Microcomputed tomography evaluation of polymerization shrinkage of different bulk fill resin composites

MICROCOMPUTED TOMOGRAPHY EVALUATION OF POLYMERIZATION SHRINKAGE OF DIFFERENT BULK FILL RESIN COMPOSITES Objective: This study aimed to quantify polymerization shrinkage of six bulk-fill composites, under standard and hight light power conditions, in Class I cavity preparations using 3D microcomputed tomography (µCT). Materials and Methods: Preparations 4,2 (±0,5) mm diameter ve 4 (±0,5) mm depth were made in 60 human extracted molars (n=5). Six bulk-fill composites were tested, SonicFill 2 (Kerr Dental, Brea, CA, USA), VisCalor (Voco GmbH, Cuxhaven, Germany), AdmiraFusion Extra (Voco GmbH, Cuxhaven, Germany), Filtek Bulkfill (3M Espe, St.Paul, MN, USA), Fill-Up (Coltene Whaledent, Alstatten, Switzerland) ve GrandioSO Heavy Flow (Voco GmbH, Cuxhaven, Germany). Teeth were divided into six groups according to restorative material used and subdivided into two subgroups, according to the presence of an light-power ( standard light power mode (1000 mW / cm2 ) and high light power mode (1400 mW / cm2 )). Each tooth was scanned three times: (1) after cavity preparation, (2) before and (3) after composite light-curing. Acquired µCT images were imported into 2D and 3D software for analysis. Results: When void ratio after the adaptation of the Bulk-fill resin composites to the cavity were examined, the lowest rate was observed in the VisCalor group and the highest rate was observed in the Fill-Up group. The volumetric polymerization shrinkage are examined, the lowest rate was found in Sonic Fill 2 and the highest rate in AdmiraFusion group when low light power was applied. Sonic Fill 2 group presented the highest volumetric polymerization shrinkage while bulk fill composites were cured with high light power. After curing, AdmiraFusion group showed the highest void ratio among all bulk fill composites in both the high and low light power groups. Significantly different volumetric shrinkage and void between high and standart light power conditions was observed only for Sonic Fill 2 group (p < 0.05), high light power presented significantly higher volumetric shrinkage and void. Conclusions: All bulk-fill resin composites that used in the study show different values from each other when both volumetric polymerization shrinkage and void ratios are considered. The curing with high light power increases the volumetric polymerization shrinkage and void ratio of all resin composites. Keywords: Bulk fill resin composite, polymerization shrinkage, microcomputed tomography, light power