Sheffield PE, Chinn C, et al. Bisphenol A and related compounds in dental materials. Pediatrics. 2010;126(4):760-768.
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23. Azarpazhooh A, Main PA. Is there a risk of harm or toxicity in the placement of pit and fissure sealant materials? A systematic review. J Can Dent Assoc. 2008;74(2):179-183.
24. Walton RE, Torabinejad M. Orthograde retreatment. In: Walton RE. Principles and Practice of Endodontics. 3rd ed. Philadelphia, PA: Saunders; 2002:357.
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About the Author
Jacob L. Masters, DDS