title: Effect of intrinsic wetness and regional difference on dentin bond strength.
abstract: OBJECTIVE
  The aim of this investigation was to determine the influence of intrinsic wetness on regional bond strengths of adhesive resins to dentin.
  
  
  METHODS
  Human caries-free third molars were randomly divided into three groups for bonding: Group 1--no pulpal pressure; Group 2--pulpal pressure of 15 cm H2O; and Group 3--dentin dried overnight in a desiccator. Clearfil Liner Bond II (Kuraray) or One Step (Bisco) adhesive resins systems were applied to the flat dentin surfaces and the teeth were restored with APX resin composite (Kuraray). After 24 h in water at 37 degrees C, the specimens were sectioned into 0.7 mm thick slabs and divided into three regional subgroups according to the remaining dentin thickness and visual criteria: pulp horn, center, and periphery. The slabs were then trimmed for the micro-tensile bond test and subjected to a tensile force and crosshead of 1 mm/min. The data were analyzed with ANOVA and Fisher's PLSD test at a confidence level of 95%. The fracture modes were determined under a scanning electron microscope (JXA-840, JEOL, Japan).
  
  
  RESULTS
  No significant regional difference was observed for the Group 1 and 2 specimens restored with Clearfil Liner Bond II (p > 0.05). However, bond strengths significantly decreased at the pulp horn region of the Group 1 and 2 specimens restored with One Step (p > 0.01). All bond strengths of Group 3 decreased significantly and regional differences were not evident (p > 0.05).
  
  
  CONCLUSIONS
  The dentin adhesive system should be chosen according to the substrate and region to be bonded, since bond strengths can vary according to the intrinsic wetness, region, and the adhesive system.
authors.affiliation: Department of Operative Dentistry, Faculty of Dentistry, Tokyo Medical and Dental University, Japan. p.pereira.odnt@dent.tmd.ac.jp
authors.forename: P N
authors.initials: PN
authors.lastname: Pereira
authors.forename: M
authors.initials: M
authors.lastname: Okuda
authors.forename: H
authors.initials: H
authors.lastname: Sano
authors.forename: T
authors.initials: T
authors.lastname: Yoshikawa
authors.forename: M F
authors.initials: MF
authors.lastname: Burrow
authors.forename: J
authors.initials: J
authors.lastname: Tagami
mesh_terms: D001840:Dental Bonding; D003799:Dental Stress Analysis; D003804:Dentin / Q000737:chemistry; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D003890:Desiccation; D006801:Humans; D006874:Hydrostatic Pressure; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D013718:Tensile Strength; D014867:Water / Q000737:chemistry; D017155:Wettability
chemical_list: C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; C112274:Clearfil Liner Bond 2; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D014867:Water