Amalgam Class II Preparation and Restoration PDF

Class II Amalgam Cavity Preparation and Restoration Dr. Khawlah Al-Othman BDS, MSc, ABGD, SBRD ILOs Identify different outline forms of class II amalgam cavity preparation. Describe the proper design of the proximal part of class II. Describe the steps of manipulation and application...

Class II Amalgam Cavity Preparation and Restoration Dr. Khawlah Al-Othman BDS, MSc, ABGD, SBRD ILOs Identify different outline forms of class II amalgam cavity preparation. Describe the proper design of the proximal part of class II. Describe the steps of manipulation and application of class II amalgam. Describe the criteria of successful class II amalgam Defenition of class II cavity preparation Preparation required to correct carious lesions that develop in the proximal surface of posterior teeth Requirement for amalgam preparation Uniform 1.5-2 mm minimum thickness >> flex and fractur occlusal load. 90 degree occlusal cavosurface angle. Remove all unsupported enamel. Undercut preparation form >> mechanically retained. Outline Form Include all carious lesions, defects, or existing restorative material. Occlusal outline form: Same as class I. Proximal outline from: 1- Occlusal portion of class II ( Isthmus) : Definition: It is the narrow part of the preparation that connect occlusal and proximal part of class II. Straight > in cases of small contact area. Outline form 2-Proximal portion of class II: Converge bucco-lingual. The buccal and lingual walls should be paralle to their corresponding surfaces. Establish not more than 0.5 mm clearance with adjacent surface facially, lingually and gingivally. The depth of the axial wall is 0.2-0.8 mm into the dentin. The axial wall should be (straight or convex) parallel to the external surface of the tooth. The gingival floor should be parallel to Primary Retention Form Retention is the features that retain (lock) the restorative mate Facio-lingual walls converge occlusally. Secondary Retention Form Secondary Retention Form Retention Grooves Recommended in tooth preparations with extensive proximal boxes. Bur: No. 169 or No. 1/4 round bur. Position: axiofacial – axiolingual line angle. Depth : 0.5 mm , 0.2 from DEJ. Occlusoginigival height : at level or just occlusal to Resistance Form Resistance is the feature help the tooth and the restoration resist fractures caused by occlusal forces. Resistance feature assist in preventing tooth fracture : Preserving dentin supporting cusps and marginal ridges. The pulpal and gingival walls being perpendicular to occlusal forces. Rounded internal preparation angle to reduce stress concentration in the tooth structure. Remove unsupported tooth structure. Resistance Form Resistance feature assist in preventing amalgam fracture : Adequate thickness of amalgam (at least 1.5–2 mm in areas of occlusal contact and 0.75 mm in axial areas). Uniform amalgam thickness. Amalgam margin of 90 degrees. Rounded axio-pulpal line angles. The outline not to be on the occlusal force areas. Convenience Form Convenience form includes features that allow adequate access and visibility of the operating site to facilitate tooth preparation and restoration. Preparation steps Maintain the same orientation of the bur parallel to the long axis of the crown. Place it over the DEJ. Preparation steps Depth of gingival floor : Cut gingivally just beyond carious lesion or the proximal contact ( when gingval contact break), which ever is greater. Preparation steps Proximal extension: The proximal extensions are completed when two cuts, one starting at the facial limit of the proximal ditch and the other starting at the lingual limit. Extending toward and perpendicular to the proximal surface, until the bur is nearly through enamel at the contact level. Preparation steps Gingival floor: Preparation steps Limits for proximal margins: 0.5 mm clearance mesiofacial, mesiolingual, gingival. Unless indicated to include carious lesion existing restorative material, or undermined enamel. Preparation steps Cavo-surface angles: 90 degrees. Ensure that no undermined enamel rods remain on the proximal margin. Maintain maximal edge strength of amalgam. Preparation steps Axial wall contour: Should follow the external wall contour. Preparation steps Axial wall depth: 0.2 - 0.8 into the dentin. 1. No retention grooves: 0.2 mm inside the DEJ. 2. Retention grooves: 0.5 mm inside the DEJ (to prevent undermining the proximal wall enamel). 3. Root surface: 0.75 to 1 mm deep. How to prevent iatrogenic damage of the proximal surface of the adjacent tooth ? Keeping the proximal enamel until the end of the preparation. 1- 2- Place matrix band around adjacent tooth. 