Dental amalagam

amalagam- material in dentistry; cavity preparation; trituration; procedure of application

1. Dental amalgam

2. What is dental amalgam?

3. composition Dental amalgam is produced by mixing liquid mercury with an alloy made of silver, tin, and copper solid particles. Small quantities of zinc, mercury and other metals may be present in some alloys. This combination of solid particles is known as amalgam alloy. The composition of the alloy particles are controlled by the ISO Standard for dental amalgam alloy in order to control properties of set amalgam such as corrosion and setting expansion. It is important to differentiate between dental amalgam and the amalgam alloy that is commercially produced and marketed as small filings, spheroid particles, or a combination of these, suitable for mixing with liquid mercury to produce the dental amalgam. Amalgam is used most commonly for direct, permanent, posterior restorations and for large foundation restorations, or cores, which are precursors to placing crowns. The reaction between mercury and alloy when mixed together is termed an amalgamation reaction. It will result in the formation of a silver-grey workable mass which can be condensed into cavities. After condensing, the dental amalgam is carved to generate the required anatomical features and then hardens with time. Conventional amalgam alloy commonly consists of silver (~65% ), tin (~29%), copper (~8%) and other trace metals ; current amalgam alloy consists of silver (40%), tin (32%), copper (30%) and other metals.

4. Why is mercury used in dental amalgam?

5. Properties of amalgam Plastic deformation (creep) Creep or plastic deformation happens when subjected to intra-oral stresses such as chewing or grinding. Creep causes the amalgam to flow and protrudes from the margin of the cavity forming unsupported edges. ‘Ditch’ is formed around the margins of the amalgam restoration after fracture due to amalgam creep at the occlusal margins. The γ2 phase of amalgam is primarily responsible for high values of creep.

6. Properties of amalgam Corrosion Corrosion occurs when an electrolytic cells of anode and cathode set up in the presence of electrolytes. The multiphase structure of dental amalgam can contribute as an anode or cathode with saliva as electrolytes. Corrosion may significantly affect the structure and mechanical properties of set dental amalgam. In conventional amalgam, γ2 phase is the most reactive and readily forms an anode. It will break down releasing corrosion products and mercury. Some of the mercury will combine rapidly with unreacted alloy and some will be ingested. The chances of ditching are further increased. Copper-enriched amalgams contain little or no γ2 phase. The copper–tin phase, which replaces γ2 in these materials, is still the most corrosion-prone phase in the amalgam. The corrosion however is still much lower than conventional amalgam. In spite of that, it is thought that corrosion actually offers a clinical advantage. The corrosion products will gather at the tooth-amalgam interface and fill the microgap (marginal gap) which helps to decrease microleakage . Even so, there are no reports of increased marginal leakage for the copper-enriched amalgams indicating that sufficient quantities of corrosion product are produced to seal the margins. Microleakage is the leakage of minute amounts of fluids, debris, and microorganisms through the microscopic space between a dental restoration and the adjacent surface of the cavity preparation. Microleakage can risk recurrent caries.

7. Properties of amalgam Strength An amalgam restoration develops its strength slowly and may take up to 24 hours or longer to reach a reasonably high value. At the time when the patient is dismissed from the surgery, typically some 15–20 minutes after placing the filling, the amalgam is relatively weak. Therefore, dentists need to instruct patients not to apply undue stress to their freshly placed amalgam fillings. In addition, amalgam restorations are brittle and susceptible to corrosion.

8. What is bioaccumulation ?

9. Why amalgam? In an age where aesthetics are becoming more vital, dental amalgam is inadequate since it has a nontooth color . This limitation usually leads to the use of amalgam fillings on mainly posterior teeth. However, in contrast to other direct restoration methods, the cost of amalgam is significantly lower . This is beneficial in poorer countries where people are likely to choose dental restorations, with costs being a more crucial factor in aesthetics. Failure rates of amalgam are low ; therefore they require replacement less often than other restoration methods. The durability of amalgam ranges from “good to excellent,” and this factor adds to the longevity of the dental restoration.

