In vitro biological response to a light-cured composite when used for cementation of composite inlays.

Objective: To define the cytotoxicity of a photo-cured composite when used as a bonding system under a composite inlay.
Methods: Composite specimens were photo-cured with or without a 2 mm composite inlay interposed between them and the light source. Samples were extracted in complete cell culture medium and the obtained eluates applied to primary cultures of human pulp and gingival fibroblasts. After 72 h of incubation, cell viability was evaluated by MTT assay. Survival rates were calculated with respect to negative controls.
Results: Both shielded and unshielded composite samples were cytotoxic to pulp and gingival cells. The inlay shielded composite samples reached a significantly higher level of cytotoxicity compared to the unshielded ones.
Significance: The results suggested that the cytotoxicity of a light-cured composite resin used as a bonding system for indirect composite restorations may be significantly increased as a result of an inlay light-shielding effect.