Dental Amalgam Lecture 1 PDF

DS1102 Week 6 Introduction to Dental Materials: Amalgam Lecture 1 Dr. Alex Dancyger – B.Sc – Honours, M.Sc – Fellow, B.Ed. BDS Learning Objectives • Describe the the function of the major elements of dental amalgams • Be able to differentiate between low-copper and highcopper amalgams • Be familia...

DS1102 Week 6 Introduction to Dental Materials: Amalgam Lecture 1 Dr. Alex Dancyger – B.Sc – Honours, M.Sc – Fellow, B.Ed. BDS Learning Objectives • Describe the the function of the major elements of dental amalgams • Be able to differentiate between low-copper and highcopper amalgams • Be familiar with the handling of lathe-cut, spherical and admixed amalgam • Understand the setting reaction of various types of dental amalgams and modifiable factors https://splan.in/1-identifying-and-assessing-the-idea/ Content • Advantages and Disadvantages • Indications and Contraindications • History • Composition • Low-Copper Amalgams • High-Copper Amalgams • Amalgamation Reactions • Low-Copper Amalgams • High-Copper Amalgams https://creativemarket.com/introwiz1/4545293-Restorative-Dentistry-Icons Introduction • Alloy: a material with metallic properties, combination of 2+ elements • Amalgam: alloy of Hg with 1+ other metals • Dental Amalgam: mix of liquid Hg with solid alloy particles • Contains mainly Ag, Sn and Cu but also Zn and Pd • Amalgam Alloy: solid metal mix • Condensed into cavity and carved • Uses • Class I, II, V • Filling buccal pits • Core for teeth prepared for crown and bridge • Filling of root apices after apicoectomies http://blog.optident.co.uk/3-steps-restorative-case-lithium-disilicate-crown https://jada.ada.org/article/S0002-8177(16)30754-1/pdf https://pocketdentistry.com/14-class-i-ii-and-vi-amalgam-restorations/ Advantages and Disadvantages Advantages • Good toughness and wear resistance • Good compressive strength • Can be used in stress-bearing areas • Good longevity • Prevents marginal leakage • Ease of Use • Easy to manipulate and insert • Economical Disadvantages • Not aesthetically pleasing • Brittle • Loss of sound tooth structure • Discoloration of tooth structure • Metallic taste • Corrosion and galvanism • Limited support for weakened tooth structure • Concerns about waste disposal and Hg toxicity Indications and Contraindications Indications Contraindications • Class I, II, III, V in unaesthetic areas • Anterior teeth or anywhere aesthetics are of concern • Moderate –large restorations • Small-moderate class I, II and VI • As a core build up – for crown/bridge restorations that can be well isolated • Restorations covering cusps – using pins • Restorations with a heavy occlusal contact • Restorations that cannot be isolated easily • In teeth acting as abutments for removal appliances History • 659 AD • 1800s • 1895 • 1946 • 1962 • 1970s • 1990s Chinese medicine mentions Hg paste Developed in France, bismuth, Pb, Sn and Hg plasticized at 100oC and poured into a cavity GV Black developed a standardized formula – 67% Ag, 27% Sn, 5% Cu, 1% Zn Skinner added a small amount Cu to the amalgam alloy which increased strength and decreased flow Introduction of a spherical lathe cut alloy Introduction of a high Cu alloy which improved clinical performance Non-Hg amalgam-like alternative Classifications • By # of allow metals • Binary alloys (Silver –Tin) • Ternary alloys (Silver-Tin-Copper) • Quaternary alloys (Silver-Tin-CopperIndium) • By unmixed or admixed alloys • 1 alloy • 1+ alloys or metals blended • By particle shape • Spherical • Lathe cut • Admixed (spherical + lathe cut) • By the amount of Zn • Containing Zn (>0.01%) • Non-containing Zn (0.01%) • By Particle size • Micro cut • Fine cut • Coarse cut • By Copper Content • Low copper content <5% • High copper content >13% • By Noble Metal • Platinum • Gold • Palladium • By Generation of Development • 1-6 Dental Amalgam Alloy Components • Main components • • • • Mercury (Hg) Silver (Ag) Tin (Sn) Copper (Cu) 45-53%, above 55% causes a decrease in strength 9-30% high Cu alloy, less than 4-6% low Cu alloy • Lesser amounts • • • • Indium (In) Palladium (Pd) Platinum (Pt) Zinc (Zn) +0.01% Zn