title: Effects of layering techniques on the micro-tensile bond strength to dentin in resin composite restorations.
abstract: OBJECTIVE
  The purpose of this work was to investigate the effects of layering techniques in resin composite restorations on the micro-tensile bond strength to the dentin of the occlusal cavity.
  
  
  METHODS
  Human premolars were extracted and randomly divided into four groups. The occlusal enamel was then removed to expose a flat superficial dentin surface. Cavities 3.5mm long and 3.5mm wide were prepared to a depth 3mm below the dentin surface. The adhesive Single Bond was applied according to the manufacturer's instructions. The teeth were then restored with Z100 resin composite as follows: Group 1 was restored in horizontal increments (three layers). Groups 2 and 3 were restored in different oblique increments (three layers). Group 4 was restored in oblique increments (four layers). After 24h storage at 37 degrees C in water, all the teeth were sectioned to obtain bar-shaped specimens with a bonded surface area of approximately 0.9 mm x 0.9 mm. Dentin micro-tensile bond strength was measured at a crosshead speed of 0.5mm/min. The results obtained were statistically analyzed using one-way ANOVA and SNK test at a significance level of P=0.05. All fractures were then observed under a scanning electron microscope (SEM).
  
  
  RESULTS
  The results showed that there is a significant difference between the strength of the micro-tensile bonds to the dentin of occlusal cavities depending on which of the four layering restorative techniques was used (P<0.01). SEM observation showed that failure patterns were most evidently interfacial cohesive failure.
  
  
  CONCLUSIONS
  Layering techniques in resin composite restorations affected the micro-tensile bond strength between the resin composite and the dentin. But the outcomes related to only Single Bond, as the same using other adhesives might have different outcomes.
authors.affiliation: Key Laboratory for Oral Biomedical Engineering of Ministry of Education, School & Hospital of Stomatology, Wuhan University, Wuhan, Hubei, China.
authors.forename: Yumei
authors.initials: Y
authors.lastname: Niu
authors.forename: Xue
authors.initials: X
authors.lastname: Ma
authors.forename: Mingwen
authors.initials: M
authors.lastname: Fan
authors.forename: Sijie
authors.initials: S
authors.lastname: Zhu
mesh_terms: D000134:Acid Etching, Dental; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000379:methods; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000379:methods; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D012822:Silicon Dioxide / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C083568:Z100 composite resin; C115612:single bond; D014867:Water; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium