techniques of placement of composite in class 1

Techniques of placement of composite in class 1 & class 2 cavity

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

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

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

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

• 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

• 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”

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

Placement techniques

• Incremental techniques– Three increment design– Horizontal layering design– Oblique layering design– U-shaped layering design– Vertical layering design– Successive cusp buildup technique

• 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

• 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

• Figure Schematic representation of wedge-shaped composite increments (1-6) used to build up the enamel proximal surface. F: Facial aspect. L: Lingual aspect.

• 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

• 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

• 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

• 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

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

Stress from polymerization shrinkage is influence by

• restorative technique• modulus of resin elasticity• polymerization rate• cavity configuration or “C-factor.”

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)

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