10. When to Use Dental Amalgam When placed correctly, dental amalgam has sufficient strength to withstand the high loads generated during mastication. It is therefore chiefly indicated for: • The restoration of Class I and Class II cavities, particularly those of moderate to large size • Core build-ups: when the definitive restoration will be a cast restoration, such as a crown or bridge retainer, as more tooth structure will need to be replaced and the tooth reinforced. Dental amalgam is used mainly in the posterior sextants of the mouth because of its unaesthetic appearance. However, as amalgam is not tooth coloured , the core material and the tooth tissue can be easily identified, ensuring that the margins of the crown are placed onto tooth tissue and not the core material .

11. Teeth 46 and 45 restored with dental amalgam – note the non-tooth coloured appearance of the restoration. Tooth 25 core restored with amalgam. Note the contrast between the amalgam core colour and tooth, facilitating identification of the margin of the core and of the preparation placed on tooth tissue.

12. Classification- Marzouk According to number of alloy metals : Binary alloys (Silver-Tin) Ternary alloys (Silver-Tin- Copper ) Quaternary alloys (Silver-Tin- Copper - Indium ).

13. Classification According to whether the powder consist of unmixed or admixed alloys : Certain amalgam powders are only made of one alloy. Others have one or more alloys or metals physically added (blended) to the basic alloy. E.g. Adding copper to a basic binary silver tin alloy . According to the shape of the powdered particles : Spherical shape (smooth surfaced spheres). 2. Lathe cut (Irregular ranging from spindles to shavings). 3. Combination of spherical and lathe cut (admixed). According to Powder particle size : Micro cut 2. Fine cut 3. Coarse cut

14. Classification According to copper content of powder : Low copper content alloy - Less than 4% 2. High copper content alloy - more than 10% According to addition of Nobel metals : Platinum Gold Pallidum According to Presence of zinc : Zinc containing (more than 0.01%). Non zinc containing (less than 0.01%).

15. Classification According to compositional changes of succeeding generations of amalgam : First generation amalgam was that of G. V Black i.e. 3 parts silver one part tin ( peritectic alloy). Second generation amalgam alloys - 3 parts silver, 1 part tin, 4% copper to decrease the plasticity and to increase the hardness and strength. 1 % zinc, acts as a oxygen scavenger and to decrease the brittleness. Third generation: First generation + Spherical amalgam – copper eutectic alloy. Fourth generation: Adding copper upto 29% to original silver and tin powder to form ternary alloy. So that tin is bounded to copper. Fifth generation. Quatemary alloy i.e. Silver, tin, copper and indium. Sixth generation (consisting eutectic alloy).

16. INDICATIONS OF AMALGAM

17. CONTRAINDICATIONS OF AMALGAM

18. Advantages

19. advantages

20. Role of individual component Silver: Constitutes approximately 2/3rd of conventional amalgam alloy. Contributes to strength of finished amalgam restoration. Decreases flow and creep of amalgam. Increases expansion on setting and offers resistance to tarnish. To some extent it regulates the setting time. Tin: Second largest component and contributes ¼th of amalgam alloy. Readily combines with mercury to form gama-2 phase, which is the weakest phase and contributes to failure of amalgam restoration. Reduce the expansion but at the same time decreases the strength of amalgam. Increase the flow. Controls the reaction between silver and mercury. Tin reduces both the rate of the reaction and the expansion to optimal values.

21. Role of individual component Copper: Contributes mainly hardness and strength. Tends to decrease the flow and increases the setting expansion Zinc: Acts as Scavenger of foreign substances such as oxides. Helps in decreasing marginal failure. The most serious problem with zinc is delayed expansion, because of which zinc free alloys are preferred now a days. Indium/Palladium: They help to increase the plasticity and the resistance to deformation.

22. Stages and steps in cavity preparation Initial cavity preparation stage : Outline form and initial depth placing the cavity margin in the final preparation form 2. Primary resistance form withstand of cavity walls and restorations occlusal forces without fracture 3. Primary retention form the shape to resist displacement through tipping and lifting forces 4. Convenience form Observation, accessability , prep, restoration

23. Stages and steps in cavity preparation Final cavity preparation stage 5. Removal of carious dentin and ….. 6. Pulp protection 7. Secondary resistance and retention forms 8. Finishing external walls 9. Cleaning 1. Slightly rounded configuration 2. Convergence occlusally of vestibular and oral walls 3. Gingival wall is min 1.2mm wide 4. Occlusal width and depth of the restauration 1.5-2 mm 5. Gingival extension 6. Margin of the cavity cca 90o 7. V-shaped side-fissure

