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Possible Hazardous Effects of Hydrofluoric Acid and Recommendations for Treatment Approach: a Review

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Possible Hazardous Effects of Hydrofluoric Acid and Recommendations for Treatment Approach: a Review View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by RERO DOC Digital Library Clin Oral Invest (2012) 16:15–23 DOI 10.1007/s00784-011-0636-6 REVIEW Possible hazardous effects of hydrofluoric acid and recommendations for treatment approach: a review Mutlu Özcan & Arezo Allahbeickaraghi & Mine Dündar Received: 2 September 2010 /Accepted: 26 October 2011 /Published online: 9 November 2011 # Springer-Verlag 2011 Abstract Hydrofluoric acid (HF) is commonly used for value, but on the toxicity of HF. Potential hazards of HF conditioning the glass ceramics either prior to cementation known from other applications than dentistry should be or for intraoral repair in prosthetic and restorative dentistry. considered also in dental applications. Especially the clini- The present study offers a review of chemical properties of HF cians, who often deal with adhesive cementation or repair of used, highlight the possible hazardous effects of this agent, glass ceramics, should take necessary precautions for possible and to recommend the treatment approach for potential risks. hazards of HF. Available published information documented in PubMed, Medline, and Picarta literature databases was reviewed. Keywords Dental ceramics . Dentistry. Hazardous Additional information was derived from scientific reports, compounds . Hydrofluoric acid medical and chemical textbooks, handbooks, product infor- mation, manufacturers’ instructions, Internet web sites of the HF manufacturers. No report was found on the incidence of Introduction the hazardous effects of HF in dentistry. Reports from other fields presented incidences of acute and chronic symptoms in Highly concentrated, pure aqueous solution of hydrofluoric exposure to HF. While acute symptoms include skin or nail acid (HF) was first prepared in 1809 and hydrogen fluoride was burns, chronic ones involve systemic toxicity, eye injuries, first obtained at the end of the eighteenth century [1, 2]. From inhalation and ingestion-related symptoms that can be even chemistry perspective, HF is the inorganic acid of elemental fatal. HF can be harmful and particularly aggressive to soft fluorine. Hydrogen fluoride is produced by the reaction of tissues, but symptoms may not be apparent immediately after calcium fluoride (CaF2) and sulfuric acid in a reaction furnace exposure. The hazardous effects are not based on the pH at 200°C, which is then cooled and stored as a colorless liquid [1, 2]. The main source of CaF2 to produce hydrogen fluoride M. Özcan (*) is the mineral fluorspar. The volatile HF is condensed and University of Zürich, Dental Materials Unit, purified by distillation [1, 2]. HF can be produced through Center for Dental and Oral Medicine, Clinic for Fixed processes such as aluminum melting, ceramic production, and and Removable Prosthodontics and Dental Materials Science, phosphate fertilizers. It may also occur as an impurity in Plattenstrasse 11, CH-8032 Zurich, Switzerland different chemicals or can be produced through the reaction of e-mail: [email protected] other chemicals [1]. It is the starting material for the production of most organic and inorganic chemicals contain- A. Allahbeickaraghi ing the fluorine atom. Fluorine gas is the most important Dental School, University of Groningen, Antonius Deusinglaan 1, fluorine compound for industrial use. 9713 AV Groningen, The Netherlands HF solutions can be formed when fluoride salts are acidified with acidic solutions. As it is a weak acid, M. Dündar hydrogen fluoride in water for instance, is not completely Department of Prosthodontics, School of Dentistry, − Ege University, ionized. Its conjugate base, the fluoride ion F , can re- 35100 Izmir, Turkey associate to form HF in solutions with low pH [3]. In strong 16 Clin Oral Invest (2012) 16:15–23 acidic solutions, the pH of the fluoride-containing mixture other fields as well as in restorative and prosthetic dentistry, to will be low and the free F− formed from the ionization of investigate the incidence of reports on hazardous effects of HF the fluoride salt in aqueous solution will exist as HF. in dentistry, to highlight the possible hazardous effects of this However, in acidic aqueous suspensions, solubility agent in general, and to recommend the treatment approach increases by the presence of the acid, and with this route for potential risks, based on the published information a significant quantity of HF can be produced [1]. available in the chemical and medical fields. Early versions of HF were aqueous solutions. Aqueous HF is commonly formulated for products with lower concentra- tion. The major use of aqueous HF for occupational