title: Effects of water-aging on self-healing dental composite containing microcapsules.
abstract: OBJECTIVE
  The objectives of this study were to develop a self-healing dental composite containing poly(urea-formaldehyde) (PUF) shells with triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid, and to investigate the mechanical properties of the composite and its self-healing efficacy after water-aging for 6 months.
  
  
  METHODS
  PUF microspheres were synthesized encapsulating a TEGDMA-DHEPT healing liquid. Composite containing 30% of a resin matrix and 70% of glass fillers by mass was incorporated with 0%, 2.5%, 5%, 7.5% and 10% of microcapsules. A flexural test was used to measure flexural strength and elastic modulus. A single edge V-notched beam method was used to measure fracture toughness (KIC) and self-healing efficacy. Specimens were water-aged at 37 °C for 1 day to 6 months and then tested for self-healing. Fractured specimens were healed while being immersed in water to examine self-healing efficacy, in comparison with that in air.
  
  
  RESULTS
  Incorporation of up to 7.5% of microcapsules into the resin composite achieved effective self-healing, without adverse effects on the virgin mechanical properties of the composite (p>0.1). An excellent self-healing efficacy of 64-77% recovery was obtained (mean±sd; n=6). Six months of water-aging did not decrease the self-healing efficacy compared to 1 day (p>0.1). Exposure to water did not decrease the healing efficacy, compared to that healed in air (p>0.1).
  
  
  CONCLUSIONS
  A composite was developed with excellent self-healing efficacy even while being immersed in water. The self-healing efficacy did not decrease with increasing water-aging time for 6 months.
  
  
  CONCLUSIONS
  The novel self-healing composite may be promising for dental applications to heal cracks, resist fracture, and increase the durability and longevity.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Jinan 250012, China; Biomaterials & Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, University of Maryland Dental School, Baltimore, MD 21201, USA. Electronic address: doctorwujunling@163.com.
authors.forename: Junling
authors.initials: J
authors.lastname: Wu
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weir
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, 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, Periodontics and Prosthodontics, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Howard E
authors.initials: HE
authors.lastname: Strassler
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, 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: D017438:Bisphenol A-Glycidyl Methacrylate / Q000494:pharmacology; D002214:Capsules / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000379:methods; D004339:Drug Compounding / Q000379:methods; D055119:Elastic Modulus; D005557:Formaldehyde / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*; D012823:Silicate Cement / Q000737:chemistry; D013718:Tensile Strength; D014052:Toluidines / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D002214:Capsules; D003188:Composite Resins; D005899:Glass Ionomer Cements; D011108:Polymers; D011109:Polymethacrylic Acids; D014052:Toluidines; C111282:dental polyglass; D014867:Water; D012823:Silicate Cement; C020946:triethylene glycol dimethacrylate; D005557:Formaldehyde; C045786:polyurea; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C038496:N,N-bis(2-hydroxyethyl)-4-toluidine
keywords: Dental composite; Mechanical property recovery; Microcapsules; Polymerizable healing liquid; Self-healing; Water-aging