OPRTVD2-MIDTERMs Amalgam PDF

MIDTERMS CONTRAINDICATIONS OF AMALGAM o Oral hygiene AMALGAM 1. Esthetics – due to metallic color o Type of alloy DEFINITION OF TERMS...

MIDTERMS CONTRAINDICATIONS OF AMALGAM o Oral hygiene AMALGAM 1. Esthetics – due to metallic color o Type of alloy DEFINITION OF TERMS 2. Small to moderate class I and class II; should be Tarnish – surface alteration or discoloration Alloy – solid mixture of two or more metals restored with composite rather than amalgam as Corrosion – total degradation of the restorative material Amalgam – an alloy of mercury and one or more other composite restoration results in more conservative 7. Tensile Strength metals tooth preparation - Force which resists deformation caused by a load Dental Amalgam – is a combination of mercury with a 3. Patients have a history of allergy to mercury or other which tends to stretch or elongate a body specially prepared silver Alloy amalgam components - Decreased tensile strength if mercury content is too HISTORY OF AMALGAM CLINICAL PROPERTIES OF AMALGAM high (>52%) 1826 – in Paris, Dr. Taveau introduced the first amalgam 1. Flow and Creep - To increase tensile strength: paste (Silver-Mercury paste) - Characteristics that deal with an amalgam o Preparation should have a butt joint (90 1833 – Crawcour Brothers (French dentists) introduced undergoing deformation when stressed degree) cavosurface margin; to avoid the first amalgam paste in the U.S. - The lower the creep value of an amalgam, the better fracture o Amalgam was first named as Royal the marginal integrity of the restoration o Use a fine cut alloy mineral succedaneum - Property that makes it easier to condense or pack 8. Thermal Conductivity o Amalgam war – started due to some the material into the cavity preparation - Ability of the material to conduct or transmit thermal opposing the use of amalgam 2. Dimensional Change changes o Chapin Harris – against the use of - Slight delayed expansion may contribute to retention - Amalgam has high thermal conductivity; thus the amalgam of the material need for placing thermal liners/barriers o Black and Foster Flagg – advocated the - Amalgam hardens at around 24 hrs; after 24 hrs, 3 BASIC TYPES OF AMALGAM ALLOY use of amalgam then finishing and polishing may be performed 1. Conventional Amalgam Alloy 1896 – Dr. G.V. Black published a basic formula for - Excessive expansion because of moisture is of great - Also known as “lathe-cut alloy” amalgam clinical significance; it may cause: - Has a rough surface finish 1919 – ADA made an intensive research program on o Post-operative pain - Requires more mercury to wet the alloy particles amalgam alloy o Cracked tooth - Has a higher compressive strength than spherical 1929 – ADA Specification #1 for amalgam was adopted o Extrusion of amalgam from cavity alloy INDICATIONS OF AMALGAM o Decreased strength - Contents: 1. Moderate to large class I preparation o Increased corrosion o Ag (Silver) – 65% 2. Class II preparation in which there is: 3. Strength o Sn (Tin) – 25-27% o Heavy occlusion - Because amalgam is developed or set slowly, o Cu (Copper) – 6% o Extension on the root surface strength is better relative to other materials o Zn (Zinc) – 2% o Problem of isolation - After 8 hrs = 80% strength 2. Spherical Alloy 3. Class V preparations in which: - After 24 hrs = final strength - Very fine compared to conventional alloys o Esthetics is not a problem - The amount of mercury in the matrix of the - Gives a very smooth surface finish of the restoration o Preparation is entirely on root surface completed restoration relates to the strength of the - Requires less mercury to wet the alloy particles o Isolation is difficult amalgam - Inferior compressive strength than conventional alloy 4. Class VI preparations o Less strength is the result if mercury 3. Dispersalloy 5. Class III preparations on distal surface of canine – content is more than 52% - New alloy system this was utilized before because the distal surface of 4. Setting Time - Mixture of bigger particle sizes and very fine particle canines were not considered as esthetic zones - Starts during trituration and progresses when sizes 6. Used as a foundation in cases of grossly decayed condensation and carving takes place - Contents: teeth while planning for cast restoration 5. Plasticity o Silver – 70% 7. Used as a post-endodontic restoration - Related to the technique employed to condense o Tin – 16% 8. Teeth having no definitive pulpal prognosis; used as amalgam o Copper – 13% a type of interim restoration before assessment of - Low plasticity requires greater condensing force for o Zinc -