title: Influence of repair procedure on composite-to-composite microtensile bond strength.
abstract: OBJECTIVE
  To investigate the effect of different repair procedures and storage time on microtensile bond strength (μTBS) of a resin composite to an older one from a simulated previous restoration.
  
  
  METHODS
  Composite disks were made by layering 2 mm-thick increments of a nanohybrid composite (Grandio) shade A1 in a Teflon mold (4 x 8 mm). Afterwards, they were light-cured and stored (37 degrees C/7 days) in a saline solution. Specimens were randomly divided into groups according to the surface treatment applied: (1) Composite surface was roughened with a bur (Cimara) and Solobond Plus adhesive was applied; (2) Sandblasting with 27 μm aluminum oxide particles (KaVo Rondoflex), and adhesive application; (3) Air-abrasion with 30 μm alumina particles coated with silica (CoJet Sand), silane (Monobond-S) and adhesive application; (4) Negative control group with only adhesive application. Afterwards, Grandio composite (shade A3.5) was packed incrementally on the treated surface obtaining another disk (4 x 8 mm). Repaired blocks were stored (24 hours or 6 months) and afterwards μTBS test was performed and failure mode was evaluated. Also, beams obtained from 8 mm-high composite blocks without any surface treatment were immediately submitted to μTBS test to determine Grandio composite cohesive bond strength (positive control group). Data were analyzed using ANOVA and Tukey's test (P < 0.05).
  
  
  RESULTS
  The repair procedure affected μTBS values (P < 0.001) while neither storage time nor interactions did (P > 0.05). All repair procedures achieved bond strength values higher than the negative control group but they did not reach the composite's cohesive bond strength. The overall conclusion was that an increased superficial roughness by means of a bur, silica coating or alumina sandblasting improved μTBS of the repaired composite and bond strength remained stable after 6 months.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Baena
authors.forename: Valeria
authors.initials: V
authors.lastname: Vignolo
authors.forename: Maria Victoria
authors.initials: MV
authors.lastname: Fuentes
authors.forename: Laura
authors.initials: L
authors.lastname: Ceballos
mesh_terms: D000268:Adhesiveness; D000537:Aluminum Oxide / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry; D045662:Dental Etching / Q000379:methods; D003764:Dental Materials / Q000737:chemistry*; D058250:Dental Restoration Repair / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D053761:Nanocomposites / Q000737:chemistry; D011897:Random Allocation; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / 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; D003738:Dental Cements; D003764:Dental Materials; C509998:Grandio; D008689:Methacrylates; C076808:Monobond S; D012821:Silanes; C488002:Solobond Plus adhesive; D012965:Sodium Chloride; D012822:Silicon Dioxide; D000537:Aluminum Oxide