In vitro evaluation of adhesive characteristics of 4-META/MMA-TBB resin with organic filler

Objectives. A commercial restorative material, BondfillSB (BF), is a modification of 4-META/MMA-TBB resin cement. BF uses a self-etching primer and added pre-polymerized organic fillers. We compared BF with another self-etching system, EasyBond (EB), in shear bond strength, bonded interface characteristics to human dentin and contraction gap when used in bulk-filling. Methods. Shear bond strength of BF and EB + Z100 (Z), bonded by different experience-level operators, was evaluated. Bonded interfaces were characterized by SEM, AFM, and AFM based nano-indentation. Contraction gaps (CG) at 0 h and 24 h after polymerization were evaluated for BF or EB bulk filled class I cavities. To meet the clinical recommendation, BF's powder was replaced by experimental radioopaque powder (BFO) for the CG study. EB was used with Z (EBZ) or with a resin marketed for bulk-fill base (SureFil-SDR-flow (EBSF)). Results. Shear bond strengths (Mean +/- Standard Deviation (S.D.)) of BF (37.4 +/- 2.6 MPa; n = 36) were higher and less variable than EBZ (18.2 +/- 7.6 MPa; n = 36) (p < 0.0001, One-way ANOVA). Weibull characteristic strength (eta) differed significantly between materials (p < 0.0001) but not between operators (p = 0.90). EBZ often had non-uniform interfaces and a wider band of reduced elastic modulus (E) of greater than 20 mu m across the interface. BF had uniform interfaces and a smaller width of affected dentin under the interface (similar to 1 mu m). There was a difference in dentin-E between EBZ and BF up to 9 mu m from the interface (mixed-effects model; P = 0.03). A stratified linear regression model used for CG. EBSF and BFO showed significantly smaller CG than EBZ at time 0. None of three combinations showed any significant change between 0h-CG and 24h-CG. Significance. BF possessed bonding characteristics required to serve as a restorative. (C) 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.