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

Abstract

Statement of the problem: Achieving a reliable bond to root canal dentin is a subject ofongoing research. Improving the bond strength between root dentin and fiber posts through differentirrigation 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 usedto 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, XPfinisher) on the push-out bond strength of fiber posts to root dentin.Materials and methods: Forty eight human premolars, with straight root canals and averageroot length of 17±1 mm were selected. The clinical crowns were cut 2mm above the cementoenameljunction. Root canal treatment was done with ProTaper universal rotary instruments to size F4 andthen obturated with lateral condensation technique and AdSeal sealer. Teeth were then stored indistilled water for 7 days at 37˚C after sealing of the access cavity with temporary filling free fromeugenol. For each tooth, post space preparation was done using gates glidden drills leaving 4-5 mmof gutta percha as apical seal. FibreKleer post tapered drill corresponding to the glass fiber postsize was used to remove any residual root filling. The prepared roots were equally and randomlydivided into two main groups (n = 18) before post cementation as follows; Group I: Irrigation with10 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 3subgroups, 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 andgentle in-and-out movements (IC, IIC). All posts were tried-in, cleaned with alcohol, and thensilanized with ceramic primer for 60 seconds then air dried. Cementation was done using Rely XUnicem 2 self adhesive resin cement.After the luting procedure, the coronal part of the posts was covered completely with resinmodifiedglass 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 ofthe 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 wasmounted in a custom made loading fixture then subjected to compressive loading with the apicalsurface 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 arepresentative 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 fromthe apical to the coronal third of the post space at 1000 magnification. Data were recorded, tabulatedand statistically analysed.Results: Regarding the push-out bond strength results; it was found that regardless of applicationtechniques or radicular regions, there was no significant difference in the push-out bond strengthbetween 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 inthe push-out bond strength between application techniques as demonstrated by three-way ANOVAtest , where (PUI ≥ XP > Syringe). Pair-wise Turkey’s post-hoc showed no significant difference inthe push-out bond strength between (PUI and XP). Regardless of irrigation solutions or applicationtechniques; there was no significant difference in the push-out bond strength between radicularregions as verified by three-way ANOVA test where (cervical ≥ apical ≥ middle). Regarding thesmear layer marking; it was found that there was non-significant difference between both irrigationsolutions as proven by Chi square test where (NaOCL+EDTA > Qmix). There was also nonsignificantdifference between irrigation application techniques as demonstrated by Chi square testwhere (Syringe ≥ PUI≥ XP). In addition, there was non-significant difference between radicularregions 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 postswhen self adhesive luting agent was used.2. The use of XP finisher and passive ultrasonic irrigation as irrigant activation devicesimproved the bond strength between root dentin and fiber posts compared to conventionalsyringe irrigation.