title: Whisker-reinforced dental core buildup composites: effect of filler level on mechanical properties.
abstract: The strength and toughness of dental core buildup composites in large stress-bearing restorations need to be improved to reduce the incidence of fracture due to stresses from chewing and clenching. The aims of the present study were to develop novel core buildup composites reinforced with ceramic whiskers, to examine the effect of filler level, and to investigate the reinforcement mechanisms. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whisker surface for improved retention in the matrix. Filler level was varied from 0 to 70%. Flexural strength, compressive strength, and fracture toughness of the composites were measured. A nano-indentation system was used to measure elastic modulus and hardness. Scanning electron microscopy (SEM) was used to examine the fracture surfaces of specimens. Whisker filler level had significant effects on composite properties. The flexural strength in MPa (mean +/- SD; n = 6) increased from (95+/-15) for the unfilled resin to (193+/- 8) for the composite with 50% filler level, then slightly decreased to (176+/-12) at 70% filler level. The compressive strength increased from (149+/-33) for the unfilled resin to (282+/-48) at 10% filler level, and remained equivalent from 10 to 70% filler level. Both the modulus and hardness increased monotonically with filler level. In conclusion, silica particle-fused ceramic single-crystalline whiskers significantly reinforced dental core buildup composites. The reinforcement mechanisms appeared to be crack deflection and bridging by the whiskers. Whisker filler level had significant effects on the flexural strength, compressive strength, elastic modulus, and hardness of composites.
authors.affiliation: Paffenbarger Research Center, American Dental Association Health Foundation, National Institute of Standards and Technology, 100 Bureau Drive Stop 8546, Building 224, Room A-153, Gaithersburg, Maryland 20899-8546, USA. hockin.xu@nist.gov
authors.forename: H H
authors.initials: HH
authors.lastname: Xu
authors.forename: D T
authors.initials: DT
authors.lastname: Smith
authors.forename: G E
authors.initials: GE
authors.lastname: Schumacher
authors.forename: F C
authors.initials: FC
authors.lastname: Eichmiller
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D002084:Butylated Hydroxytoluene / Q000737:chemistry*; D002516:Ceramics / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D019245:Compressive Strength; D003793:Dental Restoration, Permanent / Q000295:instrumentation*; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*; D011208:Powders; D012821:Silanes / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013314:Stress, Mechanical; D014052:Toluidines / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011208:Powders; D012821:Silanes; D017655:Silicon Compounds; D014052:Toluidines; C020946:triethylene glycol dimethacrylate; D002084:Butylated Hydroxytoluene; C017492:methacryloxypropyltrimethoxysilane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; C032734:silicon nitride; C038496:N,N-bis(2-hydroxyethyl)-4-toluidine