title: Effect of polishing direction on the marginal adaptation of composite resin restorations.
abstract: OBJECTIVE
  Polishing composite resin restorations may lead to marginal defects and gap formation.
  
  
  OBJECTIVE
  To assess the effect of polishing direction on the marginal adaptation of composite resin restorations using two composite resins and two polishing systems.
  
  
  METHODS
  Forty extracted human molars were sectioned along their mesio-distal axis. Buccal and lingual enamel was flattened and a triangular preparation, 0.87-mm deep and 3-mm wide, representing two 60° bevels, was performed. Specimens were randomly assigned to eight groups (N = 20) and restored with two composite resins: a nanofilled (Filtek Supreme Ultra, 3M ESPE, St. Paul, MN, USA) or a microhybrid (Point 4, Kerr, Orange, CA, USA) and finished with two polishing techniques: polishing discs (Sof-Lex XT, 3M ESPE) or rubber polishers (HiLuster Plus, Kerr, Bioggio, Switzerland). On each specimen, both margins were polished with the same technique, one margin from composite resin to tooth and the other from tooth to composite resin. Replicas were made for field emission scanning electron microscope observation (200×) and quantitative margin analysis was performed based on four criteria. Data were analyzed with a paired-sample t-test, a two-sample t-test, and one-way analysis of variance or their nonparametric analog.
  
  
  RESULTS
  Significant differences were found in most groups between polishing directions with better marginal adaptation from composite resin to tooth than from tooth to composite resin. Differences between composite resins and polishing techniques seemed to be dependent on certain combinations of composite resin, polishing technique, and polishing direction.
  
  
  CONCLUSIONS
  Polishing from composite resin to tooth leads to better marginal adaptation than polishing from tooth to composite resin.
  
  
  CONCLUSIONS
  The results obtained from this in vitro study suggest that polishing direction influences the marginal adaptation of composite resins and that polishing from composite resin to tooth structure should be clinically performed whenever possible on accessible margins to preserve marginal integrity and esthetics.
authors.affiliation: Université Laval, Quebec, QC, Canada. laurie.st-pierre@fmd.ulaval.ca
authors.forename: Laurie
authors.initials: L
authors.lastname: St-Pierre
authors.forename: Cathia
authors.initials: C
authors.lastname: Bergeron
authors.forename: Fang
authors.initials: F
authors.lastname: Qian
authors.forename: Maria Marcela
authors.initials: MM
authors.lastname: Hernández
authors.forename: Justine L
authors.initials: JL
authors.lastname: Kolker
authors.forename: Deborah S
authors.initials: DS
authors.lastname: Cobb
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Vargas
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D003775:Dental Polishing / Q000379:methods*; D003793:Dental Restoration, Permanent; D006801:Humans
chemical_list: D003188:Composite Resins; D003764:Dental Materials