Biofilm attachment and mineralizing potential of contemporary restorative materials

To evaluate and compare: (1) the effect of the bacterial biofilm on the dentin mineral density at the restoration-tooth interface and (2) the mineralization potential of three resin-based restorative materials (RBRM).

16 extracted human molars free of caries and cracks were collected and stored for disinfection. Each tooth received two standardized Class II preparations with the cervical margin placed in dentin. Teeth were secured into a dentiform with adjacent natural teeth to ensure interproximal contact. All tooth preparations were hybridized using a three-step etch-and-rinse adhesive system (OptiBond FL) and assigned randomly to three experimental groups according to the RBRM (n= 8): Group A - a nanofill resin composite (Filtek Supreme Ultra); Group B - a high-viscosity bulk-fill resin composite (Tetric Powerfill); Group C - a low-viscosity bulk-fill resin composite (SureFil SDR flow+ bulk-fill); and a positive control: Group D - bioactive resin composite (Activa Bioactive-Restorative). All materials were used according to manufacturers' instructions. All specimens were subjected to two distinct challenges: first, thermomechanical cycling was performed within 24 hours of restoring the specimens to simulate 1 year of masticatory function. Subsequently, the specimens were stored for 18 days in a laboratory biofilm model to promote biofilm formation and to mimic the effects of tooth demineralization. Two sessions of micro-CT imaging were conducted: the first immediately after the thermomechanical cycling and the second post-exposure to the biofilm model. All data on mineral profile measurements reconstructed in the Perkin-Elmer Quantum GX-II CT were transferred to Image J software for analysis and interpretation. The ANOVA test (P< 0.05) was used to analyze the mineral density values and mean mineral loss values for each group.

No statistically significant difference in mean mineral loss value (mean ΔZ) was found between the groups (P= 0.209). Regardless, increased mean ΔZ variation was found between SureFil SDR flow+ (-56.95) and the remaining groups, Filtek Supreme Ultra, Tetric Powerfill and Activa Bioactive (-1.17, -1.41, and -7.97, respectively), showing, within the limits of the present laboratory study, the remineralization potential of SureFil SDR flow+. All tested RBRM demonstrated some remineralization capacity under caries risk conditions.

The mineralization potential of some resin-based composites under caries-risk conditions can represent a paradigm shift in restorative material selection for moderate-to-high-risk patients.