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Proper Use of Beryllium Containing Alloys

Many dental prosthetic restorations placed in the United States are made of a variety of base metal alloys. Base metal alloys are composed of metallic elements other than gold, silver, platinum, palladium, ruthenium, iridium, rhodium, and osmium.

Beryllium is added to some base metal alloys for use in crowns, bridges and partial denture frameworks. Incorporation of beryllium into the base metal alloy formulation facilitates castability (lowering the melting temperature and surface tension) and increases the porcelain metal bond strength.1,2 Beryllium also allows the alloys to be electrolytically etchable for bonding veneers in conjunction with resin-bonded restorations.3

However, exposure to beryllium vapor or particles is associated with a number of diseases from contact dermatitis4,5 to chronic granulomatous lung disease, known as chronic beryllium disease (CBD). In addition, beryllium and some beryllium compounds in vapor and particulate form have been shown to be carcinogenic based on human epidemiological and animal experimental models.6 Tumors linked to beryllium include lung carcinoma6 and osteosarcoma.7

Potential hazards or risks from exposure to beryllium result from melting, grinding, polishing and finishing procedures. The risk is greatest during the casting process in the absence of an adequate exhaust and filtration system. Both the National Institute of Occupational Safety and Health (NIOSH) and the ADA8 have promulgated standard practices for the safe management of beryllium-containing alloys. These practices have focused on dental laboratories where beryllium-containing alloys are routinely used for the fabrication of crowns, bridges and partial dentures.

According to the Occupational Safety and Health Administration (OSHA) the current Permissible Exposure Limits (PELs) for beryllium allow exposure to 2 micrograms per cubic meter of air (2 µg/m3) as an 8-hour time-weighted average (TWA), between 5 µg/m3 and 25 µg/m3 exposure for up to 30 minutes at a time, and 25 µg/m3 as a maximum peak limit that can never be exceeded. However, some recent studies and reports have questioned whether the current 2 µg/m3 PEL for beryllium in the workplace is adequate to prevent the occurrence of CBD among exposed workers.9,10 A recommendation of 0.1 µg/m3 for the 8-hour TWA has been made based on a study of unaffected populations near a beryllium plant.11

In a recent Hazard Information Bulletin entitled Preventing Adverse Health Effects from Exposure to Beryllium in Dental Laboratories (“OSHA Bulletin”),12 OSHA expressed concern that cases of CBD are continuing to occur among dental laboratory technicians and cautioned the nation’s dental laboratories and lab technicians to be alert to the risk of developing CBD from exposure to dust from beryllium.

With regard to the dental office, reports of toxicity to beryllium-containing alloys are limited to a few cases of transient contact dermatitis.4,5 The recent OSHA Bulletin does not appear to question the fundamental safety and effectiveness of beryllium-containing alloys when handled appropriately, and no cases of CBD have been documented to date in dental practitioners, dental office employees, or patients. The OSHA Bulletin does, however, indicate that the precautions regarding the use of beryllium-containing alloys apply to dental offices if these are fabricated or modified there. So in cases where beryllium-containing dental prostheses are ground or polished in the dental office, precautions should be considered to minimize any exposure to beryllium-containing dust.

The following OSHA recommendations should be taken by dental practitioners using beryllium-containing alloys for dental prostheses:

  • Obtain Safety Data Sheets for all dental alloys used in the dental office;
  • Where possible, alloys that do not contain beryllium should be substituted for beryllium-containing alloys in dental prostheses (a number of other non-beryllium-containing alloys have been granted the ADA Seal of Acceptance);
  • All procedures related to grinding or polishing beryllium-containing dental alloys should be conducted using properly designed and installed local exhaust ventilation;
  • Vacuum systems and local exhaust ventilation systems should be equipped with high-efficiency particulate air (HEPA) filters;
  • When possible, use local exhaust ventilation (hoods) properly to minimize the generation of dust when working with beryllium-containing alloys;
  • Use HEPA vacuums to clean equipment and the floor around the work area;
  • Monitor employee exposures to airborne beryllium dust, using personal sampling techniques on a regular basis, to ensure that beryllium exposures are below the OSHA PELs and are as low as feasible;
  • Limit the number of office staff who have access to areas where beryllium-containing alloys are being ground or polished;
  • To minimize skin contact and to reduce take-home exposures and beryllium contamination of non-work areas, ensure that protective clothing is worn in areas where dental prostheses containing beryllium alloy are being ground or polished;
  • Recent studies suggest that exposure to beryllium at levels below OSHA’s 2 mg/m3 PEL may have caused CBD in some individuals. Therefore, even in the dental office where exposures are likely to be considerably below the 2 mg/m3 limit, dentists should consider providing their beryllium-exposed staff with National Institute of Occupational Safety and Health (NIOSH)-approved air-purifying respirators equipped with 100-series filters (either N-, P-, or R-type as applicable) or, where appropriate, powered air-purifying respirators equipped with HEPA filters. Clinicians should also note that short-term exposures may exceed the 2 mg/m3 PEL.11
  • Use of a surgical type mask does not provide adequate respiratory protection because it does not seal the face or effectively filter out fine particles.

Dentists and their staffs may obtain additional information about beryllium-containing products directly from manufacturers or at the OSHA Website. This informational statement is advisory in nature and intended to assist dentists in providing a safe and healthful workplace.

References

1. Leinfelder K. An evaluation of casting alloys used for restorative procedures. JADA 1997;128:37-45.

2. Covington J et al. Beryllium localization in base metal dental casting alloys. J Biomed Mat Res 1985;19:747-750.

3. Perez A. Given the recent controversy concerning beryllium, what should be our concern or not be our concern as dental lab managers. J Dent Tech 2000;17(5):28-29.

4. Haberman A et al. Contact dermatitis from beryllium in dental alloys. Contact Dermatitis 1993;28(3):157-62.

5. Vilaplana J et al. Occupational and non-occupational allergic contact dermatitis from beryllium. Contact Dermatitis 1992;26(5):195-8.

6. Kuschner M. The carcinogenicity of beryllium. Environ Health Perspect 1981;40:101-5.

7. Fodor I. Histogenesis of beryllium-induced bone tumors. Acta Morphol Acad Hung 1997;25(2-3):99-105.

8. Moffa, J. P. and Jenkins, W. A. Status report on base-metal crown and bridge alloys. JADA 1974; 89: 652-55

9. Balkissoon, R. C. and Newman, L. S. Beryllium Copper Alloy (2%) causes chronic beryllium disease. J. Occup Environ Med 1999; 41: 304-8.

10. Martyny J. W. Hoover, M. D. Mroz, M. M. Ellis, K. Maier, L. A. Sheff, K. L. Newman, L. S. Aerosols generated during beryllium machining. J. Occup. Environ. Med. 2000; 42: 8-18.

11. Wambach P.F. and Tuggle R.M. Development of an eight-hour occupational exposure limit for beryllium. Appl. Occup. Environ Hyg. 2000, 15. 581-87.

12. Occupational Safety and Health Administration. OSHA Hazard Information Bulletin: Preventing Adverse Health Effects from Exposure to Beryllium on the Job. September 1999.