Class 2 amalgam restoration

amalgam restoration
tooth preparation
definitions

1. Class 2 Amalgam Restoration

2. DEFINITION OF TOOTH PREPARATION Tooth preparation is defined as the mechanical alteration of a defective, injured, or diseased tooth to best receive a restorative material that will reestablish a healthy state for the tooth, including esthetic corrections where indicated, along with normal form and function

3. OBJECTIVES OF TOOTH PREPARATION (1) remove all defects and provide necessary protection to the pulp, ( 2) extend the restoration as conservatively as possible, ( 3) form the tooth preparation so that under the force of mastication the tooth or the restoration or both will not fracture and the restoration will not be displaced, and ( 4) allow for the esthetic and functional placement of a restorative material.

4. FACTORS AFFECTING TOOTH PREPARATION GENERAL FACTORS: 1. Diagnosis . Before any restorative procedure, a complete and thorough diagnosis must be made. An assessment of both pulpal and periodontal status will influence the potential treatment of the tooth, especially in terms of the choice of restorative material as well as the design of the tooth preparation .

5. 2. An assessment of the occlusal relationships must be made. Such knowledge often affects the design of the tooth preparation and the choice of material . 3. The patient's concern for esthetics should be considered when planning the restorative procedure and will influence the restorative material selected 4. Knowledge of Dental Anatomy . The direction of the enamel rods, the thickness of the enamel and dentin, the size and position of the pulp, the relationship of the tooth to supporting tissues, and other factors must all be known to facilitate accurate judgment in tooth preparation.

6. 5. Patient Factors . The patient's knowledge and appreciation of good dental health influence his or her desire for restorative care and may influence his or her choice of restorative materials. Certainly the patient's economic status is a factor in selecting the type of restorative care selected ,

7. 6. Restorative material factors: An amalgam restoration requires a specific tooth preparation form that ensures: ( 1) retention of the material within the tooth ( 2) strength of material in terms of thickness and marginal form.

8. Tooth Preparation Walls Internal Wall. An internal wall is a prepared (cut ) surface that does not extend to the external tooth surface Axial wall. An axial wall is an internal wall parallel with the long axis of the tooth Pulpal wall. Pulpal wall. A pulpal wall is an internal wall that is both perpendicular to the long axis of the tooth and occlusal of the pulp External Wall. An external wall is a prepared ( cut) surface that extends to the external tooth surface, and such a wall takes the name of the tooth surface (or aspect ) that the wall is toward

9. Tooth Preparation Walls Floor (or Seat). A floor (or seat) is a prepared ( cut)wall that is reasonably flat and perpendicular to those occlusal forces that are directed occlusogingivally ( generally parallel to the long axis of the tooth). Examples are the pulpal and gingival walls

10. Tooth Preparation Angles Line Angle. A line angle is the junction of two planal surfaces of different orientation along a line An internal line angle is a line angle whose apex points into the tooth . An external line angle is a line angle whose apex points away from the tooth . Point Angle. A point angle is the junction of three planal surfaces of different orientation

11. Illustrating tooth preparation walls: facial (f) of proximal and occlusal portions, gingival ( g), lingual (I) of proximal and occlusal portions , distal (d), pulpal (p), and axial (a).

12. Illustrating tooth preparation line angles and point angles. Line angles are distofacial (df), faciopulpal (fp), axiofacial (af), faciogingival ( fg ), axiogingival (ag ), linguogingival ( Ig ), axiolingual (al), axiopulpal ( ap ), l i nguopulpal ( Ip ), distolingual (dl), and distopulpal ( dp ). Point angles are distofaciopulpal ( dfp ), axiofaciopulpal ( afp ), axiofaciogingival ( afg ), axiolinguogingival ( alg ), axiolinguopulpal (alp), and distolinguopulpal (dip)

13. Cavosurface Angle and Cavosurface Margin. The cavosurface angle is the angle of tooth structure formed by the junction of a prepared (cut) wall and the external surface of the tooth The actual junction is referred to as the cavosurface margin The cavosurface angle may differ with the location on the tooth, the direction of the enamel rods on the prepared wall, or the type of restorative material to be used.

14. AMALGAM Dental amalgam is a metal-like restorative material composed of a mixture of silver-tin-copper alloy and mercury .

