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.     

Micromorphology of resin–dentin interfaces using self-adhesive and conventional resin cements: A confocal laser and scanning electron microscope analysis

Purpose: The aim of this study was to evaluate the resin–dentin morphology created by four dual-cured resin cements. Materials and Methods: Two self-adhesive resin cements (RelyX Unicem, 3 M ESPE and Clearfil SA Luting, Kuraray Med.) and two conventional resin cementing systems (RelyX ARC, 3 M ESPE and Clearfil Esthetic Cement, Kuraray Med.) were evaluated. Occlusal dentin surfaces of 32 extracted human third molars were flattened to expose coronal dentin. Teeth were assigned to 8 groups (n=4), according to resin cement products and microscope analysis (SEM: scanning electron microscope or CLSM: confocal laser scanning microscopy). For CLSM, two different fluorescent dyes, fluorescein isothiocyanate–dextran and rhodamine B, were incorporated into the adhesive system and resin cement, respectively. The resin cements were applied to indirect composite resin disks, which were cemented to dentin surface according to manufacturer's instructions. After 24 h, all restored teeth were vertically sectioned into 1-mm-thick slabs for SEM or CLSM analyses. Results: Scotchbond Multi-Purpose Plus/RelyX ARC cementing system formed a thin hybrid layer and resin tags penetration into the dentin tubules. Clearfil DC Bond/Clearfil Esthetic Cement showed only short resin tags. Neither hybrid layer nor resin tags were detected for self-adhesive resin cements. Conclusion: Representative SEM and CLSM images provided resin–dentin interfaces variability among resin cements studied.     

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.     

Effect of temporary cement removal methods from human dentin on zirconia-dentin adhesion

This study evaluated the effect of temporary cement residue removal methods from human coronary dentin on the bond strength of adhesively-luted zirconia on dentin. Forty non-carious human molars were embedded in acrylic resin and the dentin surfaces were exposed. Temporary acrylic crowns were provisionally cemented with zinc oxide cement without eugenol and stored in distilled water (37?°C/15?days). After crown removal, the excess temporary cement was removed from dentin according to one of the following cleaning methods: (n?=?8 per group): (a) air-water rinse (AW), (b) pumice paste (PP), (c) air-abrasion with aluminum oxide particles (Al₂O₃) (AA), (d) sodium bicarbonate spray (SB) or (e) glycine powder (CP). Forty zirconia cylinders were made and each cylinder was adhesively luted onto each tooth after adhesive resin (Scotch Bond Universal, 3?M ESPE-SBU) application using resin cement (RelyX Ultimate, 3?M ESPE) and photo-polymerized from each surface for 20?s. The bonded specimens were stored in distilled water (37?°C) for 90?days. The bonded interface was loaded under shear (1?mm/min). Data (MPa) were analyzed using 1-way ANOVA and Tukey's test (α?=?0.05). Mean bond strength was significantly affected by the cleaning method (p?=?0.0289). Cleaning with AA method resulted in significantly higher bond strength than with SB (p?<?0.05) but similar to CP, PP and AW (p?>?0.05). All cleaning methods were effective in removing temporary resin cement from dentin surfaces. Air-abrasion with aluminum oxide particles was more effective than with sodium bicarbonate spray promoting adhesion between zirconia and dentin.     

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.     

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.     

Effect of Thermocycling on the Bond Strength of Self-Adhesive Resin Cements Used for Luting CAD/CAM Ceramics to Human Dentin

The aim of the study was to evaluate the influence of thermocycling on the shear bond strength of self-adhesive, self-etching resin cements luted to human dentin and computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics. Three modern self-adhesive dental cements (Maxcem Elite, RelyX U200, Panavia SA) were used to lute three CAD/CAM ceramics (IPS Empress CAD, IPS e.max CAD, IPS e.max ZirCAD) onto the dentin. One conventional cement (Panavia V5) served as a control. After preparation, the samples were subjected to thermocycling as a method of artificial aging of dental materials applied to simulate long-term use in oral conditions. Shear bond strength was evaluated according to PN-EN ISO 29022:2013-10 and failure modes were observed under a light microscope. Statistical analysis was performed. The study demonstrated that a combination of ceramics and cements directly impacts the bond strength. The highest bond strength was observed in Panavia V5, lower in Panavia SA and Maxcem Elite and the lowest–in RelyX U200. Adhesive failure between human dentin and cements was the most common failure mode. Moreover, thermocycling highly decreased bond strength of self-adhesive, self-etching cements.     

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.     

