Influence of surface energy parameters of dental self-adhesive resin cements on bond strength to dentin

The purpose of this study was to determine the surface energy parameters of dental self-adhesive resin cements (SRCs) and to measure their bond strength to dentin. Six dental SRCs (RelyX Unicem Clicker, RU; Maxcem Elite, ME; BisCem, BC; Clearfil SA Luting, SA; Multilink Speed, MS; seT PP, SP) and one resin-modified glass ionomer cement (RelyX Luting 2, RL; control) were tested. Smear layer-covered bovine dentin was used as bonding substrate. Using the dynamic sessile drop method, surface energy, surface energy components, degree of hydrophobicity/hydrophilicity (expressed as ΔG _sws using thermodynamic notation), and apparent surface energies for each material were calculated. The luting cements were bonded to the dentin and stored in water at 37?°C for 24?h prior to shear bond strength test (n?=?10). Pearson correlation analysis was applied to detect possible correlations between surface energy parameters and measured shear bond strength (α?=?0.05). RU, SA, and MS produced negative ΔG _sws values (hydrophobic), whereas ME, BC, SP, and RL yielded positive ones (hydrophilic). RU had the highest value among all six SRCs tested, the value for MS being statistically equivalent (p?=?0.785). The base component, ΔG _sws, and surface energy determined with water showed significant negative linear correlations with dentin bond strength (r/p?=??0.801/0.030, ?0.900/0.006, and ?0.892/0.007, respectively). These results suggest that bonding to smear layer-covered bovine dentin was governed by the base component and the hydrophobicity/hydrophilicity of the SRCs.     

Bond strength and chemical interaction of self-adhesive resin cements according to the dentin region

The aim of the study is to evaluate the effectiveness and level of chemical interaction of self-adhesive resin cements (SRCs) according to the dentin region. One hundred eight sound human third molars and three SRCs were selected: Bifix SE (Voco), Maxcem Elite (Kerr), and RelyX U200 (3M ESPE). Ninety human molars were used for the bond strength test and 18 teeth for the X-ray diffraction (XRD) characterization. A flat surface of superficial, deep, or axial dentin was exposed. For bond strength evaluation, 90 indirect composite resin restorations (10 mm in diameter, 2.0 mm-thick) were built and cemented with one of the SRCs according to the manufacturer's instructions. The restored teeth were then cut into sticks with cross-sectional areas of 0.8 mm² and tested in tensile at a speed of 0.5 mm/min (n=10). The results of bond strength were statistically analyzed by two-way ANOVA and Tukey's test (α=0.05). The fractured specimens were classified under SEM. The remaining teeth were further sectioned in order to build dentin fragments with 2.0 mm² of area and 0.2 mm in thickness for XRD analysis. In general, significantly higher bond strength was found when bonding to axial and deep dentin compared to superficial dentin. Comparing the bonding effectiveness of the SRCs, taking into account the mean bond strength obtained in the 3 dentin regions, the study found no significant difference (p>0.05). Although RelyX U200 showed similar bond strength irrespective of the dentin region (p>0.05), the bonding results of the other 2 SRCs varied significantly (p<0.05). There was a higher incidence of cohesive failure in the SRCs for all groups. The XRD analysis detected different perceptual reductions of hydroxyapatite crystallinity for all SRCs, indicating a particular chemical interaction in each experimental condition. Thus, it can be concluded that the bond strength and chemical interaction of the SRCs can vary significantly according to the dentin region.     

Micro-computerized tomography analysis of cement voids and pull-out strength of glass fiber posts luted with self-adhesive and glass-ionomer cements in the root canal

