title: Bond strength and ultimate tensile strength of resin composite filled into dentine cavity; effect of bulk and incremental filling technique.
abstract: OBJECTIVE
  The aim of this study was to evaluate the relationship between micro-tensile bond strength (muTBS) and ultimate tensile strength (UTS) of resin composite restorations in cavities filled by a bulk or incremental technique using the micro-tensile test.
  
  
  METHODS
  Class I cavities (4mm long, 3mm wide, 3mm deep) were prepared into dentine of sixteen human molars. All cavities were bonded with Clearfil SE Bond and restored with AP-X composite with either a bulk or incremental technique. After storage in water for 24h, the teeth were vertically sectioned to yield two slabs. Each slab was sectioned into three sticks. Sticks of one slab were trimmed into an hourglass of 0.7 mm2 area at resin-dentine interface for bond strength measurement while the other sticks were trimmed at the centre of the restoration for UTS measurement. Specimens were tested in tension at 1mm/min until failure. The results obtained were statistically analysed using two-way ANOVA and post hoc test (alpha=0.05). Pearson's correlation test was used to identify any correlation between muTBS and UTS for each filling method.
  
  
  RESULTS
  Both muTBS and UTS of resin composite decreased towards the bottom of the cavity (p<0.05). The bulk technique group presented lower muTBS than the incremental technique groups at all regions (p<0.05). In bulk filled restoration, there was a strong positive linear relationship between mean values of muTBS and UTS of resin composite based on the depth (r2=.99; p<0.05), while in incremental restoration there was no relationship between the variables.
  
  
  CONCLUSIONS
  There was a relationship between muTBS and UTS of resin composite filled into dentin cavity in bulk technique.
authors.affiliation: Cariology and Operative Dentistry, Department of Restorative Science, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-Ku, Tokyo 113-8549, Japan. nayif.ope@tmd.ac.jp <nayif.ope@tmd.ac.jp>
authors.forename: Ma'an M
authors.initials: MM
authors.lastname: Nayif
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakajima
authors.forename: Richard M
authors.initials: RM
authors.lastname: Foxton
authors.forename: Junji
authors.initials: J
authors.lastname: Tagami
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins; D001840:Dental Bonding; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D003804:Dentin; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates; D008855:Microscopy, Electron, Scanning; D008963:Molar; D019279:Resin Cements; D013718:Tensile Strength
chemical_list: C112828:Clearfil AP-X; C438313:Clearfil SE Bond; D003188:Composite Resins; D008689:Methacrylates; D019279:Resin Cements