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A lesion developing on the proximal
surface of posterior teeth
Develops under the contact area because
it is a protected area.
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The lesion is covered on the occlusal side
by sound enamel
Proximally it is protected by the adjacent
tooth
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The least destructive path to make a cavity
in this tooth is through the occlusal enamel
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Class II cavity has two parts
1. Occlusal dovetail
2. Proximal box
Called as MO (mesio-occlusal) or
DO (disto-occlusal) depending on
involved side
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Mark the primary grooves and fossa on the
involved (proximal) half of occlusal
surface
Continue the marking to the marginal ridge
just beyond the contact area into the
buccal and lingual embrassure
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3.0 mm
Width of bur #245 is 0.8 mm
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To make a uniform cutting
To give an idea about the required cutting
1.5 mm
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This gives you the desired shape of the
walls and floors of the cavity preparation
(retention form and resistance form)
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Insert the bur 1.5mm into the tooth in the
central fossa/pit
This gives a sense about the desired depth
It has to be maintained
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Move the bur along the cusps and into the
marked pits and fissuresApply light intermittent pressure to prevent
burning of tooth.
Always keep the bur perpendicular toocclusal table
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The bur is moved at the desired depth up
to mesial fossa or distal fossa(involved
side) and into the buccal and lingual
grooves.
Dont cross the centre unless involved
Dont make the cavity wider than 1-1.5bur thickness.
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With triple syringe(three in one)
Should be done intermittently
To have an idea about the cavity features
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From the class I, extend the bur at the
same depth towards the marginal ridge to
the edge of the proximal contact(dont go
all the way to the proximal surface)
Same should be done for both the buccal
and lingual embrassure(already marked)
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The thin layer of structure is fractured and
removed using a chisel or hatchet(can be done after the next step)
The buccal and lingual wall should clearthe adjacent tooth by 0.5mm( probe just
entering between the two)
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Inside the involved proximal margin (1-1.5
bur thickness) the cavity is extendedgingivally to clear the gingival contact area
by 0.5mm
Keep the bur slanting in the opposite
direction
The gingival floor should follow externalsurface
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Buccal wall(side of 245 bur)
Lingual wall(side of 245 bur)
Gingival floor( base of 245 bur)
Axial wall (side of 245 bur)
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Axial wall
Pulpal floor
gingival floor
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The part joining the proximal box and the
occlusal dove tailIsthmus
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It is an external angle
Should be rounded with hatchet or bur
Can create stresses in restoration which
result in fracture of filling at the isthmus
Axiopulpal line angle
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Axial wall is slanting away from theproximal side ( to provide thick amalgam)
Made by moving the bur gingivally in anarc form
Keep the bur at an angle away from the
involved side
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The gingival floor should not be more than
1-1.5 bur thick
The margin of the gingival floor is alsobeveled with GMT
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Smooth curves all around (free from any
loose, short, or sharp margin)
Definite walls and angles
All pits and fissures be removed(marked)Preparation centered on central
developmental groove
Walls of the proximal box just clearing thecontact area
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Maintain uniform depth(1.50 mm)
The flat pulpal and gingival walls
Definite but round internal and external
anglesEnamel margin( 90-CSA) including the
walls of the proximal box
Smooth curves
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Maintain minimal width
Not more than two bur thickness
Keep a minimal width of gingival floor(1-
1.5 bur thickness)
Beveling of the margin of gingival floor
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1-1.5 bur thickness
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Macro mechanical retention
Slight convergence of the side of bur gives
the required occlusal convergence.
Proximal dislodgement is prevented by
occlusal dovetail and proximal grooves
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The cavity has to be wide enough for easy
manipulation
Make the cavity according to the size of
condensors
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To remove
any minute irregularities in the walls
unsupported enamel from the buccal and
lingual and proximal walls.Bevel the margin of gingival floor
Bevel the axiopulpal line angle
Hold the instrument parallel to the wall or abevel will develop
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I. Outline form:
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Out e o
Extension Properly extended Over extended Under extended
Width 1 -1.5 mm Wide Narrow
Proximal outline 0.5 mm of the contact area Wide Narrow (closed contact)
II. Resistance form:
Pulpal floor 0.5 mm below DEJ Flat Parallel to the occlusal plane
Deep Irregular
Shallow Not parallel to the occlusal plane
Marginal ridge Preserved Undermined
Mesial / distal wall Divergent Convergent
Line angles Rounded Sharp
Axial wall 0.5 mm below DEJ Deep Shallow
Isthmus Properly extended Wide Narrow
III. Retention form:
Buccal & lingual walls Slightly converge Over converge Diverge
Dovetail
Prepared
absent
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Thank you