Presentation on theme: "Class II Amalgam Cavity Preparartion"— Presentation transcript:
1 Class II Amalgam Cavity Preparartion Date: 6/11/2014Asalaam AlekumClass II Amalgam Cavity PreparartionDr. Gaurav garg ( M.D.S.)Lecturer, College of DentistryAl Zulfi, M.U.
2 Contents Outline form Retention form Secondary retention Resistance formReverse curveReferences
3 Outline formOcclusaly similar to that for the Class I tooth preparationProximally there is a box shape extension ( Occlusal Step)
4 No. 245 or no. 330 bur can be used for preparation Enter tooth with punch cut and extend distally along central fissure at uniform depth of 1.5 mm ( 0.5 mm inside DEJ)Bur position for entry- slight lingual tilt
7 BWedging. A, Round toothpick wedge placed in gingival embrasure protects gingiva and rubber dam during preparation of proximal box. B, Triangular wedge is indicated when deep gingival extension of proximal box is anticipated, because wedge's greatest cross-sectional dimension is at its base. Consequently, it will more readily engage the remaining clinical tooth surface
9 Proximal box:Buccolingual extension: there should be mm clearance from adjacent tooth buccaly & linguallyGingivally there should be a clearance of 0.5 mm from adjacent toothAxial wall should follow the external tooth contour
10 Removeremaining undermined proximal enamel with enamel hatchet on facial proximal wall (A), lingual proximal wall (B), and gingival wall (C).
12 A, Bevel of enamel portion of gingival wall is established with gingival margin trimmer to ensure full-length enamel rods forming gingival margin.B and C, Sharp angles at linguogingival and faciogingival corners are rounded by rotational sweep with gingival marginal trimmer ( GMT).
13 Retention form Occlusal convergence of buccal & lingual walls Proximal Dovetail
14 Secondary RetentionRetention Locks ( No. 169L or ¼ round bur can be used)169L¼ round
15 Resistance formMinimal extension, Ideal Isthmus width- 1/4th of Intercuspal distanceSmooth outline and smooth walls90 degree cavosurface angleFlat pulpal & gingival floorGingival floor should be bevelled( degree), to remove unsupported enamel rodsRounded all internal line angleBevelled axiopulpal line angle
16 Final finished cavities ¼ th of ICDBuccal wallPulpal floorPalatal/ Lingual wallAxiopulpal line angleAxio- buccal line angleAxio-lingual line angleAxial wallAxiogingival line angleGingival floor
17 Reverse CurveIn case of maxillary teeth, mostly the molars, the contact area is more buccally, i.e.; the lingual embrasures are more than the buccal embrasuresIn such cases, extending the bucco- proximal wall into the embrasure lead to excessive cutting of the buccal cuspsTo avoid this, a reverse curve ( S- shaped) is made in the buccal proximal wall so as to have sufficient amount of dentin in that area & also to achieve butt joint with the cavosurface marginsSuch a curve, though mostly given in maxillary molars, can be given in any tooth where the contact area is deviated or more pronounced on one side.
18 Advantages of reverse curve Conservation of tooth structure ( preserve cuspal inclines)Creation of 90 degree cavosurface angleLess display of restorative material ( enhance esthetics)
20 References & Suggested reading Sturdevant's art & science of operative dentistry Theodore M. Roberson, Harald O. Heymann, Edward J. Swift, Jr.Principles of operative dentistry (2005)- A.J.E. Qualtrough, J.D. Satterthwaite, L.A. Morrow and P.A. Brunton.Fundamentals of Operative Dentistry- 2nd Edition- Summitt & Robbins