15. INDICATIONS The following is a list of clinical indications for amalgam restorations in Classes I, 11, and VI. Moderate-to-large restorations Restorations that are not in highly esthetic areas of the mouth Restorations that have heavy occlusal contacts Restorations that cannot be well isolated Restorations that extend onto the root surface Foundations Abutment teeth for a removable partial denture Temporary or caries control restorations

16. CONTRAINDICATIONS • Esthetically prominent areas of posterior teeth • Small-to-moderate Classes I and II restorations that can be well isolated • Small Class VI restorations

17. Advantages: The primary advantages are the ease of use and the simplicity of the procedure . sections, the placing and contouring of amalgam restorations are generally easier than that for composite restorations.

18. DISADVANTAGES The primary disadvantages of using amalgam for Classes I, II, and VI restorations are: • More complex tooth preparation required for an amalgam restoration compared to a composite restoration • Potential nonesthetic appearance

19. CLASS II AMALGAM RESTORATIONS Amalgam restorations that restore one or both of the proximal surfaces of the tooth may provide years of service to the patient when the: ( 1) tooth preparation is correct, (2) matrix is suitable, ( 3) operating field is isolated , ( 4) restorative material is manipulated properly.

20. INITIAL CLINICAL PROCEDURES 1. Local anesthesia is usually required. It controls pain from the tooth and adjacent soft tissues and usually reduces salivation, because the patient is less sensitive to stimulation of the oral tissues . 2. Any opposing " plunging cusp" or other pointed cusp may need to be recontoured to reduce the risk of fracture of the new restoration or the cusp from occlusal forces. 3. Before tooth preparation for amalgam, the placement of the rubber dam is generally recommended.

21. Class II Amalgam Restorations Involving Only One Proximal Surface. Using high-speed bur with air water spray, enter the pit on occlusal surface which is nearest to the involved proximal surface. Keep long axis of the bur parallel to the long axis of the tooth and maintain the initial depth of 1.5 to 2.0 mm Extend the outline to include the central fissure while maintaining uniformity in depth of pulpal floor. Make isthmus width as narrow as possible, not wider than one fourth the inter- cuspal tip distance

22. Outline form in the proximal area is primarily determined by the faciolingual position of the contact area and the extent of carious lesion. External outline form on the occlusal portion is extended to just break contact with the adjacent tooth . While maintaining the established pulpal depth and with the bur held parallel to the long axis of the tooth , extend the preparation towards the contact area of the tooth , ending short by 0.8 mm of cutting through the marginal ridge

23. The proximal cutting is sufficiently deep into the dentin (0.5-0.6 mm) so that retentive locks are prepared into axiolingual and axiofacial line angles. Widen the preparation faciolingually to just clear the contact areas. The proximal cut is diverged gingivally . In other words, faciolingual dimension at the gingival surface is greater than the occlusal surface, this provides good retention and conservation of marginal ridge

24. Proximal margins should have a cavosurface angle of 90 ° and when completed, the walls of the proximal box should converge occlusally . Ideal clearance of facial and lingual margins of the proximal box should be 0.2 to 0.5 mm from the adjacent tooth

25. A , Bur position to begin proximal ditch cut. B , Proximal ditch is extended gingivally to desired level of gingival wall. C , Variance in pulpal depth of axiogingival line angle as extension of gingival wall varies: a, at minimal gingival extension ; b, at moderate extension; c, at extension that places gingival margin in cementum,whereupon pulpal depth is 0.75 to 0.8 mm and bur may shave side of wedge. D , Proximal ditch cut results in axial wall that follows outside contour of proximal surface . E, Position of proximal walls (i.e., facial, lingual, gingival) should not be overextended with No. 245 bur, considering additional extension provided by hand instruments once remaining spurs of enamel are removed . F , When small lesion is prepared, gingival margin should clear adjacent tooth by only 0.5 mm. This clearance may be measured with side of explorer. The diameter of the tine of a No. 23 explorer is five tenths millimeter,'/, inch (6.3 mm) from its tip. G , Faciolingual dimension of proximal ditch is greater at gingival than at occlusal level. H , To further isolate and weaken proximal enamel , bur is moved toward and perpendicular to proximal surface (parallel to direction of enamel rods). I Side of bur may emerge slightly through proximal surface at level of gingival floor.

