Polymerization shrinkage of light-cured conventional and bulk-fill composites —The effect of cavity depth and post-curing

• Published in: Dental Materials Journal Vol. 42; no. 3; pp. 426 - 432
• Main Authors: AKIYA, Satoshi, SATO, Kento, KIBE, Kouta, TICHY, Antonin, HIRAISHI, Noriko, PRASANSUTTIPORN, Taweesak, HOSAKA, Keiichi, FOXTON, Richard M., SHIMADA, Yasushi, NAKAJIMA, Masatoshi
• Format: Journal Article
• Language: English; Japanese
• Published: Japan The Japanese Society for Dental Materials and Devices 25.05.2023; Japanese Society for Dental Materials and Devices; Japan Science and Technology Agency
• Subjects: Accumulation; Bulk polymerization; Cavity depth; Composite materials; Confocal microscopy; Curing; Diamond pyramid hardness; Holes; Light-curing; Polymerization shrinkage; Post-curing; Resin composite; Scanning microscopy; Thickness; Resin composite; Light-curing; Post-curing; Polymerization shrinkage; Cavity depth
• ISSN: 0287-4547; 1881-1361
• DOI: 10.4012/dmj.2022-210

Volumetric shrinkage (VS) of conventional, bulk-fill, and core build-up resin-based composites (RBCs) of various thickness (1–5 mm) was measured using the modified bonded-disk method with confocal laser scanning microscopy. Additionally, the bottom-to-top ratio of Vickers hardness (%VH) was measured. Conventional RBCs exhibited significantly higher VS than bulk-fill and core build-up RBCs (p<0.05). As specimen thickness increased, VS relative to volume (%VS) and difference in VS at each depth (VSdepth) decreased. For conventional RBCs, there was a significant drop in VSdepth between 1 mm and 2 mm (p<0.05), and another drop was observed between 3 mm and 4 mm (p<0.05) where %VH decreased below 90%. For bulk-fill and core build-up RBCs, VSdepth decreased significantly between 2 mm and 3 mm (p<0.05), but %VH exceeded 90% even in 5 mm deep cavities. These results indicated that post-curing contributed to lower shrinkage in deeper layers, and that conventional RBCs were not adequately polymerized at the depth of over 3 mm.