The effect of different irrigation materials and application techniques on push-out bond strength of fiber post to root dentin

Statement of the problem: Achieving a reliable bond to root canal dentin is a subject of
ongoing research. Improving the bond strength between root dentin and fiber posts through different
irrigation materials and techniques used during post space preparation has been suggested; yet,
there is a few data regarding the irrigation materials and application techniques that could be used
to achieve an optimum bond.
Purpose: The aim of this invitro study was to evaluate the effect of different irrigation materials
(NaOCl + EDTA and Qmix) and application techniques (syringe, passive ultrasonic irrigation, XP
finisher) on the push-out bond strength of fiber posts to root dentin.
Materials and methods: Forty eight human premolars, with straight root canals and average
root length of 17±1 mm were selected. The clinical crowns were cut 2mm above the cementoenamel
junction. Root canal treatment was done with ProTaper universal rotary instruments to size F4 and
then obturated with lateral condensation technique and AdSeal sealer. Teeth were then stored in
distilled water for 7 days at 37˚C after sealing of the access cavity with temporary filling free from
eugenol. For each tooth, post space preparation was done using gates glidden drills leaving 4-5 mm
of gutta percha as apical seal. FibreKleer post tapered drill corresponding to the glass fiber post
size was used to remove any residual root filling. The prepared roots were equally and randomly
divided into two main groups (n = 18) before post cementation as follows; Group I: Irrigation with
10 ml of 2.6% NaOCL over 60 seconds followed by 5 ml EDTA for another 60 seconds, Group II:
Irrigation with 3 ml Q-mix for 60 seconds. Each of the two main groups was further divided into 3
subgroups, Subgroup A (n = 6): Conventional syringe irrigation (IA, IIA), Subgroup B (n = 6):
Passive ultrasonic irrigation (PUI) was performed for 60 seconds (IB, IIB), Subgroup C (n = 6):
XP finisher was used with a torque-controlled motor according to the manufacturer’s instructions.
The canal was filled with irrigant and the finisher was operated for 60 seconds using slow and
gentle in-and-out movements (IC, IIC). All posts were tried-in, cleaned with alcohol, and then
silanized with ceramic primer for 60 seconds then air dried. Cementation was done using Rely X
Unicem 2 self adhesive resin cement.
After the luting procedure, the coronal part of the posts was covered completely with resinmodified
glass ionomer cement and the roots were stored in distilled water for 7 days at 37˚C.
Roots were embedded in epoxy resin and transversely sectioned perpendicular to the long axis of
the root with an Isomet machine. It was pre-set to serially obtain six specimens (2 mm ± 0.1) thick,
where two specimens corresponded to each root third. For push-out testing, each specimen was
mounted in a custom made loading fixture then subjected to compressive loading with the apical
surface upwards at a crosshead speed of 1 mm/min via a computer controlled testing machine.
The maximum failure load was recorded in Newton and converted into MPa. Two teeth as a
representative of each subgroup were split longitudinally after post space preparation and irrigation,
and smear layer was examined using scanning electron microscope at 1, 4.5, and 8mm levels from
the apical to the coronal third of the post space at 1000 magnification. Data were recorded, tabulated
and statistically analysed.
Results: Regarding the push-out bond strength results; it was found that regardless of application
techniques or radicular regions, there was no significant difference in the push-out bond strength
between both irrigation solutions as proven by three-way ANOVA test, where (NaOCl + EDTA ≥
Q mix). Irrespective to irrigation solutions or radicular regions, there was significant difference in
the push-out bond strength between application techniques as demonstrated by three-way ANOVA
test , where (PUI ≥ XP > Syringe). Pair-wise Turkey’s post-hoc showed no significant difference in
the push-out bond strength between (PUI and XP). Regardless of irrigation solutions or application
techniques; there was no significant difference in the push-out bond strength between radicular
regions as verified by three-way ANOVA test where (cervical ≥ apical ≥ middle). Regarding the
smear layer marking; it was found that there was non-significant difference between both irrigation
solutions as proven by Chi square test where (NaOCL+EDTA > Qmix). There was also nonsignificant
difference between irrigation application techniques as demonstrated by Chi square test
where (Syringe ≥ PUI≥ XP). In addition, there was non-significant difference between radicular
regions as verified by Chi square test where (apical ≥ middle ≥ cervical).
Conclusions Within the limitations of this study it was concluded that:
1. Q mix irrigation solution decreased the bond strength between root dentin and fiber posts
when self adhesive luting agent was used.
2. The use of XP finisher and passive ultrasonic irrigation as irrigant activation devices
improved the bond strength between root dentin and fiber posts compared to conventional
syringe irrigation.