Influence Of Bulk-fill Resin-based Composite On Internal Adaption In Class ? And Class ? Restorations&Case Reports

Objectives To investigate the effects of resin-based composites(high or low viscosity bulk-fill resin-based composites and traditional resin-based composites)and cavity classification(class ? and class ?)on internal adaption of the cavities.Methods 84 extracted sound human third molars were collected and 56 of them followed root canal treatment.A class ? cavity(4x4x4 mm)was prepared in the occlusal surface of each endodontically treated tooth.For the remaining 28 teeth,2 class ? cavites(2x3x4 mm)were prepared on mesial and distal surfaces of each third molar.Class I and ? cavities were both randomly divided into 7 groups(n=8),cavities were filled with 2 low viscosity bulk-fill resin-based composites,3 high viscosity bulk-fill resin-based composites or 2 traditional resin-based composites,separately.Acoustic emission(AE)symbols were registered from the starting of light-curing of resin-based composites and lasted for 1000 s.The percentage of microleakage formation(M%)were detected by optical coherence tomography(OCT).Data of internal adaptation procured from AE and OCT were statistically analyzed using one-way analysis of variance(ANOVA)and the effects of resin-based composite type and cavity classification were analyzed by two-way ANOVA.Result For both class ? and class ? restorations,2 low viscosity bulk-fill resin-based composites presented significantly less AE events and lower microleakage formation(p<0.05)compared with other resin-based composites.Two-way ANOVA showed that composite type and cavity classification both significantly influenced internal adaption(p<0.05).Pearson correlation coefficient between AE signals and OCT results was 0.913(p<0.05).Conclusion The low-viscosity bulk-fill resin-based composites demonstrated better internal adaptation both in class ? and class ? cavities.AE and OCT can be combined to detect the marginal adaptation of resin-based composite restoraitons.Clinical significance In class ? and class ? cavities,low-viscosity bulk-fill resin composites with a favorable internal adaptation are recommended.