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Techniques of placement of composite in class 1 & class 2 cavity
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Instrument used for insertion
1. Hand instrument• Advantage
– Most popular method– Easy and fast
• Disadvantage– Air can be trapped in the tooth preparation or into the
material during the insertion procedure• Teflon coated intruments can also be used
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2. Syringe• Advantage
– A convenient means for transporting the composite to the preparation
– Reduces possibility of trapping air• Disadvantage
– Problem in small preparation with limited access• Manufacturers provides
– Preloaded syringe– Disposable needles to apply composite directly at the
surface
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3. Guns– Guns with ampules of composite are also available
supply In various sizes and shapes– Guns are used for viscous composites and syringes
for flowable composites
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Placement of composite• After the process of etching and bonding is completed, and matrix
is stabilized ,the restoration is initiated keeping in mind the volume of the cavity
• The volume of the cavity will dictate the number and location of the increments and the future stress bearing areas will dictate the operator to use particular type of composite
• The cavity for composite is always restored in increments to reduce the effects of polymerization shrinkage
• Increments can be placed in variety of designs
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• Thickness of the increment - 1-2 mm
• Each increments is cured for 15-20secs(per manufacturers instructions) before placing the next increment over it
• A hand instrument is used to adapt the composite to the preparation after placement of each increment
• The light tip is kept as close to the material as possible
• Use of bonding agent in between the increment, is not required since partially cured increments unite of their own
• A few authors advocate use of bonding agent after the last increment to have the better marginal adaptibility
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• The preparation is filled to slight excess so that positive pressure can be applied by the matrix
• Before the matrix strip is closed ,any gross excess is removed with hand intrument
• The matrix is closed and secured ,and the composite is cured
• Few authors believed that partial curing of increments would lead to better adaptation of each increment. This process is known as “soft start polymerization”
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soft-start” polymerization
• “soft-start” polymerization – The initial increments are cured for 10secs before placing
the next over the previous one– composite exhibited improved physical properties when
cured at a low intensity and with slow polymerization vs. higher intensity and faster polymerization
• initially uses low-intensity curing – for a short period to provide sufficient network formation
on the top composite surface
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Placement techniques
• Incremental techniques– Three increment design– Horizontal layering design– Oblique layering design– U-shaped layering design– Vertical layering design– Successive cusp buildup technique
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• Three increment desing– One flat increment at gingival and pulpal and two oblique
increments at proximal and occlusal box
– Simple and accepted design
– Curing done from both labial/lingual and the occlusal sides
– The first increment is always cured from the sides first rather from the occlusal end
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• Horizontal layering design• Small increment placed horizontally one above the other starting from the gingival
wall to occlusal end
• The layers can be 3,4 or 5 depending upon the the depth of proximal box
• Oblique layering design• Each increment is placed obliquely starting from any side i.e, buccal or lingual
• wedge-shaped composite increments
• prevent distortion of cavity walls and reduce the C-factor
• Curing is done from all three side i.e, sides and occlusal
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• Figure Schematic representation of wedge-shaped composite increments (1-6) used to build up the enamel proximal surface. F: Facial aspect. L: Lingual aspect.
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• U-shaped layering design– At the base, both occlusal and gingival, U-shaped
increment is placed and over that horizontal and oblique increments are placed
– Curing is carried out as in routine from all sides
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• Vertical layering design– The increments are placed in vertical fashion starting
from one wall i.e, buccal or lingual and carried on to other wall in small increments
– Curing started from behind the wall i.e, if first increment is placed in buccal wall, it is cured from outside the buccal wall
– Advantage – Reducing the gap at gingival wall created due to polymerization
shrinkage– Minimizing chances of post operative sensitivity and secondary
caries
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• Successive cusp buildup technique– the first composite increment is applied to a single
dentin surface without contacting the opposing cavity walls
– And then wedge-shaped composite increments – Each cusp then is built up separately– to minimize the C-factor in 3-D cavity preparations
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• Figure 2. Schematic representation of the flowable composite increment (1) and wedge-shaped increments (2-7) used to build up dentin;two increments (8 and 9) are used to build up enamel using the successive cusp buildup technique. F: Facial aspect. L: Lingual aspect
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Polymerization shrinkage
• formation of a gap between resin-based composite and the cavity wall
• 1.67 to 5.68 percent of the total volume
• postoperative sensitivity and recurrent caries
• bonding failure
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Stress from polymerization shrinkage is influence by
• restorative technique• modulus of resin elasticity• polymerization rate• cavity configuration or “C-factor.”
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C-factor
• ratio between bonded and unbonded surfaces• an increase in this ratio results in increased
polymerization stress -Three-dimensional cavity preparations (Class I) have the highest (most
unfavorable)
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To minimize the stress from polymerization shrinkage
• improving placement techniques– placing successive layers of wedge-shaped composite(1- to
1.5-mm) to decrease the C-factor
• improving material and composite formulation– select different composite materials to restore dentin
(flowables and microhybrids) and enamel (microhybrids)
• curing methods “soft-start” polymerization