title: Strengthening of dental adhesives via particle reinforcement.
abstract: The bond between methacrylic polymer adhesives and dental restoratives is not perfect and may fail either in the short or in the long term. This study aims to evaluate the effects of particle incorporation in a self-etch model adhesive on mechanical and physical properties that are relevant during application and service. Filled adhesives containing 5, 10, 15 or 25wt% glass fillers were compared to their unfilled counterpart in terms of water sorption and solubility; viscosity and dynamic viscosity during polymerization were recorded using rheological measurements and compared to FTIR analysis of the real-time degree of cure. Elastic modulus and ultimate tensile strength measurements were performed in uniaxial tension; the energy to fracture was used to calculate the fracture toughness of the adhesives. Finally, the experimental adhesives were applied on dentin substrate to test the bond strength using the microtensile test. Results showed that the incorporation of 5-10wt% nanofiller to self-etching dental adhesives is efficient in accelerating the polymerization reaction and increasing the degree of cure without compromising the film viscosity for good wettability or water sorption and solubility. Fillers increased the elastic modulus, tensile strength and fracture toughness to a plateau between 5 and 15wt% filler concentration, and despite the tendency to form agglomerations, active crack pinning/deflection toughening mechanisms have been observed. The bond strength between resin composite and dentin was also improved when adhesives with up to 10wt% fillers were used, with no additional improvements with further packing. The use of fillers to reinforce dental adhesives may therefore be of great practical benefit by improving curing and mechanical properties.
authors.affiliation: Laboratory for Biomaterials Research, Dental Clinic 1 - Operative Dentistry and Periodontology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91054 Erlangen, Germany.
authors.forename: Renan
authors.initials: R
authors.lastname: Belli
authors.affiliation: Institute of Biomaterials, Department of Materials Science and Engineering, Friedrich-Alexander-University of Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kreppel
authors.affiliation: Laboratory for Biomaterials Research, Dental Clinic 1 - Operative Dentistry and Periodontology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91054 Erlangen, Germany.
authors.forename: Anselm
authors.initials: A
authors.lastname: Petschelt
authors.affiliation: Institute of Biomaterials, Department of Materials Science and Engineering, Friedrich-Alexander-University of Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors.forename: Helga
authors.initials: H
authors.lastname: Hornberger
authors.affiliation: Institute of Biomaterials, Department of Materials Science and Engineering, Friedrich-Alexander-University of Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors.forename: Aldo R
authors.initials: AR
authors.lastname: Boccaccini
authors.affiliation: Laboratory for Biomaterials Research, Dental Clinic 1 - Operative Dentistry and Periodontology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91054 Erlangen, Germany. Electronic address: lohbauer@dent.uni-erlangen.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Lohbauer
mesh_terms: D003738:Dental Cements / Q000737:chemistry*; D003804:Dentin / Q000737:chemistry; D055119:Elastic Modulus; D005898:Glass / Q000737:chemistry; D008422:Materials Testing; D055595:Mechanical Phenomena; D053758:Nanoparticles / Q000737:chemistry*; D012995:Solubility; D013718:Tensile Strength; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D003738:Dental Cements; D014867:Water
keywords: Adhesives; Bond strength; Dentin; Elasticity; Nanoparticles