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FILE NAME Dental Asbestos DEN DATE 1980 DOC DEN104 DOCUMENT DESCRIPTION Journal Article General Dentistry - Asbestos A Subtle Carcinogen in the Dental Lab Asbestos a subtle carcinogen in the dental laboratory Duane E. Cutright DDS PhD Eugene F. Huget DDS MS John M. Brady DDS MS PLAINTIFF'S EXHIBIT 5400 Risks encountered in dental practice have become the foci for a number of studies Dangers associated with the inhalation of particulate matter bac- teria viruses enamel dentin calculus and amalgam from microbial aerosols produced during the use of speed rotary instruments have been addressed Investigations also have been conducted to establish and to define acceptable limits for levels of mercury vaporand nitrous oxide" in the operating room Recently there has been concern about asbestos fibers that emanate from the powder component of some periodontal dressings as well as from liners for casting rings and crucibles This study was conducted to sample and to characterize particulate debris encountered in the use of asbes- tos in the dental laboratory Material and methods A 3 segment of " wide ring liner was torn a from roll of asbestos by each of two laboratory workers Particulate matter remaining on the thumbs and index fingers of the test subjects was removed with the use of acetate tape Additionally the sites from which debris had been removed were resampled after the laboratory workers washed and dried their hands Two 3 strips of the asbestos were heated in a burnout furnace at 1,300 for 45 minutes The strips were cooled to room temperature in open air and torn by two volunteers Sampling of particulate matter from the thumbs and index fingers of these individuals was accomplished as previously described In second approach samples of debris were collected on acetate tape from a bench top on which 20 phosphate- bound investment molds had been broken from asbestos metal cast- ing rings Additional particles were removed from a wall against which the bench was located from the muffle of a furnace from a casting machine and from a drawer in a which liner had been stored roll of ring- The sampling tapes were sealed to aluminum stubs The debris taining side of each tape was coated with gold and palladium or carbon and examined with the use of a scanning electron microscope Photomicrographs of the collected matter were analyzed for determination of shape size and distribution of particulate components Elemental constituents of selected carbon particles were determined by dispersive ray microanalysis Results Scanning electron microscopic examination of the material collected from thumbs and index fingers showed aggregates of relatively straight parallel fibers and single randomly dispersed fibers Fig ) The fibers though fragmented did not have axial cleavage Diameters of the linear particles ranged from 0.10 to 1.0...mGenerally fiber length exceeded 200...m Morphologic differences between the particles that were broken from unheated and heated strips of the test ma- terial were not detected Dispersive ray analysis of selected particles showed that magnesium and silicon were the predominant con- stituents of the test material However small amounts of iron were also detected as well as sulfur and calcium Fig 2 The approximate elemental composition of the fiber was as follows magnesium 45 silicon 40 sulfur % calcium % and iron % Heat- Fig 1. Photo initial magnifica 5,000 D. Pa ing at a con temperature | composition Fibers wer ticulate matte of washed h spheroidal found in one range of e titanium sili calcium and Samples of laboratory be fragmented s Particles of si recovered fro and from the Results of an filamentous magnesium magnesium 46 GENERAL DENTISTRY 1980 stituents of cicles were lispersive croscopic collected showed ght paralomly dis- ne fibers have axial near parti- m Gener- 1 200...m tween the from unne test ma- Of selected esium and hant conHowever e also ded calcium elemental as follows % sulfur % Heat- Fig 1. Photomicrographs of particulate matter removed from thumbs and index fingers of laboratory workers A. Aggregates from dry unheated ring liner initial magnification 50 B. Aggregates from heated ring liner initial magnification 50 C. Particles of dry unheated ring liner initial magnification 5,000 D. Particles of heated ring liner initial magnification 5,000 ing at a conventional mold burnout temperature did not alter the elemental composition of the woven fibers Fibers were not detected in the par- ticulate matter removed from the digits of washed hands Occasional small spheroidal and plate particles found in one sample exhibited a broad