394130
| Pregunta | Respuesta |
| AMALGAM:an alloy with mercury and another metal | HISTORY 1833: Crawcour brothers introduced it in US - powdered silver coins with mercury - expanded on setting |
| 1895 GV BLACK: develops new formula of modern amalgam - 67% silver, 27%tin, 5% copper, 1%zinc | Overcame expansion problems! |
| 1960's - conventional low copper lathe cut alloys - smaller particles. | 1960's - 1st generation high copper alloys - admixture of spherical cut Ag-Cu particles with conventional lathe cut - This cut out gamma 2 phase |
| 1970’s first single composition spherical ternary system (silver/tin/copper) 1980’s alloys similar to those in 70’s 1990’s mercury-free alloys (gallium) Increased corrosion & excessive post setting expansion | AMALGAM TODAY: low copper alloys, admixed high copper alloys, single composition high copper alloys. TODAY:copper enriched used - encapsulated to reduce risk of mercury contamination |
| WHY AMALGAM: inexpensive, easy to use, durable (can last for 10yrs +), familiarity with material, less likely to have hypersensitivity than with comp | OUTLINE FORM: gain access to caries, leaving sliver of enamel approximally. Remove with ging marginal trimmer or excavator. Access is gained to caries |
| REMOVE CARIES: from EDJ first then base of cavity. Ensure any unsupported enamel is removed, ensure resistance/and retention features are in place | RESTORE: place lining if necessary, matrix band and pack amalgam. Trim and carve removing surface mercury layer |
| THERAPIST CONTROLLED VARIABLES: Trituration(mixing time) refer to manufacturer. Overtrituration-hot sticky mix, sets fast. Undertrituartion- grainy mix, longer to set | CONDENSATION: Force used to pack and place amalgam. LATHE CUT- small condenser with high force. SPHERICAL ALLOY-large condensor, less sens to force, vibration motion. ADMIXTURE - mix of both above |
| CONDENSATION RULES! condenser must fit.. check before mixing! Place amalgam in small increments and pack Overpack and remove mercury rich layer | CARVING RULES! carve back to cavity outline Remove mercury layer check occlusion, aim for smooth enamel margin junctions |
| BURNISHING: PRE CARVE - removes mercury and improves margins POST CARVE - improves smoothness COMBINED - less leakage | POLISHING AMALGAM: 24 hrs after setting - increases smoothness, lees corrosion and less plaque retentive Clinically effective? 'Collins and Djent' no improvement of margin integrity |
| BONDED AMALGAM RESTORATION used when there is not enough tooth substance ie missing cusp and for complete marginal seal to prevent ingress of bacteria and protects pulp | ADVANTAGES: No need to use dentine pins no retentive/resistance features required reduced marginal leakage |
| DISADVANTAGE: Time consuming costly Lack of evidence on long term prognosis | TECHNIQUE: Vitrebond liner placed Acid etch, prime and bond Rely X ARC material placed (DO NOT LIGHT CURE) amalgam packed on top |
| AMALGAM TOXICITY: Toxicity - mercury poisoning Allergy - to amalgam may cause contact dermatitis or Lichen Planus PREGNANT PT'S - theoretical rick to foetus as mercury can pass through placenta | MERCURY POISONING SYMPTOMS: headache, salivation or xerostomia, GI upset, Dyspepsia, severe gingivitis, tremors, fatigue, odema of face and neck, character changes |
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