3- Fender wedge. Variation of Class II Preparation Mandibular First Premolar Tilt bur slightly lingual to establish pulpal floor. Preserve the large transverse ridge. Prepare the proximal box 1st then continue to the occlusal prep. Variation of Class II Preparation Maxillary First molar Preserve the large oblique ridge whenever possible to preserve to Variation of Class II Preparation Maxillary First Premolar On mesial surface, facial wall extension is minimized for aesthetic reasons. If caries is limited to mesio-lingual embrasure, proximal contact is not involved in the prep. Class II amalgam Restoration Matrix placement Tofflemire- matrix system Tofflemire- matrix retainer Matrix band Tofflemire - matrix retainer Tofflemire - matrix retainer Matrix Band The characteristic of good matrix: Rigidity Establishment of proper anatomical contour Restoration of correct proximal contact relation Easy adaptation to the tooth Ability to be contoured Prevention of gingoval excess Strength to offer resisrance to condensation pressure Matrix Band Conventional, flat universal matrix band. Thikness : 0.03mm , 0.05 mm. Matrix Band Must be burnished before assembling the matrix band and the retainer. 1mm above the adjacent marginal ridge Burnish matrix against the adjacent tooth Wedge placement 1- Insert wedge with tweezer from facial or lingual embrasure ( w 2- Gingival to the gingival margin of the preparation. 3- Tight enough to prevent any possibility of an overhang of amal Insertion of the amalgam Transfer amalgam to the tooth with amalgam carrier. Condensation: Start in the deepest part of the preparation with smaller condensedr then larger. Insertion of the amalgam Condense it with suffecient force in the proximal box vertically and laterally against the walls and matrix with small condenser. Use larger condenser for occlusal surface. Overfilled to ensure adequate condensation on the occlusal surface. The condensation of a mix should Insertion of the amalgam Proper Condensation : Help to produce void free restoration. Minimize mercury content in the restoration: 1. Decrease corrosion. 2. Enhance strength and marginal integrity. The condensation should be completed within the time Insertion of the amalgam Pre-carve burnishing : Useful to finalize the condensation, remove excess mercury- rich amalgam and initiate the carving process. Insertion of the amalgam Carving: Immediately after condensing before it gets hard. Carving Occlusal Area: With sharp carving instrument, discoid–cleoid and Hollenback carver to create cusps and grooves. Insertion of the amalgam Carving Occlusal Area: With explorer tip establish occlusal embrasure area. Height of the proximal marginal ridge should be at the same level of the marginal ridge of the adjacent tooth marginal ridge should be rounded. Insertion of the amalgam Remove wedge Insertion of the amalgam Carving Facial and Lingual Areas: The side of an explorer and Hollenback carver. The cervical areas, it is important to remove any excess and develop the proper contour of the restoration, which is usually convex. Insertion of the amalgam Carving Proximal Embrasure Area: Scaler is an excellent instrument for removing proximal excess and developing proximal contours and embrasures. Place it below the gingival margin and drawn occlusally to carefully shave of excess. Insertion of the amalgam Post carve burnishing : Using a small burnisher lightly rubbing the carved surface to improve smoothness. Occlusion evaluation 1.Removal of the rubber dam 2.dry teeth and restoration for proper marking with articulating paper. 3.Articulating paper is placed over the restoration and adjacent teeth, and the patient is instructed to close gently into occlusion. Occlusion evaluation The restoration is high if: 1. Cusp tips of adjacent teeth are not in occlusal contact when it is known from the preoperative occlusal assessment that they should be touching. 2. Opposing cusp prematurely occludes with the new restoration. Identify excursive interferences by asking pt to slide the teeth lightly from “side to side” and “front to back”. Occlusion evaluation Amalgam restorations carved completely out of occlusion >> supra-eruptive tooth movement resulting in undesirable tooth contacts and this, too, should be avoided. Finally, the patient should be cautioned to protect the newly condensed restoration by not using it to chew firm food for 24 hours. Finishing and polishing Should be done after complete setting of amalgam ( after 24 hours). Finishing and polishing makes amalgam restoration less prone to tarnish and corrosion. Finishing and polishing Finishing steps : White alumina stone. If the groove and fossa features are not sufficiently defined, a small round, 12 fluets finishing bur also may accentuate them without eliminating the occlusal contact areas. Finishing and polishing Polishing steps : The polishing procedure is initiated by using a coarse, rubber abrasive point at low speed and air-water spray. Rubber points should be used at low speed ( 6000 revolutions per minute [rpm]). The system includes coarse-grit, medium-grit, and fine-grit rubber abrasive points. Using these points in sequence, from coarse to fine, produces an amalgam surface with a brilliant luster. Finishing and polishing Polishing may be accomplished using a rubber cup with pumice. Criteria for successful amalgam rest Restoration remains integral and in space. Absence of recurrent caries. Marginal accuracy and adaptation. Maintain perfect anatomy and contour. Maintain perfect relation with adjacent teeth, opposing teeth and periodontal structure. Patient comfort and satisfaction. References: 1. Sturdevant’s, Art and Science of Operative dentistry, 7th edition, Ch: 4 and 10. 2. Summitt’s, Fundamintals of Operative Dentistry, 4th editio, Ch 12. Thank you