title: Influence of the number of adhesive layers on adhesive interface properties under cariogenic challenge using streptococcus mutans.
abstract: OBJECTIVE
  To test the hypothesis that the number of adhesive layers influences the adhesive interface properties under cariogenic challenge conditions using a Streptococcus mutans model.
  
  
  METHODS
  Bovine teeth (n = 90) were sectioned into blocks of 5 mm and divided into two groups for microleakage testing (n = 60) and tensile bond strength testing (n = 30). In each group, the samples were subdivided into subgroups according to the number of adhesive layers applied on the dentin: one (SB1), two (SB2), and three adhesive layers (SB3). The samples of the control groups were placed in BHI broth medium supplemented with 2% sucrose without microorganisms, and the experimental groups were submitted to Streptococcus mutans American Type Culture Collection (ATCC) for 5 days. For the tensile strength test, samples were sectioned into 1-mm-thick slices and submitted to a constant load of 0.5 mm/min in a universal testing machine. Fractured surfaces were analyzed and characterized as adhesive, cohesive, or mixed. The microleakage test was performed with silver nitrate solution.
  
  
  RESULTS
  In experimental groups, the tensile test revealed a statistically significant difference between the one- (18.59 ± 5.3) and three-layer (11.28 ± 5.0) groups (p < 0.001; ANOVA and Tukey's test). The adhesive failure mode was slightly more frequent in the one- (60%) and three-layer (80%) adhesive application groups. On the other hand, the microleakage levels of all experimental groups were statistically similar (Kruskal-Wallis; p > 0.05).
  
  
  CONCLUSIONS
  The experimental conditions influenced tensile properties and failure modes of different adhesive interfaces; however, they did not influence microleakage.
authors.forename: Nashalie Andrade
authors.initials: NA
authors.lastname: de Alencar
authors.forename: Tatiana Kelly
authors.initials: TK
authors.lastname: Fidalgo
authors.forename: Marlus Roberto
authors.initials: MR
authors.lastname: Cajazeira
authors.forename: Lucianne Cople
authors.initials: LC
authors.lastname: Maia
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000818:Animals; D002326:Cariogenic Agents / Q000009:adverse effects; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003731:Dental Caries / Q000382:microbiology* / Q000473:pathology; D003738:Dental Cements / Q000737:chemistry; D003743:Dental Enamel / Q000382:microbiology / Q000648:ultrastructure*; D003763:Dental Leakage / Q000145:classification / Q000382:microbiology; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000382:microbiology / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000737:chemistry; D016622:Silver Staining; D013295:Streptococcus mutans / Q000502:physiology*; D013314:Stress, Mechanical; D013395:Sucrose / Q000009:adverse effects; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: C554641:Adper single bond 2; D002326:Cariogenic Agents; D003188:Composite Resins; D003738:Dental Cements; D017220:Dentin-Bonding Agents; D010756:Phosphoric Acids; C533204:filtek Z350; D013395:Sucrose; C030242:phosphoric acid