IADR Abstract Archives
Preliminary Study of Polymerization Shrinkage Gap of Bulk-Fill Resin Composites
Objectives: The trend of clinical failure of bulk-filled restoration is a concern. The objective was to evaluate polymerization shrinkage gap and depth of cure of two flowable bulk-fill composites and one dual-cure bulk-fill composite.
Methods: Two flowable bulk-fill composites, Surefil SDR Flow (SSF, Dentsply), 3M Filtek Bulk Fill Flowable Restorative (FBF, 3M ESPE), and one dual-cure flowable composite (CC Dual, Clinician’s Choice) were used in this study. 3D printed acrylic molds with 4 mm and 5 mm depth square cavities and 5 mm width were used to fill the flowable composites by using bulk-fill technique after applying universal adhesive (MPa Universal, Clinician’s Choice). The adhesive has bonding strength to the acrylic of 16.1 ± 2.7 MPa. The experiment was designed using randomized DOE for 18 runs, with two levels of restorative depth and three levels of light-curing irradiance intensity at 1300, 1000, and 800 mW/cm2 performed with a dental light curing unit (Kerr Demi Plus) for 40 seconds. Each specimen was sectioned longitudinally into 3 parts with four surfaces. Each surface was polished with 1 µm alumina paste and measured with a FESEM for the polymerization shrinkage gap at the bottom interface. The percentage of an interface gap length in relation to the whole interface distance and maximum gap height was calculated and compared. Least squares linear regression was performed to detect the effects of material type, depth, and curing intensity, and the levels were compared by post hoc Tukey test using JMP Pro 15.2.
Results: Shrinkage gap at the bottom of the restoration is shown in Figure 1. Table 1 summarizes the shrinkage gap distance and height. Shrinkage gap distance ratio was significantly impacted by material type (p = 0.007), depth (p = 0.029), and curing intensity (p = 0.016). FBF resin showed significantly higher shrinkage gap length and height than the other bulk-fill materials. The maximum desirability targeting minimized shrinkage gap length and height were determined for CC Dual, 4 mm and 1300 mW/cm2 (Figure 2)
Conclusions: Shrinkage gap at the bottom of the restoration was revealed by an in vitro model. Proper operation parameters, including higher curing energy, lower filling depth, and some types of the composite can minimize or prevent the formation of shrinkage gaps.
Methods: Two flowable bulk-fill composites, Surefil SDR Flow (SSF, Dentsply), 3M Filtek Bulk Fill Flowable Restorative (FBF, 3M ESPE), and one dual-cure flowable composite (CC Dual, Clinician’s Choice) were used in this study. 3D printed acrylic molds with 4 mm and 5 mm depth square cavities and 5 mm width were used to fill the flowable composites by using bulk-fill technique after applying universal adhesive (MPa Universal, Clinician’s Choice). The adhesive has bonding strength to the acrylic of 16.1 ± 2.7 MPa. The experiment was designed using randomized DOE for 18 runs, with two levels of restorative depth and three levels of light-curing irradiance intensity at 1300, 1000, and 800 mW/cm2 performed with a dental light curing unit (Kerr Demi Plus) for 40 seconds. Each specimen was sectioned longitudinally into 3 parts with four surfaces. Each surface was polished with 1 µm alumina paste and measured with a FESEM for the polymerization shrinkage gap at the bottom interface. The percentage of an interface gap length in relation to the whole interface distance and maximum gap height was calculated and compared. Least squares linear regression was performed to detect the effects of material type, depth, and curing intensity, and the levels were compared by post hoc Tukey test using JMP Pro 15.2.
Results: Shrinkage gap at the bottom of the restoration is shown in Figure 1. Table 1 summarizes the shrinkage gap distance and height. Shrinkage gap distance ratio was significantly impacted by material type (p = 0.007), depth (p = 0.029), and curing intensity (p = 0.016). FBF resin showed significantly higher shrinkage gap length and height than the other bulk-fill materials. The maximum desirability targeting minimized shrinkage gap length and height were determined for CC Dual, 4 mm and 1300 mW/cm2 (Figure 2)
Conclusions: Shrinkage gap at the bottom of the restoration was revealed by an in vitro model. Proper operation parameters, including higher curing energy, lower filling depth, and some types of the composite can minimize or prevent the formation of shrinkage gaps.
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