Measurement of polymerization shrinkage in dental composite resins using a multicolor confocal displacement laser

This study aimed to clarify polymerization shrinkage behavior of composite resins (CRs), widely used in clinical dentistry. Shrinkage of 18 CRs (6 paste, 5 flowable, 7 bulk) was measured using a multicolor confocal displacement laser with high precision. The final shrinkage rates and the amounts observed when shrinkage speed became constant were similar among all samples. No differences were found after CR shrinkage reached a constant level. Comparison among groups showed little difference between paste and flowable types (p>0.05), whereas bulk types showed significant differences (p<0.05). Beautifil 2 Ls (Shofu, Kyoto, Japan) exhibited the smallest values in all measurements, likely due to ML-01 as the base monomer. In addition, composites containing glass fibers showed characteristic shrinkage behavior, suggesting that fiber architecture may influence polymerization shrinkage behavior. These findings indicate that both monomer composition and fiber reinforcement may affect polymerization shrinkage behavior in CRs.