Relationship among visible light source, composite resin polymerization shrinkage, and hygroscopic expansion

Composite resins contract during polymerization, and studies have shown that light-cured composite resins shrink toward the polymerizing light source. The purpose of this study was to investigate differences in the adaptation of composite resin to the axial wall in Class V restorations following light curing from the lingual or facial aspects. Polymerization contraction in relation to hygroscopic expansion of the restoration was also investigated. Results showed no statistically significant differences P <. 05) in the adaptation of composite resin to the axial wall, regardless of the polymerization technique, the composite resin, or the effects of hygroscopic expansion.