Injectafil is a dual cure composite offered by Apex Dental Materials. As it chemically cures it releases the polymerization stress which is a big cause of sensitivity or even fracture in high “C” factor preps (all class 1's and those with tall, thin cusps). If you allow it to reach the gel stage most of that stress will be released. It's really not wear resistant enough to withstand occlusal forces (except for pediatrics) so you need to top layer it with a paste composite. In this case I'm replacing a couple of deep occlusal amalgams.
This is a great use of Injectafil. It replaces additional layering of your paste composite and letting it gel before adding light allows it to release it's shrinkage stress to protect these high “C” factor preps and tall weak cusps from curing damage. Just top layer it over with your paste composite and you'll have a great long lasting restoration without those stress/sensitivity issues. Hope this helps.