Xylene—A potential danger to the maxillofacial prosthodontist

Xylene—A potential danger to the maxillofacial prosthodontist

Xylene - A prosthodontist Andrew Miami H. Glassman, ntial danger to the maxiftl D.D.S.* Veterans Administration Medical Center, Miami, Fla. A ...

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Xylene - A prosthodontist Andrew Miami

H. Glassman,

ntial danger to the maxiftl D.D.S.*

Veterans Administration

Medical

Center, Miami,

Fla.

A

cceptable techniques for color and surface characterization of silicone facial prostheses utilizing xylene as a painting medium solvent were introduced by many prosthodontists at the beginning of the 197Os.‘-’ With minor modifications, the method described by Bartlett et al.’ has been used selectively and continuously for the past 10 years at many institutions. Clinical and didactic methodology for this and other techniques was included in the curriculum for the training of maxillofacial prosthodontists at various universities and hospitals. However, many training centers that included a biomaterials course inadvertently deleted or placed little emphasis on the clinical toxicologic effects of some of the materials uniquely used in the fabrication of facial prostheses. The omission minimized the clinician’s awareness of the necessary safety standards that should be observed when working with these materials. This article is directed to clinicians and technical assistants who use xylene as a solvent thinner in the external coloring technique for the fabrication of silicone facial prostheses. The toxicologic effects of xylene will be discussed, and a protective system that would meet acceptable safety standards is recommended. It must be emphasized that xylene’s toxicity and mutagenicity poses a valid and potential danger to the clinician and his assistants. Other materials unique to the practice of maxillofacial prosthetics should also be subjected to careful scrutiny.

PHYSICAL

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CHEMICAL

PROPERTIES

Xylene (also known as xylol or dimethylbenzene), GJUCH 3>2, exists in three isomeric forms, orthodimethylbenzene, metadimethylbenzene, and paradimethylbenzene. Commercially available xylene is a mixture of all three isomers but may also contain ethylbenzene, toluene, trimethylbenzene, phenol, thiophene, pyridine, and nonaromatic hydrocarbons. Thus, *Director.

THE

Maxillofacial

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use of xylene is accompanied by exposure to other equally hazardous substances. XyIene is a clear, colorless, aromatic hydrocarbon of characteristic odor, that is miscible with diethyl ether, acetone, ethanol, and chloroform. In the early nineteenth century, xylene was initially obtained from coal tar naphtha, which in turn was a by-product of coal-gas manufacturing. Currently it is obtained by refining, extracting, and fractionally distilling petroleum.

ROUTE OF ENTRY Xylene exhibits a relatively low vapor pressure compared to other aromatic hydrocarbons. The primary route of absorption is by vapor inhalation through the lungs. Secondary precutaneous absorption occurs to a lesser extent.* Due to xylene’s lipid solubility it may be transported in the blood on plasma lipoproteins and red cell membranes. Additionally, xylene will tend to accumulate in the tissues of the body in proportion to the specific tissue’s fat content. Metabolic end products are excreted as water soluble conjugates with glycine and glucuronic acid. The unchanged hydrocarbons are exhaled through the lungs at a rate determined by their vapor pressure.9-”

SYMPTOMATOLOGY

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TOXICOLOGY

The present federal standards for occupational exposure to xylene is 100 parts per million parts of air by volume (approximately 434 mg per cubic meter of air) determined as a time-weighted average over an 8-hour period. l2 When daily inhalation ratios exceed these standards, a series of acute and subsequent chronic responses will result in a characteristic range of biologic reactions. Initial symptoms include headaches, dizziness, malaise, anorexia, fatigue, nausea, vertigo, ataxia, substernal pain, tinnitus, and eye irritation. Mucous membranes of the respiratory tract are also subjected to irritation and concomitant inflammatory reactions.13,I4 Additional long-term exposure to xylene will produce alarming and possibly irreversible patho-

571

GLASSMAN

Fig. 1. Fume hood superstructure combined on an unobstructed laboratory table.

Fig. 2. Patient-to-clinician operating distances and their spatial relationship other is a primary concern.

logic effects. Hepatocellular injury can occur, ranging in severity from mild fatty infiltration to severe liver necrosis. Diffuse nephritis has been documented, in addition to tissue damage to the myocardium, gastrointestinal tract, neurologic and hemopoietic systems. The latter include leukopenia, relative lymphocytosis, and aplastic anemia.15-” AIR QUALITY

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PROTECTIVE

SYSTEMS

Safety standard tests for aromatic hydrocarbons were conducted using MSA detector tubes No. 93074 572

to each

(Mine Safety Appliances, Pittsburgh, Pa.) in those operatories and studios in which facial prostheses were fabricated that utilized xylene as a silicone solvent and painting medium. The concentration at nose level for the clinician in a typical operating posture was in excess of 200 ppm, based on a lo-minute exposure time.l’ Since federal safety standards for occupational exposure to xylene were exceeded, corrective measures were undertaken at this institution. Laboratory fume hoods and fume-removal systems were carefully scrutinized to permit technical proceNOVEMBER

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Fig. 3. Operating techniques are performed with maximum protection.

