Download Dental Amalgam - Operative Dentistry - Lecture Slides and more Slides Dental surgery in PDF only on Docsity! Dental Amalgam: Material Properties and its Use in Clinical Dentistry Docsity.com What is Amalgam? a·mal·gam: any alloy of mercury with another metal or other metals [silver amalgam is used as a dental filling]† †Source: Webster’s New World Dictionary of the American Language, Guralnik DB, Ed., New York: World Publishing Co., 1972. Docsity.com Amalgam Capsules • Contain (in separate compartments): – powdered amalgam alloy – liquid mercury • Some are manually activated, others self- activated • Pestle usually included Docsity.com Amalgamator (Triturator) • Speeds vary upward from 3000 rpm • Times vary from 5–20 seconds • Mix powder and liquid components to achieve a pliable mass • Reaction begins after components are mixed Docsity.com Reaction: Low-Copper Alloys Ag3Sn(γ) + Hg → Ag2Hg3(γ1) + Sn7-8Hg(γ2) + Ag3Sn(γ) Docsity.com Properties of Mercury • Only liquid metal at room temperature • Evaporation rate – Theoretical maximum is 57.9 µg·cm2·s–1 from pristine, oxide-free surface into a vacuum (= 57,900 ng·cm2·s–1) – Measured rate in vacuum is ~40 µg·cm2·s–1 (= ~40,000 ng·cm2·s–1) – Oxidation of Hg lowers rate by factor of 1000 Docsity.com Hg Evaporation from Amalgam • Baseline Hg vaporization rate (unstimulated) from amalgam in humans is 0.027 ng·cm2·s–1 • Average vaporization rate (over 24-h period) in humans is 0.048 ng·cm2·s–1 • The evaporation rate of Hg from amalgam is 800–1500 times lower than from oxidized mercury Docsity.com Mercury Dose from Amalgam • Person with average number of fillings (7) would absorb ~1.6 µg/day • Person with a moderately high number of fillings (13) would absorb ~3 µg/day • According to EPA, absorbed dose of mercury from food, water, and air is 5.7 µg/day Docsity.com