Bond Strength of Oxirane/Acrylate Resins Using Commercial Bonding Systems

Objectives: Overall Objective: To develop an Oxirane/Acrylate interpenetrating network resin System (OASys) to double the clinical lifetime of current dental restoratives. Specific Objective: To determine the dentin shear bond strength of OASys resins using commercial bonding systems.
Methods: Unfilled OASys resins (100:0 Epoxidized Hydrogenated Bisphenol A (Epalloy 5000):dipentaerythritol penta/hexaacrylate (DPHA), 75:25 Epalloy:DPHA, 50:50 Epalloy:DPHA, 25:75 Epalloy:DPHA, and 0:100 Epalloy:DPHA) were bonded to dentin using Adper Scotchbond Multi-purpose, BISCO All-Bond Universal, or Filtek LS bonding system (used to bond the silorane-based composite Filtek LS), and shear bond tests were performed. Unfilled 70:30 BisGMA:TEGDMA and Filtek LS composite served as controls. Initiators (camphorquinone and either [4-(Octyloxy)phenyl] phenyliodonium SbF₆ or 4-Isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl) borate) had been optimized for degree-of-cure (Durometer-D hardness), mechanical properties (3-point bending) and hydrophobicity (contact angle).
Results: The bond strength of BisGMA:TEGDMA control to dentin using Scotchbond and All-Bond was ~9 MPa, but only ~5 MPa when using the Filtek LS adhesive system. The Filtek LS composite did not bond to dentin using Scotchbond and All-Bond, and only had a bond strength of ~5 MPa with the Filtek LS bonding system. OASys resins did not bond well to dentin using Scotchbond and All-Bond, but the 100:0, 25:75 and 0:100 Epalloy:DPHA groups had bond strengths of ~9 MPa using the Filtek LS bonding system. The bond for 0:100 Epalloy:DPHA failed adhesively, while the other OASys groups failed in a mixed cohesive/adhesive mode.
Conclusions: OASys resins do not bond well to dentin with methacrylate-based bonding systems, however, the Filtek LS bonding system provides comparable shear bond strengths to controls. It is surprising that OASys resins had twice the bond strength of the Filtek LS composite when using the Filtek LS bonding system. Unfortunately, the Filtek LS bonding system is no longer commercially available, so a bonding system must be developed for OASys resins.