title: The influence of age and depth of dentin on bonding.
abstract: OBJECTIVE
  The purpose of this study was to investigate what influence the two variables of dentin depth and age may have on the tensile bond strengths of three bonding systems.
  
  
  METHODS
  Dentin discs prepared from human molars were divided into young and old, superficial and deep surfaces. Three bonding systems, Scotchbond Multi-purpose (3M Dental Products), Superbond D-liner (Sun Medical Co.), and Liner Bond II (Kuraray Co.) were the materials tested for tensile bond strength. In addition, the structural variation of the resin-impregnated, or hybrid, layer was compared among the two variables and three bonding systems.
  
  
  RESULTS
  Tensile bond strengths exceeding 10 MPa were obtained for all materials. After ANOVA, an effect on tensile bond strength could be attributed to dentin age or depth for only Superbond D-liner used on deep-young dentin as compared with old-superficial dentin. All other group comparisons failed to show any variation between dentin depth or age. However, specimens bonded to deeper dentin showed slightly lower strengths. SEM observations showed thicker resin-impregnated layers for Scotchbond MP and Superbond D-liner compared with Liner Bond II. Liner Bond II exhibited a thinner and more diffuse resin-impregnated layer, believed to be due to the different dentin conditioning method.
  
  
  CONCLUSIONS
  Dentin age or depth may not show as great an influence on bond strengths with the newer type of bonding systems. The resin-impregnated layer quality, rather than thickness, is believed to be the most important factor for obtaining high tensile bond strengths.
authors.affiliation: Tokyo Medical and Dental University, Department of Operative Dentistry, Japan.
authors.forename: M F
authors.initials: MF
authors.lastname: Burrow
authors.forename: H
authors.initials: H
authors.lastname: Takakura
authors.forename: M
authors.initials: M
authors.lastname: Nakajima
authors.forename: N
authors.initials: N
authors.lastname: Inai
authors.forename: J
authors.initials: J
authors.lastname: Tagami
authors.forename: T
authors.initials: T
authors.lastname: Takatsu
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D001840:Dental Bonding; D003804:Dentin / Q000033:anatomy & histology* / Q000502:physiology / Q000648:ultrastructure; D017220:Dentin-Bonding Agents; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates; D008855:Microscopy, Electron, Scanning; D009811:Odontometry; D019279:Resin Cements; D018709:Statistics, Nonparametric; D013718:Tensile Strength
chemical_list: C084544:Clearfil Linerbond System; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; C084543:Super Bond D-Liner