Effect of relining on fiber post retention to root canal

Abstract

One of the clinically relevant problems dentists face when restoring endodontically treated teeth is the mismatch between fiber post and post space diameters, which results in an excessively thick resin cement layer. Fiber post relining appears as a solution for this problem.Objectives:The aim of this study was to evaluate the effect of fiber post relining with composite resin on push-out bond strength.Material and Methods:Twenty bovine incisors were selected to assess post retention. The crowns were removed below the cementoenamel junction and the root canals were treated endodontically and flared with diamond burs. The roots were allocated into two groups (n=10): G1: fiber posts without relining and G2: fiber posts relined with composite resin. The posts were cemented with a dual-cured resin cement and the specimens were sectioned transversally. Three 1.5-mm thick slabs were obtained per root and identified as cervical, medium and apical thirds. The push-out test was performed at a crosshead speed of 0.5 mm/min until post dislodgement occurred. The failure mode of fractured specimens was analyzed under scanning electron microscopy. Data were analyzed by split-plot ANOVA and post-hoc Tukey's test at a pre-set alpha of 0.05.Results:Relined fiber posts presented higher retention values than non-relined post in all thirds. No statistically significant differences (p>0.05) were found among thirds for relined posts. All failures occurred at the interface between resin cement and root dentin.Conclusions:Relining with composite resin seems to be an effective method to improve the retention of fiber posts to flared root canals.

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

“…Adhesive failure at the cement-dentin interface was the most common defect (57%), as shown in Figure 1A, followed by mixed fracture, which represented adhesive fracture associated with cohesive failure of the cement ( Figure 1B). 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.…”

“…Therefore, the third hypothesis tested in the present study, which was that post shear bond strength would be higher in the cervical than in the other root regions, was accepted. Indeed, the highest bond strength values were found in the cervical root region, except for ARC-R and U100-NR, in which no statistical differences were found between the root thirds, as also reported by Faria-e-Silva et al 13 .…”

“…Indeed, another study showed that post relining enhanced shear bond strength, irrespective of cement type 14 . However, the hypothesis was only partially accepted since the effects of relining were observed only when RelyX ARC cement was used, as found by Faria-e-Silva et al 13 . The ARC-R treatment produced a thinner, more uniform and stronger cement layer compared with that of ARC-NR, the latter exhibiting low bond strength values in the middle and apical third of roots.…”

“…Nevertheless, this technique has a number of advantages. The relined post is tightly inserted into the root canal, so that cement pressure against the canal walls improves cement-bond contact, avoiding water absorption 13 and reducing porosity at the bond interface 13,19 . This prevents bubble formation 11 that can inhibit polymerization, if there are trapped bubbles in the cement layer 19 .…”

“…Few studies have shown the efficiency of relined posts 13,14 , also known as anatomical posts 10,12 . Some researchers 7,8 have attributed the shear strength of intraradicular fiber post cementation not only to the action of adhesive agents but also to frictional forces; however, studies that investigate this relationship are scarce, especially as regards shaped glass fiber posts.…”