title: An in vitro assessment of the effects of three surface treatments on repair bond strength of aged composites.
abstract: OBJECTIVE
  This study evaluated the effectiveness of three surface treatments on repair shear bond strength (SBS) of aged composites.
  
  
  METHODS
  A total of 120 cylindrical samples made of a micro-hybrid composite (Clearfil AP-X) were randomly assigned to one control and three experimental groups (n=30) after water storage (3 weeks). All experimental groups included surface roughening with diamond burs. Subsequent treatments were provided as follows: group 1 - only (self-etching) bonding; group 2 - silane and bonding; and group 3 - phosphoric acid etching, silane, and bonding. The composites were repaired with the same brand and were aged (water storage [48 hours] and thermocycling [2000 cycles]). Each group was divided into two subgroups (each, n=15): new - water storage at 37°C for one week; old - water storage for six months. The SBS was tested. The fracture mode was assessed under 40× magnification.
  
  
  RESULTS
  Mean SBS values (MPa) for the study subgroups were as follows: control (new: 3.38 ± 1.6; old: 1 ± 0.76), group 1 (new: 27.3 ± 1.8; old: 25.7 ± 1.9), group 2 (new: 59.1 ± 7.9; old: 50.8 ± 4.6), and group 3 (new: 48.5 ± 8.6; old: 39 ± 3.5). Significant influence of the conditioning method and the duration of water storage was observed (p<0.01 [two-way analysis of variance {ANOVA}]). The SBS of all groups were significantly different (all p values <0.01 [Tukey]). Longer water storage time significantly reduced repair bond strength in all experimental groups (p<0.01). Although the control group and group 1 showed approximately 100% and 75% adhesive failures, respectively, groups 2 and 3, respectively, demonstrated about 75% mixed and cohesive failures. Weibull analysis showed that groups 2 and 1 had the lowest and highest probabilities of failure among the experimental groups, respectively.
  
  
  CONCLUSIONS
  All experimental groups produced acceptable SBS levels; however, use of silane and bonding systems showed the most superior results. Acid etching reduced the SBS.
authors.affiliation: Department of Dental Materials, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: T S
authors.initials: TS
authors.lastname: Jafarzadeh Kashi
authors.forename: M
authors.initials: M
authors.lastname: Erfan
authors.forename: V
authors.initials: V
authors.lastname: Rakhshan
authors.forename: N
authors.initials: N
authors.lastname: Aghabaigi
authors.forename: F S
authors.initials: FS
authors.lastname: Tabatabaei
mesh_terms: D003188:Composite Resins; D001840:Dental Bonding / Q000379:methods*; D045662:Dental Etching; D019232:Dental Restoration Failure; D058250:Dental Restoration Repair / Q000379:methods; D003799:Dental Stress Analysis; D008689:Methacrylates; D011897:Random Allocation; D019279:Resin Cements; D033081:Shear Strength; D012821:Silanes; D013499:Surface Properties; D016019:Survival Analysis; D013997:Time Factors; D014867:Water
chemical_list: C112828:Clearfil AP-X; D003188:Composite Resins; D008689:Methacrylates; D019279:Resin Cements; D012821:Silanes; D014867:Water