This study evaluated the pull-out strength of different glass fiber posts and measured volume of cement and voids in the cement in the root canal utilizing micro-computerized tomography (micro-CT) analysis after they were cemented with two different luting cements. Canine teeth (N = 40) were endodontically treated and randomly divided into four groups depending on the fiber post and the cement type (n = 10 per group) as follows: Group RU: (RelyX + RelyX U200), Group PU: (PINpost + RelyX U200), Group RF: (RelyX + FujiCEM 2), Group PF: (PINpost + FujiCEM 2). Each tooth was scanned using micro-CT and the percentage of cement and void volume at the coronal, middle, and apical levels was calculated. Pull-out tests were performed by applying tensile load parallel to the long axis of the posts (0.5 mm/min). Data were analyzed using, ANOVA, Kruskal–Wallis, and Mann–Whitney U tests (α = 0.05). Regardless of cement type, the percentage (%) of cement volume in the RelyX post groups (RU:31–36; RF:29–40) was significantly higher than that in the PINpost groups (PU:19–23; PF:18–22) (p < 0.05). The percentage of void volume at the PINpost groups (PU:6–11; PF:8–13) was significantly lower than that in the RelyX groups (RU:2; RF:3) (p < 0.05). No significant differences were observed in pull-out strength (N) between the four experimental groups (RU:358.8 ± 56.2; RF:299 ± 64.8; PU:311.9 ± 61.3; PF:293.1 ± 91.3) (p > 0.05). The micro-CT analysis demonstrated that the percentage of cement and void volumes vary depending on the type of fiber post and cement used. No correlation between cement, void volume, and pull-out strength was observed.     

Effect of cyclic loading and resin cement type used for luting fiber posts on bond strength at different root levels of crown-restored human teeth

Objective: This study aimed to evaluate the bond strength (BS) of glass fiber posts (GFP) at different root levels when luted with conventional or self-adhesive cements in crown-restored human premolars subjected, or not, to cyclic mechanical loading.

Materials and Methods: Sixty lower premolar roots were endodontically treated and prepared for a GFP system. Half of the roots (n = 30) had their posts cemented with a self-adhesive resin cement, while the remaining roots followed a three-step conditioning method: acid etch, bonding agent, and a conventional resin cement. Metal crowns were luted onto the post-core preparations and the specimens were embedded to simulate the periodontium. Half of the specimens from each group (n = 15) were submitted to cyclic loading simulations (130 N; 2.0 Hz) and then sections were obtained from each root for the pushout BS test.

Results: Independently of the cyclic loading and the root level tested, the conventional resin cement provided significantly higher values of BS (p = 0.002). For either cement or either root level, cyclic loading caused a significant decrease in BS values (p = 0.023). The Tukey test indicated that, regardless of the resin cement used or the cyclic loading, BS was highest at the middle and cervical thirds of the root (p = 0.026), and their values did not differ between themselves.

Conclusions: When used for luting GFP, self-adhesive resin cement resulted in lower pushout BS than the conventional counterpart, with cyclic loading causing a decrease in BS of the GFP to dentin for both resin cements.     

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 2% chlorhexidine digluconate application and water storage on the bond strength to superficial and deep dentin

The aim of the present in vitro study was to evaluate the effect of chlorhexidine, applied before a self-etching adhesive system (Clearfil SE Bond) on microtensile bond strength to superficial and deep dentin (DD), immediately and after six months of water storage (WS). Forty dentin specimens were divided into two groups according to dentin depth: superficial and deep. The specimens were then divided according to the solution to be applied (n = 10): CLX: 2% chlorhexidine (passively applied for 60 s) and NT (no treatment). A self-etching adhesive system was applied according to the manufactures instructions, with composite restorative placed on the dentin surface. After 24 h, dentin–resin blocks were sectioned into beam-shaped specimens that were submitted to microtensile bond strength testing either immediately or after six months of WS. Data were submitted to three-way ANOVA (α = 0.05). Bond strength values for the deep dentin group were significantly lower than those observed for superficial dentin (SD) (p = 0.002), whether chlorhexidine solution had been applied or not. There was no statistical difference in bond strength for specimens tested after 24 h and 6 months of WS. The application of chlorhexidine did not affect immediate and long-term bond strength to dentin. Bond strength in deep dentin was lower than in SD.     

