OVERVIEW OF AMALGAM RESTORATION (OPERATIVE DENTISTRY LECTURE)

A SHORT REVIEW OF AMALGAM RESTORATION FROM RESTORATIVE DENTISTRY

1. OVERVIEW OF AMALGAM RESTORATION DR. SARANG SURESH HOTCHANDANI

2. CONTENTS INTRODUCTION GENERAL TOOTH PREPARATION TYPES OF AMALGAM HISTORY GENERAL CONSIDERATIONS GENERAL CLINICAL TECHNIQUE 2

3. INTRODUCTION It is a Direct Metallic Restorative material. Amalgam means alloy of mercury with another metal. Mixture of silver-tin-copper alloy and mercury. 3

4. GENERAL TOOTH PREPARATION FOR AMALGAM Possess a uniform specified minimum specified thickness for compressive strength (1.5-2 mm) Produce a 90-degree amalgam angle at the cavo-surface margin (butt joint form) Be mechanically retained to tooth (undercut formation) 4

5. TYPES OF AMALGAM Conventional amalgam restoration Desensitizer is used (5% glutaraldehyde + 35% hydroxyl-ethyl methacrylate [HEMA]) Bonded amalgam restoration Bonding, technique & isolation similar to composite Retention is minimal Strengthen the remaining tooth structure However, tooth preparation is similar to conventional amalgam restoration defined above. Sealed amalgam restoration In this light cured adhesive is placed under amalgam restoration to close dentine. 5

6. HISTORY OF AMALGAM Initially, dentists use silver coins in filling and mixing these filling with mercury, creating a putty like mass that was placed into defective tooth. 6

7. CURRENT STATUS OF AMALGAM Today popularity is decreased because of; Reduction in caries rate Esthetic concerns Development of composites (primary cause of reduction in use of amalgam) Environmental concerns 7

8. TYPES OF AMALGAM 8

9. LOW COPPER AMALGAM Prominent till 1960. Composition Silver; 65% wt. Tin; 29% wt. Copper; <6% wt. 9

10. LOW COPPER AMALGAM This type of amalgam results gamma-two phase (tin-mercury) which showed corrosion. This corrosion led to breakdown of amalgam. That’s why High copper amalgam were developed to eliminate this corrosion created by gamma-two phase. 10

11. HIGH COPPER AMALGAM Currently used today Reduces formation of gamma-two phase (reacts with tin) resulting decreased corrosion but; Corrosion still occurs which is beneficial because it provides marginal sealing of amalgam to cavity walls. Composition Silver; 40% wt. Copper; 12% - 30% wt. 11

12. HIGH COPPER AMALGAM This material can provide performance for more than 12 years Two types of high copper amalgam Spherical amalgam Admixed amalgam Zinc containing high copper amalgam does not show delayed expansion on condensation. 12

13. EFFECT OF “ZINC” IN AMALGAM Enhance mechanical properties Reduce marginal fracture Prolong the service of restoration 13

14. TRITURATION it is the process by which amalgam alloy powder is mixed with liquid mercury. The powder may be; Lathe cut ( milling(crushing) an ingot(slab) of the alloy) Spherical type (atomizing liquid alloy) Admixed Contain both lathe cut and spherical type of alloys. Filing; when dental amalgam alloys contain only lathe cut particles. 14

15. SPHERICAL AMALGAM Little condensation pressure. High early strength. 15

16. ADMIXED AMALGAM More condensation pressure (required by many dentists) Displaces matrix bands to generate proximal contacts more easily. 16

17. NEW AMALGAM ALLOYS Mercury free Lowe mercury amalgam Alloys with gallium or indium or gold alloys 17

18. POINTS TO CONSIDER… It has been theorized that during mastication, pressure of 200 MPa and this force with friction can generate heat which would break bond in amalgam and release mercury in the oral cavity. 12 amalgam restoration would release 1.7 micro gram per day. Dental amalgam restoration contains approx. 50% mercury. Hypersensitivity to mercury is extremely rare. Less than 1% showed clinical features of hypersensitivity to mercury (oral lichenoid reaction, erythematous, burning or itching) 18

19. IMPORTANT PROPERTIES OF AMALGAM Linear coefficient of thermal expansion of amalgam is 2.5 times greater than tooth structures. While it is close to composite. Linear coefficient of thermal expansion; the change in size per degree change in temperature. 19

20. IMPORTANT PROPERTIES OF AMALGAM Compressive strength is similar to tooth structure. Tensile strength less than tooth structure. Make amalgam prone to fracture Usually amalgam fracture is bulk fracture not marginal fracture. 20

21. IMPORTANT PROPERTIES OF AMALGAM Amalgam is brittle and have low edge strength Amalgam should have sufficient bulk (1.5-2 mm) and 90 degree or greater marginal configuration. 21

22. IMPORTANT PROPERTIES OF AMALGAM No clinically relevant creep or flow is shown by amalgam. Creep/flow; it is the deformation of material under load. Amalgam is good thermal conductor Always use base/liner under this material. 22

23. GENERAL CONSIDERATIONS OF AMALGAM 23

24. INDICATIONS & USES Class 1, 2 & 5 cavities, root caries or areas where isolation is not possible. Coz, amalgam has greater wear resistance than composite and There is no any effect of contamination on amalgam restoration Temporary caries control restorations till final restoration is placed. Foundations (core buildup for crown) 24

25. CONTRAINDICATIONS TO AMALGAM Allergy to alloys Esthetic areas Weakened tooth structure which can be preserved by composite do not use amalgam. 25

