Kangmin Kim1, Alexis Mascarenas2, Charles B Musgrave3, Jeffrey W Stansbury4. 1. University of Colorado, Chemistry, Boulder, CO, USA. 2. School of Dental Medicine, Craniofacial Biology, Aurora, CO, USA. 3. University of Colorado, Chemistry, Boulder, CO, USA; Chemical and Biological Engineering, Boulder, CO, USA; Materials Science and Engineering, Boulder, CO, USA; National Renewable Energy Laboratory, Golden, CO 80401, USA. 4. School of Dental Medicine, Craniofacial Biology, Aurora, CO, USA; Chemical and Biological Engineering, Boulder, CO, USA; Materials Science and Engineering, Boulder, CO, USA. Electronic address: jeffrey.stansbury@cuanschutz.edu.
Abstract
OBJECTIVES: This study demonstrates a spontaneous redox polymerization process located at the adhesive-composite interface that precedes photocure of the composite with the intent to improve bonding. METHODS: An aromatic amine and benzoyl peroxide redox initiator system was partitioned between BAPO-photoinitiated BisGMA/HEMA adhesive and BisGMA/TEGDMA resin-composites. The composite was placed on the photocured adhesive layer with a brief delay before photopolymerization of the composite layer. Micro-tensile bond strength between the adhesive and composite was assessed in comparison with the non-redox active control materials. RESULTS: The presence of amine or peroxide in these resins without the redox initiation contribution enhanced both the rate and the final conversion of the BAPO-based photopolymerizations. Control formulations using redox-only initiation showed active polymer formation starting at approximately 30 s when physical mixing of the redox components was involved; however, simply by waiting 60 s between composite placement and photocure provided adequate time for passive interfacial diffusion of benzoyl peroxide from the pre-cured adhesive into the overlaid aromatic amine-containing composite such that a sufficient degree of redox initiated interfacial polymerization occurred prior to the composite photocure. The result was a significant increase in the adhesive to composite micro-tensile bond strength with the failure site moved away from the mainly interfacial failure noted for the control. SIGNIFICANCE: The stress-free autonomous pre-conversion of a redox-initiated thin film of composite that then provides a compositionally homogeneous interface for composite photopolymerization offers a means to enhance at least short-term bond strength between the adhesive and composite phases during restorative placement.
OBJECTIVES: This study demonstrates a spontaneous redox polymerization process located at the adhesive-composite interface that precedes photocure of the composite with the intent to improve bonding. METHODS: An aromatic amine and benzoyl peroxide redox initiator system was partitioned between BAPO-photoinitiated BisGMA/HEMA adhesive and BisGMA/TEGDMA resin-composites. The composite was placed on the photocured adhesive layer with a brief delay before photopolymerization of the composite layer. Micro-tensile bond strength between the adhesive and composite was assessed in comparison with the non-redox active control materials. RESULTS: The presence of amine or peroxide in these resins without the redox initiation contribution enhanced both the rate and the final conversion of the BAPO-based photopolymerizations. Control formulations using redox-only initiation showed active polymer formation starting at approximately 30 s when physical mixing of the redox components was involved; however, simply by waiting 60 s between composite placement and photocure provided adequate time for passive interfacial diffusion of benzoyl peroxide from the pre-cured adhesive into the overlaid aromatic amine-containing composite such that a sufficient degree of redox initiated interfacial polymerization occurred prior to the composite photocure. The result was a significant increase in the adhesive to composite micro-tensile bond strength with the failure site moved away from the mainly interfacial failure noted for the control. SIGNIFICANCE: The stress-free autonomous pre-conversion of a redox-initiated thin film of composite that then provides a compositionally homogeneous interface for composite photopolymerization offers a means to enhance at least short-term bond strength between the adhesive and composite phases during restorative placement.
Authors: Kangmin Kim; Nicholas R Singstock; Kimberly K Childress; Jasmine Sinha; Austyn M Salazar; Savannah N Whitfield; Aaron M Holder; Jeffrey W Stansbury; Charles B Musgrave Journal: J Am Chem Soc Date: 2019-04-08 Impact factor: 15.419