OPD L4

• Class II Cavity


  Smooth surface cavities located on proximal surfaces of all posterior teeth
• Types of Class II Cavities

  • Simple Class II: involves 1 surface, mesial or distal
  • Compound Class II: involves 2 surfaces; MO, DO
  • Complex Class II: involves 3 or more surfaces; MOD, MOL, MOB
• Outline Form


  1. Extend until sound tooth structure is obtained and no unsupported and/or weakened enamel remains

  2. Avoid terminating the margins on extreme eminences such as cusp heights and ridge crests

  3. Extend the margins to allow access for proper manipulative procedures

  4. Restrict initial axial depth of the proximal preparation to a maximum of 0.2 – 0.8 mm into dentin

  5. Extend walls of proximal box (cervical, facial and lingual) 0.5 mm out of contact

  
• Outline Form for Amalgam


  • Must include all non-coalesced pits & fissures
  • Varies with occlusal anatomy of tooth
  • Smooth, rounded curves

  
• Outline Form Variations


  • Conventional
  • Box-only
  • Tunnel
• Resistance Form


  • There is an "S-curve or Reverse Curve" on the buccal proximal wall
  • The pulpal floor is made 1.5-2.0 mm from the deepest part of the occlusal surface OR 0.2-0.5 mm from the DEJ
  • The pulpal floor is made flat and perpendicular to the long axis of the tooth (except in Mandibular First Premolars)
  • All internal line angles are made slightly rounded
  • The axio-pulpal line angle is beveled

  
• Resistance Form (Axial Wall)

  • Parallel to the external surface bucco-lingually
  • Parallel to the long axis pulpo-occlusally
  • 1.0 mm from the external surface or 0.2-0.5 mm from the DEJ mesio-distally

  
• Convenience Form


  • Buccal, lingual & gingival walls of the proximal box are made out of contact with the adjacent tooth by 0.3-0.5 mm

  
• Retention Form


  • Buccal & Lingual walls are made to converge pulpo-occlusally
  • Inverted truncated cone form of proximal box
  • Occlusal Dovetail
  • Proximal grooves on the bucco-axial & linguo-axial line angles

  
• All cavosurface margins for amalgam must be made butt joint or = 90 ° to the external surface

  
• Strongest enamel margin is composed of full length enamel rods that are supported by shorter enamel rods and sound dentin