Comparative evaluation of effective curing depth and degree of polymerization of different flowable bulk fill composites: An in vitro study.

BACKGROUND

Adequate polymerization of resin-based composites is essential for the clinical success of restorative procedures. Depth of cure (DOC) and degree of conversion (DC) directly influence the mechanical properties, marginal integrity, wear resistance, and biocompatibility of composite restorations. Bulk-fill flowable composites permit placement in increments of up to 4 mm, reducing clinical time. Recently introduced single-shade flowable bulk-fill composites claim improved optical blending and simplified shade selection; however, comparative evidence regarding their polymerization efficiency remains limited.

AIM: To compare the DOC and DC of a single-shade flowable bulk-fill composite with two conventional flowable bulk-fill composites at a 4-mm increment.

METHODOLOGY: Thirty-six cylindrical specimens (4 mm × 6 mm) were prepared and divided into three groups (n = 12): Charisma Bulk Flow ONE, Beautifil Bulk Flowable, and SDR Flow Plus. Specimens were light-cured using an LED curing unit and stored at 37°C for 24 h. DOC was assessed using Vickers microhardness testing at top and bottom surfaces, and bottom-to-top hardness ratios (HRs) were calculated. DC (%) was evaluated using Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR). Statistical analysis was performed using one-way analysis of variance and Tukey's post hoc test (P < 0.05).

RESULTS

Beautifil Bulk Flowable demonstrated the highest DOC and DC, followed by SDR Flow Plus and Charisma Bulk Flow ONE. Charisma Bulk Flow ONE failed to achieve the clinically acceptable HR of ≥ 0.80. Significant differences were observed among all groups (P < 0.05).

CONCLUSION

Polymerization efficiency was material dependent. Conventional flowable bulk-fill composites showed superior curing behavior compared to the single-shade flowable bulk-fill composite.