Bonding of low-shrinking composites in high C-factor cavities.

OBJECTIVES

Polymerization shrinkage causes stress at the tooth-restoration interface. The magnitude of the stress depends upon several factors, such as the configuration factor (C-factor) of the cavity, the polymerization-conversion rate and filling technique. The aim of this study was to investigate the effect of curing time and filling method when high C-factor cavities were filled with low-shrinking composites.

METHODS

Three low-shrinking (Filtek Silorane, 3M ESPE: FS; N'Durance, Septodont: N'D; Kalore, GC: Ka) and one conventional composite (Z100, 3M ESPE) were bonded into standardized occlusal Class-I cavities using either a two-step self-etch adhesive (Silorane System Adhesive, 3M ESPE: SSA) or a one-step self-etch adhesive (G-Bond, GC: GB). Five experimental groups were formed according to the employed adhesive/composite combination (SSA/FS, SSA/Z100, GB/N'D, GB/Ka, GB/Z100), and further divided into three subgroups conforming to curing time and filling technique (20 s/bulk; 80 s/bulk; 80 s/layered). For each subgroup, non-trimmed 1 mm×1 mm sticks were prepared from five teeth to measure the micro-tensile bond strength (μTBS) to cavity-bottom dentine.

RESULTS

The two-step self-etch adhesive SSA generated higher bond strengths than the one-step self-etch adhesive GB, irrespective of the filling method. When GB was used, bulk filling with a low-shrinking composite revealed the highest bond strengths. For all composites, the layering method provided the highest bond strengths.

SIGNIFICANCE

The two-step self-etch adhesive Silorane System Adhesive (3M ESPE) performed better than the one-step self-etch adhesive G-Bond (GC), regardless of the composite used. When the latter all-in-one adhesive was used, effects of shrinkage stress became more apparent.