title: Shear strength evaluation of composite-composite resin associations.
abstract: OBJECTIVE
  The aim of this study was to investigate the shear strength between distinct associations of different commercial composite resins and their fracture modes.
  
  
  METHODS
  Nine composite-composite associations (n=90) were prepared for shear strength evaluation and separated into the following groups: Z/Z (Filtek Z250 UD+Filtek Z250 A2); Z/D (Filtek Z250 UD+Durafill VS A2); Z/S (Filtek Z250 UD+Filtek Supreme YT); C/C (Charisma OA2+Charisma A2); C/D (Charisma OA2+Durafill VS A2); C/S (Charisma OA2+Filtek Supreme YT); H/H (Herculite XRV B2D+Herculite XRV B2E); H/D (Herculite XRV B2D+Durafill VS A2); H/S (Herculite XRV B2D+Filtek Supreme YT). Shear tests were carried out using universal mechanical test equipment with a load of 200kgf and speed of 0.5mm/min. Ultimate shear strength data (MPa) from all tested groups were submitted to analysis of variance (one-way ANOVA) and the Tukey test. The fractured surfaces of the test samples were visually evaluated by binocular stereomicroscope at 20 times magnification. Fractures were classified as either adhesive or cohesive or mixed.
  
  
  RESULTS
  The highest ultimate shear strength observed for composite-composite associations was found for the groups: Z/Z, C/S, H/H, H/S, Z/S and C/C. Those associations containing the Durafill resin were weaker than the others.
  
  
  CONCLUSIONS
  Microparticle RBC associations presented lower shear strength than hybrid and/or nanoparticle RBC associations, once the only significant difference was found when the Durafill resin was involved.
authors.affiliation: Department of Restorative Dentistry, Dental School of Três Corações, Vale do Rio Verde University, UNINCOR, Três Corações, MG, Brazil.
authors.forename: José Carlos Rabelo
authors.initials: JC
authors.lastname: Ribeiro
authors.forename: Priscila Nogueira
authors.initials: PN
authors.lastname: Gomes
authors.forename: Marcos Ribeiro
authors.initials: MR
authors.lastname: Moysés
authors.forename: Sérgio Candido
authors.initials: SC
authors.lastname: Dias
authors.forename: Luciano José
authors.initials: LJ
authors.lastname: Pereira
authors.forename: João Gustavo Rabelo
authors.initials: JG
authors.lastname: Ribeiro
mesh_terms: D000268:Adhesiveness; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis; D006801:Humans; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D033081:Shear Strength; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: C084111:Charisma composite resin; D003188:Composite Resins; D003764:Dental Materials; C474035:Filtek Supreme; C444701:Filtek Z250; D019279:Resin Cements; C065770:Herculite XR; C039734:Durafill