Presentation on theme: "CLASS I CAVITY PREPARATION FOR AMALGAM"— Presentation transcript:
1CLASS I CAVITY PREPARATION FOR AMALGAM Date: 8/09/2015Asalaam AlekumCLASS I CAVITY PREPARATION FOR AMALGAMDr. Gaurav Garg ( M.D.S.)Lecturer, College of DentistryAl Zulfi, M.U.
2Contents Introduction Material qualities and properties of amalgam Indications for amalgam restorationContraindicationsAdvantagesDisadvantagesClinical technique for class I amalgam cavity preparation
3Introduction Class I amalgam restorations: Occlusal surface of posterior teethOcclusal two thirds of the facial and lingual surface of molarsLingual surfaces of maxillary anterior teeth
4Material qualities and properties of amalgam StrengthLongevityEase of useClinically proven successMarginal seal improves with timeLess susceptible to moisture contamination
5Indications Moderate-to-large restorations Restorations that are not in highly esthetic areas of the mouthRestorations that have heavy occlusal contactsRestorations that cannot be well isolatedRestorations that extend onto the root surfaceFoundationsAbutment teeth for a removable partial denture
6Contraindications Esthetically prominent areas of posterior teeth Small-to-moderate Classes I and II restorations that can be well isolatedSmall Class VI restorations
7Advantages Ease of use and the simplicity of the procedure Low Cost Can be placed where isolation is compromisedPlacing and contouring of amalgam restorations are generally easier than that for composite restorations.
8DisadvantagesMore complex tooth preparation required for an amalgam restoration compared to a composite restorationLess conservative tooth preparation compared with composite/GIC restorationsUnaesthetic appearance
10Initial Clinical Procedures Local Anesthesia ( if required)Isolation ( Rubber dam Recommended)
11InstrumentsNo. 245 bur ( carbide)Bur:A No. 245 bur with a head length of 3 mm and a tip diameter of 0.8 mm or a smaller No. 330 bur is recommendedSides slightly convergent toward the shank (this produces an occlusal convergence of the facial and lingual preparation walls, providing adequate retention form for the tooth preparation).The slightly rounded corners of the end of the No bur produce slightly rounded internal line angles that render the tooth more resistant to fracture from occlusal force.The No. 330 bur is a smaller and pearshaped version of the No. 245 bur.It is indicated for the most conservative amalgam preparations3 mm0.8mm
12Initial Tooth Preparation Initial tooth preparation is defined as establishing the outline form by extension of the external walls to sound tooth structure, while maintaining a specified, limited depth and providing resistance and retention forms
13Outline formThe outline form for the Class I occlusal amalgam tooth preparation should include only the faulty, defective occlusal pits and fissures (in a way that sharp angles in the marginal outline are avoided).
14Outline formExtending around the cusps to conserve tooth structure and prevent the internal line angles from approaching the pulp horns too closelyKeeping the facial and lingual margin extensions as minimal as possible between the central groove and the cusp tipsExtending the outline to include fissures, thereby placing the margins on relatively smooth, sound tooth structureMinimally extending into the marginal ridges (only enough to include the defect) without removing dentinal support
15Outline formEliminating a weak wall of enamel by joining two outlines that come close together (i.e., less than 0.5 mm apart)Extending the outline form to include enamel undermined by cariesUsing enameloplasty on the terminal ends of shallow fissures to conserve tooth structureEstablishing an optimal, conservative depth of the pulpal wall (1.5 mm)
16ProcedureBegin the Class I occlusal tooth preparation by entering the deepest or most carious pit with a punch cut using the No. 245 carbide bur at high speed with air-water spray.A punch cut is performed by orienting the bur so that its long axis parallels the long axis of the tooth crown and then the bur is inserted directly into the faulty pit.When the pits are equally faulty, enter the distal pit which provides increased visibility for the mesial extension.As the bur enters the pit, the proper depth of 1.5 mm (measured from central fissure, one half the length of the cutting portion of the bur) should be established.The desired pulpal depth is usually 0.1 to 0.2 mm into dentin.
18ProcedureMaintaining the bur's orientation and depth, extend the preparation mesially following the DEJ creating a flat pulpal floor.When the central fissure has minimal caries, one pass along the fissure at the prescribed depth provides the desired minimal width to the isthmus.Ideally the width of the isthmus need be no more than the diameter of the bur or ¼ th of intercuspal distance.the distance from the margin of the extension to the proximal surface should not be less than 1.6 mm or two diameters of the end of the No.245 bur for premolars & 2mm for molars
19ProcedureMaintaining the bur's orientation and depth, extend the preparation distofacially or distolingually to include any fissures that radiate from the pit.Care should be taken not to undermine the marginal ridge.Correct
21ProcedureRemaining fissure which is no deeper than one quarter to one third the thickness of the enamel can be eliminated by EnameloplastyEnameloplasty refers to eliminating the developmental fault by removing it with the side of a flame-shaped diamond stone, leaving a smooth surfaceThis procedure frequently reduces the need for further extension into the fissures with the No. 245 bur, thereby conserving tooth structure
22ProcedureThe cavosurface angle should be degree which will provide a 90 degree butt joint between tooth structure and amalgamThe strongest and ideal enamel margin should be made up of full-length enamel rods resting on sound dentin, supported on the preparation side by shorter rods, also resting on sound dentin
23Resistance formFlat pulpal floor in sound tooth structure to resist forces directed in the long axis of the tooth and provide a strong, stable seat for the restorationMinimal extension of external walls, which reduces weakening the toothStrong, ideal enamel marginsSufficient depth (i.e., 1.5 mm) to result in adequate thickness of the restoration, providing resistance to fracture and wear
25Final tooth preparation Removal of remaining defective enamel and infected dentin on the pulpal floorPulp protection where indicatedProcedures for finishing external wallsfinal procedures of cleaning and inspecting the prepared toothABBase application. A, Inserting RMGIwith Williams periodontal probe. B, In moderately deep excavations a base (b) thickness of 0.5 to 0.75 mm is indicated.
27Class 1 outline for different teeth Maxi 1st molarKidney Shape( Mesial cavity)Class 1 outline for different teethAMandi 1st molar- Bat shapeBMandibular 1st premolar- A. Snake eye shapeB. Butterfly shapeMandi 2nd molar- Plus shapeMandi 2nd premolar- Y ShapeMaxillary premolars-Butterfly shape
28References & Suggested reading Art and science of operative dentistry- Sturdevent’s ,2006Principles of Operative Dentistry- A.J.E. Qualtrough ,2005