26. ADVANTAGES V/S DISADVANTAGES ADVANTAGES OF AMALGAM RESTORATION DISADVANTAGES OF AMALGAM RESTORATION Ease of use/ least time consuming High compressive strength/strong Excellent wear resistance (similar to tooth) Long term durability Low cost than composite Reduced micro-leakage due to formation of corrosion products at the tooth-amalgam restoration No alteration of gingival flora as compared to composite when placed in root caries Cusp fracture is not caused by amalgam restoration but it is caused large cavity preparation used form amalgam. Non-tooth colored/non-esthetic Mechanical bonding to tooth Large natural tooth removal Difficult tooth preparation Initial marginal leakage Limited edge strength 26

27. GENERAL CLINICAL TECHNIQUE 27

28. INITIAL CLINICAL PROCEDURES/CONSIDERATIONS Complete examination, diagnosis and treatment plan before start of restoration. Assessment of occlusion. Identify contacts on tooth to be restored and opposing and adjacent teeth Help in planning outline form and occlusal contacts on restoration. 28

29. INITIAL CLINICAL PROCEDURES/CONSIDERATIONS Local anesthesia Placement of wedge in gingival embrasure. Separate the operated tooth Protect rubber dam & interdental papilla Isolation of operating site with rubber dam or cotton rolls. Visualize anticipated extension of the tooth preparation 29

30. TOOTH PREPARATION OF AMALGAM RESTORATION 30

31. REQUIREMENTS Amalgam margin 90 degree or greater (butt-joint form) coz of amalgam’s low edge strength. Adequate depth of 1.5 – 2mm thickness for adequate compressive strength. Adequate mechanical retention form (undercut form) 31

32. INITIAL TOOTH PREPARATION DEPTH Initial pulpal depth in cavity for amalgam filling should be; One half length of the No. 245 bur (1.5mm) (total length of this bur is; 3mm) OR 1.5 mm measured from central groove OR 0.2 mm inside/ internal to DEJ Depth for axial wall should be; 0.2 mm inside DEJ if retention grooves are not going to formed 0.5 mm inside DEJ if retention grooves are going to formed Axial depth on root surface 0.75 – 1 mm deep 32

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35. OUTLINE FORM The extension of cavity depends primarily on amount of caries, old restorative material or defect. Preserve the strength of cusps and marginal ridges. Try to extend cavity around the cusps and avoid undermining of dentinal support of marginal ridges. Extend facial and lingual proximal walls into facial or lingual embrasure but not beyond it The less the outline form the more conservative is the cavity and less the tooth structure is removed. 35

36. CAVOSURFACE MARGIN Must be 90 degrees or greater. Butt joint should be formed between amalgam & tooth structure. Occlusal margins should be made in such a manner that full length of enamel rods or buttressed by shorter enamel rods Central groove after carving should be rounded 36

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38. PRIMARY RETENTION FORM Mechanical locking of amalgam into surface irregularities of cavity Vertical walls especially facial/lingual should converge occlusally. These both primary retention features can be obtained by “pear shaped carbide bur No. 330 or 245) 38

39. PRIMARY RESISTANCE FORM Resistance features which prevent THE TOOTH from fracturing are obtained by; Maintaining as much unprepared tooth structure as possible (preserving cusps & marginal ridges) Making pulpal & gingival walls perpendicular to occlusal forces Having rounded line angles Removing unsupported or weakened tooth structure. 39

40. PRIMARY RESISTANCE FORM Resistance features which prevent THE AMALGAM from fracturing are obtained by; Adequate thickness of amalgam 1.5 – 2 mm occlusal cavity 0.75 mm in axial areas Margins of amalgam greater or equal to 90 degrees. Box like cavity form which provide uniform amalgam thickness. Rounded line angles. 40

41. CONVENIENCE FORM Obtained by extending outline form, walls or margins. 41

42. SECONDARY RESISTANCE FORM Obtained by pins, grooves, coves, slots, steps, amalgam pins. 42

43. RESTORATIVE TECHNIQUES 43

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46. Matrix Placement in case of Proximal Restoration Provide proper contact & contour Confine restorative material Reduce amount of excess material It should be easily applied and removed, extend below gingival margin, extend above marginal ridge height & resist deformation during insertion of restorative material. Matrix can be applied during tooth preparation. In this case matrix is applied on that tooth which is adjacent to tooth which is being prepared. 46

47. Filling or Condensation of Amalgam Spherical is easily condensed than admixed. Smaller amalgam condensers are used first to allow amalgam to be condensed in the grooves, coves, line angles etc. Burnish the amalgam with burnisher to finalize condensation. 47

48. Carving of Amalgam Occlusal areas; A discoid-cleoid instrument is used for this purpose. The rounded end (discoid end) of discoid-cleoid instrument is positioned on the unprepared enamel adjacent to the amalgam margin and pulled parallel to margin. The pointed end (cleoid end) is used for creating primary grooves, pits or cuspal inclines. Or these can also be made with Hollenbeck carver. Mesial & distal pits should be inferior to marginal ridge height to prevent wedging of food into occlusal embrasure. For large class 2 or foundation restorations, the initial carving of the occlusal surface should be rapid, concentrating primarily on the marginal ridge height and occlusal embrasure areas. These areas are developed with explorer or carving instrument by mimicking adjacent tooth. 48

49. Carving of Amalgam Facial and Lingual areas; Hollenbeck carver/ amalgam knife is useful in carving these areas. Proximal Embrasure Areas; Made by amalgam knife Assessed by visual examination & dental floss. 49

50. THE END DR. SARANG SURESH HOTCHANDANI (BDS) [email protected] Larkana, Sindh, Pakistan 50