Fiber‐post bond strength in canals obturated with a cross‐linked gutta‐percha core obturator

The aim of this in‐vitro study was to evaluate the bond strength of fiber posts cemented in a root canal filled using various root‐canal obturation techniques. A total of 33 monoradicular samples, treated endodontically, were randomly assigned to three groups according to the root‐canal obturation technique: group 1, continuous‐wave technique; group 2, plastic‐obturator‐core technique; and group 3, cross‐linked gutta‐percha obturator‐core technique. Fiber posts were luted in each sample and each was sectioned perpendicular to the post axis. The push‐out test was performed using a universal machine and the maximum failure load was recorded in MPa mm^?2. Several samples were randomly chosen for scanning electron microscopy evaluation. The mean debris and dentinal tubule‐opening scores were calculated separately in the coronal and apical portions. Bond strength was significantly higher in group 1 than in groups 2 and 3. Debris scores were significantly higher in the apical portion of groups 2 and 3 than in group 1. Within the limitations of this study it can be affirmed that thermoplasticized alpha gutta‐percha seemed to worsen the cleaning of post‐space walls and hence reduced fiber‐post bond strength.     

The influence of methodological variables on the push‐out resistance to dislodgement of root filling materials: a meta‐regression analysis

The aim of this systematic review was to evaluate the influence of several methodological variables on the push‐out resistance to dislodgment of root filling materials by a meta‐regression analysis of the literature. A systematic review was performed by searching the PubMed database using the terms ‘push‐out’ and ‘pushout’. Laboratory studies published before March 2015 were included. Two reviewers extracted data regarding country of origin, year of publication, tooth type, smear layer removal, root canal sealer, core material, obturation technique, sample storage, tooth portion, test machine load velocity and slice thickness. Pooled mean resistance to dislodgement of all groups from the included studies was used in a linear meta‐regression of random effects (α = 0.05). Of the 850 identified studies, 53 met the inclusion criteria. A meta‐regression of the 341 groups extracted from these articles was performed to analyse the influence of each variable on resistance to dislodgement (in MPa). The sealer, core material, obturation technique, slice thickness, storage time, load velocity and tooth portion significantly influence the results (P < 0.05). Irrigant solution and smear layer removal did not influence the resistance to dislodgement of the root filling materials (P > 0.05). Methodological variables such as sealer, core material, root filling technique, tooth type, tooth portion, slice thickness, storage time and load velocity influenced the resistance to dislodgment. The inclusion and standardization of all related variables could lead to a more comparable and reproducible analysis of the resistance to dislodgment of the root canal sealers.     

Bond strength of Resilon/Epiphany compared with Gutta‐percha and sealers Sealer 26 and Endo Fill

This study evaluated the bond strength of Epiphany^®/Resilon^® to radicular dentine and compared this with that of Gutta‐percha sealed with Sealer 26 and also Endo Fill^®. Fifteen human single‐rooted extracted teeth had their root canals enlarged to a standardised internal root diameter of 1.5 mm. The teeth were filled with: Group I – Epiphany^®/Resilon^® cones, Group II – Sealer 26^®/Gutta‐percha cones and Group III – Endo Fill^®/Gutta‐percha cones. Three 2 mm‐thick cross‐sections were obtained from each tooth (n = 15) and subjected to a push‐out test (1 mm min^?1). The means (MPa) were compared using anova /Newman–Keuls tests. There were no statistically significant differences between Group I and Group II (P > 0.01). Both bond strengths were significantly higher than that of Group III (P < 0.01). The root canal filling system Epiphany^®/Resilon^® showed bond strength similar to that of Sealer 26^®/Gutta‐percha. Both were higher than that of Endo Fill^®/Gutta‐percha.     

Ultramicroscopic study of the interface and sealing ability of four root canal obturation methods: Resilon versus gutta‐percha

Recently, filling materials have been introduced based on the dentine adhesion technologies used in conservative dentistry in an attempt to seal the root canal more effectively. The purpose of this study was to investigate the interface between the canal and root‐filling material. Sealing ability of four root canal obturation methods was analysed by means of scanning electron microscopy. Extracted single‐rooted teeth were endodontically treated and filled with gutta‐percha/Pulp Canal Sealer using the Thermafil (TH) technique, gutta‐percha/Pulp Canal Sealer using the System B (SB) technique, Resilon points/RealSeal (RS) and RealSeal 1/RealSeal (RS1). Specimen interfaces were analysed using field‐emission scanning electron microscopy. The adhesive groups RS and RS1, formed hybrid layers but showed areas of separation (gaps) similar to those in the conventional obturation groups. The RS and RS1 groups showed less separation in the coronal third, but the separation was similar to that in the TH and SB groups in the middle and apical thirds. The sealing ability of Resilon is not superior to that of existing materials.     

Push‐out bond strength of an experimental self‐adhesive resin cement

The adhesion of fiber posts luted with simplified adhesive systems has been a matter of great interest over the past years. The aim of this study was to assess the post retentive potential of experimental self‐adhesive resin cement (EXP) when used alone and in combination with a self‐etch adhesive. Fiber posts were placed in endodontically treated teeth and divided into four groups (n = 6) according the luting material, as follows: group 1 (EXP alone); group 2 (EXP used with self‐etch adhesive); group 3 (marketed dual‐cured cement used with self‐etch adhesive); and group 4 (marketed self‐adhesive cement). The push‐out test was used to assess the retentive strength of fiber posts (expressed in MPa), and specimens were analyzed under a stereomicroscope to determine failure mode. The adhesive interface between the cement and root canal dentin for each group was evaluated using scanning electron microscopy. The post retentive potential of group 1 (EXP) (7.48 ± 4.35 MPa) was comparable with that of marketed cements from group 4 (6.79 ± 3.68 MPa) and group 3 (8.77 ± 4.58 MPa). When EXP was used in combination with self‐etch adhesive (group 2), significantly higher push‐out bond‐strength values were measured (15.87 ± 4.68 MPa) compared with the other groups.     

