title: Novel self-healing dental resin with microcapsules of polymerizable triethylene glycol dimethacrylate and N,N-dihydroxyethyl-p-toluidine.
abstract: OBJECTIVE
  Bulk fracture is one of the primary reasons for resin-based dental restoration failures. To date, there has been no report on the use of polymerizable dental monomers with acceptable biocompatibility to develop a resin with substantial self-healing capability. The objectives of this study were to: (1) develop a self-healing resin containing microcapsules with triethylene glycol dimethacrylate (TEGDMA)-N,N-dihydroxyethyl-p-toluidine (DHEPT) healing liquid in poly(urea-formaldehyde) (PUF) shells for the first time, and (2) determine the physical and mechanical properties, self-healing efficiency, and fibroblast cytotoxicity.
  
  
  METHODS
  Microcapsules of polymerizable TEGDMA-DHEPT in PUF were prepared via an in situ polymerization method. Microcapsules were added into a BisGMA-TEGDMA resin at microcapsule mass fractions of 0%, 5%, 10%, 15% and 20%. A flexural test was used to measure composite strength and elastic modulus. A single edge V-notched beam method was used to measure fracture toughness KIC and self-healing efficiency.
  
  
  RESULTS
  Flexural strength and elastic modulus (mean±sd; n=6) of resin containing 5-15% microcapsules were similar to control without microcapsules (p>0.1). Adding microcapsules into the resin increased the virgin KIC, which was about 40% higher at 15% microcapsules than that with 0% microcapsules (p<0.05). Specimens were fractured and healed, then fractured again to measure the healed KIC. A self-healing efficiency of about 65% in KIC recovery was obtained with 10-20% microcapsules. All specimens with 0-20% microcapsules had fibroblast viability similar to control without resin eluents (p>0.1).
  
  
  CONCLUSIONS
  Self-healing dental resin containing microcapsules with polymerizable TEGDMA-DHEPT healing liquid in PUF shells were prepared for the first time with excellent self-healing capability. These microcapsules and self-healing resins containing them may be promising for dental restorations to heal cracks/damage and increase durability.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Shandong University, Shandong Provincial Key Laboratory of Oral Biomedicine, Jinan 250012, China; Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Junling
authors.initials: J
authors.lastname: Wu
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weir
authors.affiliation: Oral Implantology Center, Jinan Stomatological Hospital, Jinan 250001, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Research Institute of Polymer Materials, School of Materials Science and Engineering, Shandong University, Jinan 250061, China.
authors.forename: Chuanjian
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Mary Anne S
authors.initials: MA
authors.lastname: Melo
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA; Center for Stem Cell Biology & Regenerative Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Mechanical Engineering, University of Maryland, Baltimore County, MD 21250, USA. Electronic address: hxu@umaryland.edu.
authors.forename: Hockin H K
authors.initials: HH
authors.lastname: Xu
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry*; D002214:Capsules; D003188:Composite Resins / Q000138:chemical synthesis / Q000737:chemistry*; D003764:Dental Materials / Q000138:chemical synthesis / Q000737:chemistry*; D019232:Dental Restoration Failure; D055119:Elastic Modulus; D005557:Formaldehyde / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry*; D014052:Toluidines / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D002214:Capsules; D003188:Composite Resins; D003764:Dental Materials; D011108:Polymers; D011109:Polymethacrylic Acids; D014052:Toluidines; C020946:triethylene glycol dimethacrylate; D005557:Formaldehyde; C045786:polyurea; D011092:Polyethylene Glycols; C038496:N,N-bis(2-hydroxyethyl)-4-toluidine
keywords: Cytotoxicity; Fracture toughness recovery; Mechanical properties; Microcapsules; Polymerizable healing liquid; Self-healing dental resin