Class I Amalgam Preparation

#19 O

 

Overview

Outline Form
Resistance Form
Retention Form
Convenience Form
 
 

Armamentarium

Instruments and Materials

 

Video Demonstration

 

Procedure

Optional: Draw the outline of the cavity preparation using the red-blue pencil

Envision the cavity preparation outline and extent:  

  • Clinical note: The final preparation measurements are determined by the extent of the carious lesion or existing, faulty restoration

Obtain proper isolation of the tooth

(e.g. rubber dam, isovac/isolite, etc.)

Orient the bur perpendicular to the occlusal surface in the central fossa

  • Clinical note: Place the bur over the carious lesion or existing, faulty restoration

Bur options: pear shaped carbide bur (330) 

Penetrate the central fossa to a depth of about 1.5mm for the initial punch-cut

  • Optional: The length of the bur may be used to approximate preparation depth

  • Clinical note: The preparation depth is determined by the extent of the carious lesion or existing, faulty restoration 

Maintaining the 1.5mm depth, extend the occlusal outline to the mesial and distal pits along the central groove

  • Maintain the bur perpendicular to the long axis of the tooth

  • Clinical note: The final preparation depth must extend at least 0.5mm into dentin

Extend the occlusal outline to create the dovetails

  • Follow the anatomy of the grooves to extend:

    • Buccally along the buccal grooves

    • Buccally along the mesial and distal pits

    • Lingually along the lingual groove

Bur options: pear shaped carbide bur (330) 

Create convergence and divergence of the preparation walls

  • Bucco-lingual walls: occlusally convergent

    • Orient the bur perpendicular to the pulpal floor

  • Mesio-distal walls: occlusally divergent 

    • Place the bur in the most proximal portion of the outline, orient the bur 5º proximally, and brush upward 

Bur options: pear shaped carbide bur (330) 

Use the probe to check for appropriate dimensions of the occlusal outline and smoothness of the pulpal floor:

  • Pulpal floor: 1.5mm-2mm depth

  • BL width: at least 1mm

Clinical note: Extend the ideal preparation to remove remaining caries 

  • Check for caries using the explorer or spoon excavator

  • Remove remaining caries using the largest round bur that fits into the preparation with rotary instruments (slow speed) or the spoon excavator

 

Bur options: round carbide burs (4, 6)

Smooth the preparation with rotary instruments (high speed with water or slow speed) or hand instruments  

  • Remove unsupported enamel   

  • Remove steps/ledges  

  • Use explorer to examine smoothness

 

Bur options: straight fissure or pear shaped carbide burs (556, 330)

Hand instrument options:  enamel hatchet, enamel hoe

Clean and dry the preparation using the air-water syringe 

​​Examine the preparation and evaluate for proper dimensions

  • Use the explorer to check for smoothness 

  • Use the probe to check for appropriate depth and width

  • Clinical note: The final dimensions of the preparation are determined by the extent of the carious lesion or existing, faulty restoration

 

     

  • Smooth preparation 

  • BL walls occlusally convergent

  • MD and axial walls occlusally divergent  

  • No unsupported enamel

  • Dovetails present

  • Pulpal floor: 1.5mm-2mm depth

  • BL width: at least 1mm

C1 am prep.JPG

*Hover for summary details

Checklist