Adhesion of cast metal alloy and lithium disilicate copings luted to different core build-up materials with self-adhesive resin cement

This study evaluated the shear bond strength of two coping materials (non-nickel chrome-based cast alloy and lithium disilicate ceramic (IPS Empress) to four different core foundation materials (resin composite, cast metal alloy, lithium disilicate, and dentin), luted with adhesive resin cement (RelyX Unicem). Specimens (N = 56) were fabricated and divided into eight groups (n = 7 per group). Each coping material was luted with self-adhesive resin cement (RelyX Unicem) to the core materials. Bond strength was measured in a Universal Testing Machine (0.5 mm/min). Data were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey’s HSD tests (alpha = 0.05). Both core (p = 0.000) and coping material type (p = 0.000) significantly affected the mean bond strength (MPa) values. Interaction terms were also significant (p = 0.001). The highest bond strength results were obtained when lithium disilicate was bonded to lithium disilicate (21.48) with the resin cement tested. Lithium disilicate in general presented the highest bond results when bonded to all core materials tested (16.55–21.38) except dentin (3.56). Both cast alloy (2.9) and lithium disilicate (3.56) presented the lowest bond results on dentin followed by cast-alloy-cast alloy combination (3.82).     

The effect of different cementing strategies and adhesive interface aging on microtensile bond strength (μTBS) of lithium disilicate ceramics to dentin

This study evaluated the effect of different cementing strategies and adhesive interface aging on microtensile bond strength (μTBS) of lithium disilicate ceramic (IPS e.max CAD) to dentin. Forty coronal dentin fragments were randomly assigned to four groups according to the cementing strategy used to bond lithium disilicate ceramic to coronal dentin surface (n = 10): U200 (self-adhesive resin cement (RC) RelyX U200®/3 M ESPE), SBU (single-step self-etching adhesive system (AS) Single Bond Universal®/3 M ESPE + RelyX ARC®/3 M ESPE RC), AdperSB (two-step etch-and-rinse AS Single Bond 2®/3 M + RelyX ARC®/3 M ESPE RC) and Scotchbond (three-step etch-and-rinse AS Scotchbond Multi-Purpose®/3 M + RelyX ARC®/3 M RC). After 48 h, the ceramic-tooth blocks were sectioned perpendicular to the adhesive interface in the form of sticks and randomly subdivided into two groups according to when they were to be submitted to μTBS testing: immediately or 6 months after storage in water. Some sticks were kept for analysis of the adhesive interface by scanning electron microscopy (SEM). The μTBS test was performed in a universal testing machine (0.5 mm/min). The data (MPa) were analyzed using split-plot ANOVA and Tukey’s test (α = 0.05). Water storage decreased μTBS in all cementing strategies. The μTBS was greatest in the Scotchbond group and lowest in the U200 group, at both storage times. No signs of interface degradation were detected under SEM after water storage. In conclusion, water storage decreased bond strength, regardless of the adhesive cementation strategy, and that the three-step adhesive system/dual-cure resin cement ultimately performed better in terms of bond strength.     

Incorporation of EGCG into an etch-and-rinse adhesive system: mechanical properties and bond strength to caries affected dentin

This study evaluated how a matrix metalloproteinase (MMP) inhibitor (EGCG) incorporated into an etch-and-rinse adhesive system (AS) affects the long-term microtensile bond strength (MTBS) to caries affected dentin (CAD) and flexural strength (FS) of AS. Forty CAD surfaces received acid conditioning and were randomly divided into four groups (n?=?10): EGCG-PRE – dentin treatment with 200?μg/mL EGCG solution; EGCG-INC – 200?μg/mL EGCG solution incorporated into SA; CHX-PRE – dentin treatment with 2% digluconate solution; NT – no treatment. The AS (Adper Single Bond 2, 3M ESPE) was applied and resin composite blocks were built on the dentin. Beam-shaped specimens (0.8?mm²) were obtained submitted to MTBS testing following 24?h, 6 months or 1 year of water storage (WS). Adhesive interface was analyzed by SEM. FS testing was performed by preparing specimens with the adhesive system, with or without the EGCG solution (200?μg/mL) (n?=?10). Tests were carried out in a universal machine (0.5?mm/min). MTBS data were submitted to two-way ANOVA and Tukey’s test, whereas FS data, to the Student’s t-test (α?=?0.05). MTBS values were not affected by EGCG application, either incorporated or used as a dentin treatment agent, regardless of the WS period; however, CHX negatively affected MTBS to CAD (p?<?0.001). WS significantly reduced MTBS values (p?<?0.001) from the 6-months time point. FS was not affected by EGCG incorporation into the SA (p?=?0.2527). EGCG incorporation into AS was unable to maintain bond stability to CAD over time, whereas it did not compromise adhesive’s property.     

