2. Introduction:
The use of the composite materials to restore
form and function of posterior teeth damaged
by disease, age or trauma is gaining wide
acceptance by the dental community.
3. Indication of posterior
composites restoration
Small to moderate sized lesions in
posterior teeth.
Incipient lesions.
In premolars and first molars where
esthetics is the main concern.
Core build up
When moisture control of operating
site is possible.
4. When tooth being restored,
experience normal occlusal
stresses.
Patient with low caries risk.
Occlusal contact(s) on enamel
may be considered desirable and,
ideally,
all cavity margins should be in
enamel.
Indications cont.
5. Contraindications for Use of Posterior
Composite Restorations:
difficulty to achieve moisture control.
When large lesion is present extending onto
the root surface.
In patients with high caries risk and poor oral
hygiene.
High occlussal stresses as in patients with
para-functional habits like clenching and
bruxism.
6. Advantages of Posterior Composite
Restoration
• Good esthetics.
• Conservation of tooth structure
• Low thermal conductivity
• bonding benefits.
• cheap when compared to
indirect restorations.
• no galvanism.
• Repairable.
8. Disadvantages cont.
• Composite has not been shown
to release therapeutic levels of
fluoride.
• When compared with amalgam ,
Amalgam is more bactericidal
than composite and tends to
accumulate less decay.
10. Polymerization shrinkage
can result in:
Postoperative sensitivity
Recurrent caries
Failure of interfacial
bonding
Fracture of restoration
and tooth
11. Some of the strategies to reduce
Polymerizations Shrinkage:
C.factor
Altering Composite formulations
Incremental layering technique
Light curing procedures
Stress absorbing layers with low elastic modulus
Incorporation of macro-fillers (eg. ready made inserts) to
reduce the overall volume of composite
Preheating composites.
13. Configuration or C-factor
the ratio of bonded surface of the
restoration to the unbonded surfaces.
C-factor is internal surface area versus
external surface area.
14.
15.
16.
17. • the higher the value of ‘C’-
factor, the greater is the
polymerization shrinkage
• Realistically a number of 2 or
above is a problem when it
comes to performance of the
composite.
20. Incremental Layering Technique:
• The bonded/unbonded ratio would be
reduced and, consequently, the stress level
within the cavity might be reduced.
• Reduce volume being cured
• to facilitate proper light-activation
• development of correct anatomy.
21. Three variations
of the basic oblique-layering technique
are
described:
Successive cusp build-up
Separate dentine and enamel build-up
Separate dentine and enamel build-up
using an index.
32. The protocol proposed for
posterior reconstruction is:
1.Diagnostic and initial occlusal
check
2.Isolation and pre-wedging
3.Cavity preparation and cavity
finishing
4.Proximal reconstruction and
occlusal layering
5.Straining (Optional) and finishing
6.Polishing and final occlusal check
35. 3.Cavity preparation and cavity finishing
The main aims of
preparation
• Access should be
limited to that required
to visualize and remove
carious tooth tissue
and/or any previous
restoration
• permit access for
instruments
36. C o m p a r i s o n b e t w e e n a m a l g a m
& c o m p o s i t e c a v i t y f e a t u r e s
37. C o m p a r i s o n b e t w e e n a m a l g a m
& c o m p o s i t e c a v i t y
f e a t u r e s ( c o n t i n u e d )
The use of direct composite has been shown to be effective for the immediate treatment of painful, cracked teeth. The validity of this form of treatment and the need to provide cuspal coverage is the subject of debate and merits further investigation
Smear layer
when the monomer converts to the polymer produces a volume reduction in the polymer with a resulting decreased intermolecular distances the composite resin contracts by about 1.5% to 6%. When the gel point is reached, the material flows from unbound surfaces to accommodate for shrinkage ,As the composite resin becomes more rigid because of the increasing modulus of the composite, flow stops and the bonded composite resin transmits shrinkage stresses generated to the surrounding tooth. Shrinkage direction
Photoinitiator Systems: Changes in the photoinitiator
systems and polymerization inhibitors have also been
reported. It was shown that increased inhibitor
concentrations reduced the rate of polymerization and the
shrinkage stress without significantly compromising the
final degree of conversion [15]. It was found that
phenylpropanedione, substituting for part of the
The shrinkage can be measured as either volume or linearly. On a linear basis, most direct composites shrink 2% to 5%. All composites shrink on polymerization at this point, but the way the composite shrinks is critical and is based on the C-factor. The shape of the cavity preparation, the number of opposing walls, how they oppose one another, and the angle at which they oppose one another are extremely critical to the behavior of composite shrinkage.
The shape of the cavity preparation (Flat smooth flow surfaces and shallow cavities represent the most favorable conditions)
reduce the number of opposing walls
Increase the angle at which they oppose one another (saucer shaped) rounded line angles (obtuse)
Curing Charecteristics: These techniques of curing
provide an initial low rate of polymerization thereby
extending the time available for stress relaxation before
reaching the gel point.
Soft Start Polymerization:
This involves 100mW/cm for because they can chemically copolymerize with the 2
10 seconds followed by immediate radiance at an intensity
of 600mW/cm for 30 seconds [22]. 2
Pulse Delay Polymerization: In this method the clinician
apply the initial exposure with reduced light radiance for
a very short period of time (Seconds or minutes) and fully
radiate later.
Ramped Curing:
The intensity is gradually increased or
ramped up during the exposure. This ramping consists of
Delayed Curing: The restoration is initially cured at low
intensity. Then the restoration is contoured to the correct
occlusion and later applies the final cure. This delay
allows substantial relaxation to take place. Longer the time
period available for relaxation, the lower the shrinkage
stress.
Sited Light Curing or Transenamel Curing:
It has been
postulated that contraction takes place towards the
light source in light curing composites. To guide the
shrinkage towards the cavity walls, 3 sited light
curing has been developed. In this technique using
the light transmitting wedges, the composite is curd
from the buccal and lingual walls in addition to occlusal
[22, 24].
stepwise, linear or exponential modes [23].
side. But the efficacy of the technique is yet to be proved
Incremental Layering Technique: It is widelyaccepted incremental filling decreases shrinkage stressas a result of reduced polymerization material volume. Each increment is compensated by the next, and the
consequence of polymerization shrinkage is less
damaging since only the volume reduction of the last
layer can damage the bond surface. Theoretically, if an
infinite number of increments were used, the magnitude
of polymerization shrinkage would be insignificant [19].
The following are the best known techniques:
Here individual cusps are restored one at a time up to the level of the occlusal enamel. Small sloping increments are applied to each corner of the cavity in turn and manipulation is kept to a minimum, to avoid folding voids into the material. This method, while initially time consuming,
can greatly reduce finishing time by careful attention to progressive reconstruction of natural morphology.
Here sloping increments are again applied to cavity walls (and cured in turn) but only to the level of the amelo-dentinal junction (ADJ) occlusally (Figure 28). Final ‘enamel’ increments are then applied. Careful control of the final layer will again reduce the finishing stage.8,11 Some operators (if agreeable to the patient) place composite pit and fissure stain before placement of the final layer.8 An alternative method of achieving a more natural appearance is to use a dark (eg A4) shade of composite for the bulk of the restoration and a translucent or light shade for the ‘enamel’ increment(s).
Teflon coating
Bulk fill ORMOCER (“organically modified ceramics”)
Bulk Technique: The bulk technique reduces stress at
the cavosurface margins. Here the adhesive, flowable
composite are placed into the preparation in bulk and the
polymerized by curing through the tooth from the buccal
and lingual (Fig 2).
Use of flowable composites as a
lining is the subject of divided opinion.2,5,11,13
It is suggested that a flowable resin with
a lower modulus of elasticity may act as
a stress relaxation buffer,13 deforming to
absorb the tension stress of the overlying
composite,38 during polymerization and postcure.
Use of flowables has also been
advocated to improve composite adaptation
to the cavity.
If a decision is made to use
it, then a thin, uniform layer of maximum
0.5mm thickness is applied to the dentine.
Lighter shades may be employed as these
will cure more easily.10,11 It is applied to boxes
first and any air bubbles are popped with a
probe, before curing (Figure 26).
In this respect, flowable
composites may be best suited for
restoring small cavities in preventive resin
restorations39 (see Figure 2) and for sealing
narrow marginal defects when repairing
existing restorations.
Flowable composites from
different manufacturers show a wide
variation in formulation and offer different
Stress Absorbing Layers with Low Elastic
the shrinkage stress generated by a subsequent
layer of high modulus resin composite can be
absorbed by an elastic intermediary layer,
thereby reducing the stress at the tooth – restoration
interface manifested clinically as a reduction in cuspal
deflection.
Modulus: According to “elastic bonding concept”
Bases and linings
Glass ionomer, resin modified
glass ionomer and chemically cured
composite may also be used as part of
an open or closed ‘sandwich’ restorative
protocol.
Closed sandwich
Here a resin-modified glass
ionomer (RMGI) lining, eg Vitrebond (3M St
Paul, MN, USA), is placed over pulpal dentine
prior to etching. This will adhere to the
prepared cavity floor and may help to protect
the pulp by sealing deep dentine in an area
where bond strengths may be diminished.4
This, in turn, may lead to a reduction in postoperative sensitivity.1,4,6,11 Vitrebond may also
be used to protect calcium hydroxide pulp
caps from etchant, but should be confined
to as small an area of dentine as is practical
and must be kept well clear of cavity margins,
where it will dissolve over time.
Open sandwich
Here a glass ionomer, RMGI
or chemically cured composite is placed
over the dentine and into the cervical part
of a box. In this respect, the longevity of
restorations has been reported to be reduced
by the use of ‘elastic’ linings and base
layers.21 Potential benefits must be weighed
against reported increased fracture rates of
restorations overlying such ‘shock absorbing’
layers.
(eg ready
made inserts) to reduce the overall volume of
Composite divided into
those with and those without preparation instruments in combination with matching standardized inserts.
Preheating:
method to increase composite flow, Improve marginal adaptation and monomer conversion
has been proved. The benefits of with the application of shorter light exposure to
provide conversion values similar to those seen in
unheated condition. Increased temperature decreases
system viscosity and enhances radical mobility, resulting
in additional polymerization and higher degree
conversion. The collision frequency of unreacted active
groups and radicals could increases with elevated curing
temperature
Pre-wedging is very important and useful because
1. protect the proximal rubber to be broken during the cavity preparation
2. push the rubber and the gingiva more apically
3. separate the teeth so the proximal preparation is easier
4- guide to avoid overextension
of the gingival floor.
Smear layer diamond bur no carbide CHX disinfection
One of the most important steps in restoring Class II . In contrast to amalgam, which can be condensed to improve the proximal contact