Long-term bond strength of fiber posts cement to dentin with self-adhesive or conventional resin cements

The aim of this study was to evaluate the immediate and the long-term push-out bond strength of glass fiber posts (GFP) cemented with conventional or self-adhesive dual-curing resin cements, at different root depths. Prior to cementation, the GFP (Reforpost #3, Angelus) were etched with 37% phosphoric acid for 30 s followed by silane for 1 min. Thirty canine roots were divided into two groups (n = 15) according to resin cement type: ARC – dual resin cement (RelyX ARC/3M ESPE) combined with an three-step etch-and-rinse adhesive (Adper Scotch Bond Multi-Purpose Plus 3M/ESPE) or U200 – self-adhesive resin cement (RelyX U200/3M ESPE). The manufacturer’s instructions were followed. After 48 h, the roots were cross-sectioned at three different depths, resulting in serial slices corresponding to the cervical, middle, and apical root thirds. Slices were randomly divided into two groups, according to the period of water storage prior to push-out bond strength analysis: 48 h or 180 days. The data (MPa) were analyzed using three-way ANOVA for randomized blocks (p < 0.05), which showed no significant interaction between the three factors (p = 0.716). The main study factors were also proven not significant (cement: p = 0.711; time: 0.288; root third: p = 0.646). In conclusion, root depth, cement type (self-adhesive or conventional), and storage in water for 180 days did not influence the bond strength of GFP to intracanal dentin.     

Effects of simulated pulpal pressure,mechanical and thermocycling challenge on the microtensile bond strength of resin luting cements

This study aimed at comparing the microtensile bond strength (µTBS) of three simplified luting strategies after different aging processes. Sixty human molars were prepared to expose flat middle dentin surfaces which received the following luting procedures: (i) SB+ARC – two-step etch-and-rinse adhesive+conventional resin cement (Adper Singlebond 2+RelyX ARC, 3M-ESPE); (ii) S3+PAN – one-step self-etch adhesive+conventional resin cement (Clearfil S3+Panavia F2.0, Kuraray Medical); (iii) U200 – self-adhesive resin cement (RelyX U200,3M-ESPE). The specimens were finally restored by indirect resin composite procedures (Filtek Z100,3M-ESPE). The aging regimens were water storage at 37 °C for one week (control), one week of 20 cm H₂O simulated pulpal pressure (SPP), 200,000 mechanical loading (ML) cycles, or 5000 thermal cycles (TC). The µTBS data was analyzed by two-way ANOVA and Tukey's test (α=0.05). SB+ARC showed significantly higher µTBS for control and all aging processes (p<0.001). Nevertheless, TC had no effect on the bond strength of SB+ARC. No difference in µTBS was observed between S3+PAN and U200 after SPP (p=0.251), but significant lower values were found for U200 after ML (p=0.010) besides being superior in the control groups (p<0.001). For U200, all ageing regimens induced significant reductions in the bond strength (p<0.001) with a more pronounced negative effect after ML. S3+PAN showed significant lower bond strength (p=0.010) only after ML aging. Two-step etch-and-rinse adhesive associated with dual-curing conventional resin cement may present the highest overall µTBS. However, the use of S3 one-step self-etch adhesive along with conventional resin cements may provide the most stable luting performance under the tested aging strategy.     

Endodontic irrigants effect on long-term intraradicular adhesion of resin cements

The aim of this study was to evaluate over time the bond strength of dual-cure and self-adhesive resin cements used for bonding fiberglass posts following irrigation with different solutions. Ninety roots from single-rooted premolars were selected and divided into 6 groups (n = 15) according to the resin cement, dual-cure or self-adhesive (RelyX ARC and RelyX U100) or the endodontic irrigant used (2% chlorhexidine digluconate - CH, 1% sodium hypochlorite - SH and deionized distilled water – control). Following post cementation, the roots were cross-sectioned in order to obtain two slices from each root third (cervical, mid and apical). The specimens were stored for 7 or 180 days in water and the push-out bond strength test applied. The data was analyzed using three-way ANOVA and Tukey Kramer. The interaction endodontic irrigants-resin cement vs. storage time was significant (p = 0.008), where 7 days of storage induced no difference between the groups, however, after 180 days, the groups for which CH or SH combined with RelyX U100 were used showed higher bond strength values than RelyX ARC, regardless of the irrigant solution. There was no difference between the use of RelyX ARC after 7 and 180 days of storage. For Rely X U100 180 days of storage increased the push-out bond strength when either CH or SH was used. The dual-cure and self-adhesive resin cements associated with CH or SH demonstrated similar immediate bond strength performance. The self-adhesive cement, however, showed improved bond strength over time when either irrigant was used.     

