Configuration C- factor
Configuration C- factor
Polymerization shrinkage of resin composite restoratives remains a major impediment to their long-term clinical success
The low-shrinking composite is expected to be associated with better bonding and improved marginal seal-ability as it causes a more uniform stress distribution at the restorative composite-tooth interface.
Internal stress can be reduced in a restoration subject to potentially reduce high disruptive contraction forces by using:
- "soft-start" polymerization instead of high-intensity light curing
- incremental layering to reduce the effects of polymerization shrinkage; and
- a stress-breaking liner, such as filled adhesive, flowable composite, or resin modified glass ionomer
- the application of non or low shrinking restorative materials
- the configuration factor was first introduced by Davidson CL,1986, and later quantitavly extended . in 1987 and refers to the number of bonded surfaces to the number of un-bonded surfaces in a dental restoration . For example, for a class I preparation there would be 5 bonded surfaces and only 1 un-bonded surface; the net result would be a c-factor of 5. With an increasing C factor the developing curing contraction stresses of bonded restorations (resin composites) increases too . The developing curing contraction in a bonded restoration generate stress on the bonded interface that are in competition with the developing bond strength of the setting restorative to the cavity surfaces, which may result in (partial) debonding, marginal leakage and post-operative pain .
Increase in c-factor as in class 1 will increase shrinkage so oblique layering is a method to give more shrinkage control .
In class 3,4 More unbonded surfaces so shrinkage is less and dimensional stability is best .
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