OPD L3

• Class I cavities


  Pit & fissure cavities located on:

  • Occlusal surfaces of molars & premolars
  • Lingual surface of maxillary anterior teeth
  • Occlusal & middle thirds on buccal & lingual surfaces of teeth

  
• Outline form


  • Differs depending on the anatomy of the tooth's occlusal surface

  The principle of "extension for prevention" must take into consideration:

  • Patient's oral hygiene
  • Patient's caries index

  
• Outline form of molars

  • Pulpal floor is made perpendicular to the forces of mastication EXCEPT in MANDIBULAR FIRST PREMOLARS due to the prominent buccal pulp horn in these teeth

  Isthmus width = 1/4 the intercuspal distance for conservative cavity preparations

  Dovetail width facio-lingually = 1/3 intercuspal distance

  Isthmus width = 1/4 intercuspal distance

  
• Tooth #34 or #44

  • Pulpal floor parallel to check occlusal surface

  Making pulpal floor perpendicular to occlusal forces = encroachment on the buccal pulp horn

  Disto-lingual groove preparation: Pulpal floor is made parallel to occlusal surface to avoid prominent lingual pulp horn

  Transverse or oblique ridges may be crossed when:

  • A carious groove crosses them
  • Ridge is undermined by caries
  • There is less than 0.5mm of enamel on the ridges between the mesial & distal areas
  • Additional retention may be gained by extending the preparation into the mesial/distal areas

  
• Resistance form


  • The pulpal floor is made 1.5-2.0 mm from the deepest part of the occlusal surface OR 0.2-0.5mm from the DEJ to provide bulk for strength of amalgam

  The proximal walls must be parallel to tooth's long axis or slightly diverging to prevent undermining the marginal ridge and the eventual fracture

  Proximal walls should not be made converging pulpo-occlusally as this will undermine the marginal ridges leading to fracture

  All internal line angles must be slightly rounded to eliminate stress concentration areas

  Converging buccal & lingual walls lock the restoration in place & prevents occlusal dislodgement
• Removal of caries


  Establish the depth of the pulpal floor 1.5-2.0mm from the central pit or 0.2-0.5mm from the DEJ

  Inspect pulpal floor for remaining caries

  Remove remaining caries by:

  • Punching out with a small round bur OR
  • Scooping out using a spoon excavator
• Finish of the cavity walls

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

  Entry cut: bur held parallel to the tooth's long axis