Shear Bond Strength of Indirect Composites Luted with Three New Self-Adhesive Resin Cements to Dentin

The aim of this study was to evaluate the shear bond strengths of indirect composites (those cured outside the mouth) luted by three different, recently developed, self-adhesive resin cements to dentin. Seventy caries-free mandibular third molar teeth embedded in acrylic resin and with exposed dentin surfaces were used. Teeth were randomly divided into seven groups. The following application protocols were carried out: a) Group 1 (control group)—direct composite resin restoration (Alert) with total-etch adhesive system (Bond 1 primer/adhesive); b) Group 2—indirect composite restoration (Estenia) luted by a resin cement (Cement-It) combined with the same total-etch adhesive; c) Group 3—direct composite resin restoration with self-etch adhesive system (Nano-Bond); d) Group 4—indirect composite restoration luted by the resin cement combined with the same self-etch adhesive; e) Groups 5–7—indirect composite restoration luted with self-adhesive resin cements (RelyX Unicem®, Maxcem®, and Embrace WetBond®, respectively) onto untreated dentin surfaces. Shear bond strengths of the groups were performed with a universal testing device. Results were statistically analysed by student-t and one way ANOVA tests. The fractured surfaces were also examined by SEM. The indirect composite restorations luted with the self-adhesive resin cements (Groups 5–7) showed successful results compared with the other groups (p < 0.05). Group 4 showed the weakest bond strength (p > 0.05). Open dentin tubules were observed on the total-etch adhesive applied surfaces whereas a smear rich layer was found by SEM on the self-etch adhesive applied surfaces. The new universal self-adhesive resins may be considered an alternative for luting the indirect composite restorations onto the untreated dentin surfaces.     

Effect of timing for core preparation,luting cement type and root level on adhesion of fiber posts to intraradicular dentin

This study assessed the effect of timing of core preparation and luting cement on adhesion of fiber-reinforced composite (FRC) posts on different levels of intraradicular dentin when cemented with either conventional dual-polymerized or self-adhesive resin cement. Single-rooted human teeth (N = 80) were endodontically treated and randomly divided into 2 groups (n = 40) according to resin cement: (a) Conventional dual resin cement (Variolink II, V) or (b) Self-adhesive resin cement (RelyX U200, R). They were further divided into two subgroups according to timing of core preparation (n = 20): (a) immediate (i) or (b) delayed (d). FRC posts (Cytec Blanco) were cemented and the roots were sliced into discs at the coronal, middle, and apical levels. Push-out tests were then performed in a Universal Testing Machine (1 mm/min). Data (MPa) were analyzed using three-way ANOVA and Tukey’s tests considering the factors ‘core preparation time’, ‘luting cement’, and ‘root level’ (α = 0.05). Type of luting cement (p < 0.001), time of core preparation (p < 0.001), and root level (p < 0.001) significantly affected the bond strength results. R cement was more significantly affected by core preparation time (Ri: 2.91 ± 1.1; Rd: 4.83 ± 1.68) compared to V cement (Vi: 2.92 ± 1.63; Vd: 2.65 ± 1.6) (p < 0.05). Coronal region demonstrated significantly higher bond strength values than those of middle and apical third in all groups (coronal: 4 ± 1.9; middle: 3.1 ± 1.4; apical: 2.4 ± 1.1) (p < 0.05). Adhesive failure between cement and dentin was the most frequent (64%) followed by adhesive failure between cement and post (18%). Delayed core preparation can improve bond strength of FRC posts to intraradicular dentin when cemented with self-adhesive cement compared to conventional dual-polymerized resin cement.     

