Class 2 composite bulk filling will satisfy the c factor rule but depth of curing light is only 2mm, so by bulk filling 4mm gingival depth class 2 cavity will leave an un cured composite will affect the strength of the restoration
C factor is not the only thing tat warrants incremental buildup....Thickness of restoration,area covered also affects the curing and warrants incremental buildup I think there are so many things about composites that make it a headache for clinicians coz its super technique sensitive.... These things are improving of crse...still long way to go...
Twenty seconds is mandatory. If you are using very high intensity light curing, composite might get cured in five seconds, but the chances for bond failure is more. I prefer to use moderate intensity light curing unit and curing for twenty seconds per increment and a final cure after finishing the restoration for forty seconds
Adhesive Dentistry and Endodontics: Materials, Clinical Strategies and Procedures for Restoration of Access Cavities: A Review Richard S. Schwartz DDS, Ron Fransman DDS, in Journal of Endodontics, 2005 The problem with polymerization shrinkage is amplified in access cavities because of a concept known as C-factor or configuration factor (43, 167). C-factor refers to the ratio of bonded surfaces to free or unbonded surfaces. The higher the C-factor, the greater the stress from polymerization shrinkage (43). Restorations with C-factor higher than 3:1 are considered to be at risk for debonding and microleakage (170). In a class 5 restoration, the ratio might be 1:1. In an access cavity, the C-factor might be 6:1 or even 10:1. In a root canal system obturated with a bonded resin material, it might be 100:1 Kindly read the above article. In root canal...we should use resin with less shrinkage and minimal resin volume....