26. Reverse curve: In teeth with broader contacts, Reverse-s Shape Curve is given to both widen the box yet remove less tooth structure. Reverse curve is given to the proximal walls by curving them inwards towards the contact area . if excessive fl are is given in these teeth, proximal walls will end past the axial angle of tooth through the cusps resulting in weakening of tooth structure and fracture of restoration

27. Primary Resistance Form It is can be obtained by incorporating following features in the preparation: Shape of the preparation like a box with flat pulpal and gingival floor. Cavosurface angle of 90° Include all the weakened tooth structure Maintain minimal width of the preparation so as to preserve tooth structure Round off all the internal line and point angles Consider capping of cusp for preserving cuspal strength.

28. Primary Retention Form: Primary retention form prevents the restoration from being displaced. Retention can be increased by the following: • Occlusal convergence (about 2 to 5%) of buccal and lingual walls. • Occlusal dovetail.

29. Final Tooth Preparation: During final preparation of tooth, clean it with air/water spray or with cotton pellet and inspect it for detection and removal of debris and examine for correction of all cavosurface angles and margins. Remove remaining caries, old restorative material and adjacent deep pit and fissure involved in the preparation. In the large preparations with soft caries, the removal of carious dentin is done with spoon excavator or slow speed round bur. In this, two step pulpal floor is made , i.e . only portion of tooth which is affected by caries is removed, leaving the remaining preparation floor untouched

30. Secondary retention and resistance form: • Placing retention grooves and locks in the proximal box. Slots’ in the gingival floor may be given to provide additional retention . Pulp protection Use pulp protective materials whenever needed.

31. Finally finishing of walls and margins is done by removing all unsupported enamel. Beveling of enamel portion of gingival wall is done with the help of gingival marginal trimmer. This helps to have full length enamel rods at the gingival margin Make cavosurface angle 90° butt joint type to provide bulk to restoration, which in turn provides maximum strength • the final stage of tooth preparation is to clean the preparation thoroughly with water and air spray. Then dry it with moist air.

32. Steps of amalgam restoration Selection of amalgam alloy Mercury—alloy ratio Trituration Mulling Application of matrix bond Insertion of amalgam Condensation Burnishing Carving Finishing and polishing.

33. Selection of Amalgam Alloy Type of alloy: High copper or low copper alloys Zinc free or zinc containing alloys Size and shape of the particles . Patients with psychological problems or other diseases , requiring early disposal, indicate the use of fast setting alloy In wider and broader preparations, alloy with low creep values is preferred If it is difficult to control moisture it is preferred to use zinc-free alloy to avoid delayed expansion.

34. Mercury Alloy Ratio Eames has preferred 1:1 ratio of alloy/mercury for best results. Generally , it is 5:8 or 5:7, if mercury content is more than required amount, resultant mix will be weaker, but if it is less, it might not sufficiently wet the alloy particles. Lathecut amalgam alloys require more (45%) of mercury to wet than the spherical alloys ( 40%).

35. Trituration The purpose of trituration is to remove oxide layers from the alloy particles so as to coat each alloy particle with mercury , resulting in a homogeneous mass for condensation. Trituration can be done by hand or mechanical means . Mechanical method is done with the help of automatic amalgamator (and hand method of trituration is done with the help of mortar and pestle)

36. Objectives of trituration Achieve a workable mass of amalgam within minimum ti me Increase direct contact between the particle and mercury by removing oxides from powder Reduce particle size of powder so that fast and more complete amalgamation can be done Help in dissolving the particles of powder in mercury Reduce the amount of gamma-1 and gamma-2.

37. Test for trituration Normal trituration Good shiny mix Homogeneous mass, adheres together. Over trituration Mix is ‘warm’ Difficult to remove from capsule Shiny wet and soft . Under trituration Dry mix Crumbled mix that is very weak.

38. Mulling Mulling is done so that all alloy particles are properly coated with mercury, in other words, it is continuation of the trituration. Mulling of the amalgam can be done manually or mechanically. By hand, it can be done by squeezing the freshly mixed amalgam collected in the chamois skin. Mulling should not be done by bare hands as it can be contaminated by moisture. Mechanical mulling is done in the amalgamator by triturating it for one to two seconds.