The effect of nano-structured alumina coating on the bond strength of resin-modified glass ionomer cements to zirconia ceramics

The purpose of this study was to evaluate the effect of Y-TZP ceramic surface functionalization with a nano-structured alumina coating on bond strength of the resin modified glass ionomer dental cement. A total of 160 disc-shaped specimens were produced and randomly divided into two groups of 80. Half of the discs in each group received an alumina coating which was fabricated by exploiting the hydrolysis of aluminum nitride (AlN) powder. The shear bond strengths of the resin-modified glass ionomer cement FUJI+ (GC Japan) and the composite resin luting agent RelyX Unicem (3M ESPE, USA) were then studied for the coated and uncoated surfaces The SEM analyses revealed that the application of an alumina coating to the Y-TZP ceramics created a highly retentive surface for bonding. The bond strengths for the coated groups in both cements were significantly higher than the uncoated groups.     

The influence of endodontic sealer dentine penetration on fibreglass post retention

This study aimed to evaluate the influence of endodontic sealer inside dentinal tubules on the retention of fibreglass posts. One hundred eighty extracted teeth were instrumented with rotary instruments and divided into two groups (n = 90) according to their filling technique: (LC) lateral condensation and (CT) controlled technique, and subdivided into three subgroups according to the endodontic sealer used: (A) epoxy resin sealer, (B) zinc-oxide and eugenol sealer, and (C) bioceramic endodontic sealer. After root preparation, each subgroup received a fibreglass posts cemented with (1) adhesive resin cement, (2) self-adhesive resin cement, and (3) glass ionomer cement. After stored for 15 days at 37 °C and 100% humidity, the teeth were sectioned transversely into 1-mm thick slices and subjected to laser confocal scanning microscopy and push-out test. The failure mode was analyzed by stereo microscope, and scanning electron microscopy images of representative fractures were made. Although there were no significant differences in the dislocation resistance among the filling techniques (p > 0.05), the type of sealer used affected bond strengths on the cervical and middle thirds. Fibreglass posts cemented with glass ionomer cement presented higher values for the push-out test than those cemented with resin cements (p < 0.05). Mix failure modes were predominant and occurred in all experimental groups. The use of bioceramic endodontic sealer was able to reduce the bond strength, mainly when the fibreglass posts was cemented by resin cement.     

Resin Bonding to Silicatized Zirconia with Two Isocyanatosilanes and a Cross-linking Silane. Part II: Mechanistic Approach

In this paper we discuss and interpret the results of shear bond strengths achieved after the use of two silane coupling agents with isocyanato functionality, viz. 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane. The silanes were used alone and also blended with a non-functional cross-linking silane on silicatized zirconia before light-curing of resin stubs on the surface, as described elsewhere in the first part of our study (see “Part I: Experimental”). A series of reaction mechanisms and conceptual diagrams are also presented. The reaction mechanisms illustrating the effect of adding a cross-linking silane into a silane blend, the silane hydrolysis and the behavior of two organofunctional groups (isocyanate and alkene) of silanes upon reaction with Rely X Unicem Aplicap resin-composite cement are discussed in detail.     

Resin Bonding to Silicatized Zirconia with Two Isocyanatosilanes and a Cross-linking Silane. Part I: Experimental

In this paper we discuss and interpret the results of shear bond strengths achieved after the use of two silane coupling agents with isocyanato functionality, viz. 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane. The silanes were used alone and also blended with a non-functional cross-linking silane on silicatized zirconia before light-curing of resin stubs on the surface, as described elsewhere in the first part of our study (see “Part I: Experimental”). A series of reaction mechanisms and conceptual diagrams are also presented. The reaction mechanisms illustrating the effect of adding a cross-linking silane into a silane blend, the silane hydrolysis and the behavior of two organofunctional groups (isocyanate and alkene) of silanes upon reaction with Rely X Unicem Aplicap resin-composite cement are discussed in detail.     

