title: Hydrolytic stability of experimental hydroxyapatite-filled dental composite materials.
abstract: OBJECTIVE
  The purpose of this study was to analyze the behavior in water, related to mechanical properties, of experimental composites for dental restoration.
  
  
  METHODS
  The studied materials were composed of a visible-light-curing monomer mixture (Bis-GMA and TEGDMA or HEMA) and micrometric, nanometric or a mixture of both sizes hydroxyapatite particles as a reinforcing filler. Filler particles were modified with a coupling agent (citric, hydrosuccinic, acrylic or methacrylic acid or silane). The hydrolytic stability of the evaluated materials was studied through total elution and water-uptake tests. Percent net-mass variation was daily monitored and analyzed as a function of time. Mechanical performance was examined through flexural properties and Vickers hardness. Morphological surface changes were observed with scanning electron microscopy. ANOVA statistical analysis was performed (P<0.05).
  
  
  RESULTS
  In general, the use of HEMA instead of TEGDMA did not substantially worsen the composite quality. Dental composites containing only nanometric particles of hydroxyapatite as a filler are unsuitable for clinical performance. Midway-filled composite resins loaded with micro-HAP particles, coated with citric, acrylic or methacrylic acid displayed low percent elution and water-uptake values. Mechanical properties were similar or even superior to those measured for silane treated particles.
  
  
  CONCLUSIONS
  More research is needed to further improve the interaction of nano-HAP particles with the polymeric matrix, either as a single filler or, preferentially, mixed with micro-HAP, that will allow to increase the total loading of reinforcing filler and, hence, to improve the mechanical properties.
authors.affiliation: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Spain. conchi@icmab.es
authors.forename: C
authors.initials: C
authors.lastname: Domingo
authors.forename: R W
authors.initials: RW
authors.lastname: Arcís
authors.forename: E
authors.initials: E
authors.lastname: Osorio
authors.forename: R
authors.initials: R
authors.lastname: Osorio
authors.forename: M A
authors.initials: MA
authors.lastname: Fanovich
authors.forename: R
authors.initials: R
authors.lastname: Rodríguez-Clemente
authors.forename: M
authors.initials: M
authors.lastname: Toledano
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis; D017886:Durapatite; D004548:Elasticity; D006244:Hardness; D006860:Hydrogen Bonding; D006868:Hydrolysis; D008422:Materials Testing; D008689:Methacrylates; D010316:Particle Size; D018583:Pliability; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D012995:Solubility; D013499:Surface Properties; D014867:Water
chemical_list: D003188:Composite Resins; D008689:Methacrylates; D011109:Polymethacrylic Acids; D014867:Water; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; C005044:hydroxyethyl methacrylate; D017886:Durapatite