In dentistry, the configuration factor (or c-factor) refers to the number of bonded surfaces in an adhesive dental restoration.
Because adhesive dental restorative material will adhere to the walls of a cavity preparation made available to it during polymerization, competing forces can arise during restoration of the tooth that can have both short and long term effects that correlate to the configuration of the cavity preparation.
Because these materials are adhesive in nature, they bond to the walls of the cavity preparation during curing.
Because the material both shrinks and adheres to the walls and floor of the cavity preparation, competing forces arise that can lead to strain in the material (weaknesses in the final restoration) and subsequent early failure of the restoration, and lack of marginal integrity (small gaps between the restoration and the tooth) resulting in post-operative pain and or sensitivity.
If the restorative material is added to the cavity preparation in one application, this high c-factor will put sufficient stress on the restorative material and increase the likelihood of post-operative pain and sensitivity and early failure.