Conventional dual-cure versus self-adhesive resin cements in dentin bond integrity

Abstract

During post preparation, the root canal is exposed to the oral cavity, and endodontic treatment may fail because of coronal leakage, bacterial infection and sealing inability of the luting cement.Objectivethis study quantified the interfacial continuity produced with conventional dual-cure and self-adhesive resin cements in the cervical (C), medium (M) and apical (A) thirds of the root. Material and methodsForty single-rooted human teeth were restored using Reforpost # 01 conical glass-fiber posts and different materials (N=10 per group): group AC=Adper™ ScotchBond™ Multi-purpose Plus + AllCem; group ARC=Adper™ ScotchBond™ Multi-purpose Plus + RelyX ARC; group U100=RelyX U100; and group MXC=Maxcem Elite. After being kept in 100% humidity at 37ºC for 72 hours, the samples were sectioned parallel to their longitudinal axis and positive epoxy resin replicas were made. The scanning electron micrographs of each third section of the teeth were combined using Image Analyst software and measured with AutoCAD-2002. We obtained percentage values of the interfacial continuity. ResultsInterfacial continuity was similar in the apical, medium and cervical thirds of the roots within the groups (Friedman test, p>0.05). Comparison of the different cements in a same root third showed that interfacial continuity was lower in MXC (C=45.5%; M=48.5%; A=47.3%) than in AC (C=85.9%, M=81.8% and A=76.0%), ARC (C=83.8%, M=82.4% and A=75.0%) and U100 (C=84.1%, M=82.4% and A=77.3%) (Kruskal-Wallis test, p<0.05). ConclusionsAllcem, Rely X ARC and U100 provide the best cementation; cementation was similar among root portions; in practical terms, U100 is the best resin because it combines good cementation and easy application and none of the cements provides complete interfacial continuity.

Relining effects on the push-out shear bond strength of glass fiber posts

“…As a result, the shear bond strength data showed high variance, and were therefore analyzed by non-parametric procedures, as adopted in an earlier study 18 .…”

“…These zones consist of lateral resin projections together with discontinuous gaps along the interface between the cement-adhesive system throughout the root canal, which are probably produced by polymerization shrinkage 18 . The hygroscopic expansion of the cements produced by water sorption is believed to reduce the size of the gaps produced by shrinkage and improve marginal sealing 20 .…”

“…This is explained by the deficient dentin hybridization 18,23,24 and incomplete smear layer removal promoted by its weak-acid monomers and hydrolysis of adhesive components 7 . Given these discrepancies, the bonding behavior of cements deserves further studies, especially since the high variability of the root canal environment hinders the application of cementation techniques.…”

“…Cement shrinkage stress results from the C-factor (ratio of the bonded to the unbonded surface areas of the cavity), which is likely to exceed 200 in root canals 5 . This causes loss of integrity and gap formation at the adhesive interface 5,8,18 . Of several studies reviewed, only those of Muniz, Mathias 27 and Bitter et al 28 found higher push-out shear bond strength in the apical third.…”

“…These findings confirm the difficulty in establishing good interaction between the cement and dentin substrate, probably because of the great variability in root canal morphology and features of resin system bonding, as described in other studies 13,25 . Although some studies 10,13,18 have discussed the post relining technique, further studies are needed to safely apply this procedure. In practical terms, the post lining technique coupled with the use of multistep etch-and-rinse cements is more complex than the technique with the use of RelyX TM U100 self-adhesive cement, thus the former requires more skilled operators, material resources and longer clinical time.…”