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.     

Predictions of nucleation theory applied to ehrenfest thermodynamic transitions: II. The effects of pressure and stress

This paper is a sequel to an earlier one on the applicability of classical nucleation theory to second-order transitions in the Ehrenfest sense (1). In each case the approach was to obtain the critical size r_c and energy barrier ΔG_c for the growth of a nucleus of β-phase in an α-phase matrix by a Maclaurin series expansion of the free-energy-density g = (G_β ? G_α)/v_β as a function of θ (in BC-I) and of ΔP and Δσ in this paper where θ = (T ? T_t) is the degree of undercooling and ΔP and Δσ are analogous terms for the hydrostatic pressure shift and tensile stress shift away from the equilibrium transition. The expansion coefficients were determined by the use of thermodynamic relationships. For second-order transitions, r_c = 4γv_β T_t/ΔC_pθ², r_c = 4γ/Δβ(Δp)², and r_c = 4γ/Y_αY_β(Δσ)², respectively, for the three cases. The terms ΔC_p, Δβ, and ΔY denote the differences in heat capacity, compressibility, and Young's modulus, e.g., ΔY = Y_β ? Y_α. The interfacial energy γ_αβ is denoted by γ. The activation energy barriers for the cases developed in this paper were ΔG_c = (16π/3)γ³/(Δβ)² (Δp)⁴ and ΔG_c = (64π/3)γ³Y_α²Y_β²/(ΔY)²(Δσ)⁴. More complicated expressions are given in the paper for the r_c and ΔG_c for first-order transitions. In the long run, these expressions may prove more useful than the ones for second-order because of the modifications expressions for the kinetics of transformations.     

Effects of mixing techniques and dentin moisture conditions on push-out bond strength of ProRoot MTA and Biodentine

Objective: To evaluate the influence of manual and mechanical mixing techniques as well as the effects of moisture on the push-out bond strength of ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK, USA) and Biodentine (Septodont, Saint Maur des Fosses, France) to radicular dentin.

Material and methods: Two hundred and forty dentin discs were assigned into three groups with respect to the moisture condition tested: (1) dry, (2) paper points, (3) wet. The discs were further divided into four subgroups according to the calcium silicate cements (CSCs) and mixing techniques used: (1) ProRoot MTA mixed manually, (2) ProRoot MTA mixed mechanically, (3) Biodentine mixed manually, and (4) Biodentine mixed mechanically. Bond strengths of the cements to root canal dentin were measured using a push-out test setup. The data were statistically analyzed using three-way ANOVA and Bonferroni post hoc test p = 0.05.

Results: The data indicated that the push-out bond strength values were significantly affected by CSCs, mixing techniques, and moisture conditions (p < 0.001). Dry conditions caused a significant decrease in bond strength values for both CSCs (p < 0.001). The mean bond strength of Biodentine was significantly higher than that of ProRoot MTA, regardless of the mixing techniques and moisture conditions (p < 0.001). Mechanical mixing favored bond strength values statistically compared to manual mixing (p < .001).

Conclusion: The mixing techniques and moisture conditions have an effect on the push-out bond strengths of ProRoot MTA and Biodentine. Dry samples and manual mixing of cements deteriorate the push-out bond strengths values.     

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   

Effects of different surface treatments of zirconia on the bond strength of self-adhesive resinous cement

Purpose: The aim of this study was to evaluate the effects of different zirconia surface treatments on the bond strength of two self-adhesive resinous cements (SARC).

Methods: Two hundred and eight cylindrical specimens were obtained from Y-TZP zirconia (half with diameter 3.2 mm and half with 4.8 mm). After sintering and polishing, specimens were divided into four groups (n = 26), according to surface treatment: Control (no treatment); Sandblasting (Al₂O₃ particles); Rocatec (Al₂O₃ particles, tribochemical silica coating and silane application); Laser (Nd: YAG laser: 20 Hz, 100 mJ, 0.2 J/cm²). The surface roughness (Ra) was evaluated after the surface treatments, and the groups were divided into two subgroups (n = 13), according to the SARC tested: RelyX U200 and Bifix SE. The 2.2-mm cylinders were bonded to 4.8-mm cylinders and stressed until failure under shear using a universal testing machine. Bond strength and Ra were analyzed using ANOVA, and Tukey’s test (α = 0.05).

Results: Surface treatment was significant (p < 0.0001), but cement type (p = 0.73) was not. Related to roughness, significant differences were found for the treatment type (p < 0.0001), with laser being the treatment with higher Ra values.

Conclusions: Nd:YAG laser produced a rougher surface and a higher bond strength compared with sandblasting, silicatization, and control groups.     

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.     

