Oral corrosion

Oral corrosion of metallic restorations does not, per se, generally result in serious damage to the structure. Corrosion can result, however, in various local and systemic effects, notably the hypersensitivity and allergic reactions reported by many workers. Galvanic cells created by mixed metal couples can delay fracture healing and induce oral lesions and cancer. 

Use Level 0.25-0.75 phr 0.5 phr (Internal release In polyester) Toxicology LD50 (oral) > 5500 mg/kg pract. nontoxic orally corrosive to skin and eyes TSCA listed Storage Store in cool, dry place in closed containers Zeocros B100 [INEOS Silicas Am.]... 

Oral Corrosion occurs on dental alloys exposed to saliva. 

The forms of corrosion encounter in diverse engineering structures have a common oxidation mechanism lepiesented by an anodic reaction, such as M — M+ + ze, eq. (1.1a). Thus, corrosion may be due to chemical or electrochemical reactions. One common corrosion process is the formation of ferric hydroxide, Fe OH)3, as indicated by the sequence of reactions given by eq. (1.7. Therefore, corrosion is classified as a localized or general oxidation process. It manifests its natural or forced behavior in various forms from atmospheric corrosion of steel stmctures to oral corrosion on dental alloys due to the effect of saliva and food. 

Toxicology Mod. toxic orally corrosive to skin and eyes 50% act. Environmental Biodeg. 

Sodium trichloroacetate [650-51-17, C2Cl202Na, is used as a herbicide for various grasses and cattails (2). The free acid has been used as an astringent, antiseptic, and polymerisation catalyst. The esters have antimicrobial activity. The oral toxicity of sodium trichloroacetate is quite low (LD q rats, 5.0 g/kg). Although very corrosive to skin, trichloroacetic acid does not have the skin absorption toxicity found with chloroacetic acid (28). 

Health and Safety Factors. MSA is a strong toxic acid and is corrosive to skin. The acute oral toxicity of the sodium salt in mice LD q is 6.2 g/kg. The 1976 edition of the NIOSH Registry of Toxic Effects of Chemical Substances Hsts certain reaction products of MSA as having suspected mutagenic, teratogenic, and carcinogenic activity (410). 

Contact or ingestion of cyanamide must be avoided, and precautions taken to prevent inhalation of dust or spray mist. In rat studies cyanamide-100 toxicity ranges from a single oral dose LD q of 280 mg/kg to a single dermal dose LD q of 590 (420—820) mg/kg. The compound is, therefore, considered to be moderately toxic both by ingestion in single doses and by single-skin appHcations. An aqueous paste of the product is corrosive to rabbit skin. Small quantities of the dry product produced severe irritation when introduced into the conjunctival sac of the rabbit eye. 

Solders. Modem dental solders are made from mostly corrosion-resistant, nontoxic metals. Minimal quantities of tin and other elements are often added, some of which could produce toxic effects in the unalloyed state. Each solder is used for specific appHcations (180—188) typical compositions and properties of solders used in dentistry are presented in Table 11. Most of the ingredients of solders are resistant to corrosion, and alloying them with other ingredients renders the alloy safe for use in appHances placed in the oral environment. Silver solders corrode, but are used only for temporary appHances. Available products do not contain cadmium, although cadmium was an ingredient of some silver solders up to ca 1980. 

The acute oral toxicity and the primary skin and acute eye irritative potentials of dimer acids, distilled dimer acids, trimer acids, and monomer acids have been evaluated based on the techniques specified ia the Code of Eederal Regulatioas (CER) (81). The results of this evaluatioa are showa ia Table 7. Based oa these results, monomer acids, distilled dimer acids, dimer acids, and trimer acids are classified as nontoxic by ingestion, are not primary skin irritants or corrosive materials, and are not eye irritants as these terms are defined ia the Eederal regulatioas. 

Various materials are used in dental prosthetic practice for the preparation of dental implants, crowns, and bridges. Some of these materials contain copper, which is added in order to improve mechanical or/and chemical properties, but some of them may contain the copper as an impurity. Considering the fact that dental implants remain in the oral cavity for a long time, and that they are exposed to the corrosive action of oral fluids and various kinds of food and beverages, it is necessary to check their possible harmful effects upon the human health. 

Palaghias, G. The Role of Phosphate and Carbonic Acid-bicarbonate Buffers in the Corrosion Processes of the Oral Cavity , Dental Materials, 1, 139-144 (1985)... 

Lundstrom, I. M. C. Allergy and Corrosion of Dental Materials in Patients with Oral Lichen Planus , International Journal of Oral Surgery, 12, 1-9 (1982)... 

Bergman, M., Bergman, B and Soremark, R. Tissue Accummulation of Nickel Released due to Electrochemical Corrosion of Non-precious Dental Casting Alloys , Journal of Oral Rehabilitation 7, 325-300 (1980)... 

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