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 less than .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.