title: Effect of hydrostatic pressure on regional bond strengths of compomers to dentine.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of hydrostatic pressure on the regional bond strengths of compomers to dentine.
  
  
  METHODS
  Thirty freshly extracted molars were ground flat to expose the dentine and randomly divided into two groups for bonding: no hydrostatic pressure and hydrostatic pressure of 15cm H(2)O. Xeno CF, Dyract AP and F 2000 were applied to dentine surfaces pretreated by the respective bonding systems following the manufactures' instructions, and then restored with Clearfil AP-X. After 24h storage in water, the teeth were sectioned into 0.7-mm thick slabs and visually divided into three regional subgroups: the region communicating with the pulp through dentinal tubules (pulp horn); the region between the pulp horns (center); and the region between the pulp horn and DEJ (periphery). The specimens were trimmed to a cross-sectional area of 1mm(2) and subjected to the micro-tensile bond test. The data were analyzed by one- and three-way ANOVA, and Fisher's PLSD (p<0.05).
  
  
  RESULTS
  There were no significant regional differences of bond strengths for all the compomers tested (p>0.05). However, hydrostatic pressure significantly decreased the bond strength of F 2000 to all regions (p<0.05), while the bond strength of Dyract AP significantly decreased only at the pulp horn region (p<0.05). On the other hand, the bond strengths of Xeno CF seemed not to be affected by hydrostatic pressure (p>0.05). For Dyract AP and F 2000, the fracture modes were affected by hydrostatic pressure, while, for Xeno CF, there were no significant differences between the fracture modes with non- or positive hydrostatic pressure.
  
  
  CONCLUSIONS
  Simulated pulpal pressure of 15cm H(2)O had a greater influence on the bond strengths of compomers to dentine than did dentine regions. Therefore, when measuring the bond strengths of compomers to dentine under the simulated in vivo conditions, the wetness of the dentine surface, as well as the intrinsic properties of each material should be seriously considered.
authors.affiliation: Department of Operative Dentistry, Faculty of Dentistry, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, 113 8549, Tokyo, Japan. leizheng26@hotmail.com
authors.forename: L
authors.initials: L
authors.lastname: Zheng
authors.forename: P N
authors.initials: PN
authors.lastname: Pereira
authors.forename: P
authors.initials: P
authors.lastname: Somphone
authors.forename: T
authors.initials: T
authors.lastname: Nikaido
authors.forename: J
authors.initials: J
authors.lastname: Tagami
mesh_terms: D000704:Analysis of Variance; D020770:Compomers / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003782:Dental Pulp / Q000648:ultrastructure; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D006874:Hydrostatic Pressure; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: C112828:Clearfil AP-X; D020770:Compomers; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C088486:Dyract; C118368:F2000 cement; D005899:Glass Ionomer Cements; D008689:Methacrylates; D019279:Resin Cements; D017640:Silicates