Configuration factor

In dentistry, the configuration factor was first introduced by Davidson CL,1986, and later quantitavly extended Feilzer et al. 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 (Feilzer et al. 1987). 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 (Davidson et al. 1984).

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 ionomers
• the application of non or low shrinking restorative materials