Degree of conversion and adhesion of methacrylate-based resin cements with phosphonic or phosphoric acid acrylate to glass fiber posts at different regions of intraradicular dentin

This study evaluated the degree of conversion (DC) and adhesion of methacrylate-based resin cements to glass fiber posts at different regions of intraradicular dentin. Single-rooted teeth (N?=?24, n?=?12 per group) were cut at the cement–enamel junction (CEJ), endodontically treated and post space (depth?=?8 mm) was prepared. Teeth were randomly divided into two groups according to the resin cements: (a) Group ML: methacrylate-based cement with phosphonic acid acrylate (Multilink Automix, Ivoclar Vivadent); (b) Group RXU: methacrylate-based cement with phosphoric acid acrylate (RelyX Unicem 2 Automix, 3 M ESPE). Fiber-reinforced composite root posts (RelyX Fiber Post, 3 M ESPE) were cemented according to the manufacturers’ instructions of the resin cements. Root slices of 2-mm thickness (n?=?3 per tooth) were cut below the CEJ 1, 3, and 5 mm apically. The DC of each section was analyzed with micro-Raman spectrometer and push-out test was performed in the Universal Testing Machine (0.5 mm/min). After debonding, all specimens were analyzed using optical microscope to categorize the failure modes. While data (MPa) were statistically evaluated using Kruskal Wallis, Mann–Whitney U tests for DC data 3-way ANOVA and Tukey’s tests were used (α?=?0.05). Regardless of the resin cement type, the mean push-out bond strength results (MPa), were significantly higher for the coronal slices (ML: 9.1?±?2.7; RXU: 7.3?±?4.1) than those of the most apical ones (ML: 7?±?4.9; RXU: 2.89?±?1.5) (p?=?0.002). Resin cement type and (p?p?=?0.002) significantly affected the DC values, while the interaction terms were not significant (p?=?0.606). Overall, DC was significantly higher for ML (67?±?8.2%) than RXU (26?±?8.8%) (p?相似文献   

Deproteinization stabilises dentin bonding of self-adhesive resin cements after thermocycling

This study examined the effect of deproteinization on the microtensile dentin bond strength (µTBS) and nanoleakage (NL) of conventional and self-adhesive resin cements after 24 h or after 20,000 thermocycles. Occlusal dentin of thirty-two human molars were distributed into four groups according to the type of cement used: conventional or self-adhesive; and the strategy of luting: RelyX ARC/Single Bond 2 (RAc) following the manufacturer׳s instructions (control), RelyX ARC/Single Bond 2 (RAd) applied after dentin deproteinization; RelyX U200 (RUc) following the manufacturer´s instructions (control); RelyX U200 (RUd) applied after dentin deproteinization. The specimens were cut into non-trimmed dentin–composite sticks and the half sticks of each group were subdivided into two subgroups: 24 h water storage and after 20,000 thermal cycles, before microtensile bond test. For NL, 5 bonded sticks from each subgroup were prepared and analyzed under SEM. Three-way ANOVA showed that the dentin deproteinization increased the µTBS of both cements, although the RAd group showed a decrease on the µTBS after thermocycling. Chi-square test showed significant loss of specimens by premature failure for the groups after thermocycling, except for the RUd group. The dentin deproteinization improved the initial µTBS and decreases the NL of both cements tested, but, after thermocycling, this technique is only effective for RelyX U200.     

Bonding ability of self-adhesive resin-cements after dentin biomodification with hyaluronic acid

