title: Stability of bonds made to superficial vs. deep dentin, before and after thermocycling.
abstract: OBJECTIVE
  Bonding stability of resinous adhesives to dentin is still problematic and may involve regional variations in dentin composition. This study is to evaluate the effect of dentin depth on the stability of resin-dentin bonds under thermocycling challenge.
  
  
  METHODS
  Dentin slabs with two flat surfaces parallel to the tooth axis were obtained from extracted human third molars. The slabs were randomized into eight groups according to the location of dentin [deep dentin (DD) or superficial dentin (SD)], the adhesive treatment (Single Bond 2 or Clearfil S(3) Bond), and the storage treatment (thermocycling for 5000 times vs. no). After the adhesive treatment and composite buildup on the dentin slabs, the micro-shear bond strength (μSBS) of each group was detected. The concentrations of cross-linked carboxyterminal telopeptide of type I collagen (ICTP) were also evaluated using an immunoassay to detect the degree of collagen degradation in each group.
  
  
  RESULTS
  Dentin depth, adhesive treatment and storage treatment all showed significant effects on both the μSBSs and the ICTP values (P<0.05). Regardless of the adhesive type, thermocycling decreased the μSBSs and increased the ICTP values (P<0.05). The DD groups showed significantly lower μSBSs and higher ICTP values than SD groups after thermocycling aging (P<0.05). The treatment with Single Bond 2 significantly increased the ICTP values (P<0.05), whereas Clearfil S(3) Bond showed no effect on the ICTP values (P>0.05).
  
  
  CONCLUSIONS
  Deep dentin showed significantly more bond degradation after thermocycling than did superficial dentin.
authors.affiliation: State Key laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.affiliation: State Key laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China; Department of Stomatology, Xi'an medical university, Xi'an, China.
authors.forename: Dan-yang
authors.initials: DY
authors.lastname: Wang
authors.affiliation: Department of Endocrine & Vascular Surgery, Xi'jing Hospital, Fourth Military Medical University, Xi'an, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Fan
authors.affiliation: State Key laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Li
authors.affiliation: State Key laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Yu-jiang
authors.initials: YJ
authors.lastname: Chen
authors.affiliation: State Key laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China. Electronic address: jhchen@fmmu.edu.cn.
authors.forename: Ji-hua
authors.initials: JH
authors.lastname: Chen
mesh_terms: D003094:Collagen / Q000378:metabolism; D003804:Dentin / Q000737:chemistry*; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D020782:Matrix Metalloproteinases / Q000378:metabolism; D033081:Shear Strength; D013696:Temperature
chemical_list: D003094:Collagen; D020782:Matrix Metalloproteinases
keywords: Cross-linked carboxyterminal telopeptide of type I collagen; Dentin depth; Matrix metalloproteinases; Microshear bond strength; Stability