Push‐out bond strength of gutta‐percha with a new bioceramic sealer in the presence or absence of smear layer

The purpose of this study was to compare the bond strength of a new bioceramic sealer (EndoSequence BC Sealer) and AH Plus in the presence or absence of smear layer. Extracted single‐rooted human teeth were prepared and randomly divided into four groups. In groups 1 and 3, the root canals were finally irrigated with 5.25% NaOCl and smear layer was not removed, but in groups 2 and 4, the root canals were finally irrigated with 17% EDTA followed by 5.25% NaOCl in order to remove the smear layer. In groups 1 and 2, the root canals were obturated with gutta‐percha/AH Plus, but in groups 3 and 4, obturation was performed with gutta‐percha/EndoSequence BC Sealer. Push‐out bond strength and failure modes were evaluated. The bond strength of gutta‐percha/AH Plus and gutta‐percha/EndoSequence BC Sealer was not significantly different (P = 0.89). The presence or absence of smear layer did not significantly affect the bond strength of filling materials (P = 0.69). The mode of bond failure was mainly cohesive for all groups. In conclusion, the bond strength of the new bioceramic sealer was equal to that of AH Plus with or without the smear layer.     

Promotion of adhesive penetration and resin bond strength to dentin using non‐thermal atmospheric pressure plasma

Non‐thermal atmospheric pressure plasmas (NT‐APPs) have been shown to improve the bond strength of resin composites to demineralized dentin surfaces. Based on a wet‐bonding philosophy, it is believed that a rewetting procedure is necessary after treatment with NT‐APP because of its air‐drying effect. This study investigated the effect of ‘plasma‐drying’ on the bond strength of an etch‐and‐rinse adhesive to dentin by comparison with the wet‐bonding technique. Dentin surfaces of human third molars were acid‐etched and divided into four groups according to the adhesion procedure: wet bonding, plasma‐drying, plasma‐drying/rewetting, and dry bonding. In plasma treatment groups, the demineralized dentin surfaces were treated with a plasma plume generated using a pencil‐type low‐power plasma torch. After the adhesion procedures, resin composite/dentin‐bonded specimens were subjected to a microtensile bond‐strength test. The hybrid layer formation was characterized by micro‐Raman spectroscopy and scanning electron microscopy. The plasma‐drying group presented significantly higher bond strength than the wet‐bonding and dry‐bonding groups. Micro‐Raman spectral analysis indicated that plasma‐drying improved the penetration and polymerization efficacy of the adhesive. Plasma‐drying could be a promising method to control the moisture of demineralized dentin surfaces and improve the penetration of adhesive and the mechanical property of the adhesive/dentin interface.     

Effect of different root canal obturating materials on push-out bond strength of a fiber dowel

Purpose: During dowel space preparation, the instrumentation forms a thick smear layer along with sealer‐occluded dentinal tubules. The purpose of this study was to evaluate the effect of different obturating materials on push‐out bond strength of a fiber dowel. Materials and Methods: Fifty human uniradicular teeth were decoronated and prepared using the step‐back technique. The specimens were divided into five groups on the basis of obturating materials: group I received no obturation; group II (ZOE) gutta‐percha and zinc oxide eugenol sealer; group III (ZOAH) gutta‐percha and AH plus sealer; group IV (GF) GuttaFlow; and group V (RE) with Resilon Epiphany system. Dowel spaces were made with manufacturer's provided drills, and a fiber dowel was luted. Horizontal slices were obtained from the middle third, and push‐out bond strength (S) was evaluated. Statistical analysis was carried out using one‐way ANOVA and post hoc Tukey's test. Results: The push‐out bond strength values in the control group, ZOE, ZOAH, GF, and RE were 9.303 ± 0.565 MPa, 8.859 ± 0.539 MPa, 8.356 ± 0.618 MPa, 9.635 ± 0.435 MPa, and 8.572 ± 0.256 MPa, respectively. There was no statistically significant difference between the S values of all the groups (p > 0.05). Conclusion: There was no effect of different tested obturating materials on the push‐out bond strength of fiber dowels; however, further studies should be conducted.     

Various irrigation protocols for final rinse to improve bond strengths of fiber posts inside the root canal

Irrigation after post space preparation and its effects on the bond strength of different adhesive strategies are still an issue of interest. The aim of the present study was to investigate the effects of various irrigation protocols (IPs) on the push‐out bond strengths of fiber posts. One‐hundred and fifty extracted human anterior teeth were divided into three groups (n = 50 each) and endodontically treated. The post space was irrigated before post placement using the following five IPs in each group: IP1 (control): 5 ml of distilled water; IP2: 5.25% sodium hypochlorite (NaOCl) applied with passive ultrasonic irrigation (PUI); IP3: 1% NaOCl applied with PUI; IP4: 18% ethylenediaminetetracetic acid (EDTA) followed by 5.25% NaOCl; and IP5: 2% chlorhexidine (CHX). Fiber posts placement in each group was performed using three different adhesive strategies. A self‐etch adhesive system revealed higher bond strength (16.2 ± 6.9 MPa) compared with an etch‐and‐rinse adhesive (8.5 ± 4.2 MPa) and a self‐adhesive resin cement (9.2 ± 4.7 MPa). The use of 18% EDTA/5.25% NaOCl increased the bond strength of the self‐adhesive resin cement. Conversely, this IP decreased the bond strength for the etch‐and‐rinse adhesive system, whilst 1% NaOCl enhanced the bond strength for the same system. Consequently, each adhesive strategy may need to be adapted to a specific IP.