A tensile test to facilitate identification of defects in dentine bonded specimens.
OBJECTIVE
To determine the efficacy of a miniaturized dumbbell test procedure designed to more easily identify defect(s) in bonded dentine test specimens.


METHODS
Extracted human dentine substrates were pre-conditioned with 10-3 solution for 10, 30 or 60 s prior to dentine bonding with 4-META/MMA-TBB resin. Miniaturized dumbbell-shaped test specimens were prepared from the resin bonded samples. After 24 h storage in 37 degrees C water, the specimens were tensile-loaded to failure. Fractured surfaces and cross-sections were examined and compared under scanning electron microscopy (SEM) and transmission electron microscopy (TEM).


RESULTS
Cohesive failure within the bonding resin was observed in specimens pre-conditioned for 10 s. The tensile bond strength of these was excellent. Bond strengths of specimens that were pre-conditioned for 30 and 60 s were significantly lower, and defects in these specimens, formerly difficult or impossible to identify, were readily identified under SEM and TEM microscopy.


CONCLUSIONS
The proposed method of tensile stressing to failure and microscopically examining fractured miniaturized dumbbell-shaped test specimens is a simple and reproducible test procedure. The protocol is capable of clearly elucidating defective resin infiltration of demineralized dentine in bonded interfaces. These defects are difficult to visualize by conventional and/or ISO recommended methods.
Nakabayashi
N
N
Institute for Medical and Dental Engineering, Tokyo Medical and Dental University, Japan.
Watanabe
A
A
Arao
T
T
D000328:Adult; D001896:Boron Compounds / Q000737:chemistry; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D008689:Methacrylates / Q000737:chemistry; D020366:Methylmethacrylate; D008768:Methylmethacrylates / Q000737:chemistry; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008904:Miniaturization; D019904:Polymethyl Methacrylate / Q000737:chemistry; D015203:Reproducibility of Results; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D014867:Water
D001896:Boron Compounds; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D008768:Methylmethacrylates; D014867:Water; C009523:tri-n-butylborane; D020366:Methylmethacrylate; C034139:4-methacryloxyethyltrimellitic acid anhydride; D019904:Polymethyl Methacrylate