24. Trituration The objective of trituration is to provide proper amalgamation of the mercury and the alloy. The alloy particles are coated with a film of oxide which is removed by abrasion when alloy particles and mercury are triturated Hand mixing : •A glass mortar and pestle are used. • The mortar has its inner surface roughened to increase the friction . • Usually a period of 25 to 45 second is sufficient for hand mixing Mechanical trituration : The disposable capsule serves as a mortar and the cylindrical metal placed in the capsule serves as the pestle. The alloy and mercury are dispensed into the capsule ,it is secured in the machine and the machine is turned on. There is an automatic timer for controlling the mixing time. Mo dern amalgamator has two or more operating speeds. The mulling process generally causes the mix to cohere so that it can be readily removed from the capsule. Spherical alloy require less amalgamation time than lathe-cut alloys, amalgamation time also depends on the quantity. For a given alloy/mercury ratio increased trituration time and speed shortens the working and setting time. Amalgamat or

25. Restauration with Amalgam

26. Placing of an amalgam filling By amalgam gun

27. condensation

28. Hand condensation

29. Liners and bases Dental amalgam does not by itself bond to tooth structure. The placement of amalgam restorations can potentially cause sensitivity post-operatively. According to R. Weiner, a protective layer or liner should be placed prior to the placement of amalgam to act as a buffer, helping to reduce sensitivity to the tooth. There are different liners that can be used in dental practices today, many of which contain zinc. Examples of lining materials include zinc oxide eugenol , zinc phosphate, glass ionomer cement , zinc poly-carboxylate and resin.

30. SPEED OF PLACEMENT Once amalgam is triturated, phase formation commences and the setting reaction is underway. Amalgam must be placed in a plastic state A malgam should not be placed more than 3 minutes after the start of mixing. Attempting to condense a partly set amalgam into a cavity will result in Poor adaptation, Reduced marginal seal and A weak restoration.

31. Burnishing First Burnish (Pre-carve Burnish) Carried out using a large burnisher for 15 seconds Use light force and move from the center of the restoration outwards to the margins. Objectives of precarve burnishing : Continuation of condensation, further reduce the size and number of voids on the critical surface and marginal area of the amalgam. Brings any excess mercury to the surface, to be discarded during carving. Adapt the amalgam further to cavosurface anatomy.

32. Carving

33. Objectives of carving To produce : A restoration with no underhangs A restoration with the proper physiological contours. A restoration with minimal flash. A restoration with adequate, compatible marginal ridges. A restoration with proper size, location, extend and interrelationship of contact areas.

34. Final Burnish (Post carve burnishing)

35. Finishing & Polishing

36. Objective of finishing and polishing

37. Polishing !

38. What Is Galvanic Shock ? Have you ever experienced a zinging sensation in filled teeth when you bite down? If so, you may be experiencing galvanic shock. This term refers to the electrochemical reaction between two dental restorations made from different materials. Why It Happens ? Galvanic shock doesn’t occur very often, these days. It usually results when people have metal fillings done by different dentists who may have used materials that differed a bit. If these fillings came in contact with each other, they could send a bit of a “zap” through the tooth and other soft tissues. Most people who still suffer from this rare chemical interaction do so because they’ve got a bunch of old fillings in their mouth. You’re not likely to start experiencing galvanic shock after a dental visit these days. How To Avoid Galvanic Shock ? The majority of today’s fillings are made from combinations of glass and plastic, making them charge-free, sparing you the zing of metal ones. If you do have old metal fillings that are bothering you, dentist can swap them out for fresh white ones with no trouble.

39. sources https://en.wikipedia.org/wiki/Amalgam_(dentistry)#Amalgam's_setting_reaction https://www.fda.gov/medical-devices/dental-amalgam/about-dental-amalgam-fillings#benefits https://www.sciencedirect.com/topics/materials-science/dental-amalgams https://pocketdentistry.com/6-dental-amalgam/ https://ec.europa.eu/health/scientific_committees/opinions_layman/en/dental-amalgam/l-3/2-amalgam-preparation.htm https://en.wikipedia.org/wiki/Dental_restoration#Amalgam http://www.med-college.de/en/master_program/seminarraum/print.php?id=317&lan=2

40. Thank you !