Abstract
This in vitro study aimed to evaluate the volume of polymerization shrinkage (VS), gap (VG), and void (VV) using computerized microtomography (μCT) in bulk fill resin composites and conventional class I restorations, and to establish a correlation between these factors. Class I cavities (4 x 5 x 4 mm), C-factor = 4.2, were performed on caries-free human third molars and randomly divided into 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 VG and VV, and for VS (T1-T0). There was statistically significant difference in VS in μCT for the FSI and FSS groups and between SFS and FSS as well as some difference in VV for FSI and bulk fill resin composites and no difference in VG between the conventional technique and bulk fill composites. Bulk fill resin composites presented similar VS and gap formation to those of incrementally inserted conventional resin composites. There is a moderate and weak positive correlation between polymerization shrinkage and gap formation and void, respectively. The final gap formation was more dependent on the initial gap than on polymerization shrinkage or void volume.
Highlights
MethodologyThis study was approved by the local Human Research Ethics Committee (process no. 1708531)
Volume of polymerization shrinkage (VS) Unlike the evaluation of the volume of gap (VG) and void (VV), the analysis of volumetric polymerization shrinkage (VS) took into account the difference in the volume of Resin composite (RC) in each time period (T1-T0) as that represents the shrinkage of the studied material
Volume of gap (VG) Gap volume was measured at nine different points from the pulp wall to the restoration (Figure 2), and the sum of these points determined the total volume of gap per tooth at two different moments: VG0 and VG1
Summary
This study was approved by the local Human Research Ethics Committee (process no. 1708531). Bis-EMA: Bisphenol-A polyethylene glycol diether dimethacrylate; Bis-GMA: Bisphenol-A diglycidyl ether dimethacrylate; EBPDMA: Ethoxylated Bisphenol-A-dimethacrylate; TEGDMA: Triethylene glycol dimethacrylate; PEGDMA: polyethylene glycol dimethacrylate; UDMA: Urethane dimethacrylate, MPS: 3-(trimethoxysilyl) propyl methacrylate; HEMA: 2-Hydroxyethyl methacrylate; II: Incremental insertion; SI: single insertion; MF: manual filling; SF: sonic filling. The images were standardized using the DataViewer (V.1.5.2.4) software and the analyses were performed through the 3D analysis tool from CTAn (CT-Analyser software v1.10.1.0; Skyscan, Kontich, Belgium) based on the volume of black spaces (void spaces) present in the volume of interest (VOI), which consisted of the summation of all 2D images within the region of interest (ROI). Statistical analysis The Shapiro-Wilk test indicated that, among the three evaluated outcomes, polymerization shrinkage and void values were not normally distributed These data were analyzed using the Kruskal-Wallis test, followed by Dunn’s post-hoc test. The significance level was set as p < 0.05
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