In dentistry, the configuration factor (also known as c-factor) refers to the number of bonded to unbonded surfaces in a tooth preparation. For instance, in an occlusal class I preparation there would be 5 bonded surfaces and only 1 unbonded surface. The net result would be a C factor of 5. As the C factor increases so too does the possibility of bond disruption when using a composite resin. This effect is caused by a reduction in unbonded surfaces in which the composite can "flow" to relieve polymerization stress.
Internal stresses can be reduced in restorations subject to potentially high disruptive contraction forces by using:
i) "soft-start" polymerization instead of high-intensity of light curing. ii) incremental layering to reduce the effects of polymerization shrinkage; and iii) a stress-breaking liner, such as filled adhesive, flowable composite, or resin-modified glass ionomers.
Roberson, Theodore; Haymann, Harold; Swift, Edward (2002), Sturdevant's Art and science of Operative Dentistry, St. Louis, Missouri: Mosby.
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