purposes Materials and methods are etching and polishing glass and ceramics, removing sand from metal castings, and cleaning processes for floors and Original scientific papers listed in PubMed, Medline, walls [3]. Other important uses include fabric rust removal, Picarta up to the end of 2010 on HF were included in this etching silicon in semiconductors, cleaning stone and review using the following search terms: hydrofluoric acid, marble, and manufacturing inorganic fluoride compounds acid etching, surface conditioning, ceramics, fracture, [4, 5]. repair, hydrofluoric acid burns, hydrofluoric acid treatment, Since the introduction of glass-based ceramics and discov- hydrofluoric acid etching, workplace poisoning, poisoning, ery of the benefits of adhesive cementation in dentistry, HF fatalities, cementation, ceramics, intra-oral repair, fluorohy- started to be used to condition restorative and prosthetic dric acid, fluoric acid, and hydrogen fluoride solution. Only devices [6]. Strong bonds are formed between resin-based articles in English were selected. Additional information materials and dental ceramics that are etched with HF [7]. was derived from scientific reports, medical and chemical This is based on the affinity of fluoride to silicon that is textbooks, handbooks, product information, manufacturers’ higher than to oxygen: 4HF+SiO2→SiF4+2H2O. By the instructions, Internet web sites of the HF manufacturers. selective removal of the glassy matrix, principally micro- mechanical retention is achieved between the resin and the etched ceramic. The greatest advantage of the use of HF for Results ceramics is that its chair-side application is very simple, and for this reason, sophisticated conditioning or cleaning While no reports of incidence have been found on the methods may not be necessary [8]. hazardous effects due to exposure to HF in the dental In 1998, in fields other than dentistry, HF was literature, low incidence of reactions or even death presented acknowledged as a highly hazardous chemical due to its as case reports have been reported in the case of significant or toxicity, corrosiveness, and reactivity [1]. It can be used in long exposure to HF in other fields. Potential hazards in case the anhydrous (100%) form or in aqueous solutions where of significant exposure and the therapy approach to each of the the latter range in concentration from <1–70%. Severity and symptom could be summarized as follows. rapidity of onset of signs and symptoms depends on the concentration, duration of exposure, and penetration to the Acute hazardous effects exposed tissue [6]. When accidentally released, HF can diffuse as a dense vapor and aerosol. HF itself is not As with all inorganic acids, due to hydrogen ion degeneration flammable, explosive, or oxidizing, but it is a highly and corrosion, HF can burn the skin [11–13]. After penetrating reactive chemical. Hence, its storage conditions and into the skin, it moves quickly to the deeper tissue layers and handling must be taken into account when using this acid. releases the freely dissociable fluoride ion. Toxicity of this Also, contact with metals can lead to the formation of ion is based on its strong reactivity. The mechanism of HF hydrogen gas, which forms explosive mixtures in air at injury is thought to be binding of fluoride ions to tissue concentrations between 4% and 75% [1, 2]. The reaction calcium and magnesium cations to form insoluble salt. These occurs at concentrations of approximately less than 65% of interfere with cellular metabolism, inducing cellular death and aqueous HF but over time at higher concentrations of necrosis [4]. HF burns could be as a consequence of the anhydrous HF. In closed containers, hydrogen formation dehydrating effect of this agent and the low pH. Skin contact can cause dangerously high pressures [9, 10]. As the with HF, even dilute solutions (0.1%) can cause painful reaction of hydrogen fluoride or concentrated HF with second- and third-degree burns that heal very slowly [10]. water is exothermic, it may react violently on mixing. Burns have a rather characteristic appearance and present as Concentrated aqueous solutions can fume in the air, and severely reddened, swollen areas with blanched, whitish heat is produced upon reaction. regions that rapidly progress to blistering, and necrosis The objective of this review was to summarize the accompanied with pain [14]. Latent damages could also be chemical properties, applications of HF used in medical or observed since fluoride ion penetrates through all layers of Clin Oral Invest (2012) 16:15–23 17 the epidermis, dermis, and even the deeper subcutaneous Chronic hazardous effects tissues, causing severe destruction, necrosis, and injuries to the underlying bone due to decalcification [15]. The effect HF is not classified as a carcinogen agent since no data exists can continue
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