containing alloy, less than 0.01% non-Zn alloy Dental Amalgam Alloy Components Powers JM, Ferracane J, Sakaguchi RL. Craig’s Restorative Dental Materials. Mosby; 2018. Dental Amalgam Components https://www.marioninstitute.org/dental-amalgams-and-their-contribution-to-chronic-disease/ Lathe-cut Dental Amalgam Spherical Alloy Components Admix • Low Cu Alloys • Lathe-cut or spherical particles • High Cu Alloys • Unicompositional and Spherical • Admixed • Different allow shapes lead to differences in handling characteristics • Lathe-cut and admix resist condensation better than spherical powders • Titurated spherical powder amalgams are very plastic • Spherical alloys need less mercury than lathe-cut alloys because a smaller SA https://www.jaypeedigital.com/book/9788184487916/chapter/ch7 Dental Amalgam Alloy Components • Binds to alloy particles • Liquid at room temperature • Mercury content between 45-53% • Above 55% will cause a decrease in strength https://www.vectorstock.com/royalty-free-vector/periodic-table-element-silver-icon-vector-10965735 Dental Amalgam Alloy Components • Silver (Ag) • Tin (Sn) • Increases strength • Readily combines with Hg to form 𝛄2 – weakest phase • Causes setting expansion • Contributes of failure • Increases resistance to corrosion • Causes setting contraction • Decreases strength • Decreases resistance to corrosion https://www.vectorstock.com/royalty-free-vector/periodic-table-element-silver-icon-vector-10965735 Dental Amalgam Alloy Components • Copper (Cu) • Increases hardness and strength • Decreases tarnish and corrosion • Decreases creep • Zinc (Zn) • During manufacturing reduced oxidation of other alloy metals • Decreases marginal failure • Causes delay in setting expansion • Indium (In) /Palladium (Pd) • Increases plasticity • Increases resistance to deformation https://www.vectorstock.com/royalty-free-vector/periodic-table-element-silver-icon-vector-10965735 Low Cu Lathe Cut Alloy High Cu Admix Alloy Powers JM, Ferracane J, Sakaguchi RL. Craig’s Restorative Dental Materials. Mosby; 2018. Amalgamation Reaction • Alloy dissolves into the mercury • Immediately, new solid products crystallize • Crystallization continues until all the liquid mercury is consumes • Amalgam becomes stiffer, eventually hardens completely • Once complete, little to no mercury remains unreacted Amalgamation Reaction – Low-Copper Amalgam • Trituration mixes Ag3Sn with Hg to wet particles • Removes surface oxides that could have formed on alloy particles • 1:1 ratio, insufficient amount of Hg • Steps A. Ag and Sn dissolve in Hg B. Ppt 𝛄1 in Hg C. Consumption of remaining Hg, 𝛄1 and 𝛄2 grains grow • Early in working time - few 𝛄1 and 𝛄2 crystals • soft, condensable, carvable • Late in working time - more 𝛄1 and 𝛄2 – • harder and stronger D. Set amalgam Amalgamation Reaction – Low-Copper Amalgam 30% 60% 10% • 𝛄 Phase (Ag3Sn) (30%) • Strongest • Most corrosion resistant • 𝛄1 Phase (Ag2Hg3) (50%) • Second strongest • Somewhat corrosion resistant • Brittle • Holds multiphase material together • 𝛄2 Phase (Sn8Hg) (10%) • Weakest, softest phase • Most corrosion prone • Decreases with time due to corrosion • Cu3Sn (ε) + Sn8Hg (𝛄2) → Cu6Sn5(η) + Sn8Hg (𝛄2) Amalgamation Reaction – High-Copper Amalgam (Admix Alloy) Steps 1. Hg react with Ag-Cu and AgSn 𝛄1 and 𝛄2 formed, unreacted Ag3Sn remains (𝛄) 2. 𝛄2 reacts with Ag-Cu to form Cu6Sn5 (η) Step 1 Step 2 η Amalgamation Reaction – High-Copper Amalgam Increased % of Cu No 𝛄2 phase Trituration mixes Ag3Sn with Hg to wet particles Removes surface oxides that could have formed on alloy particles Sn + Cu forms Cu6Sn5 (η) Increased strength Decreased corrosion resistant Decreased marginal breakdown Step 1 Step 2 η References • Powers JM, Ferracane J, Sakaguchi RL. Craig’s Restorative Dental Materials. Mosby; 2018. • McCabe JF, Walls A. Applied Dental Materials. 9th ed. / John F. McCabe, Angus W.G. Walls. Blackwell Pub.; 2008. • Darvell BW. Materials Science for Dentistry . 8th ed. B.W. Darvell; 2006. • Gladwin M, Bagby M. Clinical Aspects of Dental Materials : Theory, Practice, and Cases. 3rd ed. Wolters Kluwer Health/Lippincott Williams & Wilkins; 2009.