Fig. 4. Initial processing space.

dures to be comfortably performed and to conform to federal safety standards (Fig. 1). Patient-to-clinician operating distances and their spatial relationship to each other were primary concerns (Figs. 2 and 3). The selection of a functional fume hood required evaluation of several factors: the types of materials to be utilized, the frequency of usage, the type and size of the operatory into which the unit will be placed, and the nature of the work to be performed. A laboratory fume removal system consists of three components: the fume hood, the duct system, and the blower. A class B fume hood with a 100 feet per minute average face velocity (speed of air moving into the fume hood THE

JOURNAL

OF PROSTHETIC

DENTISTRY

entrance) was determined to meet the basic minimum safety standards for the control of vapors that are generated from hazardous materials which may be used by the maxillofacial prosthodontist. Heat or moisture would also be effectively eliminated by the class B fume hood. The blower capacity was selected by calculating the diameter and length of the duct that already existed at the hospital. The exhaust volumes in cubic feet per minute needed to adjust the relative ratio of air to aromatic hydrocarbons was determined to meet the desired federal safety standards. The final selection for the maxillofacial prosthetic 573

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operatories was a fume hood superstructure (Labconco 96 fume hood model No. 22551, Kansas City, MO.) combined on an unobstructed laboratory table. Appropriately selected fume hoods were installed in the laboratory where initial processing procedures were performed (Fig. 4). Proper environmental lighting in a designated operating field requiring precise color coordination may require additional modifications of the safety system.

5. 6. 7. 8.

9. 10.

SUMMARY Basic health standards must be observed in the fabrication of facial prostheses. The hazards associated with the use of xylene must be recognized, and corrective measures should be extended for all potentially dangerous biochemical procedures and products that are uniquely used by the maxillofacial prosthodontist.

11. 12. 13. 14. 15.

REFERENCES Bartlett, S. O., Pineda, L., and Moore, D. J.: Surface characterization of silicone rubber prosthesis. J PR~.STHET D~~~25:69, 1971. Kanter, J. C.: The use of RTV silicones in maxillofacial prosthetics. J PROSTHET DENT 24646, 1970. Roberts, A. C.: Silicones for facial prosthesis. Dent Practit 21~276, 1971. Chalian, V. A., Drane, J. B., and Standish, M. S.: Maxillofacial Prosthetics. Baltimore, 1971, The William and Wilkins co.

Extra text pages added

16. 17.

Ouellette, J. E.: Spray coloring of elastomer maxillofacial prosthesis. J PROSTHET DENT 22:271, 1969. Roberts, A. C.: Facial Prosthesis. London, 1971, Henry Kimpton Publisher. Bulbulian, A. H.: Facial Prosthesis. Springfield, Ill., 1973, Charles C Thomas Publisher. Gerarde, H. W.: Toxicology and Biochemistry of Aromatic Hydrocarbons. Elsevier Monograph. Amsterdam, 1960, Elsevier/N. Holland Biomedical Press. Williams, R. F.: Detoxification Mechanism. London, 1959, Chapman and Hall. Latham, S.: Metabolism of industrial solvents. I: The biotransformation of benzene and benzene substitutes. Occup Health Rev 21:24, 1970. De Bruin, A.: Biochemical toxicology of environmental agents. Amsterdam, 1976, Elsevier/N. Holland Biomedical Press. (29 CFR 1910.93) Federal Register, vol. 39, June 27, 1974. Bush, C. L.: Xylene-Dangers of its use in the histology and cytology laboratory. Lab Clin Med 8~16, 1977. Gleason, M. N.: Clinical Toxicology of Commercial Products. Baltimore, 1969, The Williams and Wilkins Co. Jackson, P. P.: Occupational liver disease. Practitioner 223~67, 1979. Sax, N. I.: Dangerous Properties of Industrial Chemicals, ed 2. New York, 1963, Reinhold. Dean, B. J.: Genetic toxicology of benzene, toluene, xylenes and phenols. Mutat Res 47~76, 1978.

Reprint requests to: DR. ANDREW H. GLASSMAN 1621 N.W. 114th AVE. PEMBROKE PINES, FL 33026

to the

JOURNAL

In recent months the backlog of articles awaiting publication in the JOURNAL OF PROSTHETIC DENTISTRY has steadily increased.To reduce the publication delay for authors and to provide more scientificand practical information for our readers, the JOURNAL will publish 16 additional text pages in each issue beginning in September. In January 1983, another 16 text pageswill be added for a total increaseof 32 pagesper issue.This will allow an additional six articles to be published each month. To underwrite these 384 pages (approximately 72 more articles), the subscription rate for individual subscriberswill be increased $3.00 effective January 1, 1983.

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