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Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Page 1: Class I Cavity Preparation for Amalgam [Compatibility Mode]
Page 2: Class I Cavity Preparation for Amalgam [Compatibility Mode]

Class I lesion affects

�The pit and fissures of posterior teethSurfaces involved are:– Occlusal surfaces of premolars & molars– Occlusal 2/3 of the facial & lingual

surfaces of molars� Palatal surfaces of maxillary incisors

Page 3: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Page 4: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Page 5: Class I Cavity Preparation for Amalgam [Compatibility Mode]

CLASS ISIMPLE OCCLUSAL CAVITY(��� $�% �$&'%�( �) *�

Page 6: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Page 7: Class I Cavity Preparation for Amalgam [Compatibility Mode]

Resistance formis obtained by

• Outline placed equidistance from thedefective pits ,fissures on smooth ,soundtooth structure

• Sufficient width to include the defects,• Sufficient width to include the defects,pits & fissures and permit insertion of smallcondenser for placement of amalgam

But otherwise as narrow as possible(preservation of tooth structure)

Page 8: Class I Cavity Preparation for Amalgam [Compatibility Mode]

Extension for prevention

Black suggested that it was necessary to• remove additional tooth structure to gain access

Resistance

• remove additional tooth structure to gain access& visibility

• extend the cavity to self-cleansing areas toAVOID RECURENT CARIES

Black’s cavity width1/3 intercuspal distance

Page 9: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Resistance

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No extension for prevention

Page 10: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Resistance

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Page 11: Class I Cavity Preparation for Amalgam [Compatibility Mode]

� Outline should consist of smoothcurves on occlusal surface

(no sharp line angles)

Resistance

To avoid stress concentration

Page 12: Class I Cavity Preparation for Amalgam [Compatibility Mode]

• Box form (mortis form)* flat floor* definite line & point angles

Resistance

Distribution of force

Page 13: Class I Cavity Preparation for Amalgam [Compatibility Mode]

• Cavosurface margin is 90° butt joint• Remove any undermined enamel (enamel

supported with dentin)

Resistance

Page 14: Class I Cavity Preparation for Amalgam [Compatibility Mode]

• Depth* 0.5mm below DEJ (cavity in dentin)* The whole cavity depth is about

1.5 - 2 mmfrom cavity margin to pulpal floor

Resistance

from cavity margin to pulpal floor

Pulpal floorD

Page 15: Class I Cavity Preparation for Amalgam [Compatibility Mode]

�Minimal extension into the marginalridge (only enough to remove thedefect) without removing dentinalsupport

� Mesial & distal walls* di t l ll ( 10°) t f ll

Resistance

* divergent occlusally(≥≥≥≥ 10°) to followthe direction of enamel rods &prevent undermining of the marginalridge

Page 16: Class I Cavity Preparation for Amalgam [Compatibility Mode]

• Join weekend ridge between twocavities (<0.5 mm apart)

Resistance

Page 17: Class I Cavity Preparation for Amalgam [Compatibility Mode]

Retention formIs obtained through

• Converging Buccal and lingual wallsocclusally (undercut)

• Parallelism of the walls• Griping action of dentin

Page 18: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Retention

Prepared at the line angle betweenfloor of the cavity & its walls with

a ¼ round bur

Page 19: Class I Cavity Preparation for Amalgam [Compatibility Mode]

• (��������� &(���0%)�( + &(0()0��)

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Convenience form

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Page 20: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Infected carious dentin should be removedby:

• Excavators (spoon or discoid)( p )soft caries

• Large carbide Rose head at low speedhard caries

* Until the tooth structure feels hard &firm* lesion is lighter in color

Page 21: Class I Cavity Preparation for Amalgam [Compatibility Mode]

The removal of carious dentin should notaffect resistance form

Create a flat floor peripheralto the excavated area

Page 22: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Page 23: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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Compound class I

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Page 24: Class I Cavity Preparation for Amalgam [Compatibility Mode]

� Occlusal box follows the same principles forclass I simple occlusal cavity

� After preparing the occlusal cavity* #245 bur is held ⊥⊥⊥⊥ to the pulpal floor &

parallel to the long axis of the tooth crown

Cavity preparation

parallel to the long axis of the tooth crown* moved towards the buccal/lingual

direction along the fissure maintaininguniform depth until the bur reaches thebuccal/lingual surface

Page 25: Class I Cavity Preparation for Amalgam [Compatibility Mode]

• The step is prepared keeping the burparallel to the buccal/ lingual surfaceof the corresponding groove

So The axial wall will follow the contour ofthe buccal/lingual surface at athe buccal/lingual surface at auniform depth of 0.5mm inside

the DEJ (0.2mm is permissible)• Axiopulpal line angle is

roundedResistance

Page 26: Class I Cavity Preparation for Amalgam [Compatibility Mode]

• Extend the lingual box gingivally toterminate at the buccal/lingual groovecreating a flat gingival seat for

…………. Resistance• Gingival wall meets the tooth surface at 90°

& the axial wall makes an obtuse angle withthe pulpal floor ……………..Resistance

Page 27: Class I Cavity Preparation for Amalgam [Compatibility Mode]

• Mesial & distal walls of the B/L BOXare made parallel to each other withslight occlusal convergence………………………………..Retention

• Mesial & distal walls are butt joint with thecavity margins………………… Resistancecavity margins………………… Resistance

Page 28: Class I Cavity Preparation for Amalgam [Compatibility Mode]

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