Purpose: The present study evaluated the influence of the hyaluronic acid (HA) on the bonding ability of self-adhesive resin cements to dentin regarding the bond strength. Eighty bovine incisors were ground flat to obtain a 2-mm thick slices which received conical preparations. The specimens were randomly distributed into 4 groups (n = 15) according to the dentin pretreatment (1 – control: untreated dentin; 2 – application of HA) and the evaluation time (1 – control: immediate evaluation; 2 – hydrolytic degradation: 6 months of storage in water at 37 °C). Preparations received the application of a self-adhesive resin cement (RelyX U200 or MaxCem Elite). Push-out bond strength test was conducted (0.5 mm/min). The bond strength data was submitted to two-way ANOVA/Tukey’s test (α = 0.05). For U200, no significance was observed when comparing the immediate (24 h) and 6 months means for the control groups (unexposed specimens). Previous application of HA to dentin significantly reduced the bond strength of U200 to dentin in both evaluation times (p < 0.05). HA had no significant influence on the push-out bond strength means for the cement MAX in both evaluation times (p > 0.05). The type 1 failure mode (adhesive mode) occurred in 100% of the specimens, irrespective of the dentin treatment or evaluation times. Pretreatment of dentin with HA produces a material-dependent influence on the push-out bond strength. The bonding ability of RelyX U200 is negatively influenced by the pretreatment of dentin with HA, whereas the biomodification of dentin with this bioactive agent causes no impact for the cement MaxCem Elite.     

Assessment of the initial and aged dentin bond strength of universal adhesives

This study evaluated the effect of mechanical loading on microtensile bond strengths (μTBS) of universal adhesives to dentin and quantified adhesive dentin penetration using micro-Raman spectroscopy. Human molars had occlusal dentin exposed and were allocated into eight groups: All-Bond Universal and Scotchbond Universal using etch-and-rinse and self-etch approaches, Adper Prompt L-Pop, Adper Single Bond Plus, Clearfil SE Bond, and Optibond FL. Following bonding procedures and build-ups, specimens were either stored in water at 37 °C for 24 h or mechanically loaded (50,000 cycles, 50 N) prior to μTBS test. Additional teeth were prepared for micro-Raman analysis of adhesive penetration and FE-SEM. Data were analyzed by two-way ANOVA and Tukey׳s post hoc test (P<0.05). Mechanical loading had no deleterious effect on μTBS with the exception of Adper Prompt L-Pop. Incomplete infiltration of the demineralized dentin was noticed for adhesives using the etch-and-rinse approach and for Scotchbond Universal in the self-etch approach.     

The sonic application of universal adhesives in self-etch mode improves their performance on enamel

The objective of this study was to evaluate the effect of sonic application of universal adhesives on the enamel microshear bond strengths (µSBS), in situ degree of conversion (DC) and etching pattern. Ninety-six extracted third molars were sectioned in four parts (buccal, lingual, proximal) and divided into 12 groups, according to the combination of 1) adhesive system (All-Bond Universal [ABU], G-Bond Plus [GBP], Prime&Bond Elect (PBE), and Scotchbond Universal Adhesive [SBU]), and 2) adhesive application mode (manual active etch-and-rinse [M-ER], manual active self-etch [M-SE], and sonic vibration self-etch [S-SE]). Specimens were stored in water at 37 °C during 24 h and tested at 1.0 mm/min (µSBS). DC was evaluated in the enamel-resin interfaces using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a field- emission scanning electron microscope. Data were analyzed with two-way ANOVA and Tukey's test (α = 0.05). S-SE application increased µSBS and DC for all universal adhesives when compared to M-SE (p < 0.05). S-SE application resulted in mean bond strengths that were statistically similar to those obtained with the respective ER application mode (p > 0.05). A deeper enamel-etching pattern was observed for all universal adhesives in the etch-and-rinse strategy. An improvement in etching ability was observed in S-SE application compared to M-SE application. In light of the improved performance of universal adhesives when applied sonically in SE mode, selective enamel etching with phosphoric acid may not be crucial for their adhesion to enamel. The sonic application of universal adhesives in self-etch mode may be a practical alternative to enamel etching.     

Bonding of novel self-glazed zirconia dental ceramics

ABSTRACT

Bonding behaviours of a novel self-glazed zirconia dental material were investigated. The effect of a preformed porous nanoceramic bonding surface and the different cleansing methods on saliva-contaminated bonding surfaces was assessed in this in vitro study. Cleaning procedures commonly used in dental offices were tested. All specimens demonstrated adhesive fracture patterns except for airborne particle abrasion group, which resulted in mixed-type fracture pattern and the highest bonding force values. No statistically significant differences in bonding force values were found between self-glazed zirconia with and without a preformed porous nanoceramic bonding surface when bonded with the self-adhesive resin cement (RelyX? Unicem 2). Scanning electron micrographs revealed no interaction between the bonding surface and the resin cement after priming. Mechanical retention is the predominant bonding mechanism between the bonding surface and the luting resin cement.     

