Is there correlation between polymerization shrinkage, gap formation, and void in bulk fill composites? A μCT study

Abstract

This in vitro study aimed to evaluate the volume ofpolymerization shrinkage (VS), gap (VG), and void (VV) usingcomputerized microtomography (μCT) in bulk fill resin compositesand conventional class I restorations, and to establish a correlationbetween these factors. Class I cavities (4 x 5 x 4 mm), C-factor = 4.2, wereperformed on caries-free human third molars and randomly dividedinto five groups (n = 6): FSI (Filtek Supreme XTE incremental insertion);FSS [(Filtek Supreme XTE single insertion(SI)]; TBF [(Tetric Bulk Fill:SI and manual filling (MF)]; SFM (Sonic Fill: SI/MF); and SFS (SonicFill:SI and sonic filling). The teeth were scanned and analyzed by μCT at T0,after filling the cavity with resin, and at T1, after polymerization for VGand VV, and for VS (T1-T0). There was statistically significant differencein VS in μCT for the FSI and FSS groups and between SFS and FSS aswell as some difference in VV for FSI and bulk fill resin compositesand no difference in VG between the conventional technique and bulkfill composites. Bulk fill resin composites presented similar VS andgap formation to those of incrementally inserted conventional resincomposites. There is a moderate and weak positive correlation betweenpolymerization shrinkage and gap formation and void, respectively.The final gap formation was more dependent on the initial gap than onpolymerization shrinkage or void volume