Class III Resin Composite Preparation
#8 ML
Overview
Outline Form
Resistance Form
Retention Form
Convenience Form
Armamentarium
Instruments and Materials
Video Demonstration
Procedure
Select the appropriate resin composite shade using the shade-matching guide or clinical judgement
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Clinical note: Perform shade selection with natural light prior to isolation of the tooth
Envision the cavity preparation outline and extent​
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Clinical notes:
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Preparation measurements are determined by the extent of the carious lesion or existing, faulty restoration
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Class III procedure is performed when caries extends past enamel into dentin. Therefore, the mesial-distal width of the preparation will be at least 0.2 mm into dentin
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*Radiographic caries superimposed on preparation
Optional: Draw the outline of the cavity preparation using the red-blue pencil​
Obtain isolation of the tooth (e.g. rubber dam, isovac/isolite, etc.)
Position the mirror to achieve indirect vision of the preparation
Place a wedge in between the adjacent teeth to separate the contact areas
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Optional: Place a matrix band interproximally to protect the adjacent tooth from iatrogenic damage
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Orient the bur perpendicular to the lingual surface of the tooth, close to but without touching the adjacent tooth ​
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Clinical note: Position the bur over the carious lesion or existing, faulty restoration
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Bur options: pear shaped carbide bur (330)
Penetrate the tooth to an initial facio-lingual depth of 1mm-1.5mm
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Extend the preparation inciso-gingivally and mesial-distally
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Facial wall is at least 90º relative to the axial wall
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Optional:
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​Leave a small "enamel shell" interproximally
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Break the enamel shell with a hand instrument​
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Clinical note:
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Extension should remove the carious lesion or existing, faulty restoration
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Hand instrument options: enamel hatchet, enamel hoe
Use the probe to check for appropriate dimensions
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Inciso-gingival length: 2-2.5mm, no greater than 3mm, depending on the length of the contact
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Gingival floor width: 1-1.25mm
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Incisal floor width: 1.25-1.5mm
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Clinical note: The final preparation dimensions are determined by the extent of the carious lesion or existing, faulty restoration
Clinical note: Check for and remove remaining caries ​
- Assess for remaining caries using the explorer or spoon excavator
- Remove remaining carious tooth structure using the largest round bur that fits into the preparation with rotary instruments (slow speed) or a spoon excavator
Bur options: round carbide burs (4, 6)
Round internal line angles using rotary instruments (high speed with water or slow speed)​
Bur options: pear shaped carbide bur (330)
Smooth the preparation with rotary instruments (high speed with water OR slow speed) or hand instruments 
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Remove major unsupported enamel 
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Remove steps/ledges
Bur options: straight fissure or pear shaped carbide (556, 330)
Hand instrument options: enamel hatchet, enamel hoe
Create a 0.25mm-0.5mm bevel circumferentially around the preparation, orienting the bur with rotary instruments (high speed with water or slow speed) at a 45-degree angle to the cavosurface margin
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Do not bevel in areas subject to masticatory forces (e.g. incisal contact)
Bur options: coarse diamond bur (flame)
Clean and dry the preparation using the air-water syringe
Examine the preparation and evaluate for proper dimensions
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Use the explorer to check for smoothness
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Use the probe to check for appropriate depth and width
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Clinical note: the final dimensions of the preparation are determined by the extent of the carious lesion or existing, faulty restoration
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​Axial wall: flat or slightly convex
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Facial wall: at least 90º relative to the axial wall
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Facial depth: depends on the facio-lingual depth of the contact area
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Preserve the facial contact​
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Gingival floor width: 1-1.25mm
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Incisal floor width: 1.25-1.5mm
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Inciso-gingival length: 2-2.5mm, no greater than 3mm
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Depends on length of contact area​
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Preserve the incisal contact
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Gingival contacts broken by: ~0.25mm
*Hover for summary details
Checklist