Effect of root canal sealers on the push-out bond strengths of tooth-colored posts to root dentine

Objectives: This study evaluated the effect of different root canal sealers on the push-out bond strength of tooth-colored posts to root dentin. Material and methods: Eighty human mandibular premolar teeth with single roots were decoronated and randomly divided into two groups according to post material: G1–G5: Cytec blanco; G6–G10: Cosmopost. In each group, the specimens were further subgrouped according to the filling material plus sealer (n = 8): G1, G6: Gutta-percha + AH Plus; G2, G7: Resilon + Epiphany SE; G3, G8: Gutta-percha + Sealite; G4, G9: Gutta-percha + iRoot SP; and G5, G10: control (unobturated). Cytec blanco and Cosmopost of 1.4 mm diameter were adhesively luted to samples using Variolink II. Push-out test was performed in a universal testing machine, and failure modes were examined under stereomicroscope. Data were analyzed with the two-way ANOVA and post hoc Tukey’s tests. Statistical significance was set to 0.05. Results: Roots obturated with AH Plus (3.48 ± 1.41 MPa), Sealite (3.47 ± 0.65 MPa), and Resilon (3.36 ± 1.23 MPa) had the lowest bond strength (p < 0.005). iRoot SP and control group samples showed the highest bond strength values (7.38 ± 0.89 MPa and 6.43 ± 1.16 MPa, respectively) (p < 0.05). Significant differences were observed among tooth-colored posts and sealers (p < 0.05). Adhesive failures were predominant in all groups (48%). Conclusions: When the resin cement Variolink II was used, the types of root canal filling materials and sealers could affect the retentions of the fiber/zirconium posts; the fiber post revealed the higher bond values than the zirconium post; and the calcium silicate-based sealer (iRoot SP) revealed the highest bond strengths.     

Microscopic evaluation of the thickness and structure of the cement and cement–dentin interdiffusion zone after luting posts with three different luting cements

Clinical studies report that failures of fiber post cementation occur mainly at the cement–dentin interface. The aim of this in vitro study is to compare the scanning electron microscopic (SEM) evaluations of the cement thicknesses in the root canals and the thickness of cement–dentin interface zones obtained after luting standardized glass-fiber posts with three different types of luting cements. Thirty single-rooted mandibular premolars of similar sizes were prepared for post insertion after biomechanical preparation and obturation. They were divided into three groups containing 10 samples each. Standardized glass-fiber posts were cemented with zinc phosphate cement for ZNP group, with conventional adhesive resin cement for CAR group, and with self-adhesive resin cement for SAR group. The formation and thickness of cement and cement–dentin interface zone were evaluated by stereomicroscope and SEM using ×800 magnification, and the data were analyzed. There was no significant difference between groups in terms of cement thickness (p = 0.835); however, there were significant differences among the cement layer thicknesses measured at the three examined levels of the root canals (p = 0.000). The groups using conventional adhesive resin cement presented longer micromechanical interlocking while the groups using self-adhesive resin cement showed wide gaps and zinc phosphate cement showed no bonding between cement–dentin interdiffusion zones along the root canal. As a clinical consequence, the use of zinc phosphate cement may not provide strong bond between dentin–cement interface. Conventional adhesive resin cements showed reliable bond to dentin when compared to zinc phosphate and self-adhesive resin cement.     

