title: Flowable composites as intermediate agents without adhesive application in resin composite repair.
abstract: OBJECTIVE
  To evaluate the effect of different intermediate resin agents on composite-to-composite microtensile bond strength (microTBS).
  
  
  METHODS
  Composite disks (8 x 4 mm) of Gradia Direct Anterior (N = 15) and Filtek Supreme XT (N = 15), stored in a saline solution at 37 degrees C for 1 month, were sandblasted (Microetcher, 50 microm-Al2O3), cleaned (35% H3PO4), and randomly divided into five groups (N = 3) according to the intermediate agent applied. Two flowable composites (Gradia LoFlo; Filtek Supreme XT Flow) and two adhesives (Adper Scotchbond 1XT, Scotchbond Multi-Purpose) were used. As a control, no intermediate agent was applied. Each disk was incrementally repaired (8x8 mm) with the same resin as the respective substrate. By serially cutting each repaired specimen, multiple sticks of about 0.8 mm2 in cross-section were obtained and loaded in tension until failure at a cross-head speed of 0.5 mm/minute. Data were statistically analyzed. Failure mode was examined by stereo- and scanning electron-microscopy (SEM). Additional specimens were prepared to morphologically evaluate the composite-to-composite interfacial quality by SEM analysis.
  
  
  RESULTS
  Composite substrate and intermediate agent were significant factors (Two-way ANOVA, P < 0.001). Bond strengths achieved with Gradia Direct Anterior were higher than Filtek Supreme XT. The application of flowable composites resulted in statistically superior microTBS than adhesives and control (Tukey test, P < 0.001). Failure mode was predominantly cohesive (flowable composites), cohesive/adhesive (adhesives) and adhesive (no treatment). Flowable composites and adhesives showed a good interfacial quality.
authors.affiliation: University of Siena, School of Dental Medicine, Department of Dental Materials and Restorative Dentistry, Siena, 53100, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Papacchini
authors.forename: Ivana
authors.initials: I
authors.lastname: Radovic
authors.forename: Elisa
authors.initials: E
authors.lastname: Magni
authors.forename: Cecilia
authors.initials: C
authors.lastname: Goracci
authors.forename: Francesca
authors.initials: F
authors.lastname: Monticelli
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Chieffi
authors.forename: Antonella
authors.initials: A
authors.lastname: Polimeni
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
mesh_terms: D000268:Adhesiveness; D000537:Aluminum Oxide / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D045662:Dental Etching; D017269:Dental Prosthesis Repair; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D003188:Composite Resins; C467913:Filtek Flow; C474035:Filtek Supreme; C470230:Gradia; C523003:Gradia Direct LoFlo; D010756:Phosphoric Acids; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; C111840:flowable hybrid composite; D012965:Sodium Chloride; C041330:Scotchbond; C030242:phosphoric acid; D000537:Aluminum Oxide