Abstract
The purpose of this study was to investigate the polymerization shrinkage of short fiber reinforced composite (SFRC) using a multicolor confocal displacement laser that can measure the polymerization shrinkage with high accuracy. The three types of SFRCs used in this study were XD (Ever X Flow Dentin), XB (Ever X Flow Bulk), and XP (EverX Posterior). In addition, CF (Clearfil majesty ES Flow) with hybrid type filler was used as a control. The measured values of the final polymerization shrinkage rate and amount of polymerization shrinkage rate when the polymerization shrinkage rate became constant (less than 0.1 µm/s) were approximated for all SFRCs. XP had a large aspect ratio of glass fiber filler and showed a significant difference from XD with a small aspect ratio (p < 0.05). There was no significant difference in the measured value of time when the polymerization contraction reached a constant speed (0.1 µm/s or less) for all SFRCs (p > 0.05). There was no significant difference in the measured values of polymerization shrinkage rate after the polymerization shrinkage reached a constant rate for all SFRCs (p > 0.05). These results show that glass fiber with large aspect ratio can alleviate polymerization shrinkage stress. The polymerization behavior of SFRC was found to be dependent on the amount of glass fiber filler, aspect ratio, and orientation.
Highlights
Dental composite resins (CR) are widely used in restorative dentistry, because they allow us to restore teeth aesthetically while preserving healthy tooth substances using an adhesive system [1,2,3,4,5,6,7,8,9]
In the final polymerization shrinkage rate, XP showed the smallest value of −1.52%, and XD showed the largest value of −2.58%, indicating a significant difference between XP and XD (p < 0.05)
In this study, using a multicolor confocal laser displacement meter, it was found that the polymerization behavior of short fiber reinforced composite (SFRC) depended on the aspect ratio, the amount of glass fiber filler, and the orientation of the glass fiber filler
Summary
Dental composite resins (CR) are widely used in restorative dentistry, because they allow us to restore teeth aesthetically while preserving healthy tooth substances using an adhesive system [1,2,3,4,5,6,7,8,9]. Polymerization shrinkage is an unavoidable problem in CR restorations If this shrinkage forms a gap between the CR and cavity, it might cause secondary caries [3,10,11]. Compared with conventional CR, flowable composite resin has less polymerization shrinkage stress and less gaps, but its instrumental properties are small. These properties have been improved by varying the size of the filler or increasing the filling ratio of the granular filler [9,22,23]. Lippo L et al reported improved mechanical performance when used in a continuous fiber filler polymer matrix at different length scales compared to conventional CR [24,25,26]. Proper measurement of polymerization shrinkage and clarification of the behavior of polymerization shrinkage are clinically important and have been the subject of various studies
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