39. Application of Matrix Band A matrix is helpful to prevent “sliding ” during condensation and to ensure marginal adaptation and strength of the restoration. The Tofflemire matrix retainer is used to secure a matrix band to the tooth. Place the matrix band in the matrix retainer. Pass the matrix band between the contact points so that its lower edge comes just over the cervical margin of the preparation. Tighten the band and stabilize it using wedges

40. Insertion of Amalgam Pick a small amount of amalgam alloy with the help of amalgam carrier and transfer it to the preparation. Proximal box should be filled before the occlusal part of the preparation. Place the first increment of amalgam in the deepest proximal part of the preparation and condense it with flat surface of condenser .

41. Insertion of Amalgam Apply firm pressure on the amalgam mass for adequate condensation . After it, add next increment and again condense it. When the level of amalgam reaches the preparation margins , continue the packing of preparation to allow an excess to build up for better finishing

42. Condensation Various shapes (triangular, round, elliptical, trapezoidal and rectangular) and sizes of condensers are used for amalgam condensation. Working end of a condenser is usually serrated Rules of condensation Start condensation within three minutes of trituration Condense continuously Condense laterally as well as apically Apply adequate force for condensation Have a constant supply of amalgam.

43. Objectives of condensation Brings excess mercury on the surface of restoration Reduces the number and size of voids in the restoration Prepares the surface of restoration for carving To adapt amalgam to the preparation walls and floors .

44. Condensation Depends upon Following Factors Plasticity of the mass Size of the amalgam increment : A larger mass results in incomplete condensation Condenser size : the smaller the condenser working end, the greater the force Direction of force Amount of force Type of alloy: Use larger condensers when condensing spherical alloys because smaller condenser will displace the spherical particles rather than condensing them.

45. Burnishing Precarve burnishing is done after condensation . It is the process of rubbing, generally done to make the surface shiny. Amalgam is overfilled and burnished immediately with heavy strokes so as to improve marginal adaptability of the restoration and remove excess mercury from overpacked amalgam Advantages of precarve burnishing Improves the marginal integrity of restorati o n Shapes the restoration according to contours and curvatures of the tooth Helps in reducing the mercuric content of amalgam

46. Carving For adequate carving, it is preferable to overpack the preparation and then carve it to the margins . The carving instruments should have discoid and cleiod blade design. Larger instrument is used first , followed by smaller instruments . Objectives of carving are to achieve restoration with No over and under hangs Proper size, location and good interproximal contact Adequate marginal ridges Proper contours Optimal occlusal anatomy Adequate embrasures Enhancing the health of periodontium .

47. Post carve burnishing: It is done after completion of carving with the help of small sized burnishers using light strokes. Advantages of postcarve burnishing Reduces number of voids on surface of restoration Produces denser amalgam at margins Improves marginal seal Increases surface hardness Decreases rate of corrosion.

48. Finishing and Polishing Finishing amalgam restorations involves removal of marginal irregularities, defining anatomical contours, and smoothening the surface roughness of the restoration. Polishing is done to achieve a smooth, shiny luster on the surface of the amalgam. Finishing is done before polishing by use of abrasive agents that are coarse enough to remove the bulk from the surface.

49. Advantages Finishing and Polishing Improves marginal adaptation of restoration by removing flash Reduces tarnish and corrosion Polished surface is plaque resistant Polished surface is smoother and easier to clean Prevention of recurrent decay Prevention of amalgam deterioration Maintenance of periodontal health Prevention of occlusal problems.

50. A polished amalgam restoration should have following features Surface is smooth with no scratches or graininess Surface is lustrous, with a mirror like shine There is no break between margins and the tooth surface Restoration has proper contact and contour There is no damage to the restoration or adjacent tooth structure

51. Steps: Smoothen the margins by using a round bur moving it along all cavosurface margins. This procedure is done to blend the tooth structure to amalgam Use a large round finishing bur to eliminate scratches and graininess from the amalgam Using the side of the finishing bur, smoothen the occlusal surface and marginal ridges. Move the bur mesiodistally , overlapping each stroke, then do the same in a buccolingual direction

52. Steps: Use a finishing strip for smoothening and polishing of the gingival cavosurface margins and interproximal space Smoothen the facial and lingual surfaces with finishing disks Finally polish the surface by using progressively finer abrasive agents Rinse and clean out all debris completely Evaluate all margins and surfaces of the restoration