title: Resin-dentin interfacial ultrastructure and microtensile dentin bond strength after five-year water storage.
abstract: OBJECTIVE
  To evaluate a total-etch three-step adhesive system's resin-dentin interfacial ultrastructure and microtensile dentin bond strength (microTBS) after multi-year storage in water.
  
  
  METHODS
  Resin composite crowns were formed on 600 grit SiC flattened extracted human molars using a total-etch three-step adhesive system (Optibond FL, Kerr) and a hybrid resin composite (Prodigy, Kerr). microTBS specimens were fabricated and placed in water with 0.5% chloramine T at 37 degrees C until respective static load to failure testing at one-month, six-months and five-year storage. Failure modes were determined by scanning electron microscopy. The interfacial ultrastructure of the resin-dentin interface was analyzed by transmission electron microscopy (TEM) at 48-hours and 44-months storage. microTBS was modeled with Weibull distribution for survival analysis and failure curve distributions were analyzed by the Wald chi-square statistic for significant differences at alpha=0.05.
  
  
  RESULTS
  The characteristic tensile strength (sigma omicron) at one-month, six-months and five-year storage was 52.63, 14.77 and 23.57 Mpa, with a Weibull modulus of 3.04, 1.56 and 1.28, respectively. Failure distributions for all groups were significantly different (p<0.0001) with one-month > five-year > six-months. TEM interfacial morphology demonstrated hydrolytic degradation of hybrid layer components at 44-months storage.
  
  
  CONCLUSIONS
  The decrease in tensile strength and changes in ultrastructure may be caused by water sorption and resultant hydrolytic degradation of the adhesive joint.
authors.affiliation: Department of Operative Dentistry, College of Dentistry, University of Iowa, Iowa City, IA, USA. steven-armstrong@uiowa.edu
authors.forename: Steven R
authors.initials: SR
authors.lastname: Armstrong
authors.forename: M A
authors.initials: MA
authors.lastname: Vargas
authors.forename: I
authors.initials: I
authors.lastname: Chung
authors.forename: D H
authors.initials: DH
authors.lastname: Pashley
authors.forename: J A
authors.initials: JA
authors.lastname: Campbell
authors.forename: J E
authors.initials: JE
authors.lastname: Laffoon
authors.forename: F
authors.initials: F
authors.lastname: Qian
mesh_terms: D000042:Absorption; D000134:Acid Etching, Dental; D000327:Adsorption; D003188:Composite Resins / Q000737:chemistry*; D003442:Crowns; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D006868:Hydrolysis; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D016019:Survival Analysis; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; C469607:OptiBond FL; C099128:Prodigy; D019279:Resin Cements; D014867:Water