Low-shrinking composites have recently been introduced, but the effect of using them in constrained conditions is still unclear. Objectives: To investigate the effect of curing time and filling method on the micro-tensile bond strength (µTBS) to cavity-bottom dentin in occlusal Class-I cavities. Methods: Two low-shrinking composites (Kalore, GC; N'Durance, Septodont) and a conventional composite (Filtek Z100, 3M-ESPE) were bonded into standardized occlusal Class-I cavities(4.2x4.2x2.5mm) using the one-step self-etch adhesive G-Bond (GC). The cavity was filled in bulk or in 3 separately cured layers. Bulk-filled cavities were cured for 20sec, as recommended by the manufacturer, or for 80 sec. After 1-week water storage, teeth were sectioned to 1x1 mm sticks for µTBS.
Conclusions: Overall, the conventional composite bonded least effective in constrained conditions and bond strength dropped by about 50% when applied and cured in bulk. Low-shrinking composites were less affected, though a combination of increased curing time and layered application consistently revealed the most favourable results.