Adhesion of resin cements to contaminated zirconia resin cements on zirconia: effect saliva-contamination and surface conditioning

This study evaluated the adhesion of resin cements to zirconia after saliva contamination using resin cements with different chemistries. Zirconia discs (N?=?240, n?=?10 per group) were randomly divided into three groups: (a) C: No contamination (Control), (b) S: Contamination with saliva, (c) S?+?AA: Contamination with saliva followed by air-abrasion (CoJet). While half of the specimens were not conditioned, the other half were conditioned with 37.5% H₃PO₄ for 60?s. After rinsing, all specimen surfaces were silanized (Monobond Plus). Resin cements based on either methacrylate (Variolink II–VL) or MDP monomer (Panavia 21-PN) were polymerized on the substrates. The specimens were randomly divided into two further groups to be tested either after (a) 24?h dry storage at 37?°C or (b) thermocycling (×5000, 5–55?°C). Microshear bond (MSB) tests were conducted in a Universal Testing Machine and failure types were analyzed. Data were analyzed using Univariate analysis and Tukey’s tests (alpha = 0.05). While saliva contamination, 37.5% H₃PO₄ application (p?<?.001) and aging (p?<?.05) significantly affected the bond results, cement type did not show significant difference after aging (p?>?.05). Adhesive strength of PN (1.2–4.4?MPa) on saliva contaminated and etched zirconia was more stable than that of VL (0–2.8?MPa). After aging, bond strength results decreased the most with VL (3–100%) compared to PN (32–71%) but the decrease was less in the air-abraded groups after aging (VL: 3%; PN: 32%). Exclusively adhesive failures were experienced in all groups.     

Polymerization shrinkage/stress and dentin bond strength of silorane and dimethacrylate‐based dental composites

This study was designed to determine whether a new dedicated adhesive system using a silorane composite exhibits better bonding performance to human dentin than conventional dimethacrylate‐based composites. The materials were used included: Adper? Easy Bond‐Z250 (AE‐Z250), iBond‐Venus (IB‐VE), XenoIII‐TPH (XE‐TPH), Clearfil S3‐Clearfil Majesty (S3‐CM), and the Filtek silorane system (SA‐FS). Polymerization volumetric shrinkage and stress development were measured using a micro‐CT instrument and universal testing machine. The push out strength of the bonds produced using the corresponding self‐etching adhesive systems were also measured. The volumetric shrinkage of the resin composite/adhesive combinations ranged from 1.05% (SA‐FS) to 3.38% (XE‐TPH) 30 min after light curing. SA‐FS had the lowest volumetric shrinkage (P < 0.05), followed by S3‐CM, EA‐Z250, IB‐VE, and XE‐TPH. The polymerization stress of the materials ranged from 1.54 (SA‐FS) to 3.49 MPa (S3‐CM). The lowest stress was also observed in SA‐FS at 30 min during the stress test (P < 0.05). Push‐out bond strength testing revealed that IB‐VE had significantly lower bond strength than other combinations (P < 0.05). The silorane composite and dedicated adhesive system exhibited excellent characteristics of low volumetric shrinkage and stress development compared to conventional dimethacrylate‐based composites. However, the silorane composite resin system possessed similar push‐out bond strength as the other materials, with the exception of the Venus/iBond combination. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Bacterial Adhesion to Low Energy Solid Surfaces: A Surface Thermodynamics Approach

A desired approach to reduce bacterial adhesion to ship hull, heat exchanger and medical device surfaces is to make them less attractive for bacteria by applying anti-fouling or foul-release surface coatings. However, the selection of a useful anti-fouling coating is a difficult problem and surface thermodynamics may guide us in this respect. In this work, we investigated the independent contributions of substrate–water, γ _SW ^Tot, substrate–bacteria, γ _SB ^Tot, and bacteria–water, γ _BW ^Tot, interfacial free energies to the total free energy of adhesion, ΔG _SWB ^Tot, of Pseudomonas fluorescens bacteria on the Si- and SiN-doped DLC coated glass slide surfaces using the Lifshitz–van der Waals and acid–base surface free energy components theory. It was found that mostly acid–base interactions determine the bacterial removal properties. The repulsion between bacteria and the solid surface in water increases if γ _SB ^AB is large and γ _SW ^AB is small, when they are both positive. When Lifshitz–van der Waals and acid–base components of free energy of adhesion are considered, it was found that the effect of ΔG _SWB ^LW was very small and the main effect on bacterial removal was found to depend on the ΔG _SWB ^AB parameter and bacterial % removal increased linearly with the increase of both ΔG _SWB ^AB and ΔG _SWB ^Tot parameters for all the samples.