Influence of glass fiber post translucency on microhardness and dentin bond strength of resin cement at different root levels

The aims of this study were (a) to evaluate the influence of glass fiber post translucency on the hardness of a light-cure resin cement within the root canal; (b) to assess dentin bond strength at different root levels. Fifty human canine roots were randomly divided into five groups. Translucent posts (Exacto, Angelus; White Post DC, FGM; FRC Postec Plus, Ivoclar Vivadent) were used in three groups, opaque posts (Exacto Opaco, Angelus) were used in one group and no posts were used in the last group. The posts were cemented using a light-cure resin cement (Variolink N Base, Ivoclar Vivadent). The roots were cross-sectioned into slices (two from the cervical, two from the middle, and two from the apical thirds) which were then submitted to microhardness and push-out tests. Two-way analysis of variance and Tukey test were performed. Cement microhardness was significantly higher in the translucent post groups when compared to opaque posts and no post. At the apical third, the White Post DC and FRC Postec groups showed higher microhardness values than those in the Exacto Translucido group. The type of glass fiber post did not significantly influence bond strength values. White Post DC and FRC Postec Plus provided higher resin cement microhardness values, especially at the most apical thirds. Bond strength was not dependent on the type of post used. Failure mode analysis suggested superior cement curing when the translucent posts were used.     

Impact of conditioning regimens and time on adhesion of a fiber post to root dentin using two resin cements

The aim of this study was to evaluate the influence of irrigation protocols on the bond strength of a glass fiber post bonded to dentin using two resin cements. In 200 root-filled teeth, post space was prepared and divided into five groups (n?=?40) based on the irrigation protocol: group 1 (3% sodium hypochlorite), group 2 (3% sodium hypochlorite – 17% Ethylene diamine tetraacetic acid), group 3 (a mixture of sodium hypochlorite and etidronic acid), group 4 (sodium hypochlorite – QMix), and group 5 (distilled water). Samples were subdivided into two subgroups (n?= 10) and fiber posts were cemented using subgroup A (Self-adhesive dual-cure resin cement; SEA) or B (dual-cure resin cement following an etch-and-rinse protocol, ER). Push-out bond strength was performed after 24 h and four months (n?= 10) and failure modes were categorized. Statistical analysis of data was carried out by appropriate analyses (p < 0.05). The irrigation protocol and the resin cement had a significant impact on push-out bond strength. Subgroup A group showed lower bond strength than B at both time periods when 3% NaOCl–17% EDTA and 1:1 mixture of 6% NaOCl + 18%EA protocols were used. Three percent NaOCl used in combination with 17% EDTA or QMix significantly decreased the push-out bond strength of ER at the end of four months (p < 0.05). In conclusion, dual-cure resin cements bonded with etch-and-rinse protocol showed highest bond strength when a mixture of NaOCl and etidronic acid was used as root canal irrigant. These values were differentially influenced by time.     

Effect of erosive challenge and Nd:YAG laser irradiation on bond strength of adhesive systems to dentin

PurposeTo evaluate the effect of Nd:YAG laser irradiation and erosive challenge on bond strength of two adhesive systems to dentin.MethodsTwenty bovine incisors were cut and grounded to obtain eighty slabs of flat dentin. Specimens were allocated into eight groups, based on: adhesive system—a two-step etch-and-rinse and a two-step self-etch; laser irradiation—Nd:YAG (1 W/10 Hz) or control (no laser irradiation); and erosive challenge after restorative procedure—presence or absence of erosive challenge. Nd:YAG laser groups were submitted to laser irradiation before the restorative procedure. Blocks of composite resin were built up on the bonded surfaces with a Southern Dental Industries device to perform shear bond strength (SBS) test. After, each specimen of erosive challenge, groups were subjected to immersion in Sprite Zero^® (20 ml/2 h/24 °C/under agitation). The SBS test (0.5 mm/min) was performed after 24 h of water storage at 37 °C. Failure mode was evaluated with a stereomicroscope (X400). Data were analyzed with three-way ANOVA and Tukey’s post hoc tests (α=0.05).ResultsThe etch-and-rinse adhesive system presented higher bond strength values than self-etch adhesive. Laser irradiation increased the bond strengths values when erosive challenge was present. The predominant failure mode observed was adhesive.ConclusionsThe irradiation of Nd:YAG laser positively influences the bond strength values when erosive challenges are present. Moreover, the etch-and-rinse adhesive system is a better option to be used in dentin in this clinical condition.