Effect of the frequency of mechanical pulses for fatigue aging testing on push-out bond strength between glass fiber posts and root dentin

The aim of this study was to evaluate the influence of the frequency of mechanical pulses during mechanical fatigue aging on bond strength between glass fiber posts and root dentin. Fiber posts were adhesively cemented in 30 bovine roots and the core was built up with composite. All specimens were subjected to mechanical cycling (45° angle; 37 °C; 50 N; 2×10⁶ pulses) at different frequencies: 2, 4, and 8 Hz. After the fatigue, each specimen was submitted to push out test. The bond strength was calculated for data analysis (one-way ANOVA, p = 0.05). The frequency did not affect the push-out (p = 0.7). The main failure mode was between dentin and cement in all groups. The mechanical pulses were not influenced by the bond strength between root dentin and fiber posts. Thus, it is possible to decrease the time-consuming in vitro tests involving posts without damaging the reliability of the test.     

Evaluation of different desensitizing agents effect on shear bond strength of adhesive resin cement to dentin

Desensitizing agents can inhibit the bonding strength between dentin and adhesive resin cement. This study evaluated the effects of different desensitizing agents on the shear bond strength of adhesive resin cement to dentin. Sixty freshly extracted and caries free teeth were classified into five experimental groups, randomly (n?=?12). Each group was treated with a different desensitizing agent (Teethmate, Shield Force Plus, Admira Protect and Ultra-Ez) respectively, except for an untreated control group. After desensitizing agents and adhesive resin cement were applied to each dentin surface, all specimens were stored in incubator at 37?°C for 24?h. The shear bond strength was tested with a Universal testing machine at a 0.5?mm/min crosshead speed. Data were analysed by using a statistical software (SPSS 22). The results of the measurements were analysed by Kruskal Wallis test with Bonferroni correction and multiple comparisons were made by Wilcoxon test (p???.01). Specimens were examined by a scanning electron microscope, additionally. The Shield Force Plus showed significantly the highest shear bond strength compared with other groups (p?<?.01). Ultra-Ez showed the lowest shear bond strength (p?>?.01). There was no significant difference among Teethmate and Admira Protect groups (p?>?.01). Desensitizing agents containing resin monomers increased the bonding strength, however desensitizers containing calcium phosphate, potassium nitrate and fluoride did not effect the bonding strength of resin cement to dentin.     

Adhesion of conventional and self-adhesive resin cements to indirect resin composite using different surface conditioning methods

This study evaluated the adhesion of conventional and self-adhesive resin cements to indirect resin composite (IRC) using different surface conditioning methods. Cylindrical IRC specimens (N = 192) were randomly assigned to four surface conditioning methods (n = 8 per group): (a) Control group, (b) Hydrofluoric acid, (c) Tribochemical silica-coating, and (d) 50 μm Al₂O₃ air-abrasion. Specimen surfaces were finished using silicon carbide papers up to 600 grit under water irrigation, rinsed and dried. Direct composite blocks were bonded to IRC specimens using three conventional resin cements (Multilink, Panavia F2.0, and Resicem) and three self-adhesive resin cements (RelyX U100, Gcem, Speed Cem). Specimens were subjected to shear bond strength test in a Universal Testing Machine (0.5 mm/min). Failure types were categorized as mixed, adhesive and cohesive. Data were analyzed using 2-way ANOVA and Tukey’s tests. Two-parameter Weibull modulus, scale (m) and shape (0) were calculated. The bond strength results (MPa) were significantly affected by the surface conditioning method (p < 0.0001) and cement type (p < 0.001). For Panavia F2.0, Resicem, air-abrasion with 50 μm Al₂O₃ significantly increased the results (22.6 ± 6.5, 26.2 ± 6.5, respectively) compared to other conditioning methods (13.6 ± 1.4–21.9 ± 3.1) but for Multilink, hydrofluoric acid etching (20.5 ± 3.5) showed significantly higher results (p < 0.01). For the self-adhesive resin cements, air-abrasion with 50 μm Al₂O₃ significantly increased the results compared to other conditioning methods, except for RelyX U100 (p < 0.05). After air-abrasion with Al₂O₃, Gcem, (11.64), RelyX U100 (9.05), and SpeedCem (8.29) presented higher Weilbul moduli. Exclusively cohesive failure in the IRC was observed with RelyX U100 and Speedcem after Al₂O₃ air-abrasion.     

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.     

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.     

Test methods for bond strength of glass fiber posts to dentin: A review

ABSTRACT

In this paper, a review of the test methods for bond strength of glass fiber posts to dentin is presented. The main variables that influence the bond strength tests are related to substrate, to specimen properties, specimen preparation, and test methodology. The impact of these variables on the test outcome is analyzed. The search was performed on studies published between 2007 and 2015. Most of the tests carried out, in the literature, were the push-out (75%), pull-out (13%), and microtensile (11.9%) tests, showing an inversion compared to the results found in studies published between 2005 and 2010, when push-out test was used in a proportion of 2% and microtensile test in a proportion of 67%. The push-out test emerged as a practical tool for evaluating the interfacial shear strength between fiber post and root canal walls.     

Effect of dentinal surface preparation on the bonding of self-adhesive luting cements

The purpose of the present study was to evaluate the bond strength and the interaction morphology of self-adhesive resin luting cements (SLCs) to dentin prepared with different methods. Four SLCs were used: RelyX U100^®, RelyX U200^®, Clearfil SA Luting^®, and SmartCem2^®. A flat dentin surface of 40 human molars was exposed and each tooth was sectioned in four tooth-quarters, which were distributed into four groups according to the SLC used to cement indirect resin composite restorations. The tooth-quarters of each group were then distributed in four subgroups according to the method used for dentin preparation: flat-ended cylindrical fine-grit diamond, flat-ended cylindrical median-grit diamond, flat-ended cylindrical plain-cut tungsten carbide, or abraded with #600-grit SiC paper (control). The restored tooth-quarters were sectioned to obtain beams (0.8?mm²) and submitted to the microtensile bond strength test (n?=?10). The results were analyzed using two-way ANOVA/Tukey (α?=?0.05). Forty-four additional teeth were used for micromorphological investigation of the SLC/dentin interface and of the topographic aspect of the dentin surfaces after application of the SLCs. Only the bond strength of RelyX U200 was significantly influenced by the surface preparation. No interference was identified on the micromorphological aspect of the bonding interfaces. The topographic investigation of the dentinal surfaces showed that the SLCs were not able to effectively remove the smear layer and etch the underlying dentin, irrespective of the preparation method. So, the interference of the dentin preparation on the bond strength of SLCs is material dependent, but don’t influence the micromorphologic aspect of the interaction zone.     

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   

The influence of retention hole and adhesive systems on the shear bond strengths of resin composite to amalgam

The aim of the study is to evaluate the influence of surface-treatment methods with and without the use of a retention hole on the shear bond strength of a resin composite adhered to amalgam using an adhesive system. Amalgam specimens were divided into six groups. Group 1 (Bur) specimens were roughened with a diamond bur, Group 2 (Al₂O₃) specimens were sandblasted with a 50?μm aluminum oxide powder, Group 3 (CoJet^®) specimens were sandblasted with 30?μm CoJet^® Sand, Group 4 (Bur?+?Rh) specimen surfaces were prepared with a retention hole 1?mm in diameter and 1?mm deep and roughened with a diamond bur, Group 5 (Al₂O₃?+?Rh) specimens were also prepared with a retention hole and sandblasted with 50?μm aluminum oxide powder, and Group 6 (CoJet^®?+?Rh) surfaces were prepared with a retention hole and sandblasted with 30?μm CoJet^® Sand. Resin composite cylinders were bonded onto the amalgam surfaces using Xeno^® IV, Optibond? All-In-One, Clearfil? SE Bond, Adper? Single Bond Plus, and Scotchbond? Multi-Purpose adhesive systems. In addition, silane (Monobond S) was used for Groups 5 and 6. The shear bond was determined and statistically analyzed using two-way analysis of variance and post hoc Tukey’s tests (p?≤?0.05). The surface treatment significantly affected the shear bond strengths of the adhesive systems. The shear bond strengths of Optibond? All-In-One (2.661?±?0.48?MPa) in Group 1 and Scotchbond Multi-Purpose (3.818?±?0.98) in Group 4 were significantly higher than those of the other adhesive systems. Silica coating of the amalgam surface significantly improved the shear bond strength of the resin composites. The addition of a retention hole on the amalgam affects the bonding strength of the composite adhesion.     

Effect of adhesive systems on microleakage in endodontically treated teeth restored with glass fiber posts

The effect of adhesive systems on microleakage in endodontically treated teeth restored with glass fiber posts was studied. Forty carious and crack-free premolars were prepared using a stepback technique and obturated with gutta-percha. The endodontically treated roots were randomly divided into four groups (n?=?10). Glass fiber posts cemented following adhesive luting agents; group 1: All Bond 3/Duo Link (ALB/DL), group 2: One-Step Plus/Duo-Link (OSP/DL), group 3: Panavia F 2.0/Panavia ED Primer II (PAN/ED), and group 4: Rely X Unicem (RU). All specimens were thermal cycled and stored in basic fuchsin solution for one week. The roots were sectioned horizontally into three sections: apical, middle, and coronal. The occlusal direction of each section was digitally photographed under a stereomicroscope. Dye penetration area was calculated as the basic fuchsin infiltrated surface divided by total dentin. The data were statistically analyzed using the Mann–Whitney U and Wilcoxon Signed Ranks Tests (α?=?0.05). The mean area measurements were ranged between 0 and 3.7357. According to the Mann–Whitney U test, there was no significant difference among the groups and sections (p?>?0.05). Intragroup comparisons showed a significant difference between coronal-apical and middle-coronal sections in Panavia group (p?=?0.043) by Wilcoxon Signed Test. It was found that there was no significant difference among four groups and the apical, coronal, and middle sections. The only difference was found for the group of PAN/ED between coronal-apical and coronal-middle sections.     

Influence of desensitizing procedures on adhesion of resin cements to dentin

This study evaluated the effect of two desensitizer agents with different contents and Nd:YAG laser irradiation on the shear bond strength (SBS) of adhesive resin cements to dentin. New treatment options of Nd:YAG laser irradiation and tetracalcium phosphate-containing agent applications were compared with routinely used glutaraldehyde-containing agents. One hundred and twenty human, caries-free premolars were embedded in acrylic resin blocks 2 mm below the cementoenamel junction. Buccal surfaces of the teeth were ground to expose dentin. The specimens were randomly assigned into three different surface treatments (desensitizing agents, Nd:YAG laser) and the control, then into three different adhesive resin cement applications (n = 10). Resin cements (Panavia SA cement (PA), Panavia SA cement with Clearfil Universal Bond (PACU), and Multilink N (MN)) were applied to the conditioned teeth surfaces using Teflon tubes. The specimens were thermocycled (5000 cycles, 5–55 ± 1 °C, dwell time 30 s). The SBS test was performed in all groups. The results were submitted to two-way ANOVA and Tukey HSD tests (p < .05). Further, SEM analysis was performed on the dentin surfaces. SBS values were significantly difference among the surface treatment groups and also among adhesive resin cement groups (p < .05). The specimen cemented with PA showed lower SBS values than PACU- and MN-applied specimens. The highest SBS value was obtained in the Nd:YAG laser group which was cemented with PACU cement. The lowest SBS value was obtained in the control group which was cemented with PA cement. In addition, SEM evaluation revealed that desensitizing agents and Nd:YAG laser occluded dentin tubules.     

Effect of hot-etching treatment on shear bond strength of zirconia to resin cement

ABSTRACT

The purpose of this study was to evaluate the effect of hot-etching surface treatment on the shear bond strength between zirconia ceramics and resin cement. Ceramic cylinders were divided randomly into 10 groups (n?=?10) according to different surface treatments (blank control; airborne particle abrasion; hot-etching for 10?min; hot-etching for 30?min; hot-etching for 60?min) and whether or not performed thermal cycling fatigue test. Flat enamel surfaces, were prepared from human permanent incisors and were bonded to the zirconia discs. All specimens were subjected to shear bond strength test by a universal testing machine. All data were statistically analysed using one-way analysis of variance and multiple comparison least significant difference tests (α?=?0.05). Hot-etching for 60?min treatment produced higher bond strengths than the other treatment. Surface treatment of zirconia with a hot-etching solution might enhance surface roughness and bond strength between zirconia and resin cement.     

Effect of different mechanical cleansing protocols of dentin for recementation procedures on micro-shear bond strength of conventional and self-adhesive resin cements

Service life of debonded indirect dental restorations could be prolonged by recementation. This process requires removal of cement remnants from dentin. This study evaluated the effect of different mechanical cleansing protocols of dentin for recementation procedures on micro-shear bond strength (μSBS) of conventional and self-adhesive resin cements. The labial surfaces mandibular incisors (N=200) were ground with a low speed saw to expose the coronal dentin. The teeth were randomly divided into two subgroups (n: 100 per group) and received either (a) conventional (Panavia F 2.0, Kuraray, PAN) or (b) self-adhesive (Clearfil SA, Kuraray, CSA) resin cement. Resin cements were condensed into polyethylene molds incrementally and photo polymerized using an LED polymerization unit. Specimens were stored in distilled water at 37 °C for 24 h and subjected to μSBS (0.5 mm/min). Resin cement remnants on bonded dentin surfaces were removed using by (a) composite finishing bur (cb), (b) tungsten carbide bur (ob), (c) ultrasonic scaler tip (sc) or (d) pumice-water slurry (pw). Non-cleaned teeth acted as the control group (cn) (n: 20 per subgroup). After cleaning, the same cement type was rebonded simulating clinical recementation. Failure types were analyzed using optical microscope and Scanning Electron Microscope (SEM). Data (MPa) were analyzed using Wilcoxon Signed Ranks, Mann-Whitney U and Bonferroni tests (α=0.05). Overall, CSA (6.42±2.96) showed significantly lower results than that of PAN cement (7.88±3.49) (p<0.05). All cleansing protocols (4.29±2.17 to 5.82±2.5) showed significantly lower results than that of the control group (9.84±4.88) for PAN cement. For CSA cement, all cleansing protocols presented non-significant results (4.25±2.74 to 6.44±2.4 MPa) compared to control group (p>0.05) expect cb method (3.42±1.47) (p<0.05). Remnants of cements were detected on dentin surfaces in all groups at varying degrees. SEM showed that while using pumice-water slurry was the least effective for PAN, tungsten carbide bur was the most effective for both cements. All other methods showed similar cleansing efficacy. None of the cleansing protocols yielded to complete removal of resin cement rest on dentin upon recementation for both cements tested.     

Effect of adhesive type and composite viscosity on the dentin bond strength

Objectives: Evaluate the influence of composite resins viscosity and type of cure of the adhesive systems on the bond strength of composite resins submitted to artificial aging.

Methods: Dentin specimens (n = 240) were divided into 2 groups: Group GC: GrandioSO, and Group GF: GrandioSO Heavy Flow. These groups were subdivided into 6: FM: Futurabond M – light cured, FDCC: Futurabond Dual Cure – chemical cured, FDCL: Futurabond Dual Cure – light cured, CS3: Clearfil S3 – light cured, CDCC: Clearfil Dual Cure – chemical cured, and CDCL: Clearfil Dual Cure – light cured. Resin blocks were build up on the dentin surface. Half of samples on each group were cut to obtain resin/dentin sticks (1 × 1 mm). The other half was first submitted to thermomechanical aging. The dentin/resin sticks were submitted to microtensile bond strength test and the results were analyzed using three-way ANOVA and Tukey’s test (α = 5%).

Results: ANOVA showed significant influence for adhesive (p = 0.0000) and aging (p = 0.0001). No significant influence of the composite viscosity on bond strength was observed (ANOVA: p = 0.0861). For adhesive, the results of Tukey’s test (MPa) were CDCC: 13.44 (±5.13)a; FM: 14,01 (±2.71)a; CDCL: 14.51 (±4.98)a; FDCC: 18.66 (±7.13)b; CS3: 18.80 (±6.50)b; FDCL: 19.18 (±7.39)b. For aging: AGED: 14.99 (±6.32)a; NOT AGED: 17.87 (±5.97)b.

Conclusion: Composite resin viscosities did not influence on the bond strength. Type of cure of the adhesives had influence on the bond strength. Thermomechanical aging decreased the bond strength.