Effects of energy drinks on flexural and optical properties of conventional and bulk-fill resin composites: an in vitro swept-source optical coherence tomography (SS-OCT) study

BACKGROUND: Energy drinks are widely consumed acidic beverages that may compromise the longevity of resin composite restorations. Furthermore, limited information is available regarding the application of swept-source optical coherence tomography (SS-OCT) for detecting early beverage-induced alterations in resin composites.This study aimed to evaluate the effects of commercially available energy drinks on the flexural and optical properties of conventional and bulk-fill resin composites. METHODS: A total of 150 specimens were prepared from a conventional nano-hybrid resin composite (Aura Easy, AE) and a bulk-fill nano-hybrid resin composite (Aura Bulk Fill, BF). One hundred rectangular specimens (12 × 2 × 2 mm; n = 10/group) were fabricated for flexural testing, while 50 disc-shaped specimens (10 × 2 mm; n = 5/group) were prepared for optical assessment. Specimens were immersed in Red Bull, Monster, Gatorade, or Extra Joss for 7 days at 37 °C. Control specimens were stored in air for flexural testing and distilled water for optical assessment. Flexural strength and flexural modulus were evaluated using a three-point bending test. Surface and subsurface alterations were qualitatively assessed using SS-OCT. Data were analysed using one-way ANOVA and independent-samples t-tests (α = 0.05). RESULTS: No statistically significant differences in flexural strength or flexural modulus were observed between control and energy drink groups for either composite material (p > 0.05). Flexural strength values ranged from 69.16 to 87.82 MPa, while flexural modulus values ranged from 3.35 to 4.45 GPa. Despite the absence of significant mechanical deterioration, SS-OCT revealed localized increases in backscattered intensity and surface discontinuities in AE specimens immersed in Red Bull, Monster, and Extra Joss, and in BF specimens immersed in Monster and Extra Joss, suggesting early surface degradation and optical alterations. CONCLUSIONS: Short-term exposure to energy drinks did not significantly affect the flexural properties of the tested resin composites. However, qualitative SS-OCT assessment revealed localized optical alterations suggestive of possible surface and subsurface changes that were not reflected by conventional mechanical testing. These findings highlight the potential of SS-OCT as a non-destructive tool for evaluating early material alterations following acidic beverage exposure.