The purposes of this study were to investigate the reliability and efficiency of a new evaluation method for resin bonding to root canal dentin, which measures both marginal adaptation and shear bond strength simultaneously, and to determine the effects of root canal irrigants on resin bonding. A wet bonding system (Single Bond) and a self-etching primer system (Clearfil Mega Bond) were employed; NaClO was used as a root canal irrigant. No gaps or changes in bond strength were observed despite the NaClO treatment when the wet bonding system was employed, while the gap formation ratio increased, and bond strength decreased with longer NaClO treatment time when the self-etching primer system was employed. These findings suggested that this new experimental method was effective for evaluating resin systems to the root canal wall dentin which is affected by irrigation with NaClO.
ThisstudyinvestigatedthehardnessandYoung'smodulusofcoronalandradicularintertubulardentin.Tenbovineteeth were each divided into coronal and radicular groups, and the flat surfaces of the coronal and radicular dentin were subsequentlyprocessedalongthetoothaxis.ThehardnessandYoung'smodulusofthecoronalandradicularintertubular dentinwereevaluatedusingnanoindentationtests,attwolocationspertooth.MeanhardnessandYoung'smodulusvalues werestatisticallycomparedbyone-wayANOVAandFisher'sPLSDtest.Thehardnessofcoronalintertubulardentinwas 0.81±0.05GPaandthatofradiculardentinwas0.55±0.02GPa.Additionally,theYoung'smodulusofcoronalintertubular dentin was 26.60±2.19 GPa and that of radicular dentin was 20.89±1.10 GPa. Findings of this study revealed that the hardnessandYoung'smodulusofcoronalintertubulardentinweregreaterthanthoseofradicularintertubulardentin.
Bovine teeth are used for dental research as a substitute for human teeth.In the present study, the effects of storage on the tensile strength of bovine dentin were investigated. Storage conditions selected were frozen storage for 1 week, 4 weeks, and 1 year. Boiling in water for 45 minutes was also employed to clarify the effect of heat.Dumbbell-shaped specimens were prepared from teeth of each condition and tensile tests were performed immediately.The same tests were also performed on specimens, as a control, prepared from bovine teeth within 8 hours of extraction.The tensile strength of the control was 76.1MPa; 1 week frozen storage, 78.7MPa; 4 weeks, 79.9MPa; 1 year, 79.0MPa. The tensile strength of bovine dentin remained unchanged during one year frozen storage. On the other hand, the tensile strength of bovine dentin after boiling was 70.3MPa, showing that tensile strength had decreased.
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