Silorane-dimethacrylate bond: effect of different adhesion primers

Objectives: To determine the shear bond strength between the cationic polymerized Silorane composite and a conventional radical polymerized dimethacrylate composite by means of different adhesion primers.

Methods: Silorane composite (Filtek Silorane, 3M-ESPE) substrates were fabricated by placing unpolymerized silorane composite into the retentive cavity of the acrylic resin (5 mmx2.5 mm), surrounded by a stainless steel cylinder and light polymerized for 40 s with a hand lightcuring device (Elipar Freelight 2, 3M-ESPE). The substrates were randomly divided in six different groups. A conventional dimethacrylate composite (Z250, 3M-ESPE) was adhered to the silorane composite either with a dimethacrylate intermediate resin (SIL-MP-CR) (Adper Scothchbond Multipurpose Adhesive, 3M-ESPE), an experimental vinyl-oxirane adhesion primer (Sigma-Aldrich) (SIL-VO-CR), a phosphate-methacrylate resin (SE Bond, Kuraray) (SIL-SE-CR), a phosphate–acrylate resin (Silorane System Adhesive Bond, 3M-ESPE) (SIL-SA-CR), or without any intermediate resin (SIL-CR). Silorane composite adhered to fresh cured silorane substrate without any intermediate resin layers (SIL-SIL) served as control. The bonded specimens (n=12/group) were water-stored for 24 h and the shear bond strengths (SBS) were measured at a crosshead speed of 1.0 mm/min. Failure modes were assessed. Data were analysed by ANOVA followed by Scheffe's post hoc tests (p = 0.05).

Results: ANOVA showed significant differences among different groups (p<0.05). The fracture modes were also different.The mean SBS were MPa (SD):

SIL-CR	4.0   (2.1) a
SIL-MP-CR	12.3 (6.9) ab
SIL-VO-CR	5.2  (2.7) a
SIL-SE-CR	19.6 (10.3) bc
SIL-SA-CR	27.8 (5.4) c
SIL-SIL	26.7 (6.8) c

*same superscipt letter represent statistically similar groups (p<0.05)

Conclusion:To increase the bonding between dimethacrylate composite and silorane composite, a phosphate–methacrylate-based intermediate resin is required.