title: Effect of Diamond Bur Grit Size on Composite Repair.
abstract: OBJECTIVE
  This study investigated the effect of diamond bur grit size on the repair bond strength of fresh and aged resin composites.
  
  
  METHODS
  Blocks of microhybrid composite (Opallis, FGM) were stored in distilled water at 37°C for 24 h (fresh composite) or subjected to 5000 thermal cycles (aged composite). The surfaces were roughened using diamond-coated, flame-shaped carbide burs with medium grit (#3168), fine grit (#3168F), or extra-fine grit (#3168FF). The control group underwent no surface treatment. Surface roughness, water contact angle, and surface topography by scanning electron microscopy (SEM) were evaluated (n = 3). Samples were restored with resin composite and sectioned into beam-shaped specimens, which were subjected to microtensile bond testing. Failure modes were classified using a stereomicroscope. Data were statistically analyzed using the Student- Newman-Keuls test and two-way ANOVA, with significance set at p < 0.05.
  
  
  RESULTS
  Higher surface roughness was observed for groups treated with the medium- and fine-grit burs; aged composites were rougher than fresh composites. The water contact angle formed on the aged composite was lower than that on the fresh composite. The highest repair bond strength was observed for the fine-grit bur group, and the lowest was recorded for control. Interfacial failures were more predominant. SEM images showed that the surfaces treated with fine- and extra-fine-grit burs had a more irregular topography.
  
  
  CONCLUSIONS
  Surface roughening of fresh or aged resin composites with diamond burs improved retention of the repair material. Fine-grit burs generally performed better than medium- and extra-fine-grit burs.
authors.forename: Lisia L
authors.initials: LL
authors.lastname: Valente
authors.forename: Manuela F
authors.initials: MF
authors.lastname: Silva
authors.forename: Andrea S
authors.initials: AS
authors.lastname: Fonseca
authors.forename: Eliseu A
authors.initials: EA
authors.lastname: Münchow
authors.forename: Cristina P
authors.initials: CP
authors.lastname: Isolan
authors.forename: Rafael R
authors.initials: RR
authors.lastname: Moraes
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D058250:Dental Restoration Repair / Q000295:instrumentation*; D003799:Dental Stress Analysis / Q000295:instrumentation; D018130:Diamond / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry; D017155:Wettability
chemical_list: C554641:Adper single bond 2; D003188:Composite Resins; D003738:Dental Cements; D003764:Dental Materials; D014867:Water; D018130:Diamond