Do Different Durations of Hyperbaric Oxygen Therapy Affect the Microleakage of Bulk-Fill Composites?

This in vitro study evaluated the effect of exposure duration (5, 20, and 40 days) to constant increased ambient pressure (2.4 atmospheres absolute; ATA) on microleakage at the dentin-composite interface of teeth restored with two bulk-fill composites. Specimens stored in distilled water at atmospheric pressure (1 atm) served as controls. A total of 192 extracted human molars with standardized Class V cavities were randomly assigned to two groups: sonic-activated bulk-fill composite (SonicFill) or conventional bulk-fill composite (Filtek One Bulk Fill). Each group was subdivided into controls maintained under atmospheric pressure (1 atm) and specimens under hyperbaric pressure (2.4 ATA), and exposed for 5, 20, or 40 days (total of 12 groups, n = 16 per group). Microleakage was assessed using the dye penetration method and scored under a stereomicroscope according to ISO criteria. Statistical analyses were performed using Fisher's Exact chi-squared and Fisher-Freeman-Halton Exact tests (α = 0.05). No significant differences were found between materials or pressure conditions at 5 and 20 days (p > 0.05). After 40 days, both composites showed significantly higher microleakage at increased pressure than atmospheric controls (p < 0.05). Microleakage increased over time in the hyperbaric groups, while no time-dependent changes occurred at atmospheric pressure. After 40 days, prolonged exposure to elevated pressure increased microleakage, whereas shorter exposure produced no significant changes. Both materials demonstrated similar susceptibility to pressure-related deterioration.