range of elemental constituents titanium silicon chlorine potassium calcium and iron Samples of debris removed from the laboratory bench and wall contained fragmented slender particles Fig 3 Particles of similar configuration were recovered from the casting machine and from the storage drawer Fig 4 Results of analysis showed that these filamentous particles were composed of magnesium silicon sulfur calcium and iron in the same relative concentra- tion as found on the fingertips Parti- cles that were detected within the muffle of the furnace were not fibrous the ratio of length to diameter was less than 3 to 1. Constituents of these particles included silicon phosphorous cal- cium and sulfur Discussion Asbestos is a term used to identify any one of several minerals that can be crushed into fibers However a par- ticular mineral substance chrysolite is the principle source of commercial asbestos Chrysolite is a hydrated silicate of magnesium its approximate composition is 37 to 44 silicon dioxide 39 to 44 magnesium oxide 12 to 15 water and % to % iron oxide Analytical data indi- cated that the fibrous material examined in this study was chrysolite The compositional features of the nonfibrous particles removed from the fingers of washed hands and from the furnace muffle inferred the presence of debris from refractory investment materials The occupational risk associated with asbestos exposure has been well documented in several studies In man exposure to asbestos dust is associated with an increased incidence of tumors of the lung,,7 and with pleural and peritoneal mesothelioma.,,A"sbestos fibers are subtle carcinogens that do not produce an obvious exposure- _ ae GENERAL DENTISTRY 1980 47 Fig 2. Dispersive ray analysis of single fiber component arrow of asbestos casting ring liner response relationship Usually a long latency precedes the onset of fibrogenic or carcinogenic activity and the effects of repeated exposures over long periods are cumulative.19 The threshold limit value TLV below which asbestos would not ad- versely affect the health of man is not known The current eight timeweighted TLV for asbestos is two fibers per cubic centimeter of air20 however this limit has not been evaluated with regard to its effectiveness in the pre- vention of asbestos disease Additionally the mechanisms by which fibrous materials produce malignant disease are uncertain It has been shown however that the degree of carcinogenicity is related to fiber size rather than to composition.21 Data from animal experiments indicate that durable fibers less than 3...min diame- ter and more than 20...min length present the greatest hazard and the fibers described in this report fall within this range of size The actual risk incurred in the use of producing asbestos in dental lab- oratories is unknown However the potential for inhalation or ingestion of asbestos particles by dental laboratory workers appears to be greater than that for members of the general population The need for rigorous standards of personal and laboratory hygiene in the handling of asbestos is obvious For example if hands are washed as shown in this study the material is effectively removed from the fingertips Since it has been shown that cigarette smoking increases the risk of lung cancer in asbestos workers smoking should be discouraged especial within the working area. In view of the results reported her and in conformity with correct occupt tional health practices the following protective measures are suggested b dental clinics 1. All office and laboratory per sonnel should be informed of the potential danger of asbestos 2. The storage and use of asbes tos should be confined to a small area of the laboratory or to a small isolated working chamber 3. Operatories and other offices should be isolated from the dental laboratory 4. Face masks and surgical gloves should be worn when asbestos of containing debris is har dled 5. Cutting instead of tearing as bestos should be encouraged be 6. Smoking or eating should be prevented in the dental laboratory 7. Transmission of asbesto waste by sewage lines and all exhaust systems should be pre with vented to preclude discharge the community environment Summary Particles of debris emanating from containing dental laborato material were studied with the swall ning electron microscope and X debris FigFig 3. swall Photomicrog swal debris initial ma debrisdebris initial magnifica 48 CUTRIGHT CARCINOGEN Le risk of lung rkers smoking ed especially a.22 s reported here correct occupa- the following e suggested in boratory per- ormed of the bestos use of asbesed to a small or to a small ber other offices m the dental argical gloves asbestos or bris is han- f tearing asraged g should be | laboratory f asbestos es and air ld be premarge within ment ating from al laboratory th the scanand ray Fig 3. Photomicrographs of debris from laboratory bench top and laboratory wall A. field of bench top debris initial magnification 50 B. field of wall debris initial magnification 50 C. Linear component of bench top debris initial magnification 5,000 D. Bundle of linear components of wall debris initial magnification 5,000 GENERAL DENTISTRY 1980 49 microprobe The dimensions and composition of these particles suggest their potential as subtle carcinogens With almost daily use of producing asbestos in the dental laboratory the improper handling of this substance could be hazardous to the health of dental personnel It is recommended that high standards of personal and laboratory hygiene be used in the handling of asbestos Dr. Cutright is a commander with the U.S. Army Institute of Dental Research Dr. Huget is chief of the Division of Dental Materials and Dr. Brady is chief of the Department of Biophysics at the U.S. Army Institute of Dental Research Walter Reed Medical Center Washington DC Acknowledgement The views expressed herein are those of the authors and do not necessarily reflect the views of the United States Army or the Department of Defense Ceramigold Investment Whip Corp. Louisville Ken- tucky Scamming Electron Microscope model 1000 Advanced Metais Research Corp. Burlington Massachusetts II #Energy #Energy Dispersive RijAnalyzer model 707A with EDIT Software EDAX International Prairie View Illinois References 1. Travaglini E.A. Larato D.C. and Martin A. Dissemination of organism droplets by speed dental drills ~fiPros- thet Dent 132 1966 2. Micik R.E. Miller R.L. Mazzarella M.A. and Ryge G. Studies on dental pro- Fig 4. Fragmented debris from laboratory asbestos in storage drawer cedures J Dent Res 48:49 1969 3. Battistone G.C. Hefferren J.J. Miller R.A. and Cutright D.E. Mercury its rela- tion to the dentist's health and dental practice characteristics JADA 1182 1976 4. Mantyla D.G. and Wright O.D. Mercury toxicity in the dental office a neglected problem JADA 1189 1976 5. Eames W.B. Gaspar J.D. and Mohler H.C. The mercury enigma in dentistry JADA 1199 1976 6. Linde H.W. and Bruce D.L. Occupational exposure of anesthetists to halothane nitrous oxide and radiation Anesthesiology 363 1969 7. Johnson E.G. Harmful pollution by anesthetic gases Lancet 824 1972 8. Nikki P. Are anesthetic gases harmful to operating room staff Ann Clin Res 247 1972 9. 9. Burnett G. Substitute for asbestos in casting rings Brit Dent ) 171 1976 10. Council on Dental Therapeutics and Council on Dental Materials and Devices Hazards of asbestos in dentistry JADA 777 1976 11. Berg D. Inorganic insulating materials in Standard Handbook for Electrical Engineers 10th ed New York McGraw Book Co. 1968 p 355 12. 12. Enterline P.E. Type of asbestos and respiratory cancer in the asbestos industry Arch Environ Health 312 1973 13. Selikoff I.J. and Nicholson W.J. Asbestos air pollution Arch Environ Health 25 1972 14. Weill H. et al Radiographic and physiologic patterns among workers engaged in manufacture of asbestos cement products ] Occupational Med 248 1973 15. Doll R. Mortality from lung cancer in asbestos workers Br J Industr Med 12:81 1955 16. Cordova J.F. Tesluk H. and Knudtson K.P. Asbestosis and carcinoma of the lung Cancer 1181 1962 17. Huper W.C. Occupational and nonoccupational exposure to asbestos Ann NY Acad 18. Stanton M.F. and Wrench C. Mechanisms of mesothelioma induction with asbestos and fibrous glass J Natl Cancer Inst 797 1972 19. Thomson J.C. Asbestos and the urban dwel- ler Ann NY Acad Sci 196 1965 20. Nicholson W.J. Asbestos TLV approach Ann NY Acad Sci 152 1976 21. Stanton M.F. Fiber carcinogenesis is asbestos the only hazard ] Natl Cancer Inst 633 1974 22. Berry G. Combined effect of asbestos expe sure and smoking on mortality from lung cancer in factory workers Lancet 476. 1972 Ellman Rectan A new inexpe for splinting n avulsed teeth in redure The N eliminates the v pins on paper consuming In roughening on artention Thes anques often kunsen break 11 Tack rigidity an Splint ma available The res sides of the ban fark preventing displacement also act as valvo pressure in the preparation Wi Splint and composite fillin low patiesnplti procedure Ell 12 present 1 in- of 3 different slightly bendal 10 teeth The cents per splin Ellman Dental A Major Adv of Calcium H This new imp syringe contain The easiestto CAL is Radi itle paste mi needle applica facilitates pinin thin film excellent for amounts of va ew q %?~ W bn bibi s 50 CUTRIGHT CARCINOGEN