Principles and concepts of cavity preparation


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Principles and concepts of cavity preparation

  1. 1. PRINCIPLES AND CONCEPTS OF CAVITY PREPARATION • Chinthamani Laser Dental College
  2. 2. Introduction
  4. 4. BLACK’S CLASSIFICATION Class I lesion Lesions that begin in the structural defects of teeth such as pits, fissures and defective grooves. Locations include • Occlusal surface of molars and premolars • Occlusal two-thirds of buccal and lingual surfaces of molars • Lingual surface of anterior tooth
  5. 5. Class II Lesions They are found on the proximal surfaces of the bicuspids and molars. • Areas for class II decay involve: – Two-surface restoration of a posterior tooth. – Three-surface restoration of a posterior tooth. – Four- or more surface restoration of a posterior tooth.
  6. 6. Class III lesions Lesions found on the proximal surfaces of anterior teeth that do not involve or neccesitate the removal of the incisal angle.
  7. 7. Class IV lesions Lesions found on the proximal surfaces of anterior teeth that involves the incisal angle.
  8. 8. Fig. 48-9 Class IV restoration.
  9. 9. Class V lesion Lesions that are found on the gingival third of the facial and lingual surfaces of the anterior and posterior teeth. Class VI Lesions involving cuspal tips and incisal edges of teeth.
  10. 10. OTHER MODIFICATIONS CHARBENEU’S CLASSIFICATION • Class II: Cavities on single proximal surface of bicuspids and molars. • Class VI: Cavities on both mesial and distal proximal surfaces of posterior teeth that will share a common occlusal isthumus. • Lingual surfaces of upper anterior teeth • Any other usually located pit or fissure involved with decay.
  11. 11. STURDEVANT ’S CLASSIFICATION CAVITY FEATURE Simple cavity A cavity involving only one tooth surface Compound cavity A cavity involving two surfaces of a tooth Complex cavity A cavity involves more than two surfaces of a tooth.
  12. 12. FINN’S MODIFICATION OF BLACK’S CAVITY PREPARATION FOR PRIMARY TEETH • Class I: cavities involving the pits and fissures of the molar teeth and the buccal and lingual pits of all teeth. • Class II: cavities involving proximal surface of molar teeth with access established from the occlusal surface. • Class III: cavities involving proximal surfaces of anterior teeth which may or may not involve a labial or a lingual extention.
  13. 13. Class IV: • Cavities of the proximal surface of an anterior tooth which involve the restoration of an incisal angle. Class V • Cavities present on the cervical third of all teeth of all teeth including proximal surface where the marginal ridge is not included in the cavity preparation.
  14. 14. BAUME’S CLASSIFICATION • Pit and fissure cavities • Smooth surface cavities
  15. 15. CLASSIFICATION BY MOUNT AND HUME[1998] • This new system defines the extent and complexity of a cavity and at the same time encourages a conservative approach to the preservation of natural tooth structure. This system is designed to utilize the healing capacity of enamel and dentin.
  16. 16. THE THREE SITES OF CARIOUS LESIONS • SITE I: • Pits, fissures and enamel defects on occlusal surfaces of posterior teeth or other smooth surfaces. • Proximal enamel immidiately below areas in contact with adjacent teeth. • The cervical one-third of the crown or following gingival recession, the exposed root
  17. 17. THE FOUR SIZES OF CARIOUS LESION • Size 1–minimal involvement in dentin just beyond treatment by remineralisation alone • Size 2-moderate involvement of dentin. Following cavity preparation, remaining enamel is sound well supported by dentin and not likely to fail under normal occlusal load. The remaining tooth structure is sufficiently strong to support the restoration. • Size 3-the cavity is enlarged beyond
  18. 18. moderate .the remaining tooth structure is weakened to the extent that cusps or incisal edges are split or are likely to fail or left exposed to occlusal or incisal load. The cavity needs to be further enlarged so that the restoration can be designed to provide support and protection to the remaining tooth structure. Size 4-extensive caries with bulk loss of tooth structure has already occurred.
  19. 19. PRINCIPLES OF CAVITY PREPARATION Conventional concept [Black’s concept] • Incisors and canine • Molars and premolars • Gingival third cavities
  20. 20. Principles of Cavity Preparation
  21. 21. Principles of Cavity Preparation− cont’d Final cavity preparation
  22. 22. Patient Preparation for Restorative Procedures • Inform the patient of the procedure to be performed and what to expect during the treatment. • Position the patient correctly for the dentist and the type of procedure. • Explain each step as the procedure progresses.
  25. 25. CLASS I CAVITY
  26. 26. • Incipient lesion • #34 inverted cone bur is used to penetrate the enamel and 0.5mm or less into the dentin • Grooves and fissures is completed • Smoothen the walls and finish the cavity • Occlusal enamel walls will be approximately parallel to the axis of the tooth • Pulpal wall flat and smooth.
  27. 27. Extensive area #2 or #4 round bur can be used to enter and remove the decay Bur should run at a slower speed Light feather touch to sweep out deepest penetrations of decay. Smoothen the enamel walls and finishing is done
  28. 28. • Final occlusal outline form will consist of sweeping curves and be devoid of sharp angles. • Bevel on the enamel should not be placed at the cavosurface angle because of poor edge strength of amalgam.
  30. 30. PROXIMAL BOX• The farther the gingival wall is carried down, the deeper pulpally must be the axial wall to maintain the proper 1mm width . GINGIVAL WALL• Width should be approximately 1mm AXIAL WALL• Smaller restoration flat • Larger restoration-curve to parallel the outside contour
  31. 31. • CONVERGENCE-the proximal box line angles and walls should converge toward the occlusal approximately following the buccal and lingual surfaces of the tooth. • 90 degree cavosurface angle shold be maintained. • LINE ANGLES-the buccogingival and linguogingival line angles can be very slightly rounded. • CAVOSURFACE-the buccal and lingual walls should be at right angles to the surface of the tooth and in the direction of enamel rods.
  32. 32. • CERVICAL ENAMEL RODS- at the cervical margin the rods incline slightly toward the occlusal. • RETENTION-retention grooves may be placed into the buccoaxial and lingual-axial line angles ,but in a fashion which will not undermine the enamel walls. • ISTHUMUS WIDTH-on the occlusal surface the isthumus width should rarely exceed the width of a channel cut. • AXIOPULPAL LINE ANGLE-this can be rounded with a bur or hand instrument by sharp enamel hatchets.
  33. 33. PULPAL WALLthe pulpal wall may be flat or rounded slightly and should be preparedso it is about 0.5mminto the dentin OCCLUSAL WALLthe buccal and lingual walls of the occlusal step may converge slightly as they approach the occlusal surface. OCCLUSAL DOVETAILthis should be extended to include the susceptible or carious areas of each specific tooth. The outline form should be rounded,smooth,and graceful with a definite lock on the occlusal.
  36. 36. PRIMARY TEETH PERMANENT TEETH DEPTH OF THE CAVITY 0.5mm into dentin 0.2mm into dentin OCCLUSAL TABLE Occlusal table is narrow as Occlusal table is wider the buccolingual width of than the primary teeth the tooth is less CONTACT POINT /POINT Because of the presence of contact area, buccal and lingual margins of the interproximal box must extend far enough towards the embrasure at the gingival margin to make them accessible for cleaning. Because of the presence of contact area, buccal and lingual margins of the interproximal box don’t have to extend too far into the embrasure.
  37. 37. MARKED CERVICAL CONSTRICTION Because of the marked cervical constriction the floor of the cavity can become too narrow if placed more gingivally ISTHUMUS OF THE CAVITY Isthumus is narrow because the buccolingual width of the tooth is less.cavities with wide isthumus can lead to fracture of the tooth. BEVEL IN CAVOSURFACE Bevel is not given in the MARGIN OF GINGIVAL cavosurface margin of SEAT gingival seat OCCLUSAL ASPECT OF THE PROXIMAL BOX Must be kept narrow to prevent weakening of the cusp The cervical constriction is not that marked therefore sufficient width of the floor of interproximal box can be maintained. Isthumus is wider compared to primary teeth. Bevel is given in the gingival seat Its not that narrow
  38. 38. GINGIVAL SEAT PLACEMENT They are placed clear of contact with the adjacent tooth, so that the margins of the restorations can be cleaned. It is not that wide. BUCCAL AND LINGUAL WALLS OF THE PROXIMAL BOX Because of the wider contact area the buccal and the lingual walls of the interproximal diverge buccally and lingually to clear the contact area. Because of the prasence of contact point the buccal and the lingual walls of the interproximal need not be diverged towards the embrasure. MOD CAVITY Should not be restored for amalgam alone. It may be restored with amalgam.
  39. 39. THANK YOU Email